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information theory have evolved. It briefly discusses the advantages of quantum
blockchain over conventional blockchains and examines recent developments in the
field [1]. A decentralized database called blockchain is encrypted to thwart manipu-
lation. While blockchain technology shows great promise for various uses, current
blockchain-based platforms rely on outdated encryption, hashing, and digital signa-
ture algorithms that are susceptible to attacks from quantum workstations.
Individuals who have gained access to quantum computing will have an unfair ben-
efit when it comes to mining incentives because the same considerations apply to
the cryptographic hash functions or consensus that are leveraged to spawn
new blocks.
Blockchain technology quickly establishes itself as a key technology that can
address many global space industry issues. The smart contracts and blockchain
technology have the potential to open up a plethora of new prospects for the global
space industry. These include the creation of satellite payloads, supply chain man-
agement in space, and satellite as a service. Additionally, it is anticipated that block-
chain will greatly impact subsequent financial transactions. The Bitcoin blockchain
can be sent by satellite, which will be faster and more reliable, speeding up interna-
tional financial transactions. Without using the Internet, the Blockstream Satellite
Network demonstrates how satellites using the blockchain can process and send
Bitcoin around the globe [2, 3].
Scalability, effectiveness, and longevity are three significant challenges for
blockchain technology. These obstacles need to be overcome if blockchain is ever
going to develop into a mature technology that can be used responsibly. It is possi-
ble that quantum computers would have been invented before the broad implemen-
tation of blockchain technology for mission-critical tasks in financial and other
types of organizations. Quantum computing can be utilized to solve some of the
challenges that arise with the implementation of certain blockchain technologies,
such as cryptocurrencies. This can facilitate the installation of such technologies.
This article highlights the research that has already been undertaken on hybrid
quantum-classical blockchain technology, as well as the unanswered research ques-
tions [4].
Even though quantum computing, a thriving technology, poses a threat to some
of the fundamental elements of blockchain technology, it is widely recognized as a
significant future technology. According to current estimates [5, 6], there is a 15%
chance that quantum computers will be commercially available by 2026 and a 50%
chance that they will be by 2031. Since most existing blockchain systems rely
mostly on digital signatures with public keys and are used to communicate value,
they are especially a little bit susceptible to attacks from quantum workstations.
Fedorov et al. [7] say that blockchain technology as it is now might not work if
quantum technologies are not added. Existing temporary solutions, like post-
quantum cryptography [8–10], don’t guarantee solutions to the threat that are com-
pletely safe. There have been many studies [11–13] on the quantum-safe blockchain,
which could protect against attacks from future quantum computers.
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2
Blockchain and Quantum Computing
A blockchain is a type of technology that enables the formation of distributed led-
gers that are not centralized and may be used to record transactions that take place
across a computer network. On the contrary side, quantum computing is a subfield
of computer science that tries to capitalize on the power of quantum mechanics to
tackle difficulties that are now intractable with traditional computers. At the inter-
section of these two technological spheres, significant research and development
work are currently being carried out. One possible use of this intersection is quan-
tum-resistant cryptography, which leverages the principles of quantum physics to
design cryptographic algorithms and methods resistant to quantum attacks. One
further possible use case involves implementing blockchain networks with quantum
computing to boost their operational effectiveness and scalability. Although it is not
yet evident how these technologies will be combined or what specific applications
will emerge, this is undeniably an interesting field of research [14, 15].
2.1
Quantum Computing Effects
on the Blockchain Technology
The technology behind blockchain could be impacted in several different ways by
quantum computing. Developing encryption algorithms that are more resistant to
attacks from quantum algorithms is one approach that could be taken. If this were
successful, blockchain networks would be safe from harm. As a consequence of the
circumstance that quantum-based computers can defeat the encryption methods that
are now used to protect blockchain systems, new cryptographic approaches that are
immune to quantum attacks must be developed. Computing on the quantum level
could also have an impact on blockchain technology by improving the scalability
and efficiency of blockchain networks [15]. It is possible that the use of quantum
computers, which can complete certain jobs significantly more quickly than con-
ventional computers, could be put to use to improve the pace at which blockchain
networks function. This might make it possible to process more transactions per
second while at the same time reducing the amount of energy needed to keep the
network secure. It should be emphasized that even though quantum computing has
the prospective to affect blockchain technology, the arena of study is still in its
infancy, many of the proposed applications are still in the research phase, and the
nature of the effect that quantum computing will have on blockchain technology is
not yet known [16, 17].
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-14-320.jpg)
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2.2 Quantum Blockchain
The convergence of blockchain technology and quantum computing gives rise to a
captivating concept referred to as the quantum blockchain. The main goal of a quan-
tum blockchain is to establish a decentralized and distributed ledger that exhibits
resilience against potential attacks from quantum workstations. The quantum-
resistant encryption algorithm serves to enhance the safety of the network and bol-
sters its resilience against potential quantum-based attacks. One of the main
challenges confronted in the realm of quantum blockchain technology pertains to
the scarcity and nascent state of quantum computers. However, due to the antici-
pated developments and increased accessibility of quantum computers, there will be
a considerable increase of interest for quantum-resistant blockchains.
Furthermore, the utilization of quantum blockchain likely addresses scalability
concerns and enhances the efficacy of traditional blockchain systems. Quantum
algorithms possess the capacity to enhance the efficiency of transaction processing.
Quantum entanglement has the potential as a viable solution for enhancing the con-
fidentiality and integrity of blockchain transactions. It is imperative to acknowledge
that the existing level of research in this domain is in its nascent stage, and the verifi-
able feasibility of the purported advantages of quantum blockchain remains uncer-
tain. Furthermore, the amalgamation of quantum computing inside the framework
of blockchain technology may require a substantial duration to evolve into a viable
and feasible solution [18, 19].
2.3
Types of Quantum Blockchain
Multiple iterations of quantum blockchains have been suggested, each possessing
distinct merits and drawbacks. This section presents a succinct outline of the pre-
vailing categorizations of quantum blockchains, as reported in scholarly literature
[20–22], and the summary is provided in Table 1.
• The quantum-secured blockchain utilizes cryptographic techniques that are
resistant to quantum computer assaults to safeguard the network. The use of this
strategy guarantees the persistent safety of blockchain systems, notwithstanding
the escalating computational competences of quantum computers.
• Quantum-enhanced blockchain pertains to a classification of blockchain systems
that utilize quantum algorithms and quantum computation to augment the scal-
ability and performance of these networks. This has the potential to lead to an
augmentation in transaction processing capacity and a decrease in the energy
consumption associated with network security.
• The utilization of quantum entanglement in the quantum-federated blockchain
system serves to augment the levels of privacy and security associated with trans-
actions conducted on blockchain platforms. In a blockchain network, it is possi-
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Table 1 Summary of different types of quantum blockchains [20–22]
Type Description Key features
Quantum-
secured
blockchain
The network employs quantum-
resistant cryptography as a means of
safeguarding against potential assaults
from quantum computers
Offers more security steps to protect
blockchain technology from quantum
attacks. Ensures the reliability of data in
the setting of developments in quantum
computing. This project lays the
groundwork for blockchain technology
to be profitable in the long run
Quantum-
enhanced
blockchain
Quantum algorithms and quantum
processing are utilized to enhance
scalability and efficiency, with the
potential to increase transaction
throughput while decreasing energy
consumption
Using this technology makes the
transaction handling go faster. Using
this technology cuts down on the
amount of energy needed for mining
and consensus processes. The network
is now able to grow and respond better
Quantum-
federated
blockchain
Quantum entanglement is employed to
enhance the safety and security of
financial transactions. Enables several
individuals to utilize a shared
blockchain infrastructure without
necessitating the disclosure of their
respective transactional activities to one
another
Transactions are kept private because
strict security steps are put in place.
Allows more than one organization to
use a safe blockchain system. Make
sure that privacy stays the same in
consortium blockchain settings
Quantum-
hybrid
blockchain
When the benefits of quantum-secured
and quantum-enhanced blockchains are
combined, the result is a system that is
both reliable and safe
This system has both protection and
performance features that work well
together. Shows the ability to deal with
quantum threats as they change. The
proposed answer is a flexible way to
handle an extensive use cases in the
blockchain space
ble for multiple entities to participate while ensuring the confidentiality of their
transactions.
• The quantum-hybrid blockchain is a novel tactic that integrates the benefits of
quantum-secured and quantum-enhanced blockchains. This fusion results in the
development of a system that exhibits robustness, security, and a high degree of
resilience.
It is imperative to acknowledge that the investigation of quantum blockchain is
now in its nascent stage, and the most effective configuration, if one exists, has yet
to be ascertained. Furthermore, the practical ramifications of this technology remain
incompletely actualized, requiring a significant duration before it can attain its max-
imum efficacy.
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-16-320.jpg)
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2.4
Proposed Algorithms for Quantum Blockchain
Several algorithms have been proposed in current research endeavors for the cre-
ation of a quantum blockchain. The subsequent examples serve to exemplify a range
of essential algorithms. The provided text encompasses a range of numerical data.
• Quantum key distribution (QKD) is a technique that utilizes the moralities of
quantum physics to launch a secure means of communication across many enti-
ties. Subsequently, the establishment of this safe channel can be employed to
produce encryption keys, ensuring the security of blockchain transactions.
• Quantum-secured direct communication (QSDC) is a scheme that leverages the
phenomenon of quantum entanglement to obviate the necessity of a specialized
secure communication channel, hence facilitating direct communication among
several entities. The utilization of this approach possesses the capability to
enhance the confidentiality of transactions executed inside a quantum blockchain
environment.
• The quantum hash function (QHF) is a method that utilizes the fundamental
moralities of quantum physics to generate a hash function that is resilient against
collisions and preimages. The implementation of this method possesses the
capacity to augment the security of the blockchain by augmenting the amount of
complexity linked to the alteration or manipulation of the data that is documented
on the blockchain.
• The quantum random number generator (QRNG) exploits the foundational
moralities of quantum mechanics to generate random numbers. Numerical val-
ues can subsequently be employed to produce robust cryptographic keys, hence
enhancing the level of security offered by blockchain technology.
• Grover’s algorithm is a quantum computational approach that exhibits the capa-
bility to speed up locating a particular blockchain transaction by diminishing the
number of necessary searches to N, wherein N is the magnitude of the database.
It is imperative to acknowledge that most of these algorithms are now in the
research stage and have yet to be applied in real settings. Furthermore, the most
effective approach for implementing the quantum blockchain remains uncertain.
Furthermore, the incorporation of quantum algorithms into blockchain systems is a
significant barrier that necessitates considerable investments of time and resources
for its advancement.
3 Quantum Cryptography
Quantum cryptography, alternatively mentioned to as quantum key distribution
(QKD) [23], is a method employed for the protected transmission of cryptographic
keys by the application of principles derived from quantum physics. The technique
facilitates the establishment of a mutually agreed upon secret key between two
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entities, which can subsequently be utilized for the purpose of encrypting and
decrypting messages exchanged between such parties. The robustness of the key’s
security is derived from the essential moralities of quantum physics, rendering it
highly challenging for an unauthorized party to pilfer it without triggering detection
mechanisms. Quantum cryptography is based on the essential moralities of quan-
tum physics, particularly those related to the polarization and phase characteristics
of light in quantum states. The quantum state of a photon contains the encryption
key, which is then exchanged between two entities. Any endeavors to apprehend the
photon will unavoidably modify its quantum state, thereby notifying the individuals
engaged in a dialog that an act of surveillance is being conducted. Quantum cryp-
tography exhibits superior performance compared to conventional cryptography
across multiple dimensions. Therefore, the system demonstrates a significant degree
of resilience against a wide range of attacks, including those executed by quantum
workstations. Moreover, the computational ability of computers to explain mathe-
matical problems is irrelevant to the current topic under discussion. Hence, it may
be inferred that forthcoming developments in processing capacity would not have
any discernible impact [24, 25].
However, it is imperative to recognize that quantum cryptography encounters
specific obstacles, particularly in its implementation within real-world scenarios.
The methodology exhibits sensitivity to extraneous disturbances and necessitates
the utilization of reliable and robust equipment. Furthermore, it is worth noting that
there is a finite distance beyond which a quantum key distribution (QKD) system is
unable to reliably convey a secure cryptographic key. Quantum cryptography is a
cryptographic methodology that employs the underlying moralities of quantum
physics to guarantee the secure conversation with cryptographic keys. This method-
ology provides a heightened level of security in comparison with traditional proce-
dures. The technology under consideration possesses the prospective to function as
an essential element in the advancement of blockchain systems that are immune to
quantum attacks, as well as other communication systems that prioritize security.
3.1
Quantum Cryptography vs. Traditional Cryptography
There are major distinctions between traditional cryptography and quantum cryp-
tography, even though both seek to guarantee the data confidentiality through
encryption and transmit that data. In the traditional form of cryptography, the pro-
cess of encrypting and decrypting data takes place via the application of various
mathematical methods. This subfield of cryptography is sometimes mentioned to as
“classical” cryptography, particularly in specific circles. The success of these algo-
rithms is dependent on the completion of complex mathematical operations, such as
the division of a very big integer or the solution of discrete logarithms. Consider, for
instance, the operation of dividing discrete logarithms by a significant number. This
can serve as an illustration. Traditional cryptography has proven to be effective in
the past, but it is vulnerable to the potential dangers posed by quantum computers.
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-18-320.jpg)
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When it comes to the processing power they bring to bear on these mathematical
challenges, quantum computers handily beat out their more traditional counterparts.
To carry out its operations, quantum cryptography makes use of the fundamental
laws that govern quantum physics. Encryption of data is a part of this process, and
it does so by utilizing the characteristics of quantum states, more specifically polar-
ization and phase. Using the limitations imposed by quantum mechanics in the
arena of quantum cryptography makes it impossible to steal a cryptographic key in
a covert manner because any attempt to do so would always be discovered. This is
because quantum mechanics imposes these limitations. Data encryption using quan-
tum cryptography is regarded as among the safest methods available. The term
“secure” is commonly used to refer to quantum cryptography, which implies that it
is resistant to any type of decryption, including that which is performed by quantum
computers [26, 27].
Since they are based on mathematical principles, traditional encryption tech-
niques are vulnerable to being broken by quantum computers. Quantum cryptogra-
phy, on the contrary side, is founded on the theories of quantum mechanics, which
makes it fundamentally safe in every and every circumstance.
3.2
Research Gaps in Quantum Cryptography
The field of quantum cryptography is now experiencing significant growth and is
marked by some unresolved matters that necessitate more investigation and solu-
tions. There are several significant research challenges that exist within the domain
of quantum cryptography, encompassing the following concerns:
• Distance limitations: The field of quantum key distribution (QKD) encounters a
notable challenge in the shape of limitations imposed by distance. Current quan-
tum key distribution (QKD) systems suffer from constrained transmission ranges
principally caused by signal attenuation over long distances. The practical uses
of quantum key distribution (QKD) are significantly constrained by the restricted
transmission distance it can achieve. Hence, scholars are actively involved in the
formulation of approaches to overcome this constraint and enhance the extent of
transmission.
• Noise: The impact of noise on quantum key distribution systems can compro-
mise their effectiveness by introducing faults into the transmitted key. The exis-
tence of various sources of noise in practical scenarios might provide a substantial
barrier, impacting the quality and reliability of the signal. Academic scholars are
currently directing their efforts toward developing mitigation measures for the
adverse impacts of noise in quantum key distribution (QKD) systems.
• Scalability: Quantum key distribution (QKD) schemes presently exhibit
restricted scalability and lack the capability to accommodate a significant num-
ber of users. Currently, there are ongoing endeavors to augment the scalability
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and practicality of quantum key distribution (QKD) systems for their application
in practical circumstances.
• Real-world implementation: Theoretical security has been demonstrated in the
field of quantum cryptography; nevertheless, the practical implementation of this
technology in real-world scenarios remains unclear. Currently, researchers are
actively involved in the endeavor of formulating effective approaches for the
implementation of quantum cryptography in real-world scenarios.
• Security against side-channel attacks: Quantum cryptography is widely acknowl-
edged for its inherent security that is considered impervious to decryption.
Nevertheless, the level of vulnerability of the system to side-channel attacks,
which use implementation specifics or physical properties to harvest personal
data, is still undetermined.
• Quantum repeater: The limited distance capacity of existing quantum key distri-
bution (QKD) systems poses a substantial challenge for the transmission of
quantum keys over large distances. The quantum repeater intentions to overcome
the constraint of limited distance by employing a sequence of intermediary nodes
to transmit the quantum signal. The primary function of these nodes is to facili-
tate the transmission an amplification of the signal. Nevertheless, the investiga-
tion of this notion is still in premature phases, and its practical application has yet
not been comprehended.
The concerns encompass a range of unresolved obstacles in the domain of quan-
tum cryptography, compelling researchers to actively seek resolutions in order to
enhance the practicality and widespread implementation of this cryptographic
technique.
3.3
Advantages of Quantum Cryptography
Quantum key distribution, also referred to as quantum cryptography or QKD, exhib-
its several distinct advantages when compared to traditional cryptographic tech-
niques. Quantum cryptography has been extensively discussed in scholarly literature
[28–30], whereby several noteworthy advantages of this field have been highlighted.
• Unconditional security: The term “unconditional security” pertains to a condi-
tion of complete certainty or safeguarding that is not contingent upon any spe-
cific criteria or prerequisites.
• Quantum cryptography is generally recognized for its inherent security, render-
ing it invulnerable to various forms of attacks, including those that may be gener-
ated by quantum computers. The technology in question demonstrates significant
promise in enhancing the security of communication and transactions in the
future, especially considering the anticipated advancement of quantum worksta-
tions that will outperform computational power over classical systems.
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-20-320.jpg)
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3.4
Disadvantages of Quantum Cryptography
Quantum cryptography: quantum key distribution (QKD) possesses the various
benefits over the traditional cryptographic algorithms. However, it does have some
limitations. Among the principal disadvantages of quantum cryptography are as fol-
lows [31, 32]:
• Complexity: Due to the need for specialized apparatus and knowledge, the imple-
mentation of quantum cryptography presents significant obstacles. In addition,
the successful application of this technology necessitates a comprehensive
understanding of the fundamental moralities of quantum mechanics, posing
adoption challenges for certain businesses.
• Cost: The enactment of quantum cryptography requires the use and maintenance
of specialized hardware and software, which may incur significant expenses. In
addition, the implementation of quantum cryptography can incur substantial
expenses, especially in comparison with conventional encryption methods.
• Noise: Quantum cryptography systems are susceptible to noise, which can lead
to defects in the transmission of cryptographic keys. In certain circumstances,
the presence of many sources of noise might provide a substantial hindrance.
• Existing quantum key distribution (QKD) systems have a limited transmission
range due to signal intensity degradation over long distances. Consequently, the
range capabilities of these systems are limited. Quantum key distribution (QKD)
has extremely limited practical applications, and the investigation of quantum
repeaters to increase its utility is in its earliest stages of development.
• Scalability: Quantum key distribution (QKD) systems in their current state
exhibit limited scalability and user capacity. The circumstance can be problem-
atic for large organizations that must ensure communication for many users.
Quantum cryptography is an emerging arena of technology that is presently inac-
cessible to the public on a wide scale. In addition, it is essential to recognize that the
contemporary technology is still in its embryonic stage, indicating that the process
of achieving widespread adoption could take a considerable quantity of time.
Quantum cryptography has several significant disadvantages compared to conven-
tional encryption methods. Quantum cryptography, despite its inherent limitations,
possesses the property of absolute security and has the impending to provide a
sophisticated level of security in certain application scenarios compared to conven-
tional methods.
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-22-320.jpg)
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4 Consensus Algorithms
Consensus algorithms are employed in blockchain systems to guarantee unanimous
agreement among all participants in the blockchain network. A wide range of algo-
rithms have been developed to attain consensus, each with its own distinct set of
strengths and weaknesses [33].
It is remarkable. The utilization and widespread implementation of the proof-of-
work (PoW) consensus method in many blockchain systems exemplify this phe-
nomenon. In this process, miners are obligated to solve intricate mathematical
problems with the purpose of appending new blocks to the blockchain. Quantum
computers possess the ability to do operations at a significantly accelerated pace
compared to traditional computers. The increased processing speed possesses the
capacity to expedite the resolution of mathematical issues in proof-of-work (PoW)
protocols, surpassing the computational efficiency of conventional computers. The
utilization of quantum computers possesses the capacity to significantly enhance the
speed of block mining in comparison with traditional computers. Consequently, this
acceleration may result in the consolidation of mining capabilities among a limited
group of miners equipped with quantum-enabled technology. Consequently, the
concentration may give rise to a singular point of vulnerability, thereby posing a
potential security hazard [34].
On the other hand, other consensus algorithms, such as Byzantine fault tolerance
(BFT) and proof-of-stake (PoS), exhibit a reduced vulnerability to the potential
impacts of quantum computing. This phenomenon can be attributed to their depen-
dence on procedures that extend beyond computational capacity, such as token own-
ership or consensus achieved by a defined number of validators [35].
The recognition of the probable impact of quantum computing on the efficacy of
specific consensus algorithms is of utmost significance. Nevertheless, it is impera-
tive to acknowledge that quantum computing remains a dynamic discipline, wherein
various potential solutions are now being investigated and refined through ongoing
research and development efforts. Furthermore, it is anticipated that the progression
of quantum computing to a level where it can proficiently target blockchain systems
will necessitate a substantial duration.
4.1 Proof-of-Work (PoW)
The consensus process recognized as proof-of-work (PoW) is extensively employed
across several blockchain platforms. The major purpose of this system is to verify
transactions and maintain the network’s integrity. To address an intricate mathemat-
ical problem, individuals, referred to as “miners,” partake in a competitive manner
within a blockchain framework that runs based on the proof-of-work (PoW) prin-
ciple. The initial miner who successfully fulfills this task is authorized to append a
novel block of transactions to the blockchain. To provide a consistent development
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rate for the chain of blocks, the level of difficulty associated with this process is
modified accordingly [36].
The potential impact of quantum computing on blockchain systems that depend
on the proof-of-work consensus mechanism is substantial. The increased rate at
which quantum computers may execute specific operations has the potential to dras-
tically reduce the time required to solve proof-of-work (PoW) mathematical diffi-
culties, in comparison with conventional computers.The capabilities may potentially
allow quantum computers to speed up mining blocks in comparison with classical
computers. Consequently, there is a possibility that this could result in a consolida-
tion of mining authority among a limited group of miners equipped with quantum
technology. Enabling the functionality to control the network and establish a singu-
lar point of failure may potentially introduce a security vulnerability. Currently,
researchers are actively engaged in the advancement of proof-of-work (PoW) algo-
rithms that are resistant to quantum computing. The objective is to enhance the
security of blockchain networks by safeguarding them against possible dangers
posed by quantum computers. The methods under consideration would rely on com-
putationally challenging issues that are highly intricate for quantum computers,
such as the learning with errors (LWE) problem [37].
The utilization of quantum proof-of-work (PoW) as a consensus process in
blockchain networks serves to enhance their security by using principles derived
from quantum computation. Figure 1 is an exemplar pseudocode example that per-
tains to a quantum proof-of-work (PoW) algorithm [38].
It is imperative to recognize that the potential influence of quantum computing
on proof-of-work (PoW)-based blockchain systems is a significant subject matter.
However, it is imperative to acknowledge that quantum computing is a nascent dis-
cipline, and a multitude of suggested approaches are now undergoing investigation
in the research stage. Furthermore, the advancement of quantum computing to a
degree where it can proficiently engage with proof-of-work (PoW)-based block-
chain systems may need a significant duration.
4.2
Quantum Smart Contracts
Smart contracts utilize computer code to encapsulate the exact details of a transac-
tion conducted between a buyer and a seller. The utilization of blockchain technol-
ogy enables the storage and replication of contracts across the network. The network
will subsequently authenticate the fulfillment of the tasks. The facilitation of con-
tract execution automation can be achieved by the utilization of smart contracts,
which possess the ability to carry out diverse supplementary tasks such as supply
chain management, financial transactions, and voting systems. The utilization of
artificial intelligence (AI) has promised to enhance the operational efficiency of
enterprises and optimize supply chain operations through the elimination of inter-
mediaries. The field of quantum computing holds promise for significantly enhanc-
ing the velocity and efficacy of specific computational endeavors, particularly those
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-24-320.jpg)
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Fig. 1 Pseudocode snippet for quantum proof-of-work consensus algorithm [38]
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pertaining to cryptography and blockchain technology. The utilization of quantum
computing holds promises in enhancing smart contracts by enabling the execution
of contractual agreements that exhibit heightened complexity and enhanced secu-
rity. Quantum smart contracts (QSCs) represent an innovative notion that continues
to be the focus of continuing scholarly investigation. Quantum-secured communica-
tions (QSCs) possess several prospective real-time uses, encompassing the
following:
• Quality control systems (QCS) are of utmost importance in the field of supply
chain administration, as they are responsible for safeguarding the genuineness
and reliability of items during their journey across the supply chain. This mea-
sure possesses the capacity to diminish the probability of fraudulent actions and
the manufacture of counterfeit products inside the supply chain.
• Quantum-secured communications (QSCs) possess the ability to facilitate secure
and transparent transactions within the domain of financial services, encompass-
ing areas such as banking, insurance, and investment. The application of suitable
strategies can significantly decrease the occurrence of deceitful behaviors, there-
fore safeguarding the confidentiality and integrity of monetary transactions.
• Quality and security credentials (QSCs) possess the capacity to be employed
within the healthcare sector for the purpose of safeguarding patient confidential-
ity, facilitating the secure exchange of data, and enabling secure transactions
among healthcare providers.
• The integration of quantum-secured computation (QSC) into voting systems
offers a means to guarantee the secure registration and aggregation of ballots
while also facilitating transparency and verifiability at every stage of the voting
procedure.
