Secure Data Processing Algorithms in Mobile Cloud
Computing - Survey
Divya K B
Sijo Cherian
Post graduation Student,Dept. Of IT
Rajagiri College Of Engineering &Technology
Ernakulam,India
divyabhakth@gmail.com
Assistant Professor,Dept Of IT
Rajagiri College Of Engineering &Technology
Ernakulam,India
sijoc@rajagiritech.ac.in
Abstract— Mobile cloud computing is a technique to
overcome the inabilities of a mobile device due to less battery
power, storage and processing power. However cloud computing
provide an illusion of infinite computing resources. Mobile cloud
computing is a new platform to combine mobile devices and
cloud computing to create new infrastructure whereby cloud
perform computationally intensive works and storing massive
amount of data. Here the data processing and data storing done
outside of mobile device. The surveys predicts that majority of
the enterprise will change their working environment to mobile
cloud and laptop by 2017. So mobile cloud computing will be an
important concern in the coming years. However users concerns
about data security are the main obstacles that impede cloud
computing from being widely adopted. These concerns are
originated from the fact that sensitive data resides in public
clouds, which are operated by commercial service providers that
are not trusted by the data owner. Thus, new secure service
architectures are needed to address the security concerns of users
for using cloud computing techniques. This survey focusing on
different secure data processing mechanisms, and comparing
different encryption and decryption algorithms used in it.
2015 there would be more than 240 million customers using
Mobile Cloud Computing services while in 2008 there were
only 42.8 million customers[1]. Mobile devices are vulnerable
to numerous security threats that aim the theft of users data.
Moreover Cloud Computing introduces several security,
privacy and trust issues regarding the data processed in the
Cloud. Consequently to maintain consumers trust in mobile
platforms more specifically in mobile cloud applications, it is
important to secure data processing that will be used by
mobile cloud applications. The paper is organized in such a
way that the section I gives a brief about mobile cloud
computing.Section II gives basic ideas of different approaches
in secure data processing in mobilecloud. section III,IVand V
defines different encryption and decryption algorithms in data
processing mechanisms.VI th and VIIth section deals with the
defining advantages ,disadvantages and comparison. Finally
VIII and IX th section conclusion and future scope.
Keywords—:Mobile
cloud
computing;
Decryption;ABE;IB-PRE;PP-CP-ABE;
There are three types of data processing approaches are
considered here, they are secure data processing framework
for mobile cloud computing[2],SDSM: A secure data service
mechanism in mobile cloud computing[3],efficient and secure
data storage operations for mobile cloud computing[4]. The
approaches discussed here are based on bilinear pairing and
secret sharing. The next section gives a brief about each
processing mechanisms in mobile cloud, the encryption,
decryption algorithms as well.
I.
Encryption;
INTRODUCTION
Just a short time ago a user was only expecting from her/his
mobile phone to allow her/him to perform activities using just
the device resources (e.g. to take pictures and save them
locally on the device, or to read different types of data that
were saved locally). Today, the same user wants to be able to
take advantage of powerful and complex applications that
manipulate not only the mobile local resources but also
external resources as computation power and storage space.
To obtain these types of performances several improvements
have been made in the domain of mobile hardware and
network[1].Even with those improvements mobile devices still
have lack of resources and energy, an unstable connectivity
and several other security issues[1]. To resolve some of these
issues, the concept of Mobile Cloud Computing has been
proposed as a solution where the Cloud is used as a platform
to execute mobile applications. Mobile Cloud Computing as a
term was born shortly after the emergence of Cloud
Computing model in 2007 . Marketing research stated that in
II. GENERAL APPROACHES TO SECURE DATA
PROCESSING IN MOBILE CLOUD COMPUTING
A. Bilinear Pairing
Major
pairing
based
construction
is
bilinear
map[9].Consider two groups G1 and G2 are multiplicative
group with large prime order p. Now consider the mapping
e:G1× G1 → G2. Pairing has following properties
1. Bilinearity: e(Pª,Qᵇ) = e(P,Q)ªᵇ,∀ P,Q∈G1,a,b ∈ Z∗ p.
2. Nondegeneracy: e(g,g) ≠ 1 where g is the generator of G1.
3.Computability: There exists an efficient algorithm to
compute the pairing.
B. Secret Sharing
Suppose a secret is divided in to n shares and any t shares
can reconstruct the data, if the shares is less than ’t’, we
cannot expose the data in the secret[10][12]. The following
section will brief about various approaches.
III.
SECURE DATA PROCESSING FRAMEWORK IN
MOBILE CLOUD COMPUTING
The architecture consists of three main domains, cloud
mobile and sensing domain, cloud trusted domain and the
cloud public and storage domain. In this framework each
mobile device is virtualized as ESSI(Extended Semi Shadow
Image) in the cloud trusted domain, it is due to reduce the
uncertainty caused by mobility[5]. The ESSI is a partial, or an
exact clone of each mobile device. Each ESSI can be act as a
service node(SN) in a particular application. A mobile device
can outsource its computing and storage services to its
corresponding ESSI and Secure Storage (SS)[5]. The ESSIs
can be used to address communication and computation
deficiencies of a mobile device, and provide enhanced security
and privacy protections. ESSI is a virtual machine that is
designed for an end user having full control of the information
stored in its virtual hard drive. Networking functions and
running processes are done through mobile cloud service
provider. The mobile cloud data processing model includes
three main components: trust management, multi-tenant secure
data management, and ESSI data processing model.
ABE(Attribute Based Encryption) had been proposed for data
encryption and decryption.
2) ENCRYPT(PK,M,A) : The encryption algorithm takes
the public parameter PK, the message M, and the access
structure ‘A’ .The algorithm will encrypt the plain text M to
cipher text CT such that only a user that possesses a set of
attributes that satisfies the access structure will be able to
decrypt the message[6].
3) KEYGEN(MK,S) :This algorithm takes as input the master
