DATA INTEGRITY PROOFS IN

CLOUD STORAGE

by

Mohd Abdul Sameer

Index1.Cloud Computing- Services- Saas- Iaas- Paas

2.Need For Data Integrity- Future applications- Issues in cloud computing

3.Data Integrity- Proof of Retrievability- conclusion- Future Enhancement

What is Cloud Computing. . . . . . . .?

Applications and services that run on a distributed network using virtualized resources and accessed by common internet protocols and network standards (or)

Cloud Computing is a paradigm in which information is permanently stored in servers on the internet and can be accessed from anywhere

Cloud Computing

Services Provided By Cloud Computing

Cloud Services

IAAS (Infrastructure As a Service)Traditional business organizations

Data centerOffice spaceServers and storagesTeam of technical personnel'sCoolantsNetworkPower

New Model of business organizations

Provides all the infrastructure needed to run applications over the internet

Benefits

Increased storage Reduced cost Flexibility Increased mobility Highly automated

SAAS (Software As a Service) -> Sometimes referred to as "on-demand software" is a

software delivery model in which software and its associated data are hosted centrally and are typically accessed by users

Benefits No local storageSmarter to rentOn demand

PAAS (Platform As a Service)

• ….enables you to create web applications quickly, without the

• cost and complexity of buying and managing the underlying software or hardware…

• Benefits

No Frequent updatesInexpensive

Future Applications of Cloud

Vulnerabilities of Cloud Computing

Data Integrity and

Data Privacy

Availability and

Reliability

Bandwidth and Latency guarantees

Portabilityand

Compliance

Data Integrity Proofs In Cloud StorageCloud storage moves the user’s data to large data centers, which are remotely located, on which the user does not have any control

However there are lot of security issues which need to be considered

Data integrity Authentication Small devices like PDA’s, mobiles, and laptops are associated with limited battery power and computation speed

Our schemeWe provide a scheme which gives a proof of data

integrity in the cloud through which the user can verify the correctness of his data, this proof can be termed as Proof of Retrievability (POR)

This enables individual to entertain Economic advantages Zero Maintenance

Note:-> Our scheme just checks the integrity (if the data

is illegally modified) only of static data…

(SLA) Service level Agreement

This proof can be agreed upon by both the cloud and the customer and can be incorporated in SLA.

SLA is part of service contract where the level of services being offered is formally defined.

ARCHITECTURE

Key generator: A random key is generatedEncryption: A metadata of the file is generated and is encrypted using any suitable algorithmArchive: It is the data center where the data is outsourcedChallenge: Verification of data integrity by the user…Response: Proof of data integrity by data center

Existing System

A simplest Proof of Retrievability can be made using hash key function

File (F)

Data Center(archive)

Cryptographic Hash Function

Hk(F)

User DB

Hash Secret key (k)

Encrypted file(~f)

StoredRetrieves

CHALLENGE

Response

Drawbacks of this approach• Computing hash value for moderately large file might

be overhead for some device like Mobiles, PDA’s and Laptops

• For each verification request from client the archive has to process the entire file

• High resource cost and lot of ambiguity as a result of maintaining secret key and number of hash keys….

Ari Juels and Burton S.kaliski jrProposed a theory to proof the retrievability for large files using sentinels…. According to them

1 2 3 4 5 6 7

Data File( f )

s

s

s s

s

s s

s s

sss

ss s

s s s

s

s s

Data file with seven blocks

Inserting sentinels at different positions and noting their position, present at different blocks

File(~f) Encryption(~F )

Data Archive

To hide the

position of sentinels

Verification Phase

Drawbacks:Computationally burdensome for entire file to be encrypted for small devicesThis scheme is best suited for encrypted files

DataCenter

Owner challenges cloud by specifying the positions of collection of sentinels

If the file is modified then position of sentinels also changes

CloudStorage

Client

Proposed SystemIn this we provide a scheme of data integrity , which the customer can utilize to check the correctness of his data by including SLA

Note: our proof of data integrity just check the integrity of data i.e. if data has been illegally deleted or modified.Applicable only for static data We provide a scheme which does not involve the encryption of the entire file, we encrypt only few bitsVerifier stores only a single key

M bits M bits M bits M bits M bits M bits

File (F) with n blocks, and each block of size M bits

K bits

K<<<M, K bit positions are noted Where K is user defined

E

M1

K bits

E

M2

K bits

E

M3

K bits

E

M4

K bits

E

M5

K bits

E

M6

Metadata

Encrypting k bits using any appropriate algorithm

Generation of individual metadata

Fig : Generation of Metadata

File (F) Metadata

DataCenter

File is appended with metadata

New file (~F) is stored at data center

Client challenges by specifying (ith) block of file and the jth bit of i

Response and challenge should be same to accept the file

Fig : Verification Phase

Conclusion Facilitate the client for getting a

proof of integrity Computational and storage overhead

of client as well cloud is exceptionally reduced

Advantageous to thin client like PDA’s, Mobiles, Laptops Network bandwidth is minimized as the size of proof is comparatively less

Modules

1. Cloud storage:Which is supposed to be for a “FEE”. Store the data and provide it back to the owner whenever required.

2. Simply archives: obtains and verify the proof for data that is stored by user at remote data storage in the cloud

3. Sentinels:Guards the positions of bits

4. Verification phase:challenge the cloud by providing the bit positions for a correct response

Future improvement

Our scheme is only for static data

Developing for dynamic data will be a future challenge