• Quantum-safe communication (QSC) has the potential to enhance the security of
Internet of Things (IoT) devices by facilitating safe communication and data
sharing across these devices.
The utilization of quantum-resistant algorithms has the potential to enhance the
security of smart contract execution, therefore mitigating the vulnerability to unau-
thorized alterations. Moreover, the utilization of quantum computation possesses
the capability to enhance the scalability of smart contract platforms by facilitating
accelerated transaction processing. However, it is imperative to acknowledge that
the realm of quantum computation is now in its early stages of advancement, and its
potential impact on smart contracts has not been comprehensively comprehended
[39]. It is imperative to acknowledge that the predominant approach to the develop-
ment of smart contracts predominantly depends on conventional computing meth-
ods. The domain of quantum smart contracts, however, is now seeing ongoing
research and development efforts. Figure 2 illustrates the pseudocode of the quan-
tum smart contract, as presented in reference [40].
In summary, the quantum-secured blockchain (QSB) signifies a notable progres-
sion in the field of blockchain technology. The primary aim of this project is to
provide enhanced levels of security and anonymity by integrating blockchain tech-
nology and quantum cryptography. The integration of quantum computing
QSB: Smart Contracts, Consensus, and Quantum Cryptography](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-26-320.jpg)
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Fig. 2 Pseudocode snippet for quantum smart contract [40]
capabilities into the field of blockchain technology has presented new opportunities
for the advancement of more resilient and fortified blockchain solutions. The pri-
mary objective of this study was to examine the possible utilization of quantum-
secured bit (QSB) technology within the domains of smart contracts, consensus
mechanisms, and quantum cryptography. The benefits of QSB in comparison with
traditional blockchain systems were emphasized, while the challenges that neces-
sitate additional investigation were addressed. The potential of QSB appears great,
S. Jain](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-27-320.jpg)
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given the continuous improvements in quantum computing and blockchain technol-
ogy. The objective of this study is to offer relevant viewpoints to scholars and prac-
titioners in this field.
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Keywords Healthcare industry · Electronic health records · Blockchain
technology · Quantum computing · Quantum and blockchain technology
1 Introduction
The growth of industrial healthcare comes with many digitally recorded medical
databases, which require secure processing. The adoption of blockchain and IoT
(Internet of Things) significantly impacts the industrial healthcare sector owing to
the industry’s design comprising of related apparatus and IT applications. These
technologies will enhance information security, transparency, regulatory regulation,
and processing efficiency while opening up new commercial prospects [1].
Therefore, healthcare information could be assessed, evaluated, and shared and
maintain patient privacy. Blockchain technology in modern medicine has many ben-
efits, such as data management, accounting, and finance. Additionally, there are
specific issues and dangers related to blockchain-based healthcare projects and sug-
gestions for mitigating or eliminating them. The health industry is one of the areas
where the blockchain can substantially influence on both the economy and society
[2, 3]. The most significant benefit using it does not require the participation of any
centralized organization. In the medical domain, blockchain technology has been
used to share clinical data, account management, drug supply chain management,
drug development, and clinical trials. The interchange of clinical information
between the payers, patients, and partners and how we obtain and maintain clinical
details can all be entirely transformed by blockchain technology [2].
The rapidly developing technology, blockchain, is utilized in various security
applications. The Stakeholders employ a variety of implementations that use block-
chain technology that kept as a sequence of blocks, may serve as a public record for
all committed transactions. Some essential features of blockchain technology con-
tain decentralization, availability, immutability, transparency, and persistence [4].
Blockchain technology can potentially improve the clinical data-sharing aspect of
the IoT (Internet of Things). Blockchain provides a secure means of distributing
critical patient information collected by IoT devices [1, 5]. The BPIIoT (Blockchain
Platform for Industrial Internet of Things) enables the legacy shop floor device inte-
gration with an appropriate cloud environment; it would show a tremendous increase
in performance over the current CBM (cloud-based manufacturing) platform,
removing financial barrier that has stifled the development of a company ecosystem.
Using this ecosystem, the manufacturing and healthcare industries, including sup-
ply chains, logistics, healthcare, agriculture, and the energy sector, may be able to
facilitate transactions between users [1, 6, 7].
Several healthcare institutions utilize the IoHT (Internet of Healthcare Things)
for maintaining assets, monitoring infants, and tracking inventory [1, 8]. The use
cases are two types: assistance operations and clinical services. Through RPM
(remote patient monitoring), IoHT facilitates patient-centric activities in healthcare.
Internet of Healthcare Things strictly checks all vital signs and other crucial
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parameters for the investigation, like weight and blood sugar level changes [1]. The
increased utilization of mobile medical assets made possible by IoHT enhances sup-
port operations and lowers overall operating expenses. The staff can access real-
time information on the location and usage patterns of ventilators, digital X-ray
equipment, and other resources while saving money due to equipment sensors and
data collection capabilities. This allows for more effective equipment assignment
and faster location whenever and wherever needed, thereby saving valuable time for
care workers. Using IoHT sensory inputs, expensive machinery such as MRI (mag-
netic resonance imaging) equipment can also be displayed to technicians in real
time using IoHT sensory inputs. To develop digital twins of technology, medical
decision-makers are also exploring integrating augmented reality technology and
IoHT [1, 9]. The workers and clinicians are provided with practical, hands-on train-
ing opportunities and highly visual and interactive augmented reality interfaces that
can digitally reproduce complicated medical equipment and devices. The protec-
tion, security, and dependability of the servers that link IoT devices and share vital
medical records are issues to be aware of when adopting IoHT [1, 10]. A blockchain
is a logical option that can completely secure the entire process through encryption
and decentralization [1, 11]. Blockchain is gaining popularity due to its ability to
create and disseminate permanent, irrevocable transactions securely. Blockchain
builds blocks of transactions and stores them in a continuous sequence of occur-
rences shared securely with different participants. The documents are nearly impos-
sible to alter since the blocks are secured using cutting-edge cryptographic
technology [1, 12]. This technology keeps the possibility to streamline and progress
security and precision for laborious, wasteful methods [1, 13]. Examples include the
following:
• Quick medical insurance enrolment
• More streamlined claims adjudication
• Increased B2B movement throughout the healthcare value chain
The quicker and more effective certification of employees is one of the additional
blockchain prospects. The healthcare sector is a good fit for IoHT and blockchain
technologies due to its patient-centered mechanisms [1, 14]. The two technologies
working together permit for the secure, unchangeable conversation of medical data
[1]. Blockchain technology can benefit the medical field and battle the COVID-19
pandemic. Blockchain technology and its processes will indeed be employed in
upcoming smart healthcare schemes for collecting relevant information from secure
data storage, sensors, and automatic patient monitoring, according to the signifi-
cance of the blockchain. Blockchain technology significantly streamlines opera-
tions since it can preserve vast amounts of information in a distributed and more
secure manner. It provides a more excellent range of accessibility whenever and
wherever necessary [15]. Quantum computing, on the other hand, provides access
to excellent services. The quantum computing has several advantages including the
capacity to employ thermal imaging based on quantum computing and the ability to
detect and monitor patients quickly. These advantages can be completely realized
when combined with quantum blockchain [15]. Another technique that can protect
The Intersection of Blockchain Technology and the Quantum Era for Sustainable…](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-32-320.jpg)
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the reliability, confidentiality, and accessibility of data records is quantum block-
chain. If quantum computing and blockchain technologies are combined, medical
records processing will be faster and more private [15]. Therefore, the use of quan-
tum blockchain technology would benefit medical services to a great extent. The
pace of diagnosis and treatment can be accelerated with quantum blockchain tech-
nology. It also helps preserve data records’ availability and authenticity. The advan-
tages of quantum computing, like the capacity to obtain thermal imaging and the
speed with which patients can be discovered and tracked, may all be utilized to their
fullest extent with the help of quantum blockchain. Additionally, it maximizes
insurance fraud and diagnosis costs.
2
Smart Healthcare Systems
Information technology (IT) is crucial in the healthcare industry because population
health management technologies such as remote patient monitoring (RPM) and
electronic health records (EHRs) have highly improved this industry. The medical
records engendered from these references are extensive and time-consuming, result-
ing in issues with data quality, thereby making the data analysis, prediction, and
diagnosis more complicated and the threat of data protection due to increased cyber-
crime [16]. Because they provide essential data consistent with patients’ perspec-
tives, medical and healthcare records have demonstrated their value to patients. The
healthcare data repository may become a target and a moment of loss for system
attackers. It increases the risk of vulnerabilities, leading to denial-of-service (DoS)
and ransomware attacks [16]. The sharing of the patients’s medical records and
information among the healthcare providers via electronic health records may
increase diagnostic performance. In particular, difficulties with patients’ informed
consent and the scientific credibility of findings such as data missing and dredging,
endpoint flipping, and selective publication in clinical trials could be resolved by
blockchain technology. A patient’s brief medical history is included in an EHR
along with statistics, projections, and any information/data related to their ailments
and clinical progress throughout the therapy [17]. Users could access and preserve
their health data using a blockchain system for EHRs that simultaneously ensures
confidentiality and privacy [17].
EHRs allow patients to manage and share their health records with their family,
medical professionals, and friends, over an open channel and the Internet. Despite
the fact that cloud-based EHRs address difficulties, they are still susceptible to a
variety of destructive attacks, server non-repudiation, and trust management. Hence,
blockchain-based EHR solutions instill in consumers a sense of privacy, security,
and trust [18, 19]. Implementing a blockchain-based EHR system that promotes
interoperability and trust among all parties is possible. It has a distributed, time-
stamped, chronological, immutable, and auditable log to keep clinical information.
Numerous industries, including finance [20], education [21], edge computing ser-
vices [22], tourism [23], automation [19], etc., have used blockchain technology.
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The quantity of data and records has doubled in the healthcare organization 4.0,
which has a $50 billion market [24].
Additionally, the percentage of verified electronic health record systems has
doubled, from 42% to 87% [25]. Because medical professionals, hospitals, and
other service providers update their records frequently, the considerable volume of
data created from several sources could be more organized. It leads to issues related
to management, such as drug tracking, bill management, and claim settlements. The
Health Insurance Portability and Accountability Act (HIPPA) stipulates that health-
care industry stakeholders should ensure that approved data is uploaded by patients
who have certified electronic health records (EHRs) from physicians. Privacy and
data ownership concerns about patients’ sensitive data, its storage, scalability of
mined transactions, capacities, the cost of maintaining healthcare blockchain, and
quantum and collusion attacks are the difficulties of using blockchain technology.
Lattice-based cryptography offers the defense against quantum and collusion opera-
tions and the perfect answer to the issues of user privacy and data ownership. In the
random oracle concept, lattices create post-quantum blockchain networks (P-QBN)
observed as safe [26]. Therefore, lattice signature creation and verification activities
authorize certified EHRs. According to HIPPA regulations, this guarantees com-
plete record secrecy. Distributed artificial intelligence can enhance blockchain oper-
ations by addressing the scaling challenges of transactions, storage, and fee issues
with digital health records stored digitally among distributed nodes [27]. Former
conventional machine learning (ML) and statistical methods [28] were also
employed likewise, whereas they examined plain data to discover relevant attributes
and build patterns of initial intrigue. Identifying the criteria of interest is a much
time-consuming skill [29]. Deep learning (DL) techniques, on the other hand, learn
about feature selection with no human interference, allowing the finding of embed-
ded dynamic relations in between the information [18]. The benefits of blockchain-
based EHRs are numerous; some of them are records stored in a distributed manner
(open and straightforward to verify across a wide range of unaffiliated provider
organizations). Also, there is no centralized party for the attacker to crack or alter
the data; information is continually updated and made available, and information
from various means is combined into a single suitable information storage (Grey
Healthcare Group, 2017) [17].
3 Blockchain Technology
Today’s smart healthcare data management systems face serious hurdles regarding
security, privacy, trust, flexibility, provenance, audit, traceability, transparency, and
immutability. Additionally, many of the current smart medical record managing
methods are centralized, which increases the danger of a single fault point. The
blockchain, an emerging and disruptive decentralized technology, has the potential
to radically revolutionize, reconfigure, and alter data management in medical
domain [30]. Blockchain supports transaction audits in this way, going beyond
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transparency [17]. Blockchain is an innovation that encourages value sharing. It has
recently been used in several fields, with finance in healthcare being the most sig-
nificant. Blockchain is a distributed database of cryptographically linked blocks
aggregating transactions sequentially. Each block is added to the ledger over peer-
to-
peer (P2P) networks, linked to the previous block using hashing technique. These
records are built on a decentralized technology, eliminating the need for transac-
tions and assets to interact with a centralized intermediary. Digital purchases, such
as individual medical information, economic transactions, and personal records, can
be processed, encrypted, confirmed, and stored more efficiently by emerging block-
chain technology [31, 32].
Blockchain enables the decentralization and deregulation of markets of all trans-
actions between participants daily. Blockchain is an application layer that advances
the OSI layer by introducing a layer that allows instant digital currency and finan-
cial transactions. It maintains a record of all the completed transactions [31]. The
chain will continue to expand after another transaction is completed. No third-party
software is required for transactions. From a business perspective, the blockchain is
a system for exchanging assets, value, and transactions between individuals. It is a
method for validating and verifying the transactions and taking the place of trusted
parties’ entities [4]. Nowadays, every medical and healthcare system has high
dependability on blockchain technology. Blockchain technology, which is decen-
tralized and distributed, offers security services for the healthcare industry. The
existing healthcare system’s centralized design could be more secure across many
medical services, resulting in delayed access to the concerned information and sig-
nificant danger of information leakage. The medical records could then be archived
without the client’s concerns. The critical problem in the present healthcare mainte-
nance system is gaining secure network access to information. Blockchain technol-
ogy is proving to be an up-and-coming technology that is the most effective way to
access the concerned data/information. When using blockchain technology, data is
kept in a ledger feature that may be used to monitor how patients access their medi-
cal records [4].
By enabling unparalleled data efficiency and ensuring trust, blockchain helps
streamline the various healthcare data management processes [5, 30]. It provides a
vast range of built-in conspicuous capabilities, including decentralized storage,
adaptability of data access, interconnection, authentication, security, immutability,
and transparency. It also enables wider adoption of blockchain for managing health-
care information records [30, 33, 34]. Blockchain employs the idea of “smart con-
tracts,” which establish specific rules accepted by all the partners in the blockchain
environment and eliminate the need for an intermediary [30, 35, 36]. It reduces
unnecessary administrative costs. Consensus mechanisms, public-key cryptogra-
phy, and peer-to-peer networks comprise the main three ideas of blockchain [27].
Public, private, and consortium blockchains are the categories into which block-
chains are separated based on managing permission [30, 37]. Blockchain technol-
ogy is a distributed database that handles the data within an IoT application in a
chain of blocks [38, 39]. It is particularly good at securely processing relevant infor-
mation for serverless edge computing. However, block data handling decreases
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processing speed [38, 40]. The procedure must operate concurrently over several
distributed architecture nodes to verify the proof-of-work (PoW). Such systems
might be integrated into a function as a service (FaaS) platform using microser-
vices, which could be set up on a serverless pipeline. Quantum computers can pro-
vide large-scale resource management computations to address this issue [38, 41].
With numerous applications in areas like sharing patients’ medical data, preci-
sion medicine, clinical trials, drug counterfeiting, longitudinal healthcare records,
user-oriented medical research, public healthcare management, online patient
access, and automated health claims adjudication, blockchain is essential to the
healthcare industry [17]. Therefore, without needing third-party tools, blockchain
technology enables more robust and more secure transactions. There is no further
need for trust between the parties when each party to a transaction may believe in
the correctness and consistency of the records, a concept known as “trustlessness”
in the context of blockchain [1, 40]. Blockchain offers a broadly distributed, peer-
validated, and immutable digital ledger and does not need money to operate cor-
rectly. Most enterprise-level blockchain applications do not call for specific money,
coin, or token [1, 42].
3.1 Types of Blockchain
• Private and public. Who has access information to the blockchain database?
Large audiences, the general public, can upload data to the ledger via public
blockchains. A public blockchain network like Bitcoin illustrates this; there are
no restrictions on who can exchange Bitcoin. Bitcoin can be purchased, sold, or
sent to anyone. An illustration of a private solution would be a blockchain system
that tracks how donations to nonprofit organizations are used. Only appointed
authorities from the nonprofit group can disclose how funds are distributed and
used in such a way [1, 43].
• Permissioned and permissionless. Permissionless systems are available, and the
public needs more permission or role-based access. These platforms need the
natural functionality to handle identities, set permissions based on those identi-
ties, and enforce those identities. This implies that you must design and imple-
ment a system to track and manage identification and draw permissions against
that identity if you decide to do so. This does not suggest that you cannot develop
a permissioned solution on a permissionless platform. Considering whether all
participants should be treated equally or some should have access to features or
rights that others do not is a beautiful approach to narrowing down the type of
blockchain required when designing a solution. The solution to this question will
assist in informing whether to employ permissioned or permissionless block-
chain technology [1, 43].
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3.2
Advantages and Limitations of Blockchain Technology
3.2.1 Advantages of Blockchain
A business network’s organizations can share infrastructure owing to blockchain
technology. Since we lose the fact if the data is altered, corrupted, or hacked, block-
chain is more secure than a typical database. Blockchain offers robust security and
a wide range of permissions to validate and regulate who has a permit to access
information and under which conditions. Tracing the sources of all supply chain
pieces also enhances quality assurance services by reducing costs and controlling
any defective parts [1, 44, 45]. Blockchain is fault-tolerant and redundant; if any
system loses track of the database, it will stay elsewhere on the network. Consider
sending a group message to understand fault tolerance better. Since every member
in the messaging party has a replica of the party conversation, they would have to do
so on everyone else’s phone if any member wanted to delete something from the
conversation. When numerous people are involved, fault tolerance is beneficial. The
tokenization, which opens up new entrepreneurial opportunities and produces trade-
able tokens with real-world value, is another significant benefit. The term tokeniza-
tion is the digitizing representation of fractional asset ownership, such as owning
one car in one city or one hundred vehicles in one hundred. Blockchain uses a smart
contract to ensure that business operations are automated and consistent across sev-
eral enterprises. Finally, eliminating intermediaries by blockchain lowers costs and
improves the effectiveness of company operations. It enables firms to function more
quickly and respond to changes in the commercial environment considerably more
rapidly than they might otherwise [1, 44, 45].
Patients can transfer their medical records to anyone without worrying about
data tampering or corruption because the blockchain is immutable and traceable [4].
The same is true for a blockchain-generated and added medical record, which will
be completely secure. The patient can influence how the institutions utilize and dis-
seminate their medical data. Any party seeking access to the patient’s medical
records might use the blockchain to verify their eligibility [4]. A reward system can
also motivate the patient to behave well. For instance, people may receive rewards
for adhering to a care plan or maintaining good health.Additionally, they can receive
tokens in exchange for providing their data for studies and clinical trials [4]. Due to
the nature of the products they carry, pharmaceutical businesses must have a very
secure supply chain. Drugs for the pharmaceutical industry are often stolen from the
supply chain and sold illegally to various customers. Additionally, these businesses
lose almost $200 billion a year due to the sale of counterfeit pharmaceuticals. These
businesses will benefit from a transparent blockchain by closely tracking drugs back
to their point of origin, which will help remove fake medicine [4].
D. K. Atal et al.](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-37-320.jpg)
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3.2.2 Drawbacks of Blockchain
Like any other technology, blockchain has costs associated with its advantages. Its
disadvantages need to be fully considered to decide whether blockchain would be
the best option for an overall solution architecture. Best practices suggested pat-
terns, and appropriate use cases are continually being established [1, 44, 45]. The
blockchain’s scalability in comparison with traditional technology is another sig-
nificant limitation. Blockchain has a lower transaction volume processing capacity
than competing systems like Visa. For blockchain to be performance competitive,
the ability needs to be increased by several orders of magnitude. Additionally,
obtaining a thorough “God Mode” view of the answer and its information can be
difficult or impossible. Many available media and toolkits are yet in the preproduc-
tion stage and might not be ready to develop complex applications [1, 44, 45].
Energy consumption is a vital factor in the developing stage of blockchain technol-
ogy. Proof-of-work (PoW), the initial agreement algorithm utilized to mine Bitcoin,
uses 7.67 gigawatts of electricity annually. This power is comparable to the power
use of nations like Austria (8.2 gigawatts) and Ireland (3.1 gigawatts) [1, 46].
Numerous strategies have recently been put up to cut down on the energy usage for
blockchain technology and the resulting carbon footprint. One of these is switching
from PoW validation to PoS (proof of stake). This more recent blockchain consen-
sus algorithm has been suggested to solve PoW’s scalability and cost issues.
Secondly, creating blockchains that operate distinctly from those that use such large
amounts of energy, lastly, concentrate on environmentally friendly methods to mine
Bitcoin, such as solar or wind power. Assaults like 51% and denial-of-service (DoS)
attacks impact blockchain technology. A 51% assault is one of the simplest methods
for breaking the blockchain’s security since it takes advantage of the consensus
algorithm’s legal purpose. In a PoW blockchain, the branch with the most work
behind it wins in the event of a divergent blockchain. Hence the state of the block-
chain is decided by a majority vote. A PoW blockchain is controlled by an attacker
if they own 51% of its compute resources [1]. DoS attacks target the network’s
bottlenecks in conventional, centralized networks. Despite being decentralized and
lacking bottlenecks by design, DoS attacks can be successful against blockchains.
A DoS attack depends on blockchain and the locations of its operational bottle-
necks [1].
4 Blockchain Technology in Healthcare
Blockchain is a novel technology that is employed to generate innovative solutions
in a variety of industries including healthcare. Blockchain is a decentralized hyper-
ledger that aids in the copying every activity or digital event preserves and distrib-
utes. The large number of persons involved confirms every transaction. Every
transaction record is stored there [15]. A blockchain system is leveraged in the
healthcare ecosystem to aid in keeping and sharing patient medical information
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among doctors, drug companies, diagnostic labs, and hospitals. Blockchain applica-
tions can precisely identify severe issues, including possibly deadly ones, in the
medical sector. In the healthcare industry, it can enrich the privacy, translucence of
shared medical records, and efficiency. Medical organizations can obtain perception
and progress the investigation of patient information with the sustainable applica-
tion of blockchain technology. Different blockchain systems can enhance the supe-
riority of the services accessible to the medical industry. Blockchain and IoT
technologies are coupled to allow healthcare institutions to maintain records effec-
tively and accurately, which is necessary [1]. The procedure includes many parts,
from the point at which IoT collects real-time patient data to the point at which a
suitable medicine is given to ensure the patient’s happiness. The blockchain is uti-
lized in [1, 47] to maintain patients’ medical records.
When blockchain technology’s feasibility is considered, service-related indus-
tries such as healthcare are starting to transform and adapt to combine blockchain
technology into their existing condition. By 2025, industry value is anticipated to
grow by over $176 billion by 2025 and reach $3.1 trillion by 2030 [48]. According
to reports from the World Economic Forum, blockchain technology will store 10%
of the global GDP [49]. The worldwide blockchain industry’s growth rate is
expected to increase by 71.46% between 2017 and 2022, reaching $4.401 billion by
2022, up from $0.297 billion in 2017 [50]. These estimates do not surprise block-
chain start-up investors, but the potential of blockchain remains to be discovered
throughout society. Nonetheless, food procurement, mining, minerals, and banking
are already using this technology [50, 51]. It is now being discussed as a potential
application in healthcare to transform medical information systems [52] and pay-
ment systems [53, 54]. Researchers and professionals in the healthcare domain face
scattered data, improper interactions, and clinical processes with incomplete com-
ponents due to supplier-specific and unsuitable health systems. Furthermore, the
confusion about transferring clinical and financial information impacts health IT
systems. As a result, they have critical flaws in terms of privacy and security.
Providing customized patient treatment is challenging due to all of these consider-
ations [52]. The use of blockchain in the medical sector provides advantageous
solutions for safeguarding stakeholder interactions, delivering clinical reports
quickly, and combining various types of individual health records of people on a
secure infrastructure.
4.1
A New Intelligent Healthcare System
Every organization or facility must have a system for the patient. This system must
include a database to store the many distinct data sets needed by the institution and
its stakeholders. These databases are mostly decentralized, containing several other
databases working together. Decentralized databases help information manage-
ment, notably in the healthcare sector [1, 55, 56]. For example, when several users
submit scientific data, the database might grow perplexed and convoluted.
D. K. Atal et al.](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-39-320.jpg)
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Blockchain technology may supply a remedy to certain knowledge areas, such as
elderly treatment or chronic illnesses. Large healthcare databases, conflicting IT
interfaces, changes in communication standards, and incompatibility of information
processes among various therapists, medical specialists, practitioners, physicians,
research labs, and healthcare centers, etc. are just a few of the significant issues that
arise [1].
4.2
Improving the Privacy of Patients’ Medical Records
Health information generated by patients and information stored are highly crucial
[1, 57]. Wearable gadgets, such as trackers, built-in body chips, smartwatches, and
fitness bands that help monitor patients’ data, have been developed due to techno-
logical advancements in the medical sector. The flow of patient-generated informa-
tion has grown due to these wearable technologies. The difficulties posed by the
growth in healthcare data are addressed by blockchain technology [1, 56].
Health Bank’s blockchain technologies offer Swiss start-ups in digital health.
