Secure Data Sharing and Search in Cloud Based Data Using Authoritywise Dynamically Generated Aggregate Key

IOSR Journal of Computer Engineering (IOSR-JCE)
e-ISSN: 2278-0661,p-ISSN: 2278-8727, Volume 19, Issue 1, Ver. III (Jan.-Feb. 2017), PP 37-41
www.iosrjournals.org
DOI: 10.9790/0661-1901033741 www.iosrjournals.org 37 | Page
Secure Data Sharing and Search in Cloud Based Data Using
Authoritywise Dynamically Generated Aggregate Key
Chetna Waykole1
, Prof.D.D.Patil2
ME Student, Shri Sant Gadge Baba college of Engineering & Technology, Bhusawal, North Maharashtra
University, India
Assistant Professor & Head of the Computer Department, Shri Sant Gadge Baba college of Engineering &
Technology, Bhusawal, North Maharashtra University, India
Abstract: The Data sharing is an important functionality in cloud storage. We describe new public key crypto
systems which produce constant-size cipher texts such that efficient delegation of decryption rights for any set of
cipher texts are possible. The novelty is that one can aggregate any set of secret keys and make them as compact
as a single key, but encompassing the power of all the keys being aggregated. Ensuring the security of cloud
computing is second major factor and dealing with because of service availability failure the single cloud
providers demonstrated less famous failure and possibility malicious insiders in the single cloud. A movement
towards Multi-Clouds, In other words ”Inter-Clouds” or ”Cloud-Of-Clouds” as emerged recently. This works
aim to reduce security risk and better flexibility and efficiency to the user. Multi-cloud environment has ability
to reduce the security risks as well as it can ensure the security and reliability.
Keywords: Cloud Storage, Data Sharing, Key Aggregate Encryption, Multi-cloud infrastructure.
I. Introduction
Cloud storage is gaining popularity recently. In enterprise settings, we see the rise in demand for data
outsourcing, which assists in the strategic management of corporate data. It is also used as a core technology
behind many online services for personal applications. Nowadays, it is easy to apply for free accounts for email,
photo album, file sharing and/or remote access, with storage size more than 25GB (or a few dollars for more
than 1TB). Together with the current wireless technology, users can access almost all of their files and emails by
a mobile phone in any corner of the world. Considering data privacy, a traditional way to ensure it is to rely on
the server to enforce the access control after authentication, which means any unexpected privilege escalation
will expose all data. In a shared-tenancy cloud computing environment, things become even worse. Data from
different clients can be hosted on separate virtual machines (VMs) but reside on a single physical machine. Data
in a target VM could be stolen by instantiating another VM co-resident with the target one. Regarding
availability of files, there are a series of cryptographic schemes which go as far as allowing a third-party auditor
to check the availability of files on behalf of the data owner without leaking anything about the data, or without
compromising the data owners anonymity. Likewise, cloud users probably will not hold the strong belief that
the cloud server is doing a good job in terms of confidentiality. A cryptographic solution, with proven security
re-lied on number-theoretic assumptions is more desirable, whenever the user is not perfectly happy with
trusting the security of the VM or the honesty of the technical staff. These users are motivated to encrypt their
data with their own keys before uploading them to the server. Data sharing is an important functionality in cloud
storage. For example, bloggers can let their friends view a subset of their private pictures; an enterprise may
grant her employees access to a portion of sensitive data. The challenging problem is how to effectively share
encrypted data. Of course users can download the encrypted data from the storage, decrypt them, then send them
to others for sharing, but it loses the value of cloud storage. Users should be able to delegate the access rights of
the sharing data to others so that they can access these data from the server.
II. Related Work
We proposed Multi-cloud strategy. Multi-cloud strategy is the use of two or more cloud to store the
data. Cloud computing is becoming an important thing to deal with, in many organizations around the world. It
provides many benefits like 1. cost, 2.Reliability and 3.Ease in retrieval of data. Security in cloud computing is
gaining more and more importance as organizations often store sensitive data and important data on the cloud.
Security of data in cloud is an issue which should be focused carefully. Customers do not want to lose their
sensitive data due to malicious insiders and hackers in the cloud. In addition, the loss of service availability has
caused many problems for a large number of recently. Data intrusion technique create many problems for the
users of cloud computing. The other issues such as data theft, data lost should be overcome to provide better
services to the customers. It is observed that the research into the use of inter cloud providers to maintain
security has received less attention from the research community than has the use of single clouds. Multi-cloud

