International Journal of Engineering Trends and Technology (IJETT) - Volume 35 Number 3- May 2016
Proof of Retrievable Computing System for Data
Storage in Cloud
Reshma A. Hegde
Madhura Prakash,Assistant Professor
Department of ISE,
BNM Institute of Technology,Bengaluru.
Email:reshmahgd@gmail.com
Department of ISE,
BNM Institute of Technology,Bengaluru.
Email:Madhura.prakash5@gmail.com
Abstract—Cloud computing moves large amount of data to the
data centers. Users find cloud to be an efficient platform since it
provides many services and benefits. But management of data in
cloud is not completely trustworthy. The data in cloud need to be
periodically verified. To reduce the burden on client side, a new
cloud scheme is proposed which is called proof of retrievable
computing system for data storage in cloud. It involves a cloud
storage and an auditing process to periodically verify the cloud
data on clients request. To reduce large computation on user side
public verifiability is proposed. Also the model is more secure as
it prevents the reset attacks during uploading the data in
cloud.The data integrity on cloud is periodically checked by the
audit process in cloud.
Keywords-cloud computing, proof of retrievability, security, data
integrity, verifiability
I. INTRODUCTION
Cloud computing moves the huge amount of client and
organization data to the large data centers, where the
management of the data and services may not be completely
trustworthy. Though Cloud computing offers many selfservices, resources, network access it has many critical issues.
One of the biggest challenges is data integrity verification in
cloud since the service provider may cheat on client’s data. To
ensure the integrity of the data public verifiability is proposed
which reduces the burden on client side, which reduces the
burden on client side as the third party auditor performs the
integrity check.[1]
New cloud scheme, proof of retrievable computing system
for data storage in cloud is proposed which has a cloud storage
to outsource large size files of clients to cloud and an auditing
process which verifies the data on clients request periodically
which also reduces the burden on client side. It eliminates the
involvement of user and also performs data verifiability.
PoR(Proof Of Retrievability) outsources and offload the heavy
computation of the tag generation to the cloud audit server and
eliminates the involvement of user in the auditing and in the
pre-processing phases[2]. Also, proof of retrievability (PoR)
model supports dynamic data operations, as well as ensures
security against reset attacks during uploading of data in
cloud.[3]This is an efficient scheme which contributes both
public verifiability and dynamic updation while supporting
security against middle man attack.
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II. PROBLEM STATEMENT
Cloud computing helps clients to store their large amount of
files in cloud. Though Cloud Computing offers plenty of
advantages, it also brings with it challenging issues which
hinders the overall protection and performance on the system.
One of the biggest challenge for the cloud user is that of data
integrity verification at untrusted servers.[4] The serious issue
is that service providers might intentionally dispose rarely
accessed data files which belong to an ordinary client or the
service provider may hide data loss to save penny and space.
The core of the problem can be generalized as how can the
client find an resourceful way to perform periodical integrity
check without the local copy of data files[5].
A. Design goals
It can be summarized as (1) Low Computation burden on
client side: Data owner does not have heavy computation
overhead as an auditor performs auditing on clients
behalf.(2)Public auditing: Allows auditors to verify the stored
cloud data without its local copy. (3) Dynamic data operation
support: Allows clients to perform dynamic updation, deletion
and editing of the files. (4) Stateless auditing: Eliminates the
need for original data to be maintained by auditor for
verification. (5)Strengthened security model: To prevent reset
attacks during uploading the data to the cloud.
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III. SYSTEM ARCHITECTURE
Fig 1. System architecture of the model
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International Journal of Engineering Trends and Technology (IJETT) - Volume 35 Number 3- May 2016
Figure 1 shows the system design of the proposed system. The
registered users log in to the application. When user is
uploading the file to cloud, first the file will be read in byte
stream for generating the SHA1 (Secure Hash Algorithm) key
using Hashing Technique. SHA1 key will be stored in users
database Server. This file will be again encrypted using the
RNS (Residue Number System) algorithm and will be stored
in user database storage. The File content will be encrypted.
The Encrypted file will be sent to the cloud storage by
connecting through the file transfer protocol (ftp).Once the
connection is establish with the cloud storage, encrypted file
will be transferred to cloud storage .