The following are the wide range of facilities to its customers [1]:
1. Management of patient transactions and the sharing of medical information
2. Retrieving patients’ confidential information, such as lifestyle habits, health his-
tory, consumed medicines, eating habits, sleep patterns, heart rate, SpO2, and
other vitals
3. Preservation and accessibility of information for medical research
4. Storage and management of information in a secure location
4.3
Healthcare Services Provided by Blockchain
The blockchain-based medical approach comprises the patient and clinical data
generated and stored as digital resources and accessed over blockchain infrastruc-
ture. It is accessible under secure underlying architecture, seamless data usage, and
exchange across health organizations and vendors. Blockchain applications in
healthcare are health analytics, smart contracts, and a network of medical technolo-
gies that can use the complete history of timestamped records for users in terms of
services. The following medical healthcare services are provided by the blockchain
infrastructure framework [31]:
1. Services provided by the doctors. The suggested blockchain-based medical care
approach improves clinical assistance provided by physicians and other health-
care providers. Computerized cost estimation via trade networks, such as online
transportation services, contributes to translucent invoicing. Payments using
coins based on blockchain offer an efficient payment method.
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2. Notary services. A notary process for the digital transformation of vital records
such as identity cards, passports, and insurance is one of the components
employed for blockchain technology. In the proposed system, records such as
examination marks, evidence of insurance, therapy, and medication are encrypted
and validated in seconds rather than hours or days using traditional technol-
ogy [32].
3. Private blockchain technology. Permission is required to view the data on a pri-
vate blockchain. Therefore, patients grant access to their medical records to their
doctors and other parties. Based on business agreements, different permit levels
can be described to manage who can view documents, alter them, and have
supreme control in the system. In healthcare, the mixture of safety and flexibility
is preferable to the transparent public blockchain.
4. Hospital asset supply chain management. Blockchain technology can even be
leveraged in supply chain control systems to handle hospital products and con-
trol purchase-selling mechanisms for all challenging clinical aids.
5. Smart contract technology. It could reduce insurance scams at all levels, from
corporate fund management to specific claims, at a reduced cost because the
system has less load to manage and process. It primarily performs as a legal
mechanism, enabling real-time data exchange with the blockchain architecture
to design, store, and implement agreements.
6. Private genomic data. Blockchain technology enables the collection of DNA
records from various agencies and authorities without the requirement for a cen-
tralized database and the backup of a person’s DNA to spread individual genetic
material to multiple systems worldwide.
7. Confidential medical record storage and access. Clinical information enables
seamless transmission and data exchange among healthcare communities and
application merchandisers.
5
Quantum Computing in Healthcare
A promising computer method defined on quantum physics and associated excep-
tional circumstances is known as quantum computing (QC). It is a stunning combi-
nation of computational modeling, mathematics, physics, and computer science.
Controlling the behavior of microscopic physical entities like atoms, photons, elec-
trons, and other minute particles surpasses traditional computers in terms of low
energy consumption, rapid speed, and processing capacity. Since the quantum
approach is a more expansive physics model than classical physics, it adds to a uni-
versal computer system, quantum computing, which can solve issues that classical
computing cannot [15]. In contrast to traditional systems, which store and process
data using binary bits 0 and 1, quantum computing uses its quantum bits (“Qubits”).
Although quantum computing can rapidly infiltrate current cryptography methods,
the most extraordinary supercomputer currently known requires thousands of years
to complete [15].
D. K. Atal et al.](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-41-320.jpg)
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The future use of quantum computing in the medical sector may improve the data
processing capacities of various stakeholders such as therapists, medical specialists,
practitioners, physicians, research labs, and healthcare centers, which could be nec-
essary for providing uninterrupted service in a changing environment. Executives
should, however, account for (i) the current system’s issues, that is, the matter of
concern; (ii) the amount of information generated by the system; and (iii) the role in
the medical sector (pharmaceutical or insurance company) [58]. Professionals in the
medical industry, like clinicians, management staff, and insurance company support
staff, must assess the risks of using quantum computing. In silico medical difficul-
ties can be combined with quantum computing to create advanced virtual medical
studies. The benefit of quantum computing is saving lives in danger in the conven-
tional environment of clinical trials in the healthcare industry. Organizations and
experts in healthcare insurance can benefit from precise risk modeling and provide
a price when determining an individual’s needs and health conditions [58].
Interindustry and interdepartmental coordination can also be presented with the
integration of quantum computing to provide the most appropriate experience to a
client in the medical industry. After meeting all requirements, healthcare organiza-
tions can also accept auto payments and provide funds as needed. For pharmaceuti-
cal industry experts in drug production, composition, and scalability, quantum
computing can be highly profitable. The medical sector can concentrate on the
patient while maintaining the highest level of security for medical information gen-
erated by electronic health records or clinical studies [58].
Although quantum computing will be capable of breaking some of the encryp-
tion methods used today, it is anticipated that they will develop tamperproof alterna-
tives. Such tiny computers cannot use logic gates, semiconductors, and ICs. As a
result, bits of atoms, protons, electrons, and ions are employed with metadata about
their rotation and state. To create other combinations, they can be combined. As a
result, they may operate concurrently and effectively use memory, enhancing their
power. Since quantum computing is the only computer model that rejects the
Church-Turing hypothesis, it can utilize the available systems far more effectively
[15]. The essential building block of quantum theory is the qubit, which represents
fundamental particles like atoms, protons, neutrons, electrons, and other minute
particles as computer memory with their control schemes functioning as computer
processors. It can be set to a weight of 0, 1, or both at once. Its processing power is
a million times greater than the most sophisticated and powerful available today.
Qubit production and management is a big task in engineering. The computing
strength of quantum computers arrives from their digital and analog nature. Due to
their analog character, there is no distortion limit for quantum gates; however, their
digital characteristics provide a standard for overcoming this critical shortcoming
[15]. Therefore, the representations and logic gates employed in traditional systems
are meaningless in quantum computing. Mainly traditional computing rules can be
employed in quantum computing. Nevertheless, this algorithm needs an extraordi-
nary approach to eliminate processing variations and noise. It also needs its method
for fixing design flaws and troubleshooting problems.
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The three fundamental characteristics of quantum computing are entanglement,
interference, and superposition [15, 59]. Entanglement is one of the critical features
of quantum computing that guides the intimate connection between two particles or
quantum bits. Qubits are connected in an exact instantaneous relationship even if
they are split by excessive length, such as at opposite ends of the universe. They are
coupled with one another or defined by one another. The quantum computing sys-
tem simultaneously saves data in two states. In quantum computing, interference is
equivalent to wave interference in classic physics. Wave interference results from
the collision of two waves in the same space. However, imagine that all the waves
are pointing in the same path. At that point, constructive or destructive interference
happens as the generation of standing waves with individual amplitudes counted or
a resultant wave with their amplitudes swabbed out, respectively. The resultant
wave may be more or lesser than the initial wave, depending on the type of interfer-
ence. A quantum technique’s ability to live simultaneously in two separate locations
or structures is known as superposition in quantum computing. It is distinct from its
traditional companions, with binary limitations, and enables remarkable parallel
processing at a fast speed [15].
5.1
Uses of Quantum Computing
There are many uses for quantum computing. Cybersecurity [60, 61], healthcare
[62], artificial intelligence [63], weather forecasting, logistics optimization, and
financial modeling are some of the critical uses of quantum computing. The Internet
security environment has grown highly vulnerable due to the surge in cyberattacks
that occur daily around the globe [64–66]. Although organizations are putting in
place what is necessary for security standards, the process for traditional digital
devices has grown complicated and impossible to use [15].
1. Cybersecurity. Large-scale quantum systems will enhance processing capacity,
forming novel prospects for enhancing cybersecurity. Cybersecurity from the
quantum era will be able to recognize and stop assaults from that era before they
cause harm. However, it is a double-edged blade because quantum computing
also creates new security flaws, such as the ability to quickly solve the complex
mathematical equations that underlie some forms of encryption.
2. Healthcare. Integration of quantum computing with classical computing is
expected to have considerable advantages over conventional computing alone in
the healthcare sector.An extremely desirable set of skills, outstanding IT designs,
a particular form of understanding, and inventive business plans are all demanded
of quantum computing. In addition, security is impacted by technology, which is
a subject of significant importance for the medical industry due to the medical
industry’s responsibilities and challenges concerning data security and privacy.
3. Artificial intelligence. AI and quantum computing are both game changers.
Quantum computing is a necessary aspect for making significant advances in AI
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factor. While generating practical applications on traditional computers, artifi-
cial intelligence is limited by its processing capability. Quantum computing may
give artificial intelligence a boost in processing power that will let it tackle more
complex problems in various fields.
4. Financial modeling. Companies using quantum computing benefit significantly
from it. In particular, financial companies will be well prepared to evaluate large
or unstructured information volumes. For example, banks might improve their
judgments and customer service by making more timely or relevant offers.
Quantum computers are showing promise in applications where programs are
determined by actual information streams, such as livestock amounts, that
include unexpectedly high noise.
5. Logistics optimization. The logistics sector could benefit significantly from
quantum computing. Quantum computers would speed up devices using AI and
machine learning, enhancing current CPUs. Quantum computers are showing
promise in applications where programs are driven by actual information, such
as livestock amounts, including unexpectedly high noise.
6. Weather prediction. On a native and worldwide level, quantum computing might
aid to predict complex or accurate alerts of disastrous weather circumstances,
thereby reducing yearly property damage and significantly saving lives. Quantum
computing offers the ability to proceed with conventional mathematical
approaches to improve tracking or forecasting weather circumstances by han-
dling vast volumes of data with various variables fast or efficiently using the
computational capability of qubits [15].
Pharmaceutical development and formulation are the most challenging jobs in
quantum computing. Medicines are typically developed via costly, risky, or time-
consuming trial and error. Quantum computing could be a helpful technique for
examining the effects of medications on individuals, potentially saving a significant
amount of time and money for pharmaceutical organizations. Since new emergent
technologies have touched on almost every aspect of modern life, deep learning and
AI are two of the most challenging cases [15]. Many problematic computational
problems that take years to solve on traditional devices can be solved more quickly
with quantum computing. Accounting professionals oversee enormous amounts of
money, so even a slight modification in the projected return can have a significant
impact. Another application is algorithmic investing, which is advantageous, pri-
marily in high-volume trades, and involves a computer carrying out detailed algo-
rithms to automatically launch stock trading based on market conditions. A
cutting-edge, effective algorithm called quantum annealing may one day outper-
form conventional computers. On the other side, universal quantum computing is
ready to handle any computing challenge but has yet to be commercially avail-
able [15].
The Intersection of Blockchain Technology and the Quantum Era for Sustainable…](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-44-320.jpg)
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5.2
Pros of Quantum Computing Based Approaches
for Healthcare
When used in healthcare, quantum computing can [15]
1. Support quantum blockchain-based scenarios.
2. Enable innovative healthcare scenarios for better patient-centric system design
and patient handling.
3. Improve security and enhance healthcare system for all stakeholders such as
therapists, doctors, etc.
4. Speed up data availability and processing for authenticated clients.
5. Strengthen the healthcare environment security against a variety of real-time
attacks.
5.3
Cons of Quantum Computing Based Approaches
for Healthcare
Using quantum computing for healthcare systems faces several significant difficul-
ties [15]. Some of them are as follows:
1. Quantum computing may not be ecologically friendly when extensively
leveraged.
2. Deploying quantum computing possessions for the healthcare ecosystem in a
real-world scenario is difficult particularly in underdeveloped countries.
3. Building the necessary infrastructure for real-time quantum computing applica-
tions is challenging, especially for the healthcare industry. Additionally, it is a
pricey solution even though there are tools (such as Qiskit, Silq, etc.) for small-
scale computing solutions. More Qibit support machines are needed in order to
accomplish large-scale integration.
5.4
Quantum Cloud as a Service
Major cloud service providers are using serverless computing as a standard to effi-
ciently deliver cloud services to end users [67, 68]. As edge computing becomes
more prevalent, serverless computing can process work opportunities more quickly
at runtime [69, 70]. It also provides services to end users established on the aids
used by various Internet of Things (IoT) applications [71], like healthcare, smart
cities, farming, and weather forecasting [72–74]. The computation speed and secu-
rity issue for Serverless edge computing are sometimes faced due to big data pro-
cessing [75–77]. Somewhat of data processing at cloud data centers, edge computing
is a technique for handling data of IoT applications that are close to edge devices
D. K. Atal et al.](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-45-320.jpg)
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[69, 74]. Computing close to the network’s logical edge reduces latency and reac-
tion time [41], but more processing power is needed as data creation grows daily
[71, 78]. The cloud computing execution model-based service delivery to the end
users on resource usage provided by IoT apps rather than pay-per-use [70, 78]. To
manage resources and scale automatically, FaaS accomplishes the separation of the
server into independent functions [38, 68].
6
Quantum and Blockchain in Healthcare
Blockchain technology uses conventional cryptographic operations to achieve secu-
rity. Most of these functions are computationally secure, which implies that to
breach them requires significant processing power that is not always available.
These technologies will be impacted by the development of the quantum computer,
which will make it possible to decrypt data encrypted with conventional encryption
techniques. A quantum system can compromise the computational security of these
operations. In contrast to traditional computers, quantum computers may effectively
process information by taking advantage of peculiar quantum features, including
superposition and quantum entanglement [1, 79–81]. As a result, it is expected that
implementing quantum technologies in an intelligent environment would lead to
innovations and accomplishments that are still unmatched by their classical coun-
terparts. These enhancements include more affirmed security, quick computation,
and little storage usage [1, 82–84].
Current cryptography foundations are seriously threatened by quantum comput-
ing [1, 85]. Within a few decades, according to current predictions, quantum com-
putation will be potent sufficient to circumvent widely utilized privacy and security
measures [1, 86, 87]. As a result, new technologies and gadgets must design for the
environment of quantum computation and the ensuing cyberattacks. Future block-
chain implementations must also be ready for quantum computing, as any flaw
might allow for altering the database and threaten the whole organization’s integrity.
At last, legacy infrastructure will be exposed unless existing public fundamental
cryptography architecture is updated to be quantum-resistant. With the key obtained
via quantum key distribution systems, recently proven quantum blockchain infra-
structures are based on information-theoretic safe authentication. However, a pair-
wise connection between users is necessary for such a configuration [1, 88]. Using
quantum-secured direct contact for N clients with authentication or quantum digital
signatures is another method for assuring quantum security. It is crucial to compre-
hend the quantum network structure restrictions and the number of false (unreli-
able) systems in these designs. The standard family of broadcast protocols can
create quantum-secured distributed information methods once the authentication/
signature operations are finished [1].
Aspects of healthcare, from detection and therapy to data storage and communi-
cation, could be impacted by innovations established on the rules of quantum
mechanics. The fundamentals of quantum blockchain technology will increase
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medical data security and stop data leaks. Furthermore, by adopting methods like
quantum computers and laser microscopy, which depend on the rules of quantum
mechanics, we can sequence DNA more quickly and address other significant data
issues in the healthcare field. This opens the door to individualized therapy that
considers each person’s genetic composition [1]. Edge serverless services that are
secure and dependable can be offered while simultaneously enhancing security and
computation speed using quantum computing and blockchain. Blockchain [39, 40]
and quantum computing [89] are both the latest technology that can be leveraged to
deliver high-speed computation and security [41]. Additionally, a safe and trustwor-
thy theoretical ideal for serverless edge computation is required so that artificial
intelligence (AI) can be used to deliver effective service [78]. Two key ideas from
quantum physics, superposition, and entanglement are used to execute computa-
tions in quantum computing [89]. The serverless computing paradigm, now used by
the edge computational paradigm to deliver operations as a service, needs quantum
computing to handle extensive computation for load balancing and dynamic provi-
sioning [38, 41].
6.1
Importance of Quantum Blockchain
Therefore, preserving participant security and anonymity is challenging for conven-
tional healthcare infrastructure [90]. Blockchain has developed into a medium that
increases the healthcare scheme’s effectiveness while protecting all stakeholders’
privacy. In this research, motivated by their findings, the authors [91] integrate
quantum computing into the standard encryption system after looking at various
security techniques used to protect medical records. As medical knowledge devel-
ops, using EMR systems to enhance the effectiveness and dependability of health-
care has become commonplace. Sharing problems arise when electronic medical
record systems are housed independently in medical and healthcare institutions
[92]. Additionally, highly delicate EMRs are open to manipulation and exploitation,
posing privacy and security threats. The most recent developments of healthcare 4.0
integrating the IoT components [93] and cloud services to monitor clinical opera-
tions virtually have caught intellectuals’ attention from a philosophical
perspective.
7
Limitations and Scope for Future Research
When appropriately used, blockchain offers a reliable solution to problems with
specific healthcare applications, such as real-time updates, security, accessibility,
interoperability, integrity, privacy, sharing, and medical data. Blockchain, however,
has constraints. Despite the benefits of using blockchain, substantial research
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The Intersection of Blockchain Technology and the Quantum Era for Sustainable…](https://image.slidesharecdn.com/29380385-250527103440-e421cf55/85/Quantum-And-Blockchainbased-Next-Generation-Sustainable-Computing-Srikanth-Pulipeti-52-320.jpg)
Quantum And Blockchainbased Next Generation Sustainable Computing Srikanth Pulipeti
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- 5. Contributions to Environmental Sciences & Innovative BusinessTechnology Srikanth Pulipeti Adarsh Kumar Nagaraju Mysore Cathryn Peoples Editors Quantum and Blockchain-based Next Generation Sustainable Computing
- 6. Contributions to Environmental Sciences & Innovative Business Technology Editorial Board Allam Hamdan, Ahlia University, Manama, Bahrain Wesam Al Madhoun, Air Resources Research Laboratory, MJIIT, UTM, Kuala Lumpur, Malaysia Mohammed Baalousha, Department of EHS, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA Islam Elgedawy, AlAlamein International University, Alexandria, Egypt Khaled Hussainey, Faculty of Business and Law, University of Portsmouth, Portsmouth, UK Derar Eleyan, Palestine Technical University—Kadoori, Tulkarm, Palestine, State of Reem Hamdan, University College of Bahrain, Manama, Bahrain Mohammed Salem, University College of Applied Sciences, Gaza, Palestine, State of Rim Jallouli, University of Manouba, Manouba, Tunisia Abdelouahid Assaidi, Laurentian University, Sudbury, ON, Canada Noorshella Binti Che Nawi, Universiti Malaysia Kelantan, Kota Bharu, Kelantan, Malaysia Kholoud AL-Kayid, University of Wollongong, Leppington, NSW, Australia Martin Wolf, Center for Environmental Law and Policy, Yale University, New Haven, CT, USA Rim El Khoury, Accounting and Finance, Notre Dame University, Loauize, Lebanon Editor-in-Chief Bahaaeddin Alareeni, Middle East Technical University, Northern Cyprus Campus, Kalkanlı, KKTC, Türkiye
- 7. Contributions to Environmental Sciences & Innovative Business Technology (CESIBT) is an interdisciplinary series of peer-reviewed books dedicated to addressing emerging research trends relevant to the interplay between Environmental Sciences, Innovation, and Business Technology in their broadest sense. This series constitutes a comprehensive up-to-date interdisciplinary reference that develops integrated concepts for sustainability and discusses the emerging trends and practices that will define the future of these disciplines. This series publishes the latest developments and research in the various areas of Environmental Sciences, Innovation, and Business Technology, combined with scientific quality and timeliness. It encompasses the theoretical, practical, and methodological aspects of all branches of these scientific disciplines embedded in the fields of Environmental Sciences, Innovation, and Business Technology. The series also draws on the best research papers from EuroMid Academy of Business and Technology (EMABT) and other international conferences to foster the creation and development of sustainable solutions for local and international organizations worldwide. By including interdisciplinary contributions, this series introduces innovative tools that can best support and shape both the economical and sustainability agenda for the welfare of all countries, through better use of data, a more effective organization, and global, local, and individual work.The series can also present new case studies in real-world settings offering solid examples of recent innovations and business technology with special consideration for resolving environmental issues in different regions of the world. The series can be beneficial to researchers, instructors, practitioners, consultants, and industrial experts, in addition to governments from around the world. Published in collaboration with EMABT, the Springer CESIBT series will bring together the latest research that addresses key challenges and issues in the domain of Environmental Sciences & Innovative Business Technology for sustainable development.
