ISSN: 2249-5789
P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31

Secure Cloud Data Storage with Efficient Key
Exposure
P. Subhadra Devi
M. Tech,
Department of CSE,
Shri Vishnu Engineering College for
Women (A),
Vishnupur, Bhimavaram, West
Godavari District, Andhra Pradesh.

Dr. P. Kiran Sree Ph.D.
Professor
Department of CSE
Shri Vishnu Engineering College for
Women (A),
Vishnupur, Bhimavaram, West

Abstract— The world just witnessed the surge of a

new adversarial model. We then propose Bastion, a

new and powerful attacker, which was able to coerce

primitive that is secure according to our definition

operators and acquire the necessary keys to break the

and, therefore, guarantees data confidentiality even

privacy of users. Once the encryption key is exposed,

when the encryption key is exposed, as long as the

the

data

adversary cannot compromise all storage servers. We

confidentiality is to limit the adversary’s access to the

analyze the security of Bastion, and we evaluate its

ciphertext. This may be achieved, for example, using

performance

multi-cloud storage systems. These systems spread

implementation.

data

only

viable

across


measure

multiple

to

servers

preserve

in

different

administrative domains, to cater for availability and
fault tolerance. If the adversary can only compromise
a subset of these domains, multi-cloud storage
systems may prevent the adversary from accessing

Godavari District, Andhra Pradesh.

by

means

of

a


prototype

Keywords— Key exposure, cryptography,
Security, Data confidentiality.
1

Introduction

the entire ciphertext. However, if data is encrypted

The world became aware of a massive surveillance

using existing encryption schemes, spreading the

program which mined data from operators and ISPs,

ciphertext on multiple servers does not entirely solve

and performed illegal taps on digital communication

the problem since an adversary which has the

channels. This surveillance program was not hindered

encryption key, can still compromise single servers

by the various security measures deployed within the

and decrypt the ciphertext stored therein. In this


targeted services. For instance, although these

paper, we leverage multi-cloud storage systems to

services relied on secure encryption mechanisms, the

provide data confidentiality against an adversary

necessary keying material was acquired, e.g., by

which has access to the encryption key, and can

means of backdoors, bribe, or coercion. In addition to

compromise a large fraction of the storage servers.

the public and governmental outrage, another

For this purpose, we first introduce a novel security

immediate reaction from the industry was an even

definition that captures data confidentiality in the
IJCSCN | August-September 2018
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ISSN: 2249-5789

P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31

larger apprehension to use third-party services, and in

block. For example, if each server stores at least two

particular cloud services.

ciphertext blocks, a (n− 2)ke secure scheme clearly
preserves data confidentiality unless all servers are

If the encryption key is exposed, the only viable
countermeasure is to limit the adversary’s access to
the ciphertext, e.g., by spreading it across multiple
administrative domains, in the hope that the
adversary cannot compromise all of them. However,

compromised, even when the adversary has access to
the encryption key. We analyze the security of
Bastion, and we compare its performance in a
realistic implementation setup with a number of
existing encryption schemes.

this countermeasure does not entirely solve the
problem. Even if the data is encrypted and dispersed

We consider a multi-cloud storage system

across different administrative domains, an adversary


which can leverage a number of commodity cloud

equipped with the appropriate keying material can

providers with the goal of distributing trust across

compromise a single server and decrypt ciphertext

different administrative domains. This “cloud of

blocks stored therein. In this paper, we leverage

clouds” model is receiving increasing attention

multi-cloud

data

nowadays with leading cloud storage providers such

confidentiality against an adversary which knows the

as EMC, IBM, and Microsoft, offering products for

encryption key, and can compromise a large fraction

multi-cloud systems. In particular, we consider a

of the storage servers. The adversary can acquire the


system of s storage servers S1, . . . , Ss, and a

keys either by exploiting flaws or backdoors in the

collection of users. We assume that each server

key-generation software , or by compromising the

appropriately authenticates users.

storage

systems

to

provide

devices that store the keys (e.g., at the user-side or in
the cloud). As far as we are aware, this adversary

2

Related Works

i)

Enhancing

invalidates the security of most cryptographic

solutions, including those that protect the keys by
means of secret-sharing (since the keys are leaked at
generation time).

