International Journal of Engineering Research and Development (IJERD)

International Journal of Engineering Research and Development
e-ISSN: 2278-067X, p-ISSN: 2278-800X, www.ijerd.com
Volume 8, Issue 2 (August 2013), PP. 45-51
45
Analyzing the speed of combined cryptographic
algorithms with secret and public key
Florim Idrizi1
, Fisnik Dalipi2
, Ejup Rustemi3
1,2,3
Department of IT, Faculty of Natural Sciences and Mathematics, State University of Tetova
Abstract:- Secure messages and key management have been a focal point in cryptography. In the cryptographic
systems, the notion of key is referred ti an numerical value which is used by an algorithm, making the
information secure and visible only to individuals that possess the proper key to discover that information. In
this article we will explain the concepts of private key and public key cryptography, and combined cryptography
in terms of protecting information that is being sent through Internet. Further, we will analyze some secret and
public algorithms, and combined algorithms with LABView. The speed measurement of these algorithms also
represents a significant contribution of this paper.
Keywords:- Cryptography, Algorithms, LabView
I. INTRODUCTION
Security is the main part of an enterprise which can be achieved by using a combined cryptography
algorithms. However, the main purpose of cryptography is not only used toensure confidentiality, but also to
provide solutions to problems such as: hacked integrity, authentication and non-repudiation. In cryptographic
systems, the key term refers to a numerical value used by an algorithm to change the information, making that
information secure and visible only to individuals who possess the appropriate key for revealing. As a result, the
term of key management refers to secure management of keys for making them available to users when they
need them. Currently researchers continue to find new algorithms. However, this issue is a very difficult thing
because there is a need to consider many factors, such as: security, algorithm characteristics, speed and
complexity.
Fig.1: Security Services
They can be categorized into Symmetric (secret) and Asymmetric (public) keys encryption. In
Symmetric keys encryption or secret key encryption, only one key is used to encrypt and decrypt data. In
Asymmetric keys, two keys are used; private and public keys. Public key is used for encryption and private key
is used for decryption. Public key encryption is based on mathematical func tions, computationally intensive and
is not very efficient for small mobile devices [1],[2]. There are many examples of strong and weak keys of
cryptography algorithms like RC2, DES, 3DES, RC6, Blowfish, and AES. RC2 uses one 64-bit key. DES uses
one 64-bits key. Triple DES uses three 64-bits keys while AES uses various 128,192,256) bits keys. Blowfish

Analyzing the speed of combined cryptographic algorithms...
46
uses various (32-448); default 128bits while RC6 is used various (128,192,256) bits keys. The most common
classification of encryption techniques can be shown in Figure 2 [3].
Cryptography
Public keySecret key
RSADES AES Blow Fish ElGamal DSARC4IDEA TEA
Fig. 2: .Algorithms with public and secret key
Data security is an essential part of an organization; it can be achieved by the using various methods. In
order to maintain and upgrade the model still efforts are required and increase the marginally overheads. The
encrypted data is safe for some time but never think it is permanently safe. After the time goes on there is
chance of hacking the data by the hacker. Fake files are transmitted in the same manner as one can sends the
encrypted data. The information about the key is present in the encrypt data which solves the problem of secure
transport of keys from the transmitter to receiver [4],[5]. In case of practical system encrypted data is passed
through the various stations which are capable to re-encrypt the data by their own key. At the time the previous
keys are discarded, this will make the system more secure. There are many algorithms available in the market
for encrypting the data. Encryption is the process in which plaintext has been converted into the encoded format
cipher text with the help of key [6].
II. PUBLIC KEY CRYPTOGRAPHY
This section is a brief overview of the cryptography that is incorporated into a PKI. Current public key
cryptography as described in this article is mostly attributed to Diffie and Hellman and Rivest, Shamir and
Adleman. Because of its widespread use in e-commerce, this article focuses on the RSA (named for its creators:
Rivest, Shamir and Adleman) public key cryptographic system. RSA is a public key cryptographic algorithm
that is based on the hard mathematical problem of factoring composite numbers. The keys used by the RSA
crypto system are based on the product of two large prime numbers that derive their cryptographic strength from
the fact that it is difficult to factor large composite numbers of this kind. RSA uses a pair of keys: a public key
which is made known to many entities, and a private key for which secrecy and integrity are strictly controlled
and only used by the owner of that key [7].
III. SYMMETRIC KEY ENCRYPTION
An overview of public key cryptography is not complete without mentioning symmetric or secret key
cryptography. The reason for this is that public key cryptographic systems lack the positive performance
characteristics of symmetric systems. The ramification of this under performance is that, in practice, symmetric
systems such as DES, Triple-DES, or IDEA are used to perform encipherment of data for confidentiality, where
the data is more than a negligible length. In this way, symmetric key encryption supplements public key
cryptographic systems. The fundamental characteristics of symmetric cryptographic systems used with PKI are
that the same key is used for both encryption and decryption. Because of this symmetry the key must be kept
secret and shared only between two parties [7].
Table 1: Comparison of various encryption algorithms on the basis of Key size and Block size, Type and
Features [8],[9]
Algorithm Key Size
( bits)
Block Size Type Features
RSA 1024 128 Block Cipher Asymmetric algorithm, speed is low
Blowfish 32- 448 64 Block Cipher Excellent Security
AES 128 128 Block Cipher Replacement for DES, Excellent Security
DES 64 64 Block Cipher Most common, Not Strong Enough
Triple
DES
192 64 Block Cipher Modification of DES, Adequate Security