- 8. Srikanth Pulipeti • Adarsh Kumar Nagaraju Mysore • Cathryn Peoples Editors Quantum and Blockchain-based Next Generation Sustainable Computing
- 9. ISSN 2731-8303 ISSN 2731-8311 (electronic) Contributions to Environmental Sciences & Innovative Business Technology ISBN 978-3-031-58067-3 ISBN 978-3-031-58068-0 (eBook) https://doi.org/10.1007/978-3-031-58068-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland If disposing of this product, please recycle the paper. Editors Srikanth Pulipeti Mukesh Patel School of Technology Management and Engineering SVKM’s Narsee Monjee Institute of Management Studies Deemed-to-be University, Shirpur Campus Dhule, Maharashtra, India Nagaraju Mysore Department of Computer Science and Engineering, GST GITAM University Bangalore, Karnataka, India Adarsh Kumar School of Computer Science University of Petroleum and Energy Studies Dehradun, Uttarakhand, India School of Computer Science Mohammed VI Polytechnic University Benguerir, Morocco Cathryn Peoples School of Computing Ulster University Belfast, UK
- 10. v Contents QSB: Smart Contracts, Consensus, and Quantum Cryptography ������������ 1 Saurabh Jain The Intersection of Blockchain Technology and the Quantum Era for Sustainable Medical Services�������������������������������������������������������������������� 19 Dinesh Kumar Atal, Vishal Tiwari, Anjali, and Rajiv Kumar Berwer Innovative Solutions for Sustainability: Quantum and Blockchain Technologies������������������������������������������������������������������������������������������������������ 47 Ahmed Mateen Buttar, Nouman Arshad, and Muhammad Azeem Akbar Combating Counterfeit Drugs in Pharmaceutical Supply Chain (PSC) Using Hyperledger Fabric Blockchain���������������������������������������������������������� 75 Anitha Premkumar and Rajesh Natarajan Quantum and Blockchain for Sustainable Healthcare Ecosystem�������������� 105 Syed Muzammil Munawar, Dhandayuthabani Rajendiran, and Khaleel Basha Sabjan Music DApp on the Solana Blockchain Platform: Design, Development, and Analysis������������������������������������������������������������������������������������������������������ 121 Urmila Pilania, Manoj Kumar, Rohit Tanwar, Pulkit Upadhyay, and Priyanka Narayan The Role of Blockchain in Healthcare����������������������������������������������������������� 135 Radhika Sreedharan Innovative Solutions for Sustainable Medical Services: A Look into Quantum and Blockchain Technologies������������������������������������������������ 173 Reena Thakur, Parul Bhanarkar, Uma Patel Thakur, and Mustapha Hedabou Blockchain Technology and Quantum Computing: A Promising Solution for the Healthcare Industry and COVID-19 Pandemic���������������� 203 Galiveeti Poornima, Deepak S. Sakkari, P. Karthikeyan, T. N. Manjunath, and K. Saritha
- 11. vi Sustainable Solutions for Serverless Edge, Fog, and Cloud Computing Using Quantum and Blockchain Technology������������������������������������������������ 219 Sarthika Dutt, Vansh, Garima Pahwa, Aishvi Guleria, Kamya Varshney, and Deeksha Joshi Contents
- 12. 1 © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024 S. Pulipeti et al. (eds.), Quantum and Blockchain-based Next Generation Sustainable Computing, Contributions to Environmental Sciences Innovative Business Technology, https://doi.org/10.1007/978-3-031-58068-0_1 QSB: Smart Contracts, Consensus, and Quantum Cryptography Saurabh Jain Abstract The term “quantum-secured blockchain” pertains to a sort of blockchain technology designed to withstand attacks from quantum computers. Quantum com- puters are a relatively modern computers meant to work with the principles of quan- tum physics. They can perform certain computations substantially quicker than standard systems. One of the most significant worries regarding quantum computers is the possibility that these machines would be able to break down the encryption that has been employed to safeguard blockchain networks. Blockchains that are quantum-secured adopt strategies and mechanisms that are quantum-resistant to prevent quantum computers from accessing the data or information that is stored on the network. Even though this blockchain technology is only in its infancy stage now, it is anticipated that it will be one of the future possibilities for protecting data on blockchain networks. Investigation of new forms of encryption that cannot be broken by quantum computers, such as those based on lattices, codes, and multivari- ate quadratic equations, is underway. Keywords Blockchain · Smart contract · Consensus · Digital signature · Sustainability · Quantum computing · Hashing · Quantum smart contracts 1 Introduction The term “quantum blockchain” refers to decentralized databases that are encrypted, based on quantum computation and theory, and distributed throughout a network. Data saved in a quantum blockchain cannot be purposefully changed once it has been saved. A growing number of scholars have increasing interest on quantum blockchain research in the last few years as quantum computation and quantum S. Jain (*) School of Computer Science, University of Petroleum and Energy Studies, Dehradun, India e-mail: saurabh.jain@ddn.upes.ac.in
- 13. 2 information theory have evolved. It briefly discusses the advantages of quantum blockchain over conventional blockchains and examines recent developments in the field [1]. A decentralized database called blockchain is encrypted to thwart manipu- lation. While blockchain technology shows great promise for various uses, current blockchain-based platforms rely on outdated encryption, hashing, and digital signa- ture algorithms that are susceptible to attacks from quantum workstations. Individuals who have gained access to quantum computing will have an unfair ben- efit when it comes to mining incentives because the same considerations apply to the cryptographic hash functions or consensus that are leveraged to spawn new blocks. Blockchain technology quickly establishes itself as a key technology that can address many global space industry issues. The smart contracts and blockchain technology have the potential to open up a plethora of new prospects for the global space industry. These include the creation of satellite payloads, supply chain man- agement in space, and satellite as a service. Additionally, it is anticipated that block- chain will greatly impact subsequent financial transactions. The Bitcoin blockchain can be sent by satellite, which will be faster and more reliable, speeding up interna- tional financial transactions. Without using the Internet, the Blockstream Satellite Network demonstrates how satellites using the blockchain can process and send Bitcoin around the globe [2, 3]. Scalability, effectiveness, and longevity are three significant challenges for blockchain technology. These obstacles need to be overcome if blockchain is ever going to develop into a mature technology that can be used responsibly. It is possi- ble that quantum computers would have been invented before the broad implemen- tation of blockchain technology for mission-critical tasks in financial and other types of organizations. Quantum computing can be utilized to solve some of the challenges that arise with the implementation of certain blockchain technologies, such as cryptocurrencies. This can facilitate the installation of such technologies. This article highlights the research that has already been undertaken on hybrid quantum-classical blockchain technology, as well as the unanswered research ques- tions [4]. Even though quantum computing, a thriving technology, poses a threat to some of the fundamental elements of blockchain technology, it is widely recognized as a significant future technology. According to current estimates [5, 6], there is a 15% chance that quantum computers will be commercially available by 2026 and a 50% chance that they will be by 2031. Since most existing blockchain systems rely mostly on digital signatures with public keys and are used to communicate value, they are especially a little bit susceptible to attacks from quantum workstations. Fedorov et al. [7] say that blockchain technology as it is now might not work if quantum technologies are not added. Existing temporary solutions, like post- quantum cryptography [8–10], don’t guarantee solutions to the threat that are com- pletely safe. There have been many studies [11–13] on the quantum-safe blockchain, which could protect against attacks from future quantum computers. S. Jain
- 14. 3 2 Blockchain and Quantum Computing A blockchain is a type of technology that enables the formation of distributed led- gers that are not centralized and may be used to record transactions that take place across a computer network. On the contrary side, quantum computing is a subfield of computer science that tries to capitalize on the power of quantum mechanics to tackle difficulties that are now intractable with traditional computers. At the inter- section of these two technological spheres, significant research and development work are currently being carried out. One possible use of this intersection is quan- tum-resistant cryptography, which leverages the principles of quantum physics to design cryptographic algorithms and methods resistant to quantum attacks. One further possible use case involves implementing blockchain networks with quantum computing to boost their operational effectiveness and scalability. Although it is not yet evident how these technologies will be combined or what specific applications will emerge, this is undeniably an interesting field of research [14, 15]. 2.1 Quantum Computing Effects on the Blockchain Technology The technology behind blockchain could be impacted in several different ways by quantum computing. Developing encryption algorithms that are more resistant to attacks from quantum algorithms is one approach that could be taken. If this were successful, blockchain networks would be safe from harm. As a consequence of the circumstance that quantum-based computers can defeat the encryption methods that are now used to protect blockchain systems, new cryptographic approaches that are immune to quantum attacks must be developed. Computing on the quantum level could also have an impact on blockchain technology by improving the scalability and efficiency of blockchain networks [15]. It is possible that the use of quantum computers, which can complete certain jobs significantly more quickly than con- ventional computers, could be put to use to improve the pace at which blockchain networks function. This might make it possible to process more transactions per second while at the same time reducing the amount of energy needed to keep the network secure. It should be emphasized that even though quantum computing has the prospective to affect blockchain technology, the arena of study is still in its infancy, many of the proposed applications are still in the research phase, and the nature of the effect that quantum computing will have on blockchain technology is not yet known [16, 17]. QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 15. 4 2.2 Quantum Blockchain The convergence of blockchain technology and quantum computing gives rise to a captivating concept referred to as the quantum blockchain. The main goal of a quan- tum blockchain is to establish a decentralized and distributed ledger that exhibits resilience against potential attacks from quantum workstations. The quantum- resistant encryption algorithm serves to enhance the safety of the network and bol- sters its resilience against potential quantum-based attacks. One of the main challenges confronted in the realm of quantum blockchain technology pertains to the scarcity and nascent state of quantum computers. However, due to the antici- pated developments and increased accessibility of quantum computers, there will be a considerable increase of interest for quantum-resistant blockchains. Furthermore, the utilization of quantum blockchain likely addresses scalability concerns and enhances the efficacy of traditional blockchain systems. Quantum algorithms possess the capacity to enhance the efficiency of transaction processing. Quantum entanglement has the potential as a viable solution for enhancing the con- fidentiality and integrity of blockchain transactions. It is imperative to acknowledge that the existing level of research in this domain is in its nascent stage, and the verifi- able feasibility of the purported advantages of quantum blockchain remains uncer- tain. Furthermore, the amalgamation of quantum computing inside the framework of blockchain technology may require a substantial duration to evolve into a viable and feasible solution [18, 19]. 2.3 Types of Quantum Blockchain Multiple iterations of quantum blockchains have been suggested, each possessing distinct merits and drawbacks. This section presents a succinct outline of the pre- vailing categorizations of quantum blockchains, as reported in scholarly literature [20–22], and the summary is provided in Table 1. • The quantum-secured blockchain utilizes cryptographic techniques that are resistant to quantum computer assaults to safeguard the network. The use of this strategy guarantees the persistent safety of blockchain systems, notwithstanding the escalating computational competences of quantum computers. • Quantum-enhanced blockchain pertains to a classification of blockchain systems that utilize quantum algorithms and quantum computation to augment the scal- ability and performance of these networks. This has the potential to lead to an augmentation in transaction processing capacity and a decrease in the energy consumption associated with network security. • The utilization of quantum entanglement in the quantum-federated blockchain system serves to augment the levels of privacy and security associated with trans- actions conducted on blockchain platforms. In a blockchain network, it is possi- S. Jain
- 16. 5 Table 1 Summary of different types of quantum blockchains [20–22] Type Description Key features Quantum- secured blockchain The network employs quantum- resistant cryptography as a means of safeguarding against potential assaults from quantum computers Offers more security steps to protect blockchain technology from quantum attacks. Ensures the reliability of data in the setting of developments in quantum computing. This project lays the groundwork for blockchain technology to be profitable in the long run Quantum- enhanced blockchain Quantum algorithms and quantum processing are utilized to enhance scalability and efficiency, with the potential to increase transaction throughput while decreasing energy consumption Using this technology makes the transaction handling go faster. Using this technology cuts down on the amount of energy needed for mining and consensus processes. The network is now able to grow and respond better Quantum- federated blockchain Quantum entanglement is employed to enhance the safety and security of financial transactions. Enables several individuals to utilize a shared blockchain infrastructure without necessitating the disclosure of their respective transactional activities to one another Transactions are kept private because strict security steps are put in place. Allows more than one organization to use a safe blockchain system. Make sure that privacy stays the same in consortium blockchain settings Quantum- hybrid blockchain When the benefits of quantum-secured and quantum-enhanced blockchains are combined, the result is a system that is both reliable and safe This system has both protection and performance features that work well together. Shows the ability to deal with quantum threats as they change. The proposed answer is a flexible way to handle an extensive use cases in the blockchain space ble for multiple entities to participate while ensuring the confidentiality of their transactions. • The quantum-hybrid blockchain is a novel tactic that integrates the benefits of quantum-secured and quantum-enhanced blockchains. This fusion results in the development of a system that exhibits robustness, security, and a high degree of resilience. It is imperative to acknowledge that the investigation of quantum blockchain is now in its nascent stage, and the most effective configuration, if one exists, has yet to be ascertained. Furthermore, the practical ramifications of this technology remain incompletely actualized, requiring a significant duration before it can attain its max- imum efficacy. QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 17. 6 2.4 Proposed Algorithms for Quantum Blockchain Several algorithms have been proposed in current research endeavors for the cre- ation of a quantum blockchain. The subsequent examples serve to exemplify a range of essential algorithms. The provided text encompasses a range of numerical data. • Quantum key distribution (QKD) is a technique that utilizes the moralities of quantum physics to launch a secure means of communication across many enti- ties. Subsequently, the establishment of this safe channel can be employed to produce encryption keys, ensuring the security of blockchain transactions. • Quantum-secured direct communication (QSDC) is a scheme that leverages the phenomenon of quantum entanglement to obviate the necessity of a specialized secure communication channel, hence facilitating direct communication among several entities. The utilization of this approach possesses the capability to enhance the confidentiality of transactions executed inside a quantum blockchain environment. • The quantum hash function (QHF) is a method that utilizes the fundamental moralities of quantum physics to generate a hash function that is resilient against collisions and preimages. The implementation of this method possesses the capacity to augment the security of the blockchain by augmenting the amount of complexity linked to the alteration or manipulation of the data that is documented on the blockchain. • The quantum random number generator (QRNG) exploits the foundational moralities of quantum mechanics to generate random numbers. Numerical val- ues can subsequently be employed to produce robust cryptographic keys, hence enhancing the level of security offered by blockchain technology. • Grover’s algorithm is a quantum computational approach that exhibits the capa- bility to speed up locating a particular blockchain transaction by diminishing the number of necessary searches to N, wherein N is the magnitude of the database. It is imperative to acknowledge that most of these algorithms are now in the research stage and have yet to be applied in real settings. Furthermore, the most effective approach for implementing the quantum blockchain remains uncertain. Furthermore, the incorporation of quantum algorithms into blockchain systems is a significant barrier that necessitates considerable investments of time and resources for its advancement. 3 Quantum Cryptography Quantum cryptography, alternatively mentioned to as quantum key distribution (QKD) [23], is a method employed for the protected transmission of cryptographic keys by the application of principles derived from quantum physics. The technique facilitates the establishment of a mutually agreed upon secret key between two S. Jain
- 18. 7 entities, which can subsequently be utilized for the purpose of encrypting and decrypting messages exchanged between such parties. The robustness of the key’s security is derived from the essential moralities of quantum physics, rendering it highly challenging for an unauthorized party to pilfer it without triggering detection mechanisms. Quantum cryptography is based on the essential moralities of quan- tum physics, particularly those related to the polarization and phase characteristics of light in quantum states. The quantum state of a photon contains the encryption key, which is then exchanged between two entities. Any endeavors to apprehend the photon will unavoidably modify its quantum state, thereby notifying the individuals engaged in a dialog that an act of surveillance is being conducted. Quantum cryp- tography exhibits superior performance compared to conventional cryptography across multiple dimensions. Therefore, the system demonstrates a significant degree of resilience against a wide range of attacks, including those executed by quantum workstations. Moreover, the computational ability of computers to explain mathe- matical problems is irrelevant to the current topic under discussion. Hence, it may be inferred that forthcoming developments in processing capacity would not have any discernible impact [24, 25]. However, it is imperative to recognize that quantum cryptography encounters specific obstacles, particularly in its implementation within real-world scenarios. The methodology exhibits sensitivity to extraneous disturbances and necessitates the utilization of reliable and robust equipment. Furthermore, it is worth noting that there is a finite distance beyond which a quantum key distribution (QKD) system is unable to reliably convey a secure cryptographic key. Quantum cryptography is a cryptographic methodology that employs the underlying moralities of quantum physics to guarantee the secure conversation with cryptographic keys. This method- ology provides a heightened level of security in comparison with traditional proce- dures. The technology under consideration possesses the prospective to function as an essential element in the advancement of blockchain systems that are immune to quantum attacks, as well as other communication systems that prioritize security. 3.1 Quantum Cryptography vs. Traditional Cryptography There are major distinctions between traditional cryptography and quantum cryp- tography, even though both seek to guarantee the data confidentiality through encryption and transmit that data. In the traditional form of cryptography, the pro- cess of encrypting and decrypting data takes place via the application of various mathematical methods. This subfield of cryptography is sometimes mentioned to as “classical” cryptography, particularly in specific circles. The success of these algo- rithms is dependent on the completion of complex mathematical operations, such as the division of a very big integer or the solution of discrete logarithms. Consider, for instance, the operation of dividing discrete logarithms by a significant number. This can serve as an illustration. Traditional cryptography has proven to be effective in the past, but it is vulnerable to the potential dangers posed by quantum computers. QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 19. 8 When it comes to the processing power they bring to bear on these mathematical challenges, quantum computers handily beat out their more traditional counterparts. To carry out its operations, quantum cryptography makes use of the fundamental laws that govern quantum physics. Encryption of data is a part of this process, and it does so by utilizing the characteristics of quantum states, more specifically polar- ization and phase. Using the limitations imposed by quantum mechanics in the arena of quantum cryptography makes it impossible to steal a cryptographic key in a covert manner because any attempt to do so would always be discovered. This is because quantum mechanics imposes these limitations. Data encryption using quan- tum cryptography is regarded as among the safest methods available. The term “secure” is commonly used to refer to quantum cryptography, which implies that it is resistant to any type of decryption, including that which is performed by quantum computers [26, 27]. Since they are based on mathematical principles, traditional encryption tech- niques are vulnerable to being broken by quantum computers. Quantum cryptogra- phy, on the contrary side, is founded on the theories of quantum mechanics, which makes it fundamentally safe in every and every circumstance. 3.2 Research Gaps in Quantum Cryptography The field of quantum cryptography is now experiencing significant growth and is marked by some unresolved matters that necessitate more investigation and solu- tions. There are several significant research challenges that exist within the domain of quantum cryptography, encompassing the following concerns: • Distance limitations: The field of quantum key distribution (QKD) encounters a notable challenge in the shape of limitations imposed by distance. Current quan- tum key distribution (QKD) systems suffer from constrained transmission ranges principally caused by signal attenuation over long distances. The practical uses of quantum key distribution (QKD) are significantly constrained by the restricted transmission distance it can achieve. Hence, scholars are actively involved in the formulation of approaches to overcome this constraint and enhance the extent of transmission. • Noise: The impact of noise on quantum key distribution systems can compro- mise their effectiveness by introducing faults into the transmitted key. The exis- tence of various sources of noise in practical scenarios might provide a substantial barrier, impacting the quality and reliability of the signal. Academic scholars are currently directing their efforts toward developing mitigation measures for the adverse impacts of noise in quantum key distribution (QKD) systems. • Scalability: Quantum key distribution (QKD) schemes presently exhibit restricted scalability and lack the capability to accommodate a significant num- ber of users. Currently, there are ongoing endeavors to augment the scalability S. Jain
- 20. 9 and practicality of quantum key distribution (QKD) systems for their application in practical circumstances. • Real-world implementation: Theoretical security has been demonstrated in the field of quantum cryptography; nevertheless, the practical implementation of this technology in real-world scenarios remains unclear. Currently, researchers are actively involved in the endeavor of formulating effective approaches for the implementation of quantum cryptography in real-world scenarios. • Security against side-channel attacks: Quantum cryptography is widely acknowl- edged for its inherent security that is considered impervious to decryption. Nevertheless, the level of vulnerability of the system to side-channel attacks, which use implementation specifics or physical properties to harvest personal data, is still undetermined. • Quantum repeater: The limited distance capacity of existing quantum key distri- bution (QKD) systems poses a substantial challenge for the transmission of quantum keys over large distances. The quantum repeater intentions to overcome the constraint of limited distance by employing a sequence of intermediary nodes to transmit the quantum signal. The primary function of these nodes is to facili- tate the transmission an amplification of the signal. Nevertheless, the investiga- tion of this notion is still in premature phases, and its practical application has yet not been comprehended. The concerns encompass a range of unresolved obstacles in the domain of quan- tum cryptography, compelling researchers to actively seek resolutions in order to enhance the practicality and widespread implementation of this cryptographic technique. 3.3 Advantages of Quantum Cryptography Quantum key distribution, also referred to as quantum cryptography or QKD, exhib- its several distinct advantages when compared to traditional cryptographic tech- niques. Quantum cryptography has been extensively discussed in scholarly literature [28–30], whereby several noteworthy advantages of this field have been highlighted. • Unconditional security: The term “unconditional security” pertains to a condi- tion of complete certainty or safeguarding that is not contingent upon any spe- cific criteria or prerequisites. • Quantum cryptography is generally recognized for its inherent security, render- ing it invulnerable to various forms of attacks, including those that may be gener- ated by quantum computers. The technology in question demonstrates significant promise in enhancing the security of communication and transactions in the future, especially considering the anticipated advancement of quantum worksta- tions that will outperform computational power over classical systems. QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 21. 10 • Tampering detection is the term used to describe the procedure of identifying and detecting any unauthorized alterations or modifications that have been done to a system or its components. • Quantum cryptography facilitates the identification of any illegal interception or alteration of the transmitted key, a feat unattainable by conventional crypto- graphic techniques. This characteristic renders it a very secure mode of communication. • Randomness: Quantum cryptography utilizes principles derived from quantum physics to generate numbers that are truly random, thereby enabling the creation of cryptographic keys with enhanced security. In contrast to conventional cryp- tographic methods that depend on pseudorandom number generators, this char- acteristic enhances its security. • Quantum resistance: The concept of “quantum resistance” pertains to the ability of a cryptography system to survive adversarial attempts launched by quantum computers. As quantum computing progresses, the processing competences of quantum computers pose a possible vulnerability to conventional cryptography schemes. In contrast, quantum cryptography possesses the facility to withstand the computational power of quantum computers, rendering it an appealing choice for ensuring enduring security. • No secret sharing: The notion of “no secret sharing” pertains to the abstention from divulging or disseminating privileged data. In the realm of traditional cryp- tography, the distribution of keys to all pertinent entities is of extreme promi- nence. In the realm of quantum cryptography, the process of key establishment is limited to a bilateral exchange between two individuals or entities, hence obviat- ing the need for involvement from a third party. This characteristic enhances the overall security of the system. • No need for pre-distribution: In the realm of conventional cryptography, the uti- lization of keys necessitates their sharing and dissemination, hence imposing a substantial constraint. In contrast, quantum cryptography facilitates the concur- rent production and distribution of cryptographic keys, resulting in enhanced operational efficiency. Quantum cryptography has several notable advantages in comparison with con- ventional methodologies employed to address the same issue.Although, the tremen- dous benefits provided by quantum cryptography persist across various applications. Moreover, it is essential to recognize that this technology is still in the early stages of development, and numerous obstacles must be overcome before widespread application. S. Jain
- 22. 11 3.4 Disadvantages of Quantum Cryptography Quantum cryptography: quantum key distribution (QKD) possesses the various benefits over the traditional cryptographic algorithms. However, it does have some limitations. Among the principal disadvantages of quantum cryptography are as fol- lows [31, 32]: • Complexity: Due to the need for specialized apparatus and knowledge, the imple- mentation of quantum cryptography presents significant obstacles. In addition, the successful application of this technology necessitates a comprehensive understanding of the fundamental moralities of quantum mechanics, posing adoption challenges for certain businesses. • Cost: The enactment of quantum cryptography requires the use and maintenance of specialized hardware and software, which may incur significant expenses. In addition, the implementation of quantum cryptography can incur substantial expenses, especially in comparison with conventional encryption methods. • Noise: Quantum cryptography systems are susceptible to noise, which can lead to defects in the transmission of cryptographic keys. In certain circumstances, the presence of many sources of noise might provide a substantial hindrance. • Existing quantum key distribution (QKD) systems have a limited transmission range due to signal intensity degradation over long distances. Consequently, the range capabilities of these systems are limited. Quantum key distribution (QKD) has extremely limited practical applications, and the investigation of quantum repeaters to increase its utility is in its earliest stages of development. • Scalability: Quantum key distribution (QKD) systems in their current state exhibit limited scalability and user capacity. The circumstance can be problem- atic for large organizations that must ensure communication for many users. Quantum cryptography is an emerging arena of technology that is presently inac- cessible to the public on a wide scale. In addition, it is essential to recognize that the contemporary technology is still in its embryonic stage, indicating that the process of achieving widespread adoption could take a considerable quantity of time. Quantum cryptography has several significant disadvantages compared to conven- tional encryption methods. Quantum cryptography, despite its inherent limitations, possesses the property of absolute security and has the impending to provide a sophisticated level of security in certain application scenarios compared to conven- tional methods. QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 23. 12 4 Consensus Algorithms Consensus algorithms are employed in blockchain systems to guarantee unanimous agreement among all participants in the blockchain network. A wide range of algo- rithms have been developed to attain consensus, each with its own distinct set of strengths and weaknesses [33]. It is remarkable. The utilization and widespread implementation of the proof-of- work (PoW) consensus method in many blockchain systems exemplify this phe- nomenon. In this process, miners are obligated to solve intricate mathematical problems with the purpose of appending new blocks to the blockchain. Quantum computers possess the ability to do operations at a significantly accelerated pace compared to traditional computers. The increased processing speed possesses the capacity to expedite the resolution of mathematical issues in proof-of-work (PoW) protocols, surpassing the computational efficiency of conventional computers. The utilization of quantum computers possesses the capacity to significantly enhance the speed of block mining in comparison with traditional computers. Consequently, this acceleration may result in the consolidation of mining capabilities among a limited group of miners equipped with quantum-enabled technology. Consequently, the concentration may give rise to a singular point of vulnerability, thereby posing a potential security hazard [34]. On the other hand, other consensus algorithms, such as Byzantine fault tolerance (BFT) and proof-of-stake (PoS), exhibit a reduced vulnerability to the potential impacts of quantum computing. This phenomenon can be attributed to their depen- dence on procedures that extend beyond computational capacity, such as token own- ership or consensus achieved by a defined number of validators [35]. The recognition of the probable impact of quantum computing on the efficacy of specific consensus algorithms is of utmost significance. Nevertheless, it is impera- tive to acknowledge that quantum computing remains a dynamic discipline, wherein various potential solutions are now being investigated and refined through ongoing research and development efforts. Furthermore, it is anticipated that the progression of quantum computing to a level where it can proficiently target blockchain systems will necessitate a substantial duration. 4.1 Proof-of-Work (PoW) The consensus process recognized as proof-of-work (PoW) is extensively employed across several blockchain platforms. The major purpose of this system is to verify transactions and maintain the network’s integrity. To address an intricate mathemat- ical problem, individuals, referred to as “miners,” partake in a competitive manner within a blockchain framework that runs based on the proof-of-work (PoW) prin- ciple. The initial miner who successfully fulfills this task is authorized to append a novel block of transactions to the blockchain. To provide a consistent development S. Jain
- 24. 13 rate for the chain of blocks, the level of difficulty associated with this process is modified accordingly [36]. The potential impact of quantum computing on blockchain systems that depend on the proof-of-work consensus mechanism is substantial. The increased rate at which quantum computers may execute specific operations has the potential to dras- tically reduce the time required to solve proof-of-work (PoW) mathematical diffi- culties, in comparison with conventional computers.The capabilities may potentially allow quantum computers to speed up mining blocks in comparison with classical computers. Consequently, there is a possibility that this could result in a consolida- tion of mining authority among a limited group of miners equipped with quantum technology. Enabling the functionality to control the network and establish a singu- lar point of failure may potentially introduce a security vulnerability. Currently, researchers are actively engaged in the advancement of proof-of-work (PoW) algo- rithms that are resistant to quantum computing. The objective is to enhance the security of blockchain networks by safeguarding them against possible dangers posed by quantum computers. The methods under consideration would rely on com- putationally challenging issues that are highly intricate for quantum computers, such as the learning with errors (LWE) problem [37]. The utilization of quantum proof-of-work (PoW) as a consensus process in blockchain networks serves to enhance their security by using principles derived from quantum computation. Figure 1 is an exemplar pseudocode example that per- tains to a quantum proof-of-work (PoW) algorithm [38]. It is imperative to recognize that the potential influence of quantum computing on proof-of-work (PoW)-based blockchain systems is a significant subject matter. However, it is imperative to acknowledge that quantum computing is a nascent dis- cipline, and a multitude of suggested approaches are now undergoing investigation in the research stage. Furthermore, the advancement of quantum computing to a degree where it can proficiently engage with proof-of-work (PoW)-based block- chain systems may need a significant duration. 4.2 Quantum Smart Contracts Smart contracts utilize computer code to encapsulate the exact details of a transac- tion conducted between a buyer and a seller. The utilization of blockchain technol- ogy enables the storage and replication of contracts across the network. The network will subsequently authenticate the fulfillment of the tasks. The facilitation of con- tract execution automation can be achieved by the utilization of smart contracts, which possess the ability to carry out diverse supplementary tasks such as supply chain management, financial transactions, and voting systems. The utilization of artificial intelligence (AI) has promised to enhance the operational efficiency of enterprises and optimize supply chain operations through the elimination of inter- mediaries. The field of quantum computing holds promise for significantly enhanc- ing the velocity and efficacy of specific computational endeavors, particularly those QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 25. 14 Fig. 1 Pseudocode snippet for quantum proof-of-work consensus algorithm [38] S. Jain
- 26. 15 pertaining to cryptography and blockchain technology. The utilization of quantum computing holds promises in enhancing smart contracts by enabling the execution of contractual agreements that exhibit heightened complexity and enhanced secu- rity. Quantum smart contracts (QSCs) represent an innovative notion that continues to be the focus of continuing scholarly investigation. Quantum-secured communica- tions (QSCs) possess several prospective real-time uses, encompassing the following: • Quality control systems (QCS) are of utmost importance in the field of supply chain administration, as they are responsible for safeguarding the genuineness and reliability of items during their journey across the supply chain. This mea- sure possesses the capacity to diminish the probability of fraudulent actions and the manufacture of counterfeit products inside the supply chain. • Quantum-secured communications (QSCs) possess the ability to facilitate secure and transparent transactions within the domain of financial services, encompass- ing areas such as banking, insurance, and investment. The application of suitable strategies can significantly decrease the occurrence of deceitful behaviors, there- fore safeguarding the confidentiality and integrity of monetary transactions. • Quality and security credentials (QSCs) possess the capacity to be employed within the healthcare sector for the purpose of safeguarding patient confidential- ity, facilitating the secure exchange of data, and enabling secure transactions among healthcare providers. • The integration of quantum-secured computation (QSC) into voting systems offers a means to guarantee the secure registration and aggregation of ballots while also facilitating transparency and verifiability at every stage of the voting procedure. • Quantum-safe communication (QSC) has the potential to enhance the security of Internet of Things (IoT) devices by facilitating safe communication and data sharing across these devices. The utilization of quantum-resistant algorithms has the potential to enhance the security of smart contract execution, therefore mitigating the vulnerability to unau- thorized alterations. Moreover, the utilization of quantum computation possesses the capability to enhance the scalability of smart contract platforms by facilitating accelerated transaction processing. However, it is imperative to acknowledge that the realm of quantum computation is now in its early stages of advancement, and its potential impact on smart contracts has not been comprehensively comprehended [39]. It is imperative to acknowledge that the predominant approach to the develop- ment of smart contracts predominantly depends on conventional computing meth- ods. The domain of quantum smart contracts, however, is now seeing ongoing research and development efforts. Figure 2 illustrates the pseudocode of the quan- tum smart contract, as presented in reference [40]. In summary, the quantum-secured blockchain (QSB) signifies a notable progres- sion in the field of blockchain technology. The primary aim of this project is to provide enhanced levels of security and anonymity by integrating blockchain tech- nology and quantum cryptography. The integration of quantum computing QSB: Smart Contracts, Consensus, and Quantum Cryptography
- 27. 16 Fig. 2 Pseudocode snippet for quantum smart contract [40] capabilities into the field of blockchain technology has presented new opportunities for the advancement of more resilient and fortified blockchain solutions. The pri- mary objective of this study was to examine the possible utilization of quantum- secured bit (QSB) technology within the domains of smart contracts, consensus mechanisms, and quantum cryptography. The benefits of QSB in comparison with traditional blockchain systems were emphasized, while the challenges that neces- sitate additional investigation were addressed. The potential of QSB appears great, S. Jain
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- 30. 19 © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024 S. Pulipeti et al. (eds.), Quantum and Blockchain-based Next Generation Sustainable Computing, Contributions to Environmental Sciences Innovative Business Technology, https://doi.org/10.1007/978-3-031-58068-0_2 The Intersection of Blockchain Technology and the Quantum Era for Sustainable Medical Services Dinesh Kumar Atal , Vishal Tiwari , Anjali , and Rajiv Kumar Berwer Abstract Medical data has become crucial to the healthcare sector’s growth and development due to its complexity and expense of preserving security and confiden- tiality and providing services to the entire healthcare ecosystem. Therefore, an open-channel platform on the Internet enables patients to manage, share, and keep track of their electronic health records (EHRs) with friends, family members, and healthcare professionals. After that, the growth of medical data comes with the con- cern of handling it securely. So, for this, blockchain technology significantly simpli- fies the process of conducting transactions, as it can store data in vast amounts in a distributed manner which may be retrieved wherever and whenever needed, thereby improving the efficiency of today’s healthcare system. Medical records processing using quantum and blockchain technology heavily influenced the industrial health- care market. These technologies can benefit healthcare and significantly affect its transparency, information security management, business opportunities, and pro- cessing efficiency. Quantum blockchain technology is another tool that can enhance the speed of diagnosis and treatment because any delays in treatment or emergency care can compromise the security and confidentiality of medical records. This way, the medical records can be analyzed and communicated with privacy, security, availability, and authenticity. Quantum blockchain and computing have the capacity to acquire thermal imaging speedily with which patients can be located and moni- tored simultaneously, thereby optimizing diagnosis expenses and insurance fraud. This review chapter discusses how smart healthcare systems benefit from quantum and blockchain. D. K. Atal (*) · V. Tiwari · Anjali Department of Biomedical Engineering, Deenbandhu Chhotu Ram University of Science and Technology, Sonipat, Haryana, India R. K. Berwer Department of Computer Science and Engineering, Deenbandhu Chhotu Ram University of Science and Technology, Sonipat, Haryana, India
- 31. 20 Keywords Healthcare industry · Electronic health records · Blockchain technology · Quantum computing · Quantum and blockchain technology 1 Introduction The growth of industrial healthcare comes with many digitally recorded medical databases, which require secure processing. The adoption of blockchain and IoT (Internet of Things) significantly impacts the industrial healthcare sector owing to the industry’s design comprising of related apparatus and IT applications. These technologies will enhance information security, transparency, regulatory regulation, and processing efficiency while opening up new commercial prospects [1]. Therefore, healthcare information could be assessed, evaluated, and shared and maintain patient privacy. Blockchain technology in modern medicine has many ben- efits, such as data management, accounting, and finance. Additionally, there are specific issues and dangers related to blockchain-based healthcare projects and sug- gestions for mitigating or eliminating them. The health industry is one of the areas where the blockchain can substantially influence on both the economy and society [2, 3]. The most significant benefit using it does not require the participation of any centralized organization. In the medical domain, blockchain technology has been used to share clinical data, account management, drug supply chain management, drug development, and clinical trials. The interchange of clinical information between the payers, patients, and partners and how we obtain and maintain clinical details can all be entirely transformed by blockchain technology [2]. The rapidly developing technology, blockchain, is utilized in various security applications. The Stakeholders employ a variety of implementations that use block- chain technology that kept as a sequence of blocks, may serve as a public record for all committed transactions. Some essential features of blockchain technology con- tain decentralization, availability, immutability, transparency, and persistence [4]. Blockchain technology can potentially improve the clinical data-sharing aspect of the IoT (Internet of Things). Blockchain provides a secure means of distributing critical patient information collected by IoT devices [1, 5]. The BPIIoT (Blockchain Platform for Industrial Internet of Things) enables the legacy shop floor device inte- gration with an appropriate cloud environment; it would show a tremendous increase in performance over the current CBM (cloud-based manufacturing) platform, removing financial barrier that has stifled the development of a company ecosystem. Using this ecosystem, the manufacturing and healthcare industries, including sup- ply chains, logistics, healthcare, agriculture, and the energy sector, may be able to facilitate transactions between users [1, 6, 7]. Several healthcare institutions utilize the IoHT (Internet of Healthcare Things) for maintaining assets, monitoring infants, and tracking inventory [1, 8]. The use cases are two types: assistance operations and clinical services. Through RPM (remote patient monitoring), IoHT facilitates patient-centric activities in healthcare. Internet of Healthcare Things strictly checks all vital signs and other crucial D. K. Atal et al.