When Users wants to verify the files from the auditor,
auditor going to check the integrity checking process .While
auditor checking the integrity check for the file verification
process he has to request for web server storage to get the
digital signature of the uploaded file instead of file which is
present in the cloud storage and has to get the original digital
signature. Finally web server storage will compare the both
digital signatures for integrity checking process. If both are
identical then his file is not modified or else appropriate
message will be display.
the particular file using RNS(Residual Number System)
algorithm it will decrypt the file to download the original file.
5)Public auditing process.
Third party auditor audits the files stored in cloud. He checks
for data integrity using two hash keys. He does not have
original file while he performs auditing using the hash keys of
files.
IV. IMPLEMENTATION OF ALGORITHMS
A.Pseudocode for SHA1 Algorithm for hashing
In cryptography, SHA-1 (Secure Hash Algorithm 1) is a
hashing function in cryptography. SHA-1 produces a 160-bit
(20-byte) hash value known as a message digest.
1)Initialize variables which are unsigned 32 bits.
2)Preprocessing
• Append bit 1 to the message
•
Append 0<=k<512 bits ‘0’,so that the resulting
message length is congruent to 448=-64(mod 512)
•
Append length of message in bits, as 64 bit big
integer
A. System modules of the model
1)Hashing processing
When user is uploading the File to cloud, first the File will be
read in byte stream for generating the SHA1 key using
Hashing Technique. The SHA1 Key will produce a message
digest of size 20 bytes and SHA1 key will be generating based
on the content of the uploading File. This SHA1 key will be
stored in users database Server.
2)File Upload Process with Encryption
User has to login to upload the File, when user wants to
upload data file to the cloud storage he has to select the file
from his storage. When file is uploading to the cloud, we are
generating the digital signature of the file and keep a copy of
the digital signature in the users database storage .The File
content will be encrypted using RNS Algorithm. The
Encrypted file will be sent to the cloud storage by connecting
through the file transfer protocol (ftp).Once the connection is
established with the cloud storage, encrypted file will be
transferred to cloud storage.
3)Integrity Checking Process
When users wants to verify the files from the auditor, auditor
checks for the integrity of files. While auditor checking the
integrity check for the file verification process he has to
request for audit process to get the hash key of the uploaded
file instead of file which is present in the cloud storage and
has to get the original hash key. Finally audit server will
compare the both digital signatures for integrity checking
process. If both are identical then user’s file is not modified or
else appropriate message will be display.
4)File Download Process with Decryption
User wants to download the file from the cloud storage he has
to select the particular file while downloading. The Cloud
connection is established using File Transfer Protocol. Select
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3) Process the message in successive 512 bit chunks
4) Extend sixteen 32 –bit words into eighty 32 –bit words
5)Initialize hash value for this chunk and add the chunk’s
value to the result so far.
6) Generating the final hash value.
B.Pseudocode for RNS Algorithm for cryptography
To perform efficient computation, using small set of integers
residue numeral system (RNS) is used which represents a
large.It is based on the Chinese remainder theorem of modular
arithmetic.
1.Get Random prime numbers using random generator
2.Consider “N” to be the data.P1 and P2 are two random
prime numbers.
3.Key Generation: M=P1*P2
A1=M/P1
A2=M/P2
4.Let T be anything: T1=(A1*T)mod P1
T2=(A2*T)modP2
Encryption:
int r1=N%P1;
int r2=N%P2;
N=r1+”_”r2
return N;
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International Journal of Engineering Trends and Technology (IJETT) - Volume 35 Number 3- May 2016
Decryption:
int e=(A1*T1*r1)+(A2*T2*r2)
int e1=e%N
return e1;
[1]
CONCLUSION
[2]
REFERENCES
A new proof of retrievability for cloud storage Proof of
retrievable computing system for data storage in cloud is
proposed in which a cloud storage manages the huge data of
the clients and an auditor is introduced to preprocess and
perform data integrity verification of the outsourced cloud
data upon client’s request. This reduces the computation
overhead on the client side significantly. It makes the auditor
to verify the integrity of files using two hash keys thus
eliminating the need for him to maintain the state information.
This proof of retrievable model also provides enhanced
security against reset attacks during the upload phase. The
scheme efficiently supports public verifiability and dynamic
data operations simultaneously. It is the more efficient
construction requiring less storage space thus solving problem
of resource constrainability.
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