47
ECDSA 163 / Block Cipher
RC4 128 128 Stream Cipher Fast Stream Cipher in SSL
IV. COMBINED CRYPTOGRAPHY
Combining the secret key and public cryptography can result in better results regarding the encryption.
In this process, one must take into account the points where one algorithm is weaker than another. Encryption
starts by generating secret key. The secret key used is safe and fast. During the public key encryption, a major
problem was how to reach the receiver by using secret key. This is enabled by public key. In this case, the
public key of the receiver is used for encrypting only the secret key. Normally, the public key cryptography is
slower, nevertheless, the size of the secret key is little and this would not affect the speed limitation of
encryption and decryption.
Text sekret key encrypted key
public key
encrypting secret key
encrypted secret key and
encrypted text
Rinori
Bank
Fig. 3: Combined encryption
The last process is connecting the encrypted secret key with the encrypted text for transferring the
message to the receiver. We must emphasize that transferring messages through Internet, unknown individuals
cannot read this text because the secret key is encrypted by the secret key of receiver. It is only the sender who
can decrypt that with the help of his private key.
The use of public/secret encryption for encrypting the secret key offers reasonable solutions by
protecting the secret key from copying it through the transmission process. Also, there is no need for prior deals
between peers that participate in the transmission for exchanging the secret key.
Decryption starts with the acceptation of the encrypted secret key and the encrypted text. Afterwards,
the encrypted key and the encrypted text are decrypted in this way. After encrypting the secret key of the sender
with the public key of the receiver, the encrypted secret key will be decrypted with the receiver secret key,
which results with gaining the sender secret key. The sender secret key is used for decrypting the encrypted text
where the original text appears.
sender secret key
decrypting secret
key
receiver sekret key
Bank
Erditi
encrypted secret key and
encrypted text
encrypted key
encrypted
secret key
Text
Fig. 4: Combined decryption

48
The combined cryptography represents the foundation for many modern encryption solutions, such as:
e-main encryption, VPN encryption etc.
However, combined cryptography must assure that the encrypted message comes from the sender. It
can happen that a third person can make use of the receiver public key and encrypts the secret key used for
encrypting the message. The third person can share that on Internet. The receiver initially decrypts the secret key
by using his private key and the message by using the secret key of the sender. The receiver has received one
unwanted message by an unwanted receiver. To make sure that the message comes from the right sender, we use
digital certificates
V. ANALISYS OF RSA ALGORITHM BY USING LABVIEW
RSA is a public key algorithm that is used for Encryption, Signature and Key Agreement. RSA
typically uses keys of size 1024 to 2048. Since public key cryptography involves mathematical operation on
large numbers, these algorithms are considerably slow compared to the symmetric key algorithm. They are so
slow that it is infeasible to encrypt large amount of data. Public key encryption algorithm such as RSA can be
used to encrypt small data such as „keys‟ used in private key algorithm. RSA is thus used as key agreement
algorithm. [10]
Fig.5: The realization of RSA algorithm using LabVIEW
Table 2: The speed of RSA in terms of character number encrypted and decrypted
From the table we can conclude that by having 32 bit key and by increasing the number of characters
for encryption and decryption, the time will be delayed progressively. This means that the speed of the
algorithm depends on the number of characters that are to be encrypted and decrypted.
VI. ANALISYS OF RC4 ALGORITHM BY USING LABVIEW
RC4 stream cipher most preferred Stream cipher algorithm. In the RC4 algorithm, there are two stages
process during encryption as well as decryption. The algorithm is dividing into the two parts KSA (Key
scheduling Algorithm) and PRGA (Pseudo Random Generator Algorithm). KSA as the first stage of algorithm
also knows as initialization of S (s is state vector ) and PRGA known as stream generation in the RC4 whole
process of algorithm, mean RC4 basically two stages process. In the first stages of RC4 Stream Cipher
algorithm on the bases of variable sized key from 1 to 256 a State Vector (State Table) of fixed length 256
bytes is generated, after on the base of State Table, we generate the key stream that XOR with plaintext and
Character
number
1000 2000 3000 4000 5000 10000
Time 5.5s 10.3s 14.6s 19.3s 24.6s 53.2s