- 32. 21 parameters for the investigation, like weight and blood sugar level changes [1]. The increased utilization of mobile medical assets made possible by IoHT enhances sup- port operations and lowers overall operating expenses. The staff can access real- time information on the location and usage patterns of ventilators, digital X-ray equipment, and other resources while saving money due to equipment sensors and data collection capabilities. This allows for more effective equipment assignment and faster location whenever and wherever needed, thereby saving valuable time for care workers. Using IoHT sensory inputs, expensive machinery such as MRI (mag- netic resonance imaging) equipment can also be displayed to technicians in real time using IoHT sensory inputs. To develop digital twins of technology, medical decision-makers are also exploring integrating augmented reality technology and IoHT [1, 9]. The workers and clinicians are provided with practical, hands-on train- ing opportunities and highly visual and interactive augmented reality interfaces that can digitally reproduce complicated medical equipment and devices. The protec- tion, security, and dependability of the servers that link IoT devices and share vital medical records are issues to be aware of when adopting IoHT [1, 10]. A blockchain is a logical option that can completely secure the entire process through encryption and decentralization [1, 11]. Blockchain is gaining popularity due to its ability to create and disseminate permanent, irrevocable transactions securely. Blockchain builds blocks of transactions and stores them in a continuous sequence of occur- rences shared securely with different participants. The documents are nearly impos- sible to alter since the blocks are secured using cutting-edge cryptographic technology [1, 12]. This technology keeps the possibility to streamline and progress security and precision for laborious, wasteful methods [1, 13]. Examples include the following: • Quick medical insurance enrolment • More streamlined claims adjudication • Increased B2B movement throughout the healthcare value chain The quicker and more effective certification of employees is one of the additional blockchain prospects. The healthcare sector is a good fit for IoHT and blockchain technologies due to its patient-centered mechanisms [1, 14]. The two technologies working together permit for the secure, unchangeable conversation of medical data [1]. Blockchain technology can benefit the medical field and battle the COVID-19 pandemic. Blockchain technology and its processes will indeed be employed in upcoming smart healthcare schemes for collecting relevant information from secure data storage, sensors, and automatic patient monitoring, according to the signifi- cance of the blockchain. Blockchain technology significantly streamlines opera- tions since it can preserve vast amounts of information in a distributed and more secure manner. It provides a more excellent range of accessibility whenever and wherever necessary [15]. Quantum computing, on the other hand, provides access to excellent services. The quantum computing has several advantages including the capacity to employ thermal imaging based on quantum computing and the ability to detect and monitor patients quickly. These advantages can be completely realized when combined with quantum blockchain [15]. Another technique that can protect The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 33. 22 the reliability, confidentiality, and accessibility of data records is quantum block- chain. If quantum computing and blockchain technologies are combined, medical records processing will be faster and more private [15]. Therefore, the use of quan- tum blockchain technology would benefit medical services to a great extent. The pace of diagnosis and treatment can be accelerated with quantum blockchain tech- nology. It also helps preserve data records’ availability and authenticity. The advan- tages of quantum computing, like the capacity to obtain thermal imaging and the speed with which patients can be discovered and tracked, may all be utilized to their fullest extent with the help of quantum blockchain. Additionally, it maximizes insurance fraud and diagnosis costs. 2 Smart Healthcare Systems Information technology (IT) is crucial in the healthcare industry because population health management technologies such as remote patient monitoring (RPM) and electronic health records (EHRs) have highly improved this industry. The medical records engendered from these references are extensive and time-consuming, result- ing in issues with data quality, thereby making the data analysis, prediction, and diagnosis more complicated and the threat of data protection due to increased cyber- crime [16]. Because they provide essential data consistent with patients’ perspec- tives, medical and healthcare records have demonstrated their value to patients. The healthcare data repository may become a target and a moment of loss for system attackers. It increases the risk of vulnerabilities, leading to denial-of-service (DoS) and ransomware attacks [16]. The sharing of the patients’s medical records and information among the healthcare providers via electronic health records may increase diagnostic performance. In particular, difficulties with patients’ informed consent and the scientific credibility of findings such as data missing and dredging, endpoint flipping, and selective publication in clinical trials could be resolved by blockchain technology. A patient’s brief medical history is included in an EHR along with statistics, projections, and any information/data related to their ailments and clinical progress throughout the therapy [17]. Users could access and preserve their health data using a blockchain system for EHRs that simultaneously ensures confidentiality and privacy [17]. EHRs allow patients to manage and share their health records with their family, medical professionals, and friends, over an open channel and the Internet. Despite the fact that cloud-based EHRs address difficulties, they are still susceptible to a variety of destructive attacks, server non-repudiation, and trust management. Hence, blockchain-based EHR solutions instill in consumers a sense of privacy, security, and trust [18, 19]. Implementing a blockchain-based EHR system that promotes interoperability and trust among all parties is possible. It has a distributed, time- stamped, chronological, immutable, and auditable log to keep clinical information. Numerous industries, including finance [20], education [21], edge computing ser- vices [22], tourism [23], automation [19], etc., have used blockchain technology. D. K. Atal et al.
- 34. 23 The quantity of data and records has doubled in the healthcare organization 4.0, which has a $50 billion market [24]. Additionally, the percentage of verified electronic health record systems has doubled, from 42% to 87% [25]. Because medical professionals, hospitals, and other service providers update their records frequently, the considerable volume of data created from several sources could be more organized. It leads to issues related to management, such as drug tracking, bill management, and claim settlements. The Health Insurance Portability and Accountability Act (HIPPA) stipulates that health- care industry stakeholders should ensure that approved data is uploaded by patients who have certified electronic health records (EHRs) from physicians. Privacy and data ownership concerns about patients’ sensitive data, its storage, scalability of mined transactions, capacities, the cost of maintaining healthcare blockchain, and quantum and collusion attacks are the difficulties of using blockchain technology. Lattice-based cryptography offers the defense against quantum and collusion opera- tions and the perfect answer to the issues of user privacy and data ownership. In the random oracle concept, lattices create post-quantum blockchain networks (P-QBN) observed as safe [26]. Therefore, lattice signature creation and verification activities authorize certified EHRs. According to HIPPA regulations, this guarantees com- plete record secrecy. Distributed artificial intelligence can enhance blockchain oper- ations by addressing the scaling challenges of transactions, storage, and fee issues with digital health records stored digitally among distributed nodes [27]. Former conventional machine learning (ML) and statistical methods [28] were also employed likewise, whereas they examined plain data to discover relevant attributes and build patterns of initial intrigue. Identifying the criteria of interest is a much time-consuming skill [29]. Deep learning (DL) techniques, on the other hand, learn about feature selection with no human interference, allowing the finding of embed- ded dynamic relations in between the information [18]. The benefits of blockchain- based EHRs are numerous; some of them are records stored in a distributed manner (open and straightforward to verify across a wide range of unaffiliated provider organizations). Also, there is no centralized party for the attacker to crack or alter the data; information is continually updated and made available, and information from various means is combined into a single suitable information storage (Grey Healthcare Group, 2017) [17]. 3 Blockchain Technology Today’s smart healthcare data management systems face serious hurdles regarding security, privacy, trust, flexibility, provenance, audit, traceability, transparency, and immutability. Additionally, many of the current smart medical record managing methods are centralized, which increases the danger of a single fault point. The blockchain, an emerging and disruptive decentralized technology, has the potential to radically revolutionize, reconfigure, and alter data management in medical domain [30]. Blockchain supports transaction audits in this way, going beyond The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 35. 24 transparency [17]. Blockchain is an innovation that encourages value sharing. It has recently been used in several fields, with finance in healthcare being the most sig- nificant. Blockchain is a distributed database of cryptographically linked blocks aggregating transactions sequentially. Each block is added to the ledger over peer- to- peer (P2P) networks, linked to the previous block using hashing technique. These records are built on a decentralized technology, eliminating the need for transac- tions and assets to interact with a centralized intermediary. Digital purchases, such as individual medical information, economic transactions, and personal records, can be processed, encrypted, confirmed, and stored more efficiently by emerging block- chain technology [31, 32]. Blockchain enables the decentralization and deregulation of markets of all trans- actions between participants daily. Blockchain is an application layer that advances the OSI layer by introducing a layer that allows instant digital currency and finan- cial transactions. It maintains a record of all the completed transactions [31]. The chain will continue to expand after another transaction is completed. No third-party software is required for transactions. From a business perspective, the blockchain is a system for exchanging assets, value, and transactions between individuals. It is a method for validating and verifying the transactions and taking the place of trusted parties’ entities [4]. Nowadays, every medical and healthcare system has high dependability on blockchain technology. Blockchain technology, which is decen- tralized and distributed, offers security services for the healthcare industry. The existing healthcare system’s centralized design could be more secure across many medical services, resulting in delayed access to the concerned information and sig- nificant danger of information leakage. The medical records could then be archived without the client’s concerns. The critical problem in the present healthcare mainte- nance system is gaining secure network access to information. Blockchain technol- ogy is proving to be an up-and-coming technology that is the most effective way to access the concerned data/information. When using blockchain technology, data is kept in a ledger feature that may be used to monitor how patients access their medi- cal records [4]. By enabling unparalleled data efficiency and ensuring trust, blockchain helps streamline the various healthcare data management processes [5, 30]. It provides a vast range of built-in conspicuous capabilities, including decentralized storage, adaptability of data access, interconnection, authentication, security, immutability, and transparency. It also enables wider adoption of blockchain for managing health- care information records [30, 33, 34]. Blockchain employs the idea of “smart con- tracts,” which establish specific rules accepted by all the partners in the blockchain environment and eliminate the need for an intermediary [30, 35, 36]. It reduces unnecessary administrative costs. Consensus mechanisms, public-key cryptogra- phy, and peer-to-peer networks comprise the main three ideas of blockchain [27]. Public, private, and consortium blockchains are the categories into which block- chains are separated based on managing permission [30, 37]. Blockchain technol- ogy is a distributed database that handles the data within an IoT application in a chain of blocks [38, 39]. It is particularly good at securely processing relevant infor- mation for serverless edge computing. However, block data handling decreases D. K. Atal et al.
- 36. 25 processing speed [38, 40]. The procedure must operate concurrently over several distributed architecture nodes to verify the proof-of-work (PoW). Such systems might be integrated into a function as a service (FaaS) platform using microser- vices, which could be set up on a serverless pipeline. Quantum computers can pro- vide large-scale resource management computations to address this issue [38, 41]. With numerous applications in areas like sharing patients’ medical data, preci- sion medicine, clinical trials, drug counterfeiting, longitudinal healthcare records, user-oriented medical research, public healthcare management, online patient access, and automated health claims adjudication, blockchain is essential to the healthcare industry [17]. Therefore, without needing third-party tools, blockchain technology enables more robust and more secure transactions. There is no further need for trust between the parties when each party to a transaction may believe in the correctness and consistency of the records, a concept known as “trustlessness” in the context of blockchain [1, 40]. Blockchain offers a broadly distributed, peer- validated, and immutable digital ledger and does not need money to operate cor- rectly. Most enterprise-level blockchain applications do not call for specific money, coin, or token [1, 42]. 3.1 Types of Blockchain • Private and public. Who has access information to the blockchain database? Large audiences, the general public, can upload data to the ledger via public blockchains. A public blockchain network like Bitcoin illustrates this; there are no restrictions on who can exchange Bitcoin. Bitcoin can be purchased, sold, or sent to anyone. An illustration of a private solution would be a blockchain system that tracks how donations to nonprofit organizations are used. Only appointed authorities from the nonprofit group can disclose how funds are distributed and used in such a way [1, 43]. • Permissioned and permissionless. Permissionless systems are available, and the public needs more permission or role-based access. These platforms need the natural functionality to handle identities, set permissions based on those identi- ties, and enforce those identities. This implies that you must design and imple- ment a system to track and manage identification and draw permissions against that identity if you decide to do so. This does not suggest that you cannot develop a permissioned solution on a permissionless platform. Considering whether all participants should be treated equally or some should have access to features or rights that others do not is a beautiful approach to narrowing down the type of blockchain required when designing a solution. The solution to this question will assist in informing whether to employ permissioned or permissionless block- chain technology [1, 43]. The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 37. 26 3.2 Advantages and Limitations of Blockchain Technology 3.2.1 Advantages of Blockchain A business network’s organizations can share infrastructure owing to blockchain technology. Since we lose the fact if the data is altered, corrupted, or hacked, block- chain is more secure than a typical database. Blockchain offers robust security and a wide range of permissions to validate and regulate who has a permit to access information and under which conditions. Tracing the sources of all supply chain pieces also enhances quality assurance services by reducing costs and controlling any defective parts [1, 44, 45]. Blockchain is fault-tolerant and redundant; if any system loses track of the database, it will stay elsewhere on the network. Consider sending a group message to understand fault tolerance better. Since every member in the messaging party has a replica of the party conversation, they would have to do so on everyone else’s phone if any member wanted to delete something from the conversation. When numerous people are involved, fault tolerance is beneficial. The tokenization, which opens up new entrepreneurial opportunities and produces trade- able tokens with real-world value, is another significant benefit. The term tokeniza- tion is the digitizing representation of fractional asset ownership, such as owning one car in one city or one hundred vehicles in one hundred. Blockchain uses a smart contract to ensure that business operations are automated and consistent across sev- eral enterprises. Finally, eliminating intermediaries by blockchain lowers costs and improves the effectiveness of company operations. It enables firms to function more quickly and respond to changes in the commercial environment considerably more rapidly than they might otherwise [1, 44, 45]. Patients can transfer their medical records to anyone without worrying about data tampering or corruption because the blockchain is immutable and traceable [4]. The same is true for a blockchain-generated and added medical record, which will be completely secure. The patient can influence how the institutions utilize and dis- seminate their medical data. Any party seeking access to the patient’s medical records might use the blockchain to verify their eligibility [4]. A reward system can also motivate the patient to behave well. For instance, people may receive rewards for adhering to a care plan or maintaining good health.Additionally, they can receive tokens in exchange for providing their data for studies and clinical trials [4]. Due to the nature of the products they carry, pharmaceutical businesses must have a very secure supply chain. Drugs for the pharmaceutical industry are often stolen from the supply chain and sold illegally to various customers. Additionally, these businesses lose almost $200 billion a year due to the sale of counterfeit pharmaceuticals. These businesses will benefit from a transparent blockchain by closely tracking drugs back to their point of origin, which will help remove fake medicine [4]. D. K. Atal et al.
- 38. 27 3.2.2 Drawbacks of Blockchain Like any other technology, blockchain has costs associated with its advantages. Its disadvantages need to be fully considered to decide whether blockchain would be the best option for an overall solution architecture. Best practices suggested pat- terns, and appropriate use cases are continually being established [1, 44, 45]. The blockchain’s scalability in comparison with traditional technology is another sig- nificant limitation. Blockchain has a lower transaction volume processing capacity than competing systems like Visa. For blockchain to be performance competitive, the ability needs to be increased by several orders of magnitude. Additionally, obtaining a thorough “God Mode” view of the answer and its information can be difficult or impossible. Many available media and toolkits are yet in the preproduc- tion stage and might not be ready to develop complex applications [1, 44, 45]. Energy consumption is a vital factor in the developing stage of blockchain technol- ogy. Proof-of-work (PoW), the initial agreement algorithm utilized to mine Bitcoin, uses 7.67 gigawatts of electricity annually. This power is comparable to the power use of nations like Austria (8.2 gigawatts) and Ireland (3.1 gigawatts) [1, 46]. Numerous strategies have recently been put up to cut down on the energy usage for blockchain technology and the resulting carbon footprint. One of these is switching from PoW validation to PoS (proof of stake). This more recent blockchain consen- sus algorithm has been suggested to solve PoW’s scalability and cost issues. Secondly, creating blockchains that operate distinctly from those that use such large amounts of energy, lastly, concentrate on environmentally friendly methods to mine Bitcoin, such as solar or wind power. Assaults like 51% and denial-of-service (DoS) attacks impact blockchain technology. A 51% assault is one of the simplest methods for breaking the blockchain’s security since it takes advantage of the consensus algorithm’s legal purpose. In a PoW blockchain, the branch with the most work behind it wins in the event of a divergent blockchain. Hence the state of the block- chain is decided by a majority vote. A PoW blockchain is controlled by an attacker if they own 51% of its compute resources [1]. DoS attacks target the network’s bottlenecks in conventional, centralized networks. Despite being decentralized and lacking bottlenecks by design, DoS attacks can be successful against blockchains. A DoS attack depends on blockchain and the locations of its operational bottle- necks [1]. 4 Blockchain Technology in Healthcare Blockchain is a novel technology that is employed to generate innovative solutions in a variety of industries including healthcare. Blockchain is a decentralized hyper- ledger that aids in the copying every activity or digital event preserves and distrib- utes. The large number of persons involved confirms every transaction. Every transaction record is stored there [15]. A blockchain system is leveraged in the healthcare ecosystem to aid in keeping and sharing patient medical information The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 39. 28 among doctors, drug companies, diagnostic labs, and hospitals. Blockchain applica- tions can precisely identify severe issues, including possibly deadly ones, in the medical sector. In the healthcare industry, it can enrich the privacy, translucence of shared medical records, and efficiency. Medical organizations can obtain perception and progress the investigation of patient information with the sustainable applica- tion of blockchain technology. Different blockchain systems can enhance the supe- riority of the services accessible to the medical industry. Blockchain and IoT technologies are coupled to allow healthcare institutions to maintain records effec- tively and accurately, which is necessary [1]. The procedure includes many parts, from the point at which IoT collects real-time patient data to the point at which a suitable medicine is given to ensure the patient’s happiness. The blockchain is uti- lized in [1, 47] to maintain patients’ medical records. When blockchain technology’s feasibility is considered, service-related indus- tries such as healthcare are starting to transform and adapt to combine blockchain technology into their existing condition. By 2025, industry value is anticipated to grow by over $176 billion by 2025 and reach $3.1 trillion by 2030 [48]. According to reports from the World Economic Forum, blockchain technology will store 10% of the global GDP [49]. The worldwide blockchain industry’s growth rate is expected to increase by 71.46% between 2017 and 2022, reaching $4.401 billion by 2022, up from $0.297 billion in 2017 [50]. These estimates do not surprise block- chain start-up investors, but the potential of blockchain remains to be discovered throughout society. Nonetheless, food procurement, mining, minerals, and banking are already using this technology [50, 51]. It is now being discussed as a potential application in healthcare to transform medical information systems [52] and pay- ment systems [53, 54]. Researchers and professionals in the healthcare domain face scattered data, improper interactions, and clinical processes with incomplete com- ponents due to supplier-specific and unsuitable health systems. Furthermore, the confusion about transferring clinical and financial information impacts health IT systems. As a result, they have critical flaws in terms of privacy and security. Providing customized patient treatment is challenging due to all of these consider- ations [52]. The use of blockchain in the medical sector provides advantageous solutions for safeguarding stakeholder interactions, delivering clinical reports quickly, and combining various types of individual health records of people on a secure infrastructure. 4.1 A New Intelligent Healthcare System Every organization or facility must have a system for the patient. This system must include a database to store the many distinct data sets needed by the institution and its stakeholders. These databases are mostly decentralized, containing several other databases working together. Decentralized databases help information manage- ment, notably in the healthcare sector [1, 55, 56]. For example, when several users submit scientific data, the database might grow perplexed and convoluted. D. K. Atal et al.
