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