Secure Data Sharing and Search in Cloud Based Data Using Authoritywise Dynamically Generated ..
environment has ability to reduce the security risks as well as it can ensure the security and reliability. Multi-
cloud strategy minimize the risk of:-
1. service availability failure
2. Loss and corruption of data
3. loss of privacy
4. vender lock-in
5. the possibility of malicious insiders in the single cloud.
III. Proposed Approach
The data owner establishes the public system parameter via Setup and generates a public/master-secret
key pair via KeyGen. Messages can be encrypted via Encrypt by anyone who also decides what ciphertext class
is associated with the plaintext message to be encrypted. The data owner can use the master-secret to generate
an aggregate decryption key for a set of ciphertext classes via Extract. The generated keys can be passed to
delegates securely (via secure e-mails or secure devices) Finally, any user with an aggregate key can decrypt
any ciphertext provided that the ciphertexts class is contained in the aggregate key via Decrypt.
The key aggregation property is especially useful when we expect the delegation to be efficient and
flexible. The schemes enable a content provider to share her data in a confidential and selective way, with a
fixed and small ciphertext expansion, by distributing to each authorized user a single and small aggregate key.
Here, we describe the main idea of data sharing in cloud storage using KAC, illustrated in Fig. Suppose Suhas
wants to share her data m1;m2;.....;m on the server. He first performs Setup1; n to get param and execute
KeyGen to get the public/mastersecret key pair pk; msk. The system parameter param and public-key pk can be
made public and master-secret key msk should be kept secret by Suhas. Anyone (including Suhas herself) can
then encrypt each mi by Ci Encrypt pk; i; mi. The encrypted data are uploaded to the server. With param and pk,
people who cooperate with Suhas can update Suhass data on the server. Once Suhas is willing to share a set S of
her data with a friend Pritam, He can compute the aggregate key KS for Pritam by performing Extract msk; S.
Since KS is just a constant-size key, it is easy to be sent to Pritam via a secure e-mail. After obtaining the
aggregate key, Pritam can download the data he is authorized to access. That is, for each i 2 S, Pritam
downloads Ci (and some needed values in param) from the server. With the aggregate key KS, Pritam can
decrypt each Ci by Decrypt KS; S; i; Ci for each i 2 S.
Fig.1 System Architecture
3.1 Algorithm:
1. Setup (1, n) The data owner establishes public system parameter via Setup. On input of a security level
parameter 1 and number of cipher text classs n, it outputs the public system parameter param
2. KeyGen It is for generation of public or master key secret pair.
3. Encrypt (pk, i, m) It is executed by data owner and for message m and index i, it computes the cipher text as
C.
4. Extract (msk, S) It is executed by data owner for delegating the decrypting power for a certain set of
ciphertext classes and it outputs the aggregate key for set S denoted by Ks.
5. Decrypt (Ks,S,i,C)) When an appointee receives aggregate key Ks as exhibited by the previous step, it can
execute Decrypt. The decrypted original message m is displayed on entering Ks, S, i, and C, if and only if I
belongs to the set S

3.2 Aggregate Key Generation Algorithm
1. First Setup Data
2. All the key like k1,k2 ,k3 are in string format then it will converted into bytes using Byte Encoder.
3. Then every string converted in string to number like,
K1=12356, K2=56423, K3=35641
4. All set key combine then it can give separator for that different key like,12356 0 56423 0 35641 here
no value consider as separator.
5. secrete key i.e, S.
6. key convolution : we are use the quadratic equation, f(x)=(n1x + n2x + S)/n1=94,n2/66 here the x is
consider as 2 or any number.
7. Then it calculation getting the number like 254631 then that no again converted in String.
8. Display String format of key.
3.3 Implementation Details:
AES Encryption Algorithm:
 After Files will be uploaded by a registered user will encrypted by using Improved AES Encryption
technique then file will be stored on cloud.
 First we process file using base64 encoder to convert it in byte array.
 Then this byte array will be encrypted using AES technique.
Fig. 2 AES Encryption Algorithm
IV. Result
Fig. 3 User Selection

Fig. 4 Multiple File Selection
Fig. 5 Aggregate Key Generation
V. Conclusion
In this work we have reviewed three authentication techniques: Attribute based encryption (ABE),
Identity Based Encryption (IBE) and Key Aggregate Cryptosystem (KAC). The major concern in ABE is
collusion resistance but not compression of secret keys. Definitely, the ciphertext size is not constant. In IBE,
random set of identities are not match with our design of key aggregation. Key Aggregate Cryptosystem protects
users data privacy by compressing the secret key in public key cryptosystem which supports delegation of secret
key for different cipher text classes. For future extension it is necessary to reserve enough cipher texts classes
because in cloud cipher texts grows rapidly and the limitation is that bound of the number of maximum cipher
text classes. To share data exibly is vital thing in cloud computing. Users prefer to upload there data on cloud
and among different users. Outsourcing of data to server may lead to leak the private data of user to everyone.
Encryption is a one solution which provides to share selected data with desired candidate. Sharing of decryption
keys in secure way plays important role. Public-key cryptosystems provides delegation of secret keys for
different ciphertext classes in cloud storage.
VI. Future Work
There are some limitation to the existing system like predefined bound of the number of maximum
ciphertext classes and system is prompt to leakage of key. In cloud storage, the number of cipher texts usually
grows rapidly. So we have to reserve enough cipher text classes forces the future extension. Otherwise, we need
to expand the public-key. Although the parameter can be downloaded with cipher texts, it would be better if its
size is independent of the maximum number of ciphertext classes. On the other hand, when one carries the
delegated keys around in a mobile device without using special trusted hardware, the key is prompt to leakage,
designing a leakage resilient cryptosystem yet allows efficient and flexible key delegation is also an interesting
direction.

References
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Biography
Ms. Chetna Waykole is a student in Computer Science Department, college of ShriSant Gadge Baba college of
Engineering &Technology, Bhusawal, North Maharashtra University, India. She received Bachelor of
Engineering degree in 2012 from JTM college of Engineering, Faizpur, North Maharashtra University, India.
Her research interests are in Cloud Computing

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