- 40. 29 Blockchain technology may supply a remedy to certain knowledge areas, such as elderly treatment or chronic illnesses. Large healthcare databases, conflicting IT interfaces, changes in communication standards, and incompatibility of information processes among various therapists, medical specialists, practitioners, physicians, research labs, and healthcare centers, etc. are just a few of the significant issues that arise [1]. 4.2 Improving the Privacy of Patients’ Medical Records Health information generated by patients and information stored are highly crucial [1, 57]. Wearable gadgets, such as trackers, built-in body chips, smartwatches, and fitness bands that help monitor patients’ data, have been developed due to techno- logical advancements in the medical sector. The flow of patient-generated informa- tion has grown due to these wearable technologies. The difficulties posed by the growth in healthcare data are addressed by blockchain technology [1, 56]. Health Bank’s blockchain technologies offer Swiss start-ups in digital health. The following are the wide range of facilities to its customers [1]: 1. Management of patient transactions and the sharing of medical information 2. Retrieving patients’ confidential information, such as lifestyle habits, health his- tory, consumed medicines, eating habits, sleep patterns, heart rate, SpO2, and other vitals 3. Preservation and accessibility of information for medical research 4. Storage and management of information in a secure location 4.3 Healthcare Services Provided by Blockchain The blockchain-based medical approach comprises the patient and clinical data generated and stored as digital resources and accessed over blockchain infrastruc- ture. It is accessible under secure underlying architecture, seamless data usage, and exchange across health organizations and vendors. Blockchain applications in healthcare are health analytics, smart contracts, and a network of medical technolo- gies that can use the complete history of timestamped records for users in terms of services. The following medical healthcare services are provided by the blockchain infrastructure framework [31]: 1. Services provided by the doctors. The suggested blockchain-based medical care approach improves clinical assistance provided by physicians and other health- care providers. Computerized cost estimation via trade networks, such as online transportation services, contributes to translucent invoicing. Payments using coins based on blockchain offer an efficient payment method. The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 41. 30 2. Notary services. A notary process for the digital transformation of vital records such as identity cards, passports, and insurance is one of the components employed for blockchain technology. In the proposed system, records such as examination marks, evidence of insurance, therapy, and medication are encrypted and validated in seconds rather than hours or days using traditional technol- ogy [32]. 3. Private blockchain technology. Permission is required to view the data on a pri- vate blockchain. Therefore, patients grant access to their medical records to their doctors and other parties. Based on business agreements, different permit levels can be described to manage who can view documents, alter them, and have supreme control in the system. In healthcare, the mixture of safety and flexibility is preferable to the transparent public blockchain. 4. Hospital asset supply chain management. Blockchain technology can even be leveraged in supply chain control systems to handle hospital products and con- trol purchase-selling mechanisms for all challenging clinical aids. 5. Smart contract technology. It could reduce insurance scams at all levels, from corporate fund management to specific claims, at a reduced cost because the system has less load to manage and process. It primarily performs as a legal mechanism, enabling real-time data exchange with the blockchain architecture to design, store, and implement agreements. 6. Private genomic data. Blockchain technology enables the collection of DNA records from various agencies and authorities without the requirement for a cen- tralized database and the backup of a person’s DNA to spread individual genetic material to multiple systems worldwide. 7. Confidential medical record storage and access. Clinical information enables seamless transmission and data exchange among healthcare communities and application merchandisers. 5 Quantum Computing in Healthcare A promising computer method defined on quantum physics and associated excep- tional circumstances is known as quantum computing (QC). It is a stunning combi- nation of computational modeling, mathematics, physics, and computer science. Controlling the behavior of microscopic physical entities like atoms, photons, elec- trons, and other minute particles surpasses traditional computers in terms of low energy consumption, rapid speed, and processing capacity. Since the quantum approach is a more expansive physics model than classical physics, it adds to a uni- versal computer system, quantum computing, which can solve issues that classical computing cannot [15]. In contrast to traditional systems, which store and process data using binary bits 0 and 1, quantum computing uses its quantum bits (“Qubits”). Although quantum computing can rapidly infiltrate current cryptography methods, the most extraordinary supercomputer currently known requires thousands of years to complete [15]. D. K. Atal et al.
- 42. 31 The future use of quantum computing in the medical sector may improve the data processing capacities of various stakeholders such as therapists, medical specialists, practitioners, physicians, research labs, and healthcare centers, which could be nec- essary for providing uninterrupted service in a changing environment. Executives should, however, account for (i) the current system’s issues, that is, the matter of concern; (ii) the amount of information generated by the system; and (iii) the role in the medical sector (pharmaceutical or insurance company) [58]. Professionals in the medical industry, like clinicians, management staff, and insurance company support staff, must assess the risks of using quantum computing. In silico medical difficul- ties can be combined with quantum computing to create advanced virtual medical studies. The benefit of quantum computing is saving lives in danger in the conven- tional environment of clinical trials in the healthcare industry. Organizations and experts in healthcare insurance can benefit from precise risk modeling and provide a price when determining an individual’s needs and health conditions [58]. Interindustry and interdepartmental coordination can also be presented with the integration of quantum computing to provide the most appropriate experience to a client in the medical industry. After meeting all requirements, healthcare organiza- tions can also accept auto payments and provide funds as needed. For pharmaceuti- cal industry experts in drug production, composition, and scalability, quantum computing can be highly profitable. The medical sector can concentrate on the patient while maintaining the highest level of security for medical information gen- erated by electronic health records or clinical studies [58]. Although quantum computing will be capable of breaking some of the encryp- tion methods used today, it is anticipated that they will develop tamperproof alterna- tives. Such tiny computers cannot use logic gates, semiconductors, and ICs. As a result, bits of atoms, protons, electrons, and ions are employed with metadata about their rotation and state. To create other combinations, they can be combined. As a result, they may operate concurrently and effectively use memory, enhancing their power. Since quantum computing is the only computer model that rejects the Church-Turing hypothesis, it can utilize the available systems far more effectively [15]. The essential building block of quantum theory is the qubit, which represents fundamental particles like atoms, protons, neutrons, electrons, and other minute particles as computer memory with their control schemes functioning as computer processors. It can be set to a weight of 0, 1, or both at once. Its processing power is a million times greater than the most sophisticated and powerful available today. Qubit production and management is a big task in engineering. The computing strength of quantum computers arrives from their digital and analog nature. Due to their analog character, there is no distortion limit for quantum gates; however, their digital characteristics provide a standard for overcoming this critical shortcoming [15]. Therefore, the representations and logic gates employed in traditional systems are meaningless in quantum computing. Mainly traditional computing rules can be employed in quantum computing. Nevertheless, this algorithm needs an extraordi- nary approach to eliminate processing variations and noise. It also needs its method for fixing design flaws and troubleshooting problems. The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 43. 32 The three fundamental characteristics of quantum computing are entanglement, interference, and superposition [15, 59]. Entanglement is one of the critical features of quantum computing that guides the intimate connection between two particles or quantum bits. Qubits are connected in an exact instantaneous relationship even if they are split by excessive length, such as at opposite ends of the universe. They are coupled with one another or defined by one another. The quantum computing sys- tem simultaneously saves data in two states. In quantum computing, interference is equivalent to wave interference in classic physics. Wave interference results from the collision of two waves in the same space. However, imagine that all the waves are pointing in the same path. At that point, constructive or destructive interference happens as the generation of standing waves with individual amplitudes counted or a resultant wave with their amplitudes swabbed out, respectively. The resultant wave may be more or lesser than the initial wave, depending on the type of interfer- ence. A quantum technique’s ability to live simultaneously in two separate locations or structures is known as superposition in quantum computing. It is distinct from its traditional companions, with binary limitations, and enables remarkable parallel processing at a fast speed [15]. 5.1 Uses of Quantum Computing There are many uses for quantum computing. Cybersecurity [60, 61], healthcare [62], artificial intelligence [63], weather forecasting, logistics optimization, and financial modeling are some of the critical uses of quantum computing. The Internet security environment has grown highly vulnerable due to the surge in cyberattacks that occur daily around the globe [64–66]. Although organizations are putting in place what is necessary for security standards, the process for traditional digital devices has grown complicated and impossible to use [15]. 1. Cybersecurity. Large-scale quantum systems will enhance processing capacity, forming novel prospects for enhancing cybersecurity. Cybersecurity from the quantum era will be able to recognize and stop assaults from that era before they cause harm. However, it is a double-edged blade because quantum computing also creates new security flaws, such as the ability to quickly solve the complex mathematical equations that underlie some forms of encryption. 2. Healthcare. Integration of quantum computing with classical computing is expected to have considerable advantages over conventional computing alone in the healthcare sector.An extremely desirable set of skills, outstanding IT designs, a particular form of understanding, and inventive business plans are all demanded of quantum computing. In addition, security is impacted by technology, which is a subject of significant importance for the medical industry due to the medical industry’s responsibilities and challenges concerning data security and privacy. 3. Artificial intelligence. AI and quantum computing are both game changers. Quantum computing is a necessary aspect for making significant advances in AI D. K. Atal et al.
- 44. 33 factor. While generating practical applications on traditional computers, artifi- cial intelligence is limited by its processing capability. Quantum computing may give artificial intelligence a boost in processing power that will let it tackle more complex problems in various fields. 4. Financial modeling. Companies using quantum computing benefit significantly from it. In particular, financial companies will be well prepared to evaluate large or unstructured information volumes. For example, banks might improve their judgments and customer service by making more timely or relevant offers. Quantum computers are showing promise in applications where programs are determined by actual information streams, such as livestock amounts, that include unexpectedly high noise. 5. Logistics optimization. The logistics sector could benefit significantly from quantum computing. Quantum computers would speed up devices using AI and machine learning, enhancing current CPUs. Quantum computers are showing promise in applications where programs are driven by actual information, such as livestock amounts, including unexpectedly high noise. 6. Weather prediction. On a native and worldwide level, quantum computing might aid to predict complex or accurate alerts of disastrous weather circumstances, thereby reducing yearly property damage and significantly saving lives. Quantum computing offers the ability to proceed with conventional mathematical approaches to improve tracking or forecasting weather circumstances by han- dling vast volumes of data with various variables fast or efficiently using the computational capability of qubits [15]. Pharmaceutical development and formulation are the most challenging jobs in quantum computing. Medicines are typically developed via costly, risky, or time- consuming trial and error. Quantum computing could be a helpful technique for examining the effects of medications on individuals, potentially saving a significant amount of time and money for pharmaceutical organizations. Since new emergent technologies have touched on almost every aspect of modern life, deep learning and AI are two of the most challenging cases [15]. Many problematic computational problems that take years to solve on traditional devices can be solved more quickly with quantum computing. Accounting professionals oversee enormous amounts of money, so even a slight modification in the projected return can have a significant impact. Another application is algorithmic investing, which is advantageous, pri- marily in high-volume trades, and involves a computer carrying out detailed algo- rithms to automatically launch stock trading based on market conditions. A cutting-edge, effective algorithm called quantum annealing may one day outper- form conventional computers. On the other side, universal quantum computing is ready to handle any computing challenge but has yet to be commercially avail- able [15]. The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 45. 34 5.2 Pros of Quantum Computing Based Approaches for Healthcare When used in healthcare, quantum computing can [15] 1. Support quantum blockchain-based scenarios. 2. Enable innovative healthcare scenarios for better patient-centric system design and patient handling. 3. Improve security and enhance healthcare system for all stakeholders such as therapists, doctors, etc. 4. Speed up data availability and processing for authenticated clients. 5. Strengthen the healthcare environment security against a variety of real-time attacks. 5.3 Cons of Quantum Computing Based Approaches for Healthcare Using quantum computing for healthcare systems faces several significant difficul- ties [15]. Some of them are as follows: 1. Quantum computing may not be ecologically friendly when extensively leveraged. 2. Deploying quantum computing possessions for the healthcare ecosystem in a real-world scenario is difficult particularly in underdeveloped countries. 3. Building the necessary infrastructure for real-time quantum computing applica- tions is challenging, especially for the healthcare industry. Additionally, it is a pricey solution even though there are tools (such as Qiskit, Silq, etc.) for small- scale computing solutions. More Qibit support machines are needed in order to accomplish large-scale integration. 5.4 Quantum Cloud as a Service Major cloud service providers are using serverless computing as a standard to effi- ciently deliver cloud services to end users [67, 68]. As edge computing becomes more prevalent, serverless computing can process work opportunities more quickly at runtime [69, 70]. It also provides services to end users established on the aids used by various Internet of Things (IoT) applications [71], like healthcare, smart cities, farming, and weather forecasting [72–74]. The computation speed and secu- rity issue for Serverless edge computing are sometimes faced due to big data pro- cessing [75–77]. Somewhat of data processing at cloud data centers, edge computing is a technique for handling data of IoT applications that are close to edge devices D. K. Atal et al.
- 46. 35 [69, 74]. Computing close to the network’s logical edge reduces latency and reac- tion time [41], but more processing power is needed as data creation grows daily [71, 78]. The cloud computing execution model-based service delivery to the end users on resource usage provided by IoT apps rather than pay-per-use [70, 78]. To manage resources and scale automatically, FaaS accomplishes the separation of the server into independent functions [38, 68]. 6 Quantum and Blockchain in Healthcare Blockchain technology uses conventional cryptographic operations to achieve secu- rity. Most of these functions are computationally secure, which implies that to breach them requires significant processing power that is not always available. These technologies will be impacted by the development of the quantum computer, which will make it possible to decrypt data encrypted with conventional encryption techniques. A quantum system can compromise the computational security of these operations. In contrast to traditional computers, quantum computers may effectively process information by taking advantage of peculiar quantum features, including superposition and quantum entanglement [1, 79–81]. As a result, it is expected that implementing quantum technologies in an intelligent environment would lead to innovations and accomplishments that are still unmatched by their classical coun- terparts. These enhancements include more affirmed security, quick computation, and little storage usage [1, 82–84]. Current cryptography foundations are seriously threatened by quantum comput- ing [1, 85]. Within a few decades, according to current predictions, quantum com- putation will be potent sufficient to circumvent widely utilized privacy and security measures [1, 86, 87]. As a result, new technologies and gadgets must design for the environment of quantum computation and the ensuing cyberattacks. Future block- chain implementations must also be ready for quantum computing, as any flaw might allow for altering the database and threaten the whole organization’s integrity. At last, legacy infrastructure will be exposed unless existing public fundamental cryptography architecture is updated to be quantum-resistant. With the key obtained via quantum key distribution systems, recently proven quantum blockchain infra- structures are based on information-theoretic safe authentication. However, a pair- wise connection between users is necessary for such a configuration [1, 88]. Using quantum-secured direct contact for N clients with authentication or quantum digital signatures is another method for assuring quantum security. It is crucial to compre- hend the quantum network structure restrictions and the number of false (unreli- able) systems in these designs. The standard family of broadcast protocols can create quantum-secured distributed information methods once the authentication/ signature operations are finished [1]. Aspects of healthcare, from detection and therapy to data storage and communi- cation, could be impacted by innovations established on the rules of quantum mechanics. The fundamentals of quantum blockchain technology will increase The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 47. 36 medical data security and stop data leaks. Furthermore, by adopting methods like quantum computers and laser microscopy, which depend on the rules of quantum mechanics, we can sequence DNA more quickly and address other significant data issues in the healthcare field. This opens the door to individualized therapy that considers each person’s genetic composition [1]. Edge serverless services that are secure and dependable can be offered while simultaneously enhancing security and computation speed using quantum computing and blockchain. Blockchain [39, 40] and quantum computing [89] are both the latest technology that can be leveraged to deliver high-speed computation and security [41]. Additionally, a safe and trustwor- thy theoretical ideal for serverless edge computation is required so that artificial intelligence (AI) can be used to deliver effective service [78]. Two key ideas from quantum physics, superposition, and entanglement are used to execute computa- tions in quantum computing [89]. The serverless computing paradigm, now used by the edge computational paradigm to deliver operations as a service, needs quantum computing to handle extensive computation for load balancing and dynamic provi- sioning [38, 41]. 6.1 Importance of Quantum Blockchain Therefore, preserving participant security and anonymity is challenging for conven- tional healthcare infrastructure [90]. Blockchain has developed into a medium that increases the healthcare scheme’s effectiveness while protecting all stakeholders’ privacy. In this research, motivated by their findings, the authors [91] integrate quantum computing into the standard encryption system after looking at various security techniques used to protect medical records. As medical knowledge devel- ops, using EMR systems to enhance the effectiveness and dependability of health- care has become commonplace. Sharing problems arise when electronic medical record systems are housed independently in medical and healthcare institutions [92]. Additionally, highly delicate EMRs are open to manipulation and exploitation, posing privacy and security threats. The most recent developments of healthcare 4.0 integrating the IoT components [93] and cloud services to monitor clinical opera- tions virtually have caught intellectuals’ attention from a philosophical perspective. 7 Limitations and Scope for Future Research When appropriately used, blockchain offers a reliable solution to problems with specific healthcare applications, such as real-time updates, security, accessibility, interoperability, integrity, privacy, sharing, and medical data. Blockchain, however, has constraints. Despite the benefits of using blockchain, substantial research D. K. Atal et al.
- 48. 37 obstacles existed before its development and deployment in the healthcare sector, necessitating its further study. 7.1 Challenges Related to Security Blockchain technology has several distinct security faults in its application. Problems with the conventional agreement process utilized to validate the transac- tions are frequently connected to blockchain security concerns. Some security flaws are the 51% attack, block withholding, eclipse, selfish mining, block discarding, difficulty in rising, transaction malleability, and DDoS attacks. The distributed blockchain technique’s agreement method cannot preclude these security risks. Because of the high resources needed, theoretical analysis cannot resolve the threats. The architecture of consensus methods is not particularly important for addressing these security issues. Due to the blockchain network’s public nature, blockchain application introduces another possible vulnerability, pseudo-anonymity, where transactions can be tracked to discover physical identities or other data. 7.2 Challenges Related to Privacy Users’ or patients’ privacy is not respected by the present secure communication architectures of EHR, as evidenced by noise in the data requester summary or the transfer system releasing all the information without the client’s consent. To provide individualized services, the requester needs exact patient data if the current EHR systems are blockchain-based. Proposing a system that leverages cryptography algorithms for the privacy of information on blockchain-based EHRs is the main problem in ensuring the confidentiality of patient data. Due to this characteristic, it is challenging to determine any specific user using his current account number. Defects in protecting patient privacy data should be addressed in any framework of a similar nature. Integrating blockchain-based systems within EHRs demands increased processing capability and takes time to accomplish every operation, so patients should submit their data efficiently. Second, multiple processes are neces- sary to authenticate the sincere patient before joining a new system to the network, which is what new clients require. 7.3 Challenges Related to Restrictions and Latency Integrating blockchain with applications in the medical field that respond to data and events in real time may be difficult because most blockchain technologies require much time to reach desired consensus and complete transactions that need The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 49. 38 to be completed. A blockchain needs time to process transactions when there is transaction latency. Contrarily, most conventional database infrastructures only need a few beats to approve an entry. Due to throughput limitations, EHRs and RPM in the IoT are built on a blockchain. Procedures often require enormous processing amounts of transactions per second, posing a potential difficulty for blockchains. 7.4 Challenges Related to Blockchain Size Blockchains grow more complex as more devices execute transactions, such as EHRs and IoT-RPM, necessitating the deployment of more powerful miners. The old IoMT devices cannot handle even the smallest blockchains because of resource limitations. Therefore, it is important to research other compression techniques in the blockchain, such as mini-blockchains. 7.5 Challenges Related to Computing Power Limitations Blockchain data from IoMT devices are frequently computationally constrained, making it possible that no encryption techniques will be required. Cryptosystems in devices with limited computational resources, such as memory and processing power, handle sensor and actuator protection in many health-related applications. In other words, they are met with current, safe public-key cryptography techniques. Most blockchains use public-key cryptosystems, which have efficiency and security difficulties, making it challenging to choose practical cryptography. Blockchain cryptosystems must be familiar with the threat posed by post-quantum computing and seek energy-efficient quantum-safe methods to maintain data security for pro- longed periods. 7.6 Challenges Related to Storage Restrictive systems that transmit information to the network may run into issues because a blockchain needs much storage to record complete network transactions. Blockchain can guarantee that the distributed, large-scale EHR data is neither altered, unforgeable, nor falsifiable, but it may suffer from the storage requirements of such data. D. K. Atal et al.
- 50. 39 7.7 Challenges Related to Scalability Blockchain’s infrastructure could need to handle computing requirements due to the issue of increased number of system users. Because the computing power of many smart devices or sensors is less than that of a typical computer, the problem becomes more challenging. 7.8 Challenges Related to Interoperability and Standardization Healthcare application interoperability needs to be improved by a lack of informa- tion collection, exchange, and analysis frameworks. The management of the current EHR systems relies on offline architecture and centralized local databases, whereas cloud-based blockchain technology is decentralized. As a result, if healthcare orga- nizations use blockchain technology, an effective electronic health record system that can promote communication and cooperation between the medical and scien- tific communities is a prerequisite. Many technical issues need to be resolved regarding the moved EHR information. Data processing in the healthcare ecosystem is primarily manual in large hospi- tals, huge drug industries, and pharmacy shops. The external parties that affect an organization’s operations are excluded from organizational information processing theory. For instance, the functions of a hospital are directly impacted by the health insurance company, and these activities also affect the pharmaceutical industry, which impacts the patient. Building a quantum computing ecosystem requires a fundamental computing infrastructure and operations volume. The future study may consider a sizable sample of well-known actors from the hospital, pharmaceutical, and health insurance sectors to grasp the geographic advancements. Although the findings do not specifically mention the importance of machine learning and artifi- cial intelligence, it is clear how beneficial quantum computing might be for the medical sector. Therefore, future research can examine how artificial intelligence and machine learning enable quantum computing in the medical industry. Future research should also account for how quantum computing affects the healthcare sector in a post-COVID era and how it is essential in bringing together the various players, including insurance agents, hospitals, pharmaceutical firms, payers, and patients. For a particular group or kind of subindustry, it is possible to identify standard quantum computing techniques, for instance, the size, industry, and type of data that a hospital, pharmaceutical, or health insurance company pro- duces daily. The Intersection of Blockchain Technology and the Quantum Era for Sustainable…
- 51. 40 8 Conclusion Blockchain technology in healthcare has been introduced to enhance extensive data analysis, administration, and security. Considering the sensitivity and real-time pro- cessing requirement of patients’ clinical data, the agreement algorithm, working medium, and blockchain type need to be focused on ensuring proper blockchain access to safeguard the patient’s personal information. It has been observed that while implementing blockchain and IoHT, healthcare executives are accelerating the adoption process of the leading technologies, and now it is the time to value artificial intelligence, which collects and extracts insights from massive amounts of data by identifying patterns and correlations. In addition to artificial intelligence, hybrid clouds are suggested as a solid blockchain and IoHT foundation. These new AI-based hybrid clouds at client sites deliver highly scalable cloud services and applications while maintaining medical information behind the firewalls to meet organizational and regulatory requirements. This technology enables users to access large amounts of data at any time by storing it orderly and securely. It is possible to hide data in a quantum blockchain while ensuring its security and accessibility. Quantum blockchain technology made it feasible to process user data faster while keeping its virtue by utilizing both quantum computing and blockchain technologies. References 1. Farouk, A., Alahmadi, A., Ghose, S., Mashatan, A. (2020). Blockchain platform for indus- trial healthcare: Vision and future opportunities. In Computer communications (Vol. 154, pp. 223–235). Elsevier B.V. https://doi.org/10.1016/j.comcom.2020.02.058 2. Ivanteev, A., Ilin, I., Iliashenko, V. (2020). Possibilities of blockchain technology applica- tion for the health care system. In IOP conference series: Materials science and engineering (Vol. 940(1)). IOP Publishing. https://doi.org/10.1088/1757-899X/940/1/012008 3. Liang, X., Zhao, J., Shetty, S., Liu, J., Li, D. (2017). Integrating blockchain for data shar- ing and collaboration in mobile healthcare applications. In 2017 Presented at: Personal, indoor, Mobile radio communications (PIMRC), IEEE 28th annual international symposium; Montreal (pp. 1–5). 4. Arora, S., Lamba, D., V. (2020). A study of technologies to further research in health care data security in medical report using block chain. International Journal of Advanced Engineering Research and Science, 7(6), 248–252. https://doi.org/10.22161/ijaers.76.31 5. Christidis, K., Devetsikiotis, M. (2016). Blockchains and smart contracts for the Internet of Things. IEEE Access, 4, 2292–2303. 6. Liu, D., Alahmadi, A., Ni, J., Lin, X., Shen, X. (2019). Anonymous reputation system for IIoT-enabled retail marketing atop PoS blockchain. IEEE Transactions on Industrial Informatics, 15(6), 3527–3537. 7. Ali, A., Rahouti, M., Latif, S., Kanhere, S., Singh, J., Janjua, U., Crowcroft, J. (2019). Blockchain and the future of the internet: A comprehensive review. arXiv preprint arXiv: 1904.00733. 8. Islam, S. R., Kwak, D., Kabir, M. H., Hossain, M., Kwak, K. S. (2015). The Internet of Things for health care: A comprehensive survey. IEEE Access, 3, 678–708. D. K. Atal et al.