Data

Security

In

Cloud Storage Auditing With Key
Abstraction

In this work, we propose Bastion, an efficient
primitive that requires only one round of block cipher
encryption, followed by a linear transformation.
Bastion is (n− 2)ke secure, i.e., it ensures that
plaintext data cannot be recovered as long as the
adversary has access up to all but two ciphertext
blocks, even when the encryption key is exposed. As
such, Bastion relaxes the notion of all-or-nothing at
the benefit of improved performance. This is
reasonable since, in a multi-cloud storage system,
each server is likely to store more than one ciphertext

IJCSCN | August-September 2018
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We


have

examined

working

framework plan for information security in
distributed

storage.

we

talked

about

engineering segments for giving information
security at the two levels (User furthermore,
Administrator). To guarantee the rightness
of client's information in cloud information
stockpiling, we proposed a powerful and
adaptable

appropriated

conspire

with


unequivocal powerful information bolster,

26


ISSN: 2249-5789
P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31

counting square refresh, erase, and attach

initially as opposed to applying the visually

tasks. For information security we have

impaired strategy amid the reviewing

utilized

procedure.

DES

which

lets

Discovering

that


the

information put away in the database as

information

figure content and on ask for information is

remain online practically speaking, with a

accessible in the required organization. We

specific end goal to keep the capacity

depend on erasure correcting code in the

accessible what's more, certain after a

document dissemination planning to give

noxious defilement, we present a semi-

excess equality vectors and certification the

confided

information steadfastness. By using the

framework show and give a benefit to the


Homomorphic token with dispersed check

intermediary to deal with the reparation of

of eradication coded information, our plan

the coded squares and authenticators. To

accomplishes the mix of capacity rightness

better correct for the recovering code-

protection

and

information

situation, we outline our authenticator in

limitation,

i.e.,

at

whatever

blunder


proprietor

in

can't

intermediary

generally

into

the

point

view

been

authenticator can be proficiently produced

distinguished amid the capacity rightness

by the information proprietor all the while

confirmation over the appropriated servers,

with the encoding methodology. Extra


we can nearly ensure the synchronous

investigation demonstrates that our plan is

distinguishing

provable

information

ii)

calculation,

debasement

proof

of

has

the

acting

of

the


BLS

secure,

and

signature.

the

This

execution

mischievously server(s). We have utilized

assessment demonstrates that our plan is

DES calculation with eradication adjusting

profoundly viable t and can be plausibly

procedure for giving information security

incorporated into a recovering code-based

respectability.

distributed storage framework.


An Efficient Cloud Storage Batch
Auditing Without Key Exposure

iii)

Privacy-preserving public auditing
for secure cloud storage

Resistance Using Public Verifier
Utilizing distributed storage, clients
From this the giving safeguarding
open examining to recovering code based
distributed storage has been actualized.
Where the information proprietors are
special to assign TPA for checking entitled
their information legitimacy. To secure the
first information protection against the
TPA,

we

randomize

IJCSCN | August-September 2018
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the

coefficients


can remotely store their information and
appreciate

the

on-request

amazing

applications and administrations from a
common pool of configurable processing
assets, without the weight of nearby
information stockpiling and support. In any
case, the way that clients never again have
physical

ownership

of

the

outsourced

27


ISSN: 2249-5789
P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31


information

makes

the

uprightness

security

information

in

information

distributed

in

outsourcing

stockpiling administration. In this

computing an imposing errand, particularly

paper, we propose an agreeable

for clients with obliged registering assets. In
addition, clients ought to have the capacity


provable

to simply utilize the distributed storage as

conspire in half and half mists to

though

without

help adaptability of administration

agonizing over the need to confirm its

and information movement, in which

it

is

neighborhood,

trustworthiness. In this manner, empowering

information

ownership

we consider the presence of various


open auditability for distributed storage is of
basic significance with the goal that clients

cloud specialist organizations to

can turn to an outsider inspector (TPA) to

helpfully store and keep up the

check the trustworthiness of outsourced

customers' information. Our tests

information and be straightforward. To

demonstrate that the check of our

safely

present

a

powerful

TPA,

the


plan requires a little, steady measure

evaluating procedure ought to acquire no
new

vulnerabilities

toward

of

client

overhead,

which

limits

correspondence many-sided quality.

information protection, and acquaint no
extra online weight with client. In this paper,
we propose a safe distributed storage
framework supporting security safeguarding
open reviewing. We additionally stretch out
our outcome to empower the TPA to
perform reviews for numerous clients at the
same time and effectively. Broad security
and execution examination demonstrate the

proposed plans are provably secure and very
proficient. Our primer analysis directed on
Amazon

EC2

occurrence

additionally

exhibits the quick execution of the plan.

iv)

Efficient provable data possession
for hybrid clouds
Provable
ownership

is

information
method

Algorithms

Algorithm 1 Encryption in Bastion:1.
2.
3.
4.

