This document discusses cloud computing and proposes a scheme for proof of data integrity in the cloud. It begins by defining cloud computing and describing the infrastructure needed to run applications over the internet. It then discusses security issues with cloud storage, where users do not have control over remotely stored data. The proposed scheme generates encrypted metadata for files and allows users to verify integrity by challenging the data center to provide specific bits, proving the file was not illegally modified. The scheme is best suited for encrypted static files stored in the cloud.

4. Applications and services
that run on a distributed network
using virtualized resources and accessed
by common internet protocols and
network standards
Cloud Computing is a paradigm in
which information is permanently
stored in servers on the internet and
can be accessed from anywhere

6. Data center
Office space
Servers and storages
Team of technical personnel's
Coolants
Network
Power

7. Provides all the infrastructure needed to run
applications over the internet
 Increased storage
 Reduced cost
 Flexibility
 Increased mobility
 Highly automated

8. -> 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

9. • ….enables you to create web
applications quickly, without the
• cost and complexity of buying and
managing the underlying software
or hardware…
No Frequent updates
Inexpensive

11. Data Integrity
and
Data Privacy
Availability
and
Reliability
Bandwidth and
Latency guarantees
Portability
and
Compliance

12. Cloud 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

13. We 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…

14.  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.

15. Key generator:
A random key is generated
Encryption:
A metadata of the file is
generated and is encrypted using any suitable algorithm
Archive:
It is the data center where the data is outsourced
Challenge:
Verification of data integrity by the user…
Response:
Proof of data integrity by data center

16. 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
C
H
A
L
L
E
N
G
E
Response

17. • 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….

18. Proposed 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
s
s
s
s
s 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

19. Computationally burdensome for entire file to be
encrypted for small devices
This scheme is best suited for encrypted files
Data
Center
Cloud
Storage
Client

20. In this we provide a scheme of data integrity , which
the customer can utilize to check the correctness of his
data by including SLA

21. 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

22. File (F) Metadata
Data
Center
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

25. Our scheme is only for static data
Developing for dynamic data will
be a future challenge