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- 56. A CHAPTER V THE FATAL DROPS T home, the life in the bungalow and at the farm followed its usual routine as it had before the departure of Tarzan. Korak, sometimes on foot and sometimes on horseback, followed the activities of the farm hands and the herders, sometimes alone, but more often in company with the white foreman, Jervis, and often, especially when they rode, Jane accompanied them. The golden lion Korak exercised upon a leash, since he was not at all confident of his powers of control over the beast, and feared lest, in the absence of his master, Jad-bal-ja might take to the forest and revert to his natural savage state. Such a lion, abroad in the jungle, would be a distinct menace to human life, for Jad-bal-ja, reared among men, lacked that natural timidity of men that is so marked a trait of all wild beasts. Trained as he had been to make his kill at the throat of a human effigy, it required no considerable powers of imagination upon the part of Korak to visualize what might occur should the golden lion, loosed from all restraint, be thrown upon his own resources in the surrounding jungle. It was during the first week of Tarzan’s absence that a runner from Nairobi brought a cable message to Lady Greystoke, announcing the serious illness of her father in London. Mother and son discussed the situation. It would be five or six weeks before Tarzan could return, even if they sent a runner after him, and, were Jane to await him, there would be little likelihood of her reaching her father in time. Even should she depart at once, there seemed only a faint hope that she would arrive early enough to see him alive. It was decided, therefore, that she should set out immediately, Korak accompanying her as far as Nairobi, and then returning to the ranch and resuming its general supervision until his father’s return. It is a long trek from the Greystoke estate to Nairobi, and Korak had not yet returned when, about three weeks after Tarzan’s
- 57. departure, a black, whose duty it was to feed and care for Jad-bal- ja, carelessly left the door of the cage unfastened while he was cleaning it. The golden lion paced back and forth while the black wielded his broom within the cage. They were old friends, and the Waziri felt no fear of the great lion, with the result that his back was as often turned to him as not. The black was working in the far corner of the cage when Jad-bal-ja paused a moment at the door at the opposite end. The beast saw that the gate hung slightly ajar upon its hinges. Silently he raised a great padded paw and inserted it in the opening—a slight pull and the gate swung in. Instantly the golden lion inserted his snout in the widened aperture, and as he swung the barrier aside the horrified black looked up to see his charge drop softly to the ground outside. “Stop, Jad-bal-ja! Stop!” screamed the frightened black, leaping after him. But the golden lion only increased his pace, and leaping the fence, loped off in the direction of the forest. The black pursued him with brandishing broom, emitting loud yells that brought the inmates of the Waziri huts into the open, where they joined their fellow in pursuit of the lion. Across the rolling plains they followed him, but as well have sought to snare the elusive will-o’-the-wisp as this swift and wary fugitive, who heeded neither their blandishments nor their threats. And so it was that they saw the golden lion disappear into the primeval forest and, though they searched diligently until almost dark, they were forced at length to give up their quest and return crestfallen to the farm. “Ah,” cried the unhappy black, who had been responsible for the escape of Jad-bal-ja, “what will the Big Bwana say to me, what will he do to me when he finds that I have permitted the golden lion to get away!” “You will be banished from the bungalow for a long time, Keewazi,” old Muviro assured him. “And doubtless you will be sent to the grazing ground far to the east to guard the herd there, where you will have plenty of lions for company, though they will not be as friendly as was Jad-bal-ja. It is not half what you deserve, and were the heart of the Big Bwana not filled with love for his black children
- 58. —were he like other white Bwanas old Muviro has seen—you would be lashed until you could not stand, perhaps until you died.” “I am a man,” replied Keewazi. “I am a warrior and a Waziri. Whatever punishment the Big Bwana inflicts I will accept as a man should.” It was that same night that Tarzan approached the camp-fires of the strange party he had been tracking. Unseen by them, he halted in the foliage of a tree directly in the center of their camp, which was surrounded by an enormous thorn boma, and brilliantly lighted by numerous fires which blacks were diligently feeding with branches from an enormous pile of firewood that they had evidently gathered earlier in the day for this purpose. Near the center of the camp were several tents, and before one, in the light of a fire, sat four white men. Two of them were great, bull-necked, red-faced fellows, apparently Englishmen of the lower class, the third appeared to be a short, fat, German Jew, while the fourth was a tall, slender, handsome fellow, with dark, wavy brown hair and regular features. He and the German were most meticulously garbed for Central African traveling, after the highly idealized standard of motion pictures, in fact either one of them might have stepped directly from a screening of the latest jungle thriller. The young man was evidently not of English descent and Tarzan mentally cataloged him, almost immediately, as a Slav. Shortly after Tarzan’s arrival this one arose and entered one of the nearby tents, from which Tarzan immediately heard the sound of voices in low conversation. He could not distinguish the words, but the tones of one seemed quite distinctly feminine. The three remaining at the fire were carrying on a desultory conversation, when suddenly from near at hand beyond the boma wall, a lion’s roar broke the silence of the jungle. With a startled shriek the Jew leaped to his feet, so suddenly that he cleared the ground a good foot, and then, stepping backward, he lost his balance, tripped over his camp-stool, and sprawled upon his back. “My Gord, Adolph!” roared one of his companions. “If you do that again, damn me if I don’t break your neck. ’Ere we are, and that’s that.”
- 59. “Blime if ’e aint worse’n a bloomin’ lion,” growled the other. The Jew crawled to his feet. “Mein Gott!” he cried, his voice quavering, “I t’ought sure he vas coming over the fence. S’elp me if I ever get out of diss, neffer again—not for all der gold in Africa vould I go t’rough vat I haf been t’rough dese past t’ree mont’s. Oi! Oi! ven I t’ink of it, Oi! Oi! Lions, und leopards, und rhinoceroses und hippopotamuses, Oi! Oi!” His companions laughed. “Dick and I tells you right along from the beginning that you ’adn’t oughter come into the interior,” said one of them. “But for vy I buy all dese clo’s?” wailed the German. “Mein Gott, dis suit, it stands me tventy guineas, vot I stand in. Ach, had I know somet’ing, vun guinea vould have bought me my whole wardrobe— tventy guineas for dis und no vun to see it but niggers und lions.” “And you look like ’ell in it, besides,” commented one of his friends. “Und look at it, it’s all dirty and torn. How should I know it I spoil dis suit? Mit mine own eyes I see it at der Princess Teayter, how der hero spend t’ree mont’s in Africa hunting lions und killing cannibals, und ven he comes ouid he hasn’t even got a grease spot on his pants—how should I know it Africa was so dirty und full of thorns?” It was at this point that Tarzan of the Apes elected to drop quietly into the circle of firelight before them. The two Englishmen leaped to their feet, quite evidently startled, and the Jew turned and took a half step as though in flight, but immediately his eyes rested upon the ape-man he halted, a look of relief supplanting that of terror which had overspread his countenance, as Tarzan had dropped upon them apparently from the heavens. “Mein Gott, Esteban,” shrilled the German, “vy you come back so soon, and for vy you come back like dot, sudden—don’t you suppose ve got nerves?” Tarzan was angry, angry at these raw intruders, who dared enter without his permission, the wide domain in which he kept peace and order. When Tarzan was angry there flamed upon his forehead the scar that Bolgani, the gorilla, had placed there upon that long-gone day when the boy Tarzan had met the great beast in mortal combat,
- 60. and first learned the true value of his father’s hunting knife—the knife that had placed him, the comparatively weak little Tarmangani, upon an even footing with the great beasts of the jungle. His gray eyes were narrowed, his voice came cold and level as he addressed them. “Who are you,” he demanded, “who dare thus invade the country of the Waziri, the land of Tarzan, without permission from the Lord of the Jungle?” “Where do you get that stuff, Esteban,” demanded one of the Englishmen, “and wat in ’ell are you doin’ back ’ere alone and so soon? Where are your porters, where is the bloomin’ gold?” The ape-man eyed the speaker in silence for a moment. “I am Tarzan of the Apes,” he said. “I do not know what you are talking about. I only, know that I come in search of him who slew Gobu, the great ape; him who slew Bara, the deer, without my permission.” “Oh, ’ell,” exploded the other Englishman, “stow the guff, Esteban —if you’re tryin’ for to be funny we don’t see the joke, ’ere we are, and that’s that.” Inside the tent, which the fourth white man had entered while Tarzan was watching the camp from his hiding place in the tree above, a woman, evidently suddenly stirred by terror, touched the arm of her companion frantically, and pointed toward the tall, almost naked figure of the ape-man as he stood revealed in the full light of the beast fires. “God, Carl,” she whispered, in trembling tones, “look!” “What’s wrong, Flora?” inquired her companion. “I see only Esteban.” “It is not Esteban,” hissed the girl. “It is Lord Greystoke himself— it is Tarzan of the Apes!” “You are mad, Flora,” replied the man, “it cannot be he.” “It is he, though,” she insisted. “Do you suppose that I do not know him? Did I not work in his town house for years? Did I not see him nearly every day? Do you suppose that I do not know Tarzan of the Apes? Look at that red scar flaming on his forehead—I have heard the story of that scar and I have seen it burn scarlet when he was aroused to anger. It is scarlet now, and Tarzan of the Apes is angry.”
- 61. “Well, suppose it is Tarzan of the Apes, what can he do?” “You do not know him,” replied the girl. “You do not guess the tremendous power he wields here—the power of life and death over man and beast. If he knew our mission here not one of us would ever reach the coast alive. The very fact that he is here now makes me believe that he may have discovered our purpose, and if he has, God help us—unless—unless——” “Unless what?” demanded the man. The girl was silent in thought for a moment. “There is only one way,” she said finally. “We dare not kill him. His savage blacks would learn of it, and no power on earth could save us then. There is a way, though, if we act quickly.” She turned and searched for a moment in one of her bags, and presently she handed the man a small bottle, containing liquid. “Go out and talk to him,” she said, “make friends with him. Lie to him. Tell him anything. Promise anything. But get on friendly enough terms with him so that you can offer him coffee. He does not drink wine or anything with alcohol in it, but I know that he likes coffee. I have often served it to him in his room late at night upon his return from the theater or a ball. Get him to drink coffee and then you will know what to do with this.” And she indicated the bottle which the man still held in his hand. Kraski nodded. “I understand,” he said, and, turning, left the tent. He had taken but a step when the girl recalled him. “Do not let him see me. Do not let him guess that I am here or that you know me.” The man nodded and left her. Approaching the tense figures before the fire he greeted Tarzan with a pleasant smile and a cheery word. “Welcome,” he said, “we are always glad to see a stranger in our camp. Sit down. Hand the gentleman a stool, John,” he said to Peebles. The ape-man eyed Kraski as he had eyed the others. There was no answering friendly light in his eyes responding to the Russian’s greeting.
- 62. “I have been trying to find out what your party is doing here,” he said sharply to the Russian, “but they still insist that I am someone whom I am not. They are either fools or knaves, and I intend to find out which, and deal with them accordingly.” “Come, come,” cried Kraski, soothingly. “There must be some mistake, I am sure. But tell me, who are you?” “I am Tarzan of the Apes,” replied the ape-man. “No hunters enter this part of Africa without my permission. That fact is so well known that there is no chance of your having passed the coast without having been so advised. I seek an explanation, and that quickly.” “Ah, you are Tarzan of the Apes,” exclaimed Kraski. “Fortunate indeed are we, for now may we be set straight upon our way, and escape from our frightful dilemma is assured. We are lost, sir, inextricably lost, due to the ignorance or knavery of our guide, who deserted us several weeks ago. Surely we knew of you; who does not know of Tarzan of the Apes? But it was not our intention to cross the boundaries of your territory. We were searching farther south for specimens of the fauna of the district, which our good friend and employer, here, Mr. Adolph Bluber, is collecting at great expense for presentation to a museum in his home city in America. Now I am sure that you can tell us where we are and direct us upon our proper course.” Peebles, Throck, and Bluber stood fascinated by Kraski’s glib lies, but it was the German Jew who first rose to the occasion. Too thick were the skulls of the English pugs to grasp quickly the clever ruse of the Russian. “Vy yes,” said the oily Bluber, rubbing his palms together, “dot iss it, yust vot I vas going to tell you.” Tarzan turned sharply upon him. “Then what was all this talk about Esteban?” he asked. “Was it not by that name that these others addressed me?” “Ah,” cried Bluber, “John will haf his leetle joke. He iss ignorant of Africa; he has neffer been here before. He t’ought perhaps dat you vere a native. John he calls all der natives Esteban, und he has great jokes by himself mit dem, because he knows dey cannot onderstand
- 63. vot he says. Hey John, iss it not so, vot it iss I say?” But the shrewd Bluber did not wait for John to reply. “You see,” he went on, “ve are lost, und you take us ouid mit dis jungle, ve pay you anyt’ing—you name your own price.” The ape-man only half believed him, yet he was somewhat mollified by their evidently friendly intentions. Perhaps after all they were telling him a half-truth and had, really, wandered into his territory unwittingly. That, however, he would find out definitely from their native carriers, from whom his own Waziri would wean the truth. But the matter of his having been mistaken for Esteban still piqued his curiosity, also he was still desirous of learning the identity of the slayer of Gobu, the great ape. “Please sit down,” urged Kraski. “We were about to have coffee and we should be delighted to have you join us. We meant no wrong in coming here, and I can assure you that we will gladly and willingly make full amends to you, or to whomever else we may have unintentionally wronged.” To take coffee with these men would do no harm. Perhaps he had wronged them, but however that might be a cup of their coffee would place no great obligation upon him. Flora had been right in her assertion that if Tarzan of the Apes had any weakness whatsoever it was for an occasional cup of black coffee late at night. He did not accept the proffered camp-stool, but squatted, ape- fashion, before them, the flickering light of the beast fires playing upon his bronzed hide and bringing into relief the gracefully contoured muscles of his godlike frame. Not as the muscles of the blacksmith or the professional strong man were the muscles of Tarzan of the Apes, but rather those of Mercury or Apollo, so symmetrically balanced were their proportions, suggesting only the great strength that lay in them. Trained to speed and agility were they as well as to strength, and thus, clothing as they did his giant frame, they imparted to him the appearance of a demi-god. Throck, Peebles, and Bluber sat watching him in spellbound fascination, while Kraski walked over to the cook fire to arrange for the coffee. The two Englishmen were as yet only half awakened to the fact that they had mistaken this newcomer for another, and as it
- 64. was, Peebles still scratched his head and grumbled to himself in inarticulate half-denial of Kraski’s assumption of the new identity of Tarzan. Bluber was inwardly terror-stricken. His keener intelligence had quickly grasped the truth of Kraski’s recognition of the man for what he was rather than for what Peebles and Throck thought him to be, and, as Bluber knew nothing of Flora’s plan, he was in quite a state of funk as he tried to visualize the outcome of Tarzan’s discovery of them at the very threshold of Opar. He did not realize, as did Flora, that their very lives were in danger—that it was Tarzan of the Apes, a beast of the jungle, with whom they had to deal, and not John Clayton, Lord Greystoke, an English peer. Rather was Bluber considering the two thousand pounds that they stood to lose through this deplorable termination of their expedition, for he was sufficiently familiar with the reputation of the ape-man to know that they would never be permitted to take with them the gold that Esteban was very likely, at this moment, pilfering from the vaults of Opar. Really Bluber was almost upon the verge of tears when Kraski returned with the coffee, which he brought himself. From the dark shadows of the tent’s interior Flora Hawkes looked nervously out upon the scene before her. She was terrified at the possibility of discovery by her former employer, for she had been a maid in the Greystokes’ London town house as well as at the African bungalow and knew that Lord Greystoke would recognize her instantly should he chance to see her. She entertained for him, now, in his jungle haunts, a fear that was possibly greater than Tarzan’s true character warranted, but none the less real was it to the girl whose guilty conscience conjured all sorts of possible punishments for her disloyalty to those who had always treated her with uniform kindliness and consideration. Constant dreaming of the fabulous wealth of the treasure vaults of Opar, concerning which she had heard so much in detail from the conversations of the Greystokes, had aroused within her naturally crafty and unscrupulous mind a desire for possession, and in consequence thereof she had slowly visualized a scheme whereby she might loot the treasure vaults of a sufficient number of the golden ingots to make her independently wealthy for life. The entire
- 65. plan had been hers. She had at first interested Kraski, who had in turn enlisted the coöperation of the two Englishmen and Bluber, and these four had raised the necessary money to defray the cost of the expedition. It had been Flora who had searched for a type of man who might successfully impersonate Tarzan in his own jungle, and she had found Esteban Miranda, a handsome, powerful, and unscrupulous Spaniard, whose histrionic ability aided by the art of make-up, of which he was a past master, permitted him to almost faultlessly impersonate the character they desired him to portray, in so far, as least, as outward appearances were concerned. The Spaniard was not only powerful and active, but physically courageous as well, and since he had shaved his beard and donned the jungle habiliments of a Tarzan, he had lost no opportunity for emulating the ape-man in every way that lay within his ability. Of jungle craft he had none of course, and personal combats with the more savage jungle beasts caution prompted him to eschew, but he hunted the lesser game with spear and with arrow and practiced continually with the grass rope that was a part of his make-up. And now Flora Hawkes saw all her well-laid plans upon the verge of destruction. She trembled as she watched the men before the fire, for her fear of Tarzan was very real, and then she became tense with nervous anticipation as she saw Kraski approaching the group with the coffee pot in one hand and cups in the other. Kraski set the pot and the cups upon the ground a little in the rear of Tarzan, and, as he filled the latter, she saw him pour a portion of the contents of the bottle she had given him into one of the cups. A cold sweat broke out upon her forehead as Kraski lifted this cup and offered it to the ape-man. Would he take it? Would he suspect? If he did suspect what horrible punishment would be meted to them all for their temerity? She saw Kraski hand another cup to Peebles, Throck, and Bluber, then return to the circle with the last one for himself. As the Russian raised it before his face and bowed politely to the ape- man, she saw the five men drink. The reaction which ensued left her weak and spent. Turning, she collapsed upon her cot, and lay there trembling, her face buried in her arm. And, outside, Tarzan of the Apes drained his cup to the last drop.
- 67. D CHAPTER VI DEATH STEALS BEHIND URING the afternoon of the day that Tarzan discovered the camp of the conspirators, a watcher upon the crumbling outer wall of the ruined city of Opar descried a party of men moving downward into the valley from the summit of the encircling cliff. Tarzan, Jane Clayton, and their black Waziri were the only strangers that the denizens of Opar had ever seen within their valley during the lifetime of the oldest among them, and only in half-forgotten legends of a by-gone past was there any suggestion that strangers other than these had ever visited Opar. Yet from time immemorial a guard had always remained upon the summit of the outer wall. Now a single knurled and crippled man-like creature was all that recalled the numerous, lithe warriors of lost Atlantis. For down through the long ages the race had deteriorated and finally, through occasional mating with the great apes, the men had become the beast-like things of modern Opar. Strange and inexplicable had been the providence of nature that had confined this deterioration almost solely to the males, leaving the females straight, well-formed, often of comely and even beautiful features, a condition that might be largely attributable to the fact that female infants possessing ape- like characteristics were immediately destroyed, while, on the other hand, boy babies who possessed purely human attributes were also done away with. Typical indeed of the male inhabitants of Opar was the lone watcher upon the outer city wall, a short, stocky man with matted hair and beard, his tangled locks growing low upon a low, receding forehead; small, close-set eyes and fang-like teeth bore evidence of his simian ancestry, as did his short, crooked legs and long, muscular ape-like arms, all scantily hair-covered as was his torso. As his wicked, blood-rimmed eyes watched the progress of the party across the valley toward Opar, evidences of his growing
- 68. excitement were manifested in the increased rapidity of his breathing, and low, almost inaudible growls that issued from his throat. The strangers were too far distant to be recognizable only as human beings, and their number to be roughly approximated as between two and three score. Having assured himself of these two facts the watcher descended from the outer wall, crossed the space between it and the inner wall, through which he passed, and at a rapid trot crossed the broad avenue beyond and disappeared within the crumbling but still magnificent temple beyond. Cadj, the High Priest of Opar, squatted beneath the shade of the giant trees which now overgrew what had once been one of the gardens of the ancient temple. With him were a dozen members of the lesser priesthood, the intimate cronies of the High Priest, who were startled by the sudden advent of one of the inferior members of the clan of Opar. The fellow hurried breathlessly to Cadj. “Cadj,” he cried, “strange men descend upon Opar! From the northwest they have come into the valley from beyond the barrier cliffs—fifty of them at least, perhaps half again that number. I saw them as I watched from the summit of the outer wall, but further than they are men I cannot say, for they are still a great distance away. Not since the great Tarmangani came among us last have there been strangers within Opar.” “It has been many moons since the great Tarmangani who called himself Tarzan of the Apes was among us,” said Cadj. “He promised us to return before the rain to see that no harm had befallen La, but he did not come back and La has always insisted that he is dead. Have you told any other of what you have seen?” he demanded, turning suddenly upon the messenger. “No,” replied the latter. “Good!” exclaimed Cadj. “Come, we will all go to the outer wall and see who it is who dares enter forbidden Opar, and let no one breathe a word of what Blagh has told us until I give permission.” “The word of Cadj is law until La speaks,” murmured one of the priests. Cadj turned a scowling face upon the speaker. “I am High Priest of Opar,” he growled. “Who dares disobey me?”
- 69. “But La is High Priestess,” said one, “and the High Priestess is the queen of Opar.” “But the High Priest can offer whom he will as sacrifice in the Chamber of the Dead or to the Flaming God,” Cadj reminded the other meaningly. “We shall keep silence, Cadj,” replied the priest, cringing. “Good!” growled the High Priest and led the way from the garden through the corridors of the temple back toward the outer wall of Opar. From here they watched the approaching party that was in plain view of them, far out across the valley. The watchers conversed in low gutturals in the language of the great apes, interspersed with which were occasional words and phrases of a strange tongue that were doubtless corrupted forms of the ancient language of Atlantis handed down through countless generations from their human progenitors—that now extinct race whose cities and civilization lie buried deep beneath the tossing waves of the Atlantic, and whose adventurous spirit had, in remote ages, caused them to penetrate into the heart of Africa in search of gold and to build there, in duplication of their far home cities, the magnificent city of Opar. As Cadj and his followers watched from beneath shaggy brows the strangers plodding laboriously beneath the now declining equatorial sun across the rocky, barren valley, a gray little monkey eyed them from amidst the foliage of one of the giant trees that had forced its way through the pavement of the ancient avenue behind them. A solemn, sad-faced little monkey it was, but like all his kind overcome by curiosity, and finally to such an extent that his fear of the fierce males of Opar was so considerably overcome that he at last swung lightly from the tree to the pavement, made his way through the inner wall and up the inside of the outer wall to a position in their rear where he could hide behind one of the massive granite blocks of the crumbling wall in comparative safety from detection, the while he might overhear the conversation of the Oparians, all of which that was carried on in the language of the great apes he could understand perfectly.
- 70. The afternoon was drawing to a close before the slowly moving company approaching Opar was close enough for individuals to be recognizable in any way, and then presently one of the younger priests exclaimed excitedly: “It is he, Cadj. It is the great Tarmangani who calls himself Tarzan of the Apes. I can see him plainly; the others are all black men. He is urging them on, prodding them with his spear. They act as though they were afraid and very tired, but he is forcing them forward.” “You are sure,” demanded Cadj, “you are sure that it is Tarzan of the Apes?” “I am positive,” replied the speaker, and then another of the priests joined his assurances to that of his fellow. At last they were close enough so that Cadj himself, whose eyesight was not as good as that of the younger members of the company, realized that it was indeed Tarzan of the Apes who was returning to Opar. The High Priest scowled angrily in thought. Suddenly he turned upon the others. “He must not come,” he cried; “he must not enter Opar. Hasten and fetch a hundred fighting men. We will meet them as they come through the outer wall and slay them one by one.” “But La,” cried he who had aroused Cadj’s anger in the garden, “I distinctly recall that La offered the friendship of Opar to Tarzan of the Apes upon that time, many moons ago, that he saved her from the tusks of infuriated Tantor.” “Silence,” growled Cadj, “he shall not enter; we shall slay them all, though we need not know their identity until it is too late. Do you understand? And know, too, that whosoever attempts to thwart my purpose shall die—and he die not as a sacrifice, he shall die at my hands, but die he shall. You hear me?” And he pointed an unclean finger at the trembling priest. Manu, the monkey, hearing all this, was almost bursting with excitement. He knew Tarzan of the Apes—as all the migratory monkeys the length and breadth of Africa knew him—he knew him for a friend and protector. To Manu the males of Opar were neither beast, nor man, nor friend. He knew them as cruel and surly
- 71. creatures who ate the flesh of his kind, and he hated them accordingly. He was therefore greatly exercised at the plot that he had heard discussed which was aimed at the life of the great Tarmangani. He scratched his little gray head, and the root of his tail, and his belly, as he attempted to mentally digest what he had heard, and bring forth from the dim recesses of his little brain a plan to foil the priests and save Tarzan of the Apes. He made grotesque grimaces that were aimed at the unsuspecting Cadj and his followers, but which failed to perturb them, possibly because a huge granite block hid the little monkey from them. This was quite the most momentous thing that had occurred in the life of Manu. He wanted to jump up and down and dance and screech and jabber—to scold and threaten the hated Oparians, but something told him that nothing would be gained by this, other than, perhaps, to launch in his direction a shower of granite missiles, which the priests knew only too well how to throw with accuracy. Now Manu is not a deep thinker, but upon this occasion he quite outdid himself, and managed to concentrate his mind upon the thing at hand rather than permit its being distracted by each falling leaf or buzzing insect. He even permitted a succulent caterpillar to crawl within his reach and out again with impunity. Just before darkness fell, Cadj saw a little gray monkey disappear over the summit of the outer wall fifty paces from where he crouched with his fellows, waiting for the coming of the fighting men. But so numerous were the monkeys about the ruins of Opar that the occurrence left Cadj’s mind almost as quickly as the monkey disappeared from his view, and in the gathering gloom he did not see the little gray figure scampering off across the valley toward the band of intruders who now appeared to have stopped to rest at the foot of a large kopje that stood alone out in the valley, about a mile from the city. Little Manu was very much afraid out there alone in the growing dusk, and he scampered very fast with his tail bowed up and out behind him. All the time he cast affrighted glances to the right and left. The moment he reached the kopje he scampered up its face as fast as he could. It was really a huge, precipitous granite rock with
- 72. almost perpendicular sides, but sufficiently weather-worn to make its ascent easy to little Manu. He paused a moment at the summit to get his breath and still the beatings of his frightened little heart, and then he made his way around to a point where he could look down upon the party beneath. There, indeed, was the great Tarmangani Tarzan, and with him were some fifty Gomangani. The latter were splicing together a number of long, straight poles, which they had laid upon the ground in two parallel lines. Across these two, at intervals of a foot or more, they were lashing smaller straight branches about eighteen inches in length, the whole forming a crude but substantial ladder. The purpose of all this Manu, of course, did not understand, nor did he know that it had been evolved from the fertile brain of Flora Hawkes as a means of scaling the precipitous kopje, at the summit of which lay the outer entrance to the treasure vaults of Opar. Nor did Manu know that the party had no intention of entering the city of Opar and were therefore in no danger of becoming victims of Cadj’s hidden assassins. To him, the danger to Tarzan of the Apes was very real, and so, having regained his breath, he lost no time in delivering his warning to the friend of his people. “Tarzan,” he cried, in the language that was common to both. The white man and the blacks looked up at the sound of his chattering voice. “It is Manu, Tarzan,” continued the little monkey, “who has come to tell you not to go to Opar. Cadj and his people await within the outer wall to slay you.” The blacks, having discovered that the author of the disturbance was nothing but a little gray monkey, returned immediately to their work, while the white man similarly ignored his words of warning. Manu was not surprised at the lack of interest displayed by the blacks, for he knew that they did not understand his language, but he could not comprehend why Tarzan failed to pay any attention whatsoever to him. Again and again he called Tarzan by name. Again and again he shrieked his warning to the ape-man, but without eliciting any reply or any information that the great Tarmangani had either heard or understood him. Manu was
- 73. mystified. What had occurred to render Tarzan of the Apes so indifferent to the warnings of his old friend? At last the little monkey gave it up and looked longingly back in the direction of the trees within the walled city of Opar. It was now very dark and he trembled at the thought of recrossing the valley, where he knew enemies might prowl by night. He scratched his head and he hugged his knees, then sat there whimpering, a very forlorn and unhappy little ball of a monkey. But however uncomfortable he was upon the high kopje, he was comparatively safe, and so he decided to remain there during the night rather than venture the terrifying return trip through the darkness. Thus it was that he saw the ladder completed and erected against the side of the kopje; and when the moon rose at last and lighted the scene, he saw Tarzan of the Apes urging his men to mount the ladder. He had never seen Tarzan thus rough and cruel with the blacks who accompanied him. Manu knew how ferocious the great Tarmangani could be with an enemy, whether man or beast, but he had never seen him accord such treatment to the blacks who were his friends. One by one and with evident reluctance the blacks ascended the ladder, continually urged forward to greater speed by the sharp spear of the white man; when they had all ascended Tarzan followed, and Manu saw them disappear apparently into the heart of the great rock. It was only a short time later that they commenced to reappear, and now each was burdened by two heavy objects which appeared to Manu to be very similar to some of the smaller stone blocks that had been used in the construction of the buildings in Opar. He saw them take the blocks to the edge of the kopje and cast them over to the ground beneath, and when the last of the blacks had emerged with his load and cast it to the valley below, one by one the party descended the ladder to the foot of the kopje. But this time Tarzan of the Apes went first. Then they lowered the ladder and took it apart and laid its pieces close to the foot of the cliff, after which they took up the blocks which they had brought from the heart of the kopje, and following Tarzan, who set out in the lead, they commenced to retrace their steps toward the rim of the valley.