secret key (MK) and set of attributes S that describe the
key.It outputs a private key (SK) with S [6].
4)DECRYPT(CT,SK) :The decryption algorithm takes as
input the public parameters PK, a ciphertext CT, which
contains an access policy A, and a private key SK, which is a
private key for a set S of attributes. If the set S of attributes
satisfies the access structure ’A’ then the algorithm will
decrypt the ciphertext and return a message M[6].
IV. SDSM: A SECURE DATA SERVICE MECHANISM
IN MOBILE CLOUD COMPUTING
The network model[3] consists of data owner(mobile
device with internet connection),data sharer(mobile device
with internet connection) and the cloud service provider. To
protect data to third party data must be encrypted before
sending to cloud server to either for file sharing or for personal
use. The one who want to share the data must be authorized by
the data owner to decrypt the file. This particular model
emphasizes on confidentiality and access control of mobile
user’s outsourced data in cloud environment. This method
employ identity based proxy re-encryption to realize the
secrecy of data.
Figure 2: Model for SDSM
Figure 1: Service Model of mobile cloud
A. Attribute Based Encryption(ABE)
In ABE cipher text and secret keys are associated with sets
of attributes. Here AND gates and OR gates are used to
represent the access structure. Attribute based encryption
consists of mainly four algorithms (i) setup(ii) key gen(iii)
encryption (iv)decryption.
1)SETUP (λ ,U) : On inputting security parameters and
attributes, obtain output as public parameters and master secret
key. The public parameter is used for encryption and master
secret key is used for generating user secret keys[6].
In this work, considers the threats from semi-trusted cloud
server in the data storing and malicious sharer in the data
sharing. Here the system considers the cloud server to be semitrusted. That is to say, cloud servers will honestly implement
the proposed protocol in general, but try to find out as much
secret information as possible based on user’s inputs.
Malicious sharer may try to access the data without permission
by the data owner. In short only authorized sharer can access
the data and unauthorized sharer learn nothing. Moreover the
collusion attack of the malicious sharers and the semi-trusted
cloud servers should also be considered.
A) Five phases in this protocol
1) Setup: By using the Setup and KeyGen algorithms in
the IB-PRE system parameters and master secret key are builds
up. Master secret key is used only at the time of user
registration to the system. The one who registered to the
system only gets the private key corresponding to his identity.
The data owner can share his data only by giving[7] the
identity of the sharers.
2) Data Encryption :The data is divided into different
blocks, each block encrypts the message separately. The
corresponding cipher text of each block is upload to the cloud.
3) Data Sharing :In this phase the data owner runs the
KeyGen algorithm to generate the proxy key/re-generation key
to the cloud. The cloud then encrypts the cipher text again
using the proxy key on behalf of data owner under the sharer’s
public key. The cloud can deploy the re-encrypt key ‘rk’ to
permit the authorized user to get the cipher text decrypted with
his own secret key. The cloud can deploy the re-encrypt key to
permit the authorized user to get the cipher text decrypted with
his own secret key.
4) Access Data :When the sharer want to access the file,
he sends a request to the cloud server. The cloud then checks
the validity of the sharer , ie it has a re-encryption key to the
sharer. The cloud server then runs the RKGen algorithm and
achieves the re-encryption cipher text. The sharer then fetches
the re-encrypted data from the cloud server and run the decrypt
algorithm with the secret key. As doing so, the sharer will get
the original data file.
5). Re-encrypt(params,re-encryption key,cipher text):
Inputs are parameters, re-encryption key and the cipher text.
Output will be re-encrypted cipher text.
6). Decrypt(params, secret key, re-encrypted cipher
text): Decrypts the cipher text using the secret key and outputs
the plaintext.
V. EFFICIENT AND SECURE DATA STORAGE
OPERATIONS FOR MOBILE CLOUD COMPUTING
This is a framework to secure data storage in public cloud
which focus on light weight wireless devices store and retrieve
data without exposing the data content to the cloud. To achieve
data security, the method uses an encryption technique known
as PP-CP-ABE. Using PP-CP-ABE, user can outsource
intensive computation for encryption and decryption to cloud
service provider without exposing user’s data and secret keys.
It proposes an Attribute Based Data Storage(ABDS) system as
cryptographic access control mechanism. It achieves optimality
in minimizing computation, storage and communication
overheads[4].
This is the general working of SDSM. Next section will
explain the re-encryption algorithm used in SDSM for secure
data processing.
B) Identity-Based Proxy Re-Encryption
It is an identity based encryption[11] technique in which
sender uses ID as public key of recipient to encrypt message.
Here the fundamental concept of IB-PRE scheme is that the
proxy is not fully trusted[7].It doesn’t have any idea of sender
and recipients secret keys and about the plain text. The proxy
server or the recipient, any one of them should be honest. This
IB-PRE scheme allow a proxy to translate an encryption under
Alice’s identity in to one computed under Bob’s identity[7].
The users request key from trusted private key
generator(PKG). IB-PRE scheme is a tuple of algorithms ie
Setup, KeyGen, Encrypt, Decrypt, RKGen, Re-encrypt[7].
1) Setup(lª,maximum level): On inputting security
parameters and the number of re-encryption, it outputs a master
public parameter that are distributed to user and a master secret
key(msk) kept private.
2) KeyGen(params,msk,ID) : Inputs are the identity and
the master secret key ,outputs a decryption key corresponding
to given identity.
3) Encrypt(params,ID,m):On inputting parameters,
identity and the plain text m ,it outputs the ciphertext.
corresponding to the given identity.
4)RKGen(params,sk,ID1,ID2):Inputting
security
parameters , secret keys and identities the obtained output is the
re-encryption key corresponding to both the identities.
Figure 3: System Architecture
The proposed model consists of a Data Owner, it can be a
wireless device or a sensor that can request and/or store
information in the cloud. Data is secured using PP-CP-ABE
scheme. There are many data receivers who subscribe the data
from data owner. This model has some following properties