5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.

procedure Enc(K, x = x[1] . . . x[m])
n = m + 1, Storage blocks : n
y′[n] {0, 1}l ⊲ y’[n] is the IV for CTR
for i = 1 . . . n − 1 do
y′[i] = x[i] FK(y′[n] + i)
end for
t = 0l
for i = 1 . . . n do
t = t y′[i]
end for
for i = 1 . . . n do
y[i] = y′[i] t
end for
return y ⊲ y = y[1] . . . y[n]
end procedure

for


A plaintext of m blocks, the CTR

guaranteeing the respectability of

encryption mode outputs n = m + 1

IJCSCN | August-September 2018
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a

3

28


ISSN: 2249-5789
P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31

ciphertext blocks. computed with (n− 1)

Algorithm

block cipher operations and (n
− 1) XOR

Algorithm:-

operations. The CTR encryption mode is
secure.


Polynomial

Time

input:n: number keys

Algorithm 2 Decryption in Bastion:1. procedureDec(K, y = y[1] . . . y[n])
,K ∈ {0, 1}k
2. t = 0l
3. for i = 1 . . . n do
4. t = t y[i]
5. end for
6. for i = 1 . . . n do
7. y′[i] = y[i] t
8. end for
9. for i = 1 . . . n − 1 do
10. x[i] = y′[i] F−1
11. K (y′[n] + i)
12. end for
13. return x ⊲ x = x[1] . . . x[n − 1]
14. end procedure

3

output:Polynomial keys
1.
2.
3.
4.

5.
6.
7.
8.

proceed(an , x[n] = x[1] . . . x[n])
if x not null
for x[i] in Xn do i ∈n
an = randomValue(); // to generate
random values
expireAfterWrite(10,
TimeUnit.MINUTES);
end for
end if
return an ;

Any party with access to all the
ciphertext blocks and the encryption key can
recover the plaintext. This requirement is
essential
subsequent

for

the
linear

correctness

of


the

transform

on

the

ciphertext blocks. That is, if m is even, then
the transform is not invertible. l is the block
size of the particular block cipher used. 0l
and 1l denote a bit-string of l zeros and a bitstream of l ones, respectively.

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ISSN: 2249-5789
P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31

4

Results

No. of File Character
No of different Characters


200
180
160
140
120
100
80
60
40
20
0
NO. Of character

1
0

2
40

3
80

4
120

5
160

No of different characters


0

50

100

150

200

Fig: Performance Analysis Graph
NO. Of character

No of different characters

0
0
40
50
80
100
120
150
160
200
Table: Performance Analysis

The graph is drawn between the

the system that has been proposed by the


number of file character that are being used

author. Uses the characters on completion of

for the encryption and decryption v/s

the rotation, this makes the algorithms to

number of different characters that are using

take little less character than this proposed

by the algorithm. the algorithm used in this

method.

system takes more characters to replace than

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ISSN: 2249-5789
P Subhadra Devi et al, International Journal of Computer Science & Communication Networks,Vol 8(4),25-31

5


Conclusion

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407.

In this paper, we tended to the issue of

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securing information outsourced to the cloud against

Vukolic, "Ground-breaking Information Sharing with

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that catches information privacy against the new

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that


International Workshop on Coding and Cryptology

guarantees

the

classification

of

encoded

information notwithstanding when the enemy has the

(IWCC), 2011, pp. 11– 46.

encryption key, and everything except two figure

[6] A. Bessani, M. Correia, B. Quaresma, F. André,

content blocks. Bastion is most appropriate for

and P. Sousa, "DepSky: Dependable and Secure

settings where the cipher text blocks are put away in

Storage in a Cloud-ofclouds," in Sixth Conference on

multi-Cloud storage frameworks. In these settings,


Computer Systems (EuroSys), 2011, pp. 31– 46.

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recoup any single piece of plaintext. We broke down

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[8] V. Boyko, "On the Security Properties of OAEP

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as an Allor-nothing Change," in Advances in

the execution of existing natives which offer

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