- 74. Manu would have been very much mystified had he been a man, but being only a monkey he saw only what he saw without attempting to reason very much about it. He knew that the ways of men were peculiar, and oftentimes unaccountable. For example, the Gomangani who could not travel through the jungle and the forest with the ease of any other of the animals which frequented them, added to their difficulties by loading themselves down with additional weights in the form of metal anklets and armlets, with necklaces and girdles, and with skins of animals, which did nothing more than impede their progress and render life much more complicated than that which the untrammeled beasts enjoyed. Manu, whenever he gave the matter a thought, congratulated himself that he was not a man—he pitied the foolish, unreasonable creatures. Manu must have slept. He thought that he had only closed his eyes a moment, but when he opened them the rosy light of dawn had overspread the desolate valley. Just disappearing over the cliffs to the northeast he could see the last of Tarzan’s party commencing the descent of the barrier, then Manu turned his face toward Opar and prepared to descend from the kopje, and scamper back to the safety of his trees within the walls of Opar. But first he would reconnoiter—Sheeta, the panther, might be still abroad, and so he scampered around the edge of the kopje to a point where he could see the entire valley floor between himself and Opar. And there it was that he saw again that which filled him with greatest excitement. For, debouching from the ruined outer wall of Opar was a large company of Opar’s frightful men—fully a hundred of them Manu could have counted had Manu been able to count. They seemed to be coming toward the kopje, and he sat and watched them as they approached, deciding to defer his return to the city until after the path was cleared of hated Oparians. It occurred to him that they were coming after him, for the egotism of the lower animals is inordinate. Because he was a monkey, the idea did not seem at all ridiculous and so he hid behind a jutting rock, with only one little, bright eye exposed to the enemy. He saw them
- 75. come closer and he grew very much excited, though he was not at all afraid, for he knew that if they ascended one side of the kopje he could descend the other and be half-way to Opar before they could possibly locate him again. On and on they came, but they did not stop at the kopje—as a matter of fact they did not come very close to it, but continued on beyond it. Then it was that the truth of the matter flashed into the little brain of the monkey—Cadj and his people were pursuing Tarzan of the Apes to slay him. If Manu had been offended by Tarzan’s indifference to him upon the night before, he had evidently forgotten it, for now he was quite as excited about the danger which he saw menace the ape-man as he had been upon the afternoon previous. At first he thought of running ahead, and again warning Tarzan, but he feared to venture so far from the trees of Opar, even if the thought of having to pass the hated Oparians had not been sufficient to deter him from carrying out this plan. For a few minutes he sat watching them, until they had all passed the kopje, and then it became quite clear to him that they were heading directly for the spot at which the last of Tarzan’s party had disappeared from the valley—there could be no doubt that they were in pursuit of the ape- man. Manu scanned the valley once more toward Opar. There was nothing in sight to deter him from an attempted return, and so, with the agility of his kind, he scampered down the vertical face of the kopje and was off at great speed toward the city’s wall. Just when he formulated the plan that he eventually followed it is difficult to say. Perhaps he thought it all out as he sat upon the kopje, watching Cadj and his people upon the trail of the ape-man, or perhaps it occurred to him while he was scampering across the barren waste toward Opar. It may just have popped into his mind from a clear sky after he had regained the leafy sanctuary of his own trees. Be that, however as it may, the fact remains, that as La, High Priestess and princess of Opar, in company with several of her priestesses, was bathing in a pool in one of the temple gardens, she was startled by the screaming of a monkey, swinging frantically by his tail from the branch of a great tree which overspread the pool—it was a little gray
- 76. monkey with a face so wise and serious that one might easily have imagined that the fate of nations lay constantly upon the shoulders of its owner. “La, La,” it screamed, “they have gone to kill Tarzan. They have gone to kill Tarzan.” At the sound of that name La was instantly all attention. Standing waist deep in the pool she looked up at the little monkey questioningly. “What do you mean, Manu?” she asked. “It has been many moons since Tarzan was at Opar. He is not here now. What are you talking about?” “I saw him,” screamed Manu, “I saw him last night with many Gomangani. He came to the great rock that lies in the valley before Opar; with all his men he climbed to the top of it, went into the heart of it, and came out with stones which they threw down into the valley. Afterward they descended from the rock, and picked up the stones again and left the valley—there,” and Manu pointed toward the northeast with one of his hairy little fingers. “How do you know it was Tarzan of the Apes?” asked La. “Does Manu not know his cousin and his friend?” demanded the monkey. “With my eyes I saw him—it was Tarzan of the Apes.” La of Opar puckered her brows in thought. Deep in her heart smoldered the fires of her great love for Tarzan. Fires that had been quenched by the necessity that had compelled her marriage with Cadj since last she had seen the ape-man. For it is written among the laws of Opar that the High Priestess of the Flaming God must take a mate within a certain number of years after her consecration. For many moons had La longed to make Tarzan that mate. The ape- man had not loved her, and finally she had come to a realization that he could never love her. Afterward she had bowed to the frightful fate that had placed her in the arms of Cadj. As month after month had passed and Tarzan had not returned to Opar, as he had promised he would do, to see that no harm befell La, she had come to accept the opinion of Cadj that the ape-man was dead, and though she hated the repulsive Cadj none the less, her love for Tarzan had gradually become little more than a sorrowful memory. Now to learn that he was alive and had been so
- 77. near was like re-opening an old wound. At first she comprehended little else than that Tarzan had been close to Opar, but presently the cries of Manu aroused her to a realization that the ape-man was in danger—just what the danger was, she did not know. “Who has gone to kill Tarzan of the Apes?” she demanded suddenly. “Cadj, Cadj!” shrieked Manu. “He has gone with many, many men, and is following upon the spoor of Tarzan.” La sprang quickly from the pool, seized her girdle and ornaments from her attendant and adjusting them hurriedly, sped through the garden and into the temple.
- 78. W CHAPTER VII “YOU MUST SACRIFICE HIM” ARILY CADJ and his hundred frightful followers, armed with their bludgeons and knives, crept stealthily down the face of the barrier into the valley below, upon the trail of the white man and his black companions. They made no haste, for they had noted from the summit of Opar’s outer wall, that the party they were pursuing moved very slowly, though why, they did not know, for they had been at too great a distance to see the burden that each of the blacks carried. Nor was it Cadj’s desire to overtake his quarry by daylight, his plans contemplating a stealthy night attack, the suddenness of which, together with the great number of his followers, might easily confuse and overwhelm a sleeping camp. The spoor they followed was well marked. There could be no mistaking it, and they moved slowly down the now gentle declivity, toward the bottom of the valley. It was close to noon that they were brought to a sudden halt by the discovery of a thorn boma recently constructed in a small clearing just ahead of them. From the center of the boma arose the thin smoke of a dying fire. Here, then, was the camp of the ape-man. Cadj drew his followers into the concealment of the thick bushes that bordered the trail, and from there he sent ahead a single man to reconnoiter. It was but a few moments later that the latter returned to say that the camp was deserted, and once again Cadj moved forward with his men. Entering the boma they examined it in an effort to estimate the size of the party that accompanied Tarzan. As they were thus occupied Cadj saw something lying half concealed by bushes at the far end of the boma. Very warily he approached it, for there was that about it which not only aroused his curiosity but prompted him to caution, for it resembled indistinctly the figure of a man, lying huddled upon the ground.
- 79. With ready bludgeons a dozen of them approached the thing that had aroused Cadj’s curiosity, and when they had come close to it they saw lying before them the lifeless figure of Tarzan of the Apes. “The Flaming God has reached forth to avenge his desecrated altar,” cried the High Priest, his eyes glowing with the maniacal fires of fanaticism. But another priest, more practical, perhaps, or at least more cautious, kneeled beside the figure of the ape-man and placed his ear against the latter’s heart. “He is not dead,” he whispered; “perhaps he only sleeps.” “Seize him, then, quickly,” cried Cadj, and an instant later Tarzan’s body was covered by the hairy forms of as many of the frightful men as could pile upon him. He offered no resistance—he did not even open his eyes, and presently his arms were securely bound behind him. “Drag him forth where the eye of the Flaming God may rest upon him,” cried Cadj. They dragged Tarzan out into the center of the boma into the full light of the sun, and Cadj, the High Priest, drawing his knife from his loin cloth, raised it above his head and stood over the prostrate form of his intended victim. Cadj’s followers formed a rough circle about the ape-man and some of them pressed close behind their leader. They appeared uneasy, looking alternately at Tarzan and their High Priest, and then casting furtive glances at the sun, riding high in a cloud-mottled sky. But whatever the thoughts that troubled their half-savage brains, there was only one who dared voice his, and he was the same priest who, upon the preceding day, had questioned Cadj’s proposal to slay the ape-man. “Cadj,” he said now, “who are you to offer up a sacrifice to the Flaming God? It is the privilege alone of La, our High Priestess and our queen, and indeed will she be angry when she learns what you have done.” “Silence, Dooth!” cried Cadj; “I, Cadj, am the High Priest of Opar. I, Cadj, am the mate of La, the queen. My word, too, is law in Opar. And you would remain a priest, and you would remain alive, keep silence.” “Your word is not law,” replied Booth, angrily, “and if you anger La, the High Priestess, or if you anger the Flaming God, you may be
- 80. punished as another. If you make this sacrifice both will be angry.” “Enough,” cried Cadj; “the Flaming God has spoken to me and has demanded that I offer up as sacrifice this defiler of his temple.” He knelt beside the ape-man and touched his breast above the heart with the point of his sharp blade, and then he raised the weapon high above him, preparatory to the fatal plunge into the living heart. At that instant a cloud passed before the face of the sun and a shadow rested upon them. A murmur rose from the surrounding priests. “Look,” cried Dooth, “the Flaming God is angry. He has hidden his face from the people of Opar.” Cadj paused. He cast a half-defiant, half-frightened look at the cloud obscuring the face or the sun. Then he rose slowly to his feet, and extending his arms upward toward the hidden god of day, he remained for a moment silent in apparently attentive and listening attitude. Then, suddenly, he turned upon his followers. “Priests of Opar,” he cried, “the Flaming God has spoken to his High Priest, Cadj. He is not angered. He but wishes to speak to me alone, and he directs that you go away into the jungle and wait until he has come and spoken to Cadj, after which I shall call you to return. Go!” For the most part they seemed to accept the word of Cadj as law, but Dooth and a few others, doubtless prompted by a certain skepticism, hesitated. “Be gone!” commanded Cadj. And so powerful is the habit of obedience that the doubters finally turned away and melted into the jungle with the others. A crafty smile lighted the cruel face of the High Priest as the last of them disappeared from sight, and then he once again turned his attention to the ape-man. That, deep within his breast however, lurked an inherent fear of his deity, was evidenced by the fact that he turned questioning glances toward the sky. He had determined to slay the ape-man while Dooth and the others were absent, yet the fear of his god restrained his hand until the light of his deity should shine forth upon him once more and assure him that the thing he contemplated might meet with favor.
- 81. It was a large cloud that overcast the sun, and while Cadj waited his nervousness increased. Six times he raised his knife for the fatal blow, yet in each instance his superstition prevented the consummation of the act. Five, ten, fifteen minutes passed, and still the sun remained obscured. But now at last Cadj could see that it was nearing the edge of the cloud, and once again he took his position kneeling beside the ape-man with his blade ready for the moment that the sunlight should flood again, for the last time, the living Tarzan. He saw it sweeping slowly across the boma toward him, and as it came a look of demoniacal hatred shone in his close- set, wicked eyes. Another instant and the Flaming God would have set the seal of his approval upon the sacrifice. Cadj trembled in anticipation. He raised the knife a trifle higher, his muscles tensed for the downward plunge, and then the silence of the jungle was broken by a woman’s voice, raised almost to a scream. “Cadj!” came the single word, but with all the suddenness and all the surprising effect of lightning from a clear sky. His knife still poised on high, the High Priest turned in the direction of the interruption to see at the clearing’s edge the figure of La, the High Priestess, and behind her Dooth and a score of the lesser priests. “What means this, Cadj?” demanded La, angrily, approaching rapidly toward him across the clearing. Sullenly the High Priest rose. “The Flaming God demanded the life of this unbeliever,” he cried. “Speaker of lies,” retorted La, “the Flaming God communicates with men through the lips of his High Priestess only. Too often already have you attempted to thwart the will of your queen. Know, then, Cadj, that the power of life and death which your queen holds is as potent over you as another. During the long ages that Opar has endured, our legends tell us that more than one High Priest has been offered upon the altar to the Flaming God. And it is not unlikely that yet another may go the way of the presumptuous. Curb, therefore, your vanity and your lust for power, lest they prove your undoing.” Cadj sheathed his knife and turned sullenly away, casting a venomous look at Dooth, to whom he evidently attributed his
- 82. undoing. That he was temporarily abashed by the presence of his queen was evident, but to those who knew Cadj there was little doubt that he still harbored his intention to despatch the ape-man, and if the opportunity ever presented itself that he would do so, for Cadj had a strong following among the people and priests of Opar. There were many who doubted that La would ever dare to incur the displeasure and anger of so important a portion of her followers as to cause the death or degradation of their high priest, who occupied his office by virtue of laws and customs so old that their origin had been long lost in antiquity. For years she had found first one excuse and then another to delay the ceremonies that would unite her in marriage to the High Priest. She had further aroused the antagonism of her people by palpable proofs of her infatuation for the ape-man, and even though at last she had been compelled to mate with Cadj, she had made no effort whatsoever to conceal her hatred and loathing for the man. How much further she could go with impunity was a question that often troubled those whose position in Opar depended upon her favor, and, knowing all these conditions as he did, it was not strange that Cadj should entertain treasonable thoughts toward his queen. Leagued with him in his treachery was Oah, a priestess who aspired to the power and offices of La. If La could be done away with, then Cadj had the influence to see that Oah became High Priestess. He also had Oah’s promise to mate with him and permit him to rule as king, but as yet both were bound by the superstitious fear of their flaming deity, and because of this fact was the life of La temporarily made safe. It required, however, but the slightest spark to ignite the flames of treason that were smoldering about her. So far, she was well within her rights in forbidding the sacrifice of Tarzan by the High Priest. But her fate, her very life, perhaps, depended upon her future treatment of the prisoner. Should she spare him, should she evidence in any way a return of the great love she had once almost publicly avowed for him, it was likely that her doom would be sealed. It was even questionable whether or not she might with impunity spare his life and set him at liberty.
- 83. Cadj and the others watched her closely now as she crossed to the side of Tarzan. Standing there silently for several moments she looked down upon him. “He is already dead?” she asked. “He was not dead when Cadj sent us away,” volunteered Dooth. “If he is dead now it is because Cadj killed him while we were away.” “I did not kill him,” said Cadj. “That remains, as La, our queen, has told you, for her to do. The eye of the Flaming God looks down upon you, High Priestess of Opar. The knife is at your hip, the sacrifice lies before you.” La ignored the man’s words and turned toward Dooth. “If he still lives,” she said, “construct a litter and bear him back to Opar.” Thus, once more, came Tarzan of the Apes into the ancient colonial city of the Atlantians. The effects of the narcotic that Kraski had administered to him did not wear off for many hours. It was night when he opened his eyes, and for a moment he was bewildered by the darkness and the silence that surrounded him. All that he could scent at first was that he lay upon a pile of furs and that he was uninjured; for he felt no pain. Slowly there broke through the fog of his drugged brain recollection of the last moment before unconsciousness had overcome him, and presently he realized the trick that had been played upon him. For how long he had been unconscious and where he then was he could not imagine. Slowly he arose to his feet, finding that except for a slight dizziness he was quite himself. Cautiously he felt around in the darkness, moving with care, a hand outstretched, and always feeling carefully with his feet for a secure footing. Almost immediately a stone wall stopped his progress, and this he followed around four sides of what he soon realized was a small room in which there were but two openings, a door upon each of the opposite sides. Only his senses of touch and smell were of value to him here. These told him only at first that he was imprisoned in a subterranean chamber, but as the effects of the narcotic diminished, the keenness of the latter returned, and with its return there was borne in upon Tarzan’s brain an insistent impression of familiarity in certain fragrant odors that impinged upon his olfactory organs—a haunting suggestion that he
- 84. had known them before under similar circumstances. Presently from above, through earth and masonry, came the shadow of an uncanny scream—just the faintest suggestion of it reached the keen ears of the ape-man, but it was sufficient to flood his mind with vivid recollections, and, by association of ideas, to fix the identity of the familiar odors about him. He knew at last that he was in the dark pit beneath Opar. Above him, in her chamber in the temple, La, the High Priestess, tossed upon a sleepless couch. She knew all too well the temper of her people and the treachery of the High Priest, Cadj. She knew the religious fanaticism which prompted the ofttime maniacal actions of her bestial and ignorant followers, and she guessed truly that Cadj would inflame them against her should she fail this time in sacrificing the ape-man to the Flaming God. And it was the effort to find an escape from her dilemma that left her sleepless, for it was not in the heart of La to sacrifice Tarzan of the Apes. High Priestess of a horrid cult, though she was, and queen of a race of half-beasts, yet she was a woman, too, a woman who had loved but once and given that love to the godlike ape-man who was again within her power. Twice before had he escaped her sacrificial knife; in the final instance love had at last triumphed over jealousy and fanaticism, and La, the woman, had realized that never again could she place in jeopardy the life of the man she loved, however hopeless she knew that love to be. Tonight she was faced with a problem that she felt almost beyond her powers of solution. The fact that she was mated with Cadj removed the last vestige of hope that she had ever had of becoming the wife of the ape-man. Yet she was no less determined to save Tarzan if it were possible. Twice had he saved her life, once from a mad priest, and once from Tantor in must. Then, too, she had given her word that when Tarzan came again to Opar he came in friendship and would be received in friendship. But the influence of Cadj was great, and she knew that that influence had been directed unremittingly against the ape-man—she had seen it in the attitude of her followers from the very moment that they had placed Tarzan upon a litter to bear him back to Opar—she had seen it in the
- 85. evil glances that had been cast at her. Sooner or later they would dare denounce her—all that they needed was some slight, new excuse, that, she knew, they eagerly awaited in her forthcoming attitude toward Tarzan. It was well after midnight when there came to her one of the priestesses who remained always upon guard outside her chamber door. “Dooth would speak with you,” whispered the hand-maiden. “It is late,” replied La, “and men are not permitted in this part of the temple. How came he here, and why?” “He says that he comes in the service of La, who is in great danger,” replied the girl. “Fetch him here then,” said La, “and as you value your life see that you tell no one.” “I shall be as voiceless as the stones of the altar,” replied the girl, as she turned and left the chamber. A moment later she returned, bringing Dooth, who halted a few feet from the High Priestess and saluted her. La signaled to the girl who had brought him, to depart, and then she turned questioningly to the man. “Speak, Dooth!” she commanded. “We all know,” he said, “of La’s love for the strange ape-man, and it is not for me, a lesser priest, to question the thoughts or acts of my High Priestess. It is only for me to serve, as those would do better to serve who now plot against you.” “What do you mean, Dooth? Who plots against me?” “Even at this minute are Cadj and Oah and several of the priests and priestesses carrying out a plan for your undoing. They are setting spies to watch you, knowing that you would liberate the ape- man, because there will come to you one who will tell you that to permit him to escape will be the easiest solution of your problem. This one will be sent by Cadj, and then those who watch you will report to the people and to the priests that they have seen you lead the sacrifice to liberty. But even that will avail you nothing, for Cadj and Oah and the others have placed upon the trail from Opar many men in hiding, who will fall upon the ape-man and slay him before
- 86. L CHAPTER VIII MYSTERY OF THE PAST A had breakfasted the following morning, and had sent Dooth with food for Tarzan, when there came to her a young priestess, who was the sister of Oah. Even before the girl had spoken La knew that she was an emissary from Cadj, and that the treachery of which Dooth had warned her was already under way. The girl was ill at ease and quite evidently frightened, for she was young and held in high revere the queen whom she had good reason to know was all- powerful, and who might even inflict death upon her if she so wished. La, who had already determined upon a plan of action that she knew would be most embarrassing to Cadj and his conspirators, waited in silence for the girl to speak. But it was some time before the girl could muster up her courage or find a proper opening. Instead, she spoke of many things that had no bearing whatsoever upon her subject, and La, the High Priestess, was amused at her discomfiture. “It is not often,” said La, “that the sister of Oah comes to the apartments of her queen unless she is bidden. I am glad to see that she at last realizes the service that she owes to the High Priestess of the Flaming God.” “I come,” said the girl, at last, speaking almost as one who has learned a part, “to tell you that I have overheard that which may be of interest to you, and which I am sure that you will be glad to hear.” “Yes?” interrogated La, raising her arched eyebrows. “I overheard Cadj speaking with the lesser priests,” the girl continued, “and I distinctly heard him say that he would be glad if the ape-man escaped, as that would relieve you, and Cadj as well, of much embarrassment. I thought that La, the queen, would be glad to know this, for it is known by all of us that La has promised
- 87. friendship to the ape-man, and therefore does not wish to sacrifice him upon the altar of the Flaming God.” “My duty is plain to me,” replied La, in a haughty voice, “and I do not need Cadj nor any hand-maiden to interpret it to me. I also know the prerogatives of a High Priestess, and that the right of sacrifice is one of them. For this reason I prevented Cadj from sacrificing the stranger. No other hand than mine may offer his heart’s blood to the Flaming God, and upon the third day he shall die beneath my knife upon the altar of our temple.” The effect of these words upon the girl were precisely what La had anticipated. She saw disappointment and chagrin written upon the face of Cadj’s messenger, who now had no answer, for her instructions had not foreseen this attitude upon the part of La. Presently the girl found some lame pretext upon which to withdraw, and when she had left the presence of the High Priestess, La could scarcely restrain a smile. She had no intention of sacrificing Tarzan, but this, of course, the sister of Oah did not know. So she returned to Cadj and repeated as nearly as she could recall it, all that La had said to her. The High Priest was much chagrined, for his plan had been now, not so much to encompass the destruction of Tarzan as to lead La into the commission of an act that would bring upon her the wrath of the priests and people of Opar, who, properly instigated, would demand her life in expiation. Oah, who was present when her sister returned, bit her lips, for great was her disappointment. Never before had she seen so close at hand the longed-for possibility of becoming High Priestess. For several minutes she paced to and fro in deep thought, and then, suddenly, she halted before Cadj. “La loves this ape-man,” she said, “and even though she may sacrifice him, it is only because of fear of her people. She loves him still—loves him better, Cadj, than she has ever loved you. The ape- man knows it, and trusts her, and because he knows it there is a way. Listen, Cadj, to Oah. We will send one to the ape-man who shall tell him that she comes from La, and that La has instructed her to lead him out of Opar and set him free. This one shall lead him into our ambush and when he is killed we shall go, many of us,
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