Data must be encrypted before storing it into Storage
Service Provider(SSP).
ESP(Encryption Service Provider ) provides
encryption without knowing the actual data and the
encryption key.

DSP(Decryption Service Provider) decrypts the data
without knowing data.
 Even ESP,DSP,SSP collude,the data contents cannot
exposed.
By doing so the encryption and decryption overheads of the
mobile user can be completely outsource to a high capacity
cloud infrastructure.That will reduce the time for computation
in the mobile device without compromising security.
VI. ADVANTAGES AND DISADVANTAGES
A) Attribute Based Encryption(ABE)
1)Advantages

It is good for one to many communication .

Using ABE we can divide a group in to
different communicating sub groups.ie,
A) Privacy Preserving CP-ABE
PP-CP-ABE is an extension of actual CP-ABE. Here Data
Owner outsource intensive computation required for
encryption and decryption to powerful cloud service providers
without disclosing the data contents and keys[4]. PP-CP-ABE
consists of four fundamental algorithms.
1). Setup(lk ,k):On inputting security parameters and
number of system attributes it outputs public key(PK) used for
encryption and master secret key which is used for private key
generation.
Figure 4: Sample access policy tree
2). KeyGen(PK,MSK,L): It takes public key(PK), master
secret key(MSK) generated by Setup algorithm, and the list of
attributes(L), outputs the private key .