49
cipher text during encryption and decryption. During encryption the key stream is XOR with the plaintext and
during decryption the cipher text XOR with key stream then convert into the plaintext. In the description of
RC4, first we discussing the first stage of the algorithm known as KSA, in this stage [11]
Fig.6: The realization of RC4 algorithm using LabVIEW
Table 3: The speed of RC4 in terms of character number encrypted and decrypted
From the table we can conclude that by increasing the number of characters for encryption and
decryption, the time will not change. This means that the speed of the algorithm is high and depends on the
number of characters that are to be encrypted and decrypted.
VII. ANALISYS OF COMBINED CRYPTOGRAPHY RC4 – RSA BY USING LABVIEW
Erditi wants to send a message to Rinor. Erdit generates a one key. He uses this key together with the
RC-4 algorithm to encrypt his message. After this is done, he encrypts the temporary key with Rinor public key,
using RSA. He sends the encrypted message that was encrypted with RC-4 together with the temporary key that
was encrypted with RSA. When Rinor receives the message, she decrypts the key with her private key. She then
uses the temporary key to decrypt the message. Since only she has her private key, she will be the only person
who is able to decrypt the temporary key and thus the message.
Fig. 7: The realization of RC4 – RSA algorithm using LabVIEW
Table 4: The speed of RC4 – RSA in terms of character number encrypted and decrypted
Character number 1000 2000 3000 4000 5000 10000
Time 0.0s 0.0s 0.0s 0.0s 0.0s 0.0s
Character
number
1000 2000 3000 4000 5000 10000
Time 0.1s 0.1 0.2 0.2 0.4 0.6

50
From the table we can conclude that by increasing the number of characters for encryption and
decryption, the time will not change. This means that the speed of the algorithm is high and depends on the
number of characters that are to be encrypted and decrypted.
VIII. ANALISYS OF COMBINED CRYPTOGRAPHY DES – RSA BY USING LABVIEW
RSA has two keys – one private and one public. RSA is implemented as software. It is hard to code the
plaintext and to decode the ciphertext with RSA. DES has the same key for encryption and decryption. DES is
implemented in hardware and it is fast. Any communication between two businesses can use different keys, and
the key can be exchanged. If the key is sent separately encrypted with RSA, then the receiver can use it for
decrypting the encrypted message with DES. DES is faster for generating signature but is slower in encryption.
It is faster when decryption and the security can be considered comparable in equivalent way with RSA key
with same size [12].
Fig. 8: The realization of DES – RSA algorithm using LabVIEW
Table 5: The speed of DES – RSA in terms of character number encrypted and decrypted
From the table we can conclude that DES-RSA algorithm is slower compared to RC4-RSA, where the
encryption and decryption speed was lower.
IX. CONCLUSIONS
Consequently, the information security is very important issue for companies or individuals in the global market.
For this purpose, the application of cryptographic methods represents the main condition to enable a secure
business communication. Due to the massive electronic communication the importance of cryptography is
significant: sending sensitive data, and distance access to various information systems. On one hand, our
analysis prove that secret key algorithms are faster than public key algorithms, and on the other hand we
conclude that the speed of combined algorithms is not that slow.
Character
number
1000 2000 3000 4000 5000 10000
Time 0.2s 0.4s 0.5s 0.6s 0.8s 1.4s

51
REFERENCES
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[4]. Ajay Kakkar, Dr. M. L. Singh, Dr. P. K. Bansal, “Efficient Key Mechanisms in Multinode Network for
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[5]. Davis, R, “The data encryption standard in perspective”, Communications Society Magazine, IEEE,
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[6]. Ajay Kakkar, M. L. Singh, P.K. Bansal, Comparison of Various Encryption Algorithms and
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[7]. Public Key Infrastructure Overview, By JoelWeise - SunPSSM Global Security Practice, Sun
BluePrints™ OnLine - August 2001
[8]. “Cryptography Basics” available at weblink:
http://media.wiley.com/product_data/excerpt/94/07645487/0764548794.pdf.
[9]. A Study of the Energy Consumption Characteristics of Cryptographic Algorithms and Security
Protocols, IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 5, NO. 2, FEBRUARY
[10]. Public Key Cryptography - Applications Algorithms and Mathematical Explanations
[11]. International Journal of Computer Science and Network (IJCSN), Volume 1, Issue 3, June 2012
www.ijcsn.org ISSN 2277-5420
[12]. "Proposed Federal Information Processing Standard for Digital Signature Standard (DSS)," Federal
Register, v. 56, n. 169, 30 Aug 1991, pp. 42980-42982.

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