3) Encrypt(PK,W,M): This algorithm takes public
key(PK), the access policy tree(W) ,which will describe later
in this section, and the original message to send as input. It
outputs the cipher text (CT) such that only user with attribute
list which satisfying the access policy can decrypt the cipher
text (CT).
2) Disadvantages
4).Decrypt(PK,SK,CT): Inputs given are the public
key(PK),private key(SK)and the cipher text (CT).Output will
be the original text message the one who satisfying the access
policy tree can disclose the original message .
B) Access Policy Tree
Access policy tree consists of leaf nodes and internal nodes.
Leaf nodes are system attributes and internal nodes are logic
gates AND,OR. Several functions and terms are defined as
follows


parent(x): It returns the parent node of x.
att(x) :Defines the attribute associated with leaf node
x. The access tree consists of leaf nodes and internal
nodes. The one who owns the set of attributes
satisfying access policy and to reach the root of the
tree, it can access the secret secured in the access
policy tree. User has private key corresponding to
access policy tree.
 num x : Returns number of children in the node x[8].
The figure is shown below.
suppose Alice upload her photo to a site and she
wishes to seen these photo to only her female
friends. She may not know the exact identities of
all her friends, rather she may only have a way to
describe them in terms of descriptive attributes.
But this is difficult to solve in common cryptosystems.

The mobile user must know the sharer’s attribute
list before performing encryption.

Sharers satisfying the access policy may consist
of few persons, that make the data owner difficult
to implement the access control of data.

The decryption algorithm is computationally
expensive because bilinear pairing operations over
ciphertext and private key is a computational
intensive operation.
B) IB-PRE
1) Advantages

ID-PRE has strong access control.ie only
authorized user can decrypt the data. Data owner
can distinguish the identity information of sharers.

Flexible, to provide mobile users to change the
access policies when needed.

It protect the mobile user’s data from leaking to
the cloud.

Reduce the communication cost of mobile user.
2)Disadvantages
VIII. CONCLUSION

The File to be transmitted is divided into a number of blocks ,which increases the overhead in
user.

An extra key ie a re-encryption key is required.
In this paper we present different secure mechanism
for data processing in mobile cloud computing. Each of
these methods used different algorithms for data
encryption and decryption .They are Attribute Based
Encryption, PP-CP- ABE and IB-PRE. Made a survey
based on the algorithms, advantages and disadvantages
were found. Finally we concluded that each of these
algorithms have both advantages and disadvantages, and
PP-CP-ABE has good performance in mobile cloud
comparing the others. Compared with existing CP-ABE
constructions, PP-CP-ABE significantly reduces the
ciphertext size from linear to constant and supports
expressive access policies.
C) PP-CP-ABE
1) Advantages

In PP-CP-ABE ,for decryption securely
blinding the private key and outsource the
expensive operations to the Decryption
Service provider(DSP).

Outsourcing will not expose the data content
of the cipher text to DSP. Because the final
step of decryption is performed at the user.

Expensive operation ie encryption and
decryptions are outsource to cloud ,that will
reduce the cost of the mobile user.

Even if the Encryption Service Provider(ESP)
possesses secrets of most but not all parts of
the access policy tree, the master secret is still
secure given there at least one secret that is
unknown to ESP.
2) Disadvantages

Time consuming, comparing with other
methods it will take more time for
encryption and decryption. But looking at
the overall performance ,it is negligible .

PP-CP-ABE is based on BGW CP-ABE
scheme[8], which suffers from linearly
growing ciphertext size.
VII. COMPARISON
This section makes a simple comparison of the given
three approaches.
Table 1: Comparison of algorithms
Characteristics
CPABE
IB-PRE
PP-CPABE
Key used
Public
key
Public
key
Public
key
2
Encryption
based on
Identity
Identity
identity
3
Number of
encryption
Once
Twice
Once
Encryption
done by
Data
owner
User
and
proxy
Outsource
to ESP
Decryption
done by
User
User
Outsource
to DSP
Sno
1
4
5
IX. FUTURE WORK
In PP-CP-ABE, size of the cipher text grows linearly
as the number of attribute increases, because it is now
based on BGW scheme[8], so new policy which should be
constant cipher text size with PP-CP-ABE can be
developed. Energy efficiency can be added for further
improvement. Moreover in future hidden access policies
can be used and the policy may be flexible in future.
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