Enhancing Selective Encryption Algorithm for Secured MANET

Ajay Kushwaha Department of Computer Science and Engineering

Rungta College of Engineering & Technology Bhilai, India

ajay.kushwaha@ieee.org

Hariram Sharma Department of Computer Science and Engineering

Rungta College of Engineering & Technology Bhilai, India

hrsharma44@gmail.com

Abstract— Mobile Ad hoc Network (MANET) technology is spreading widely these days because of its independence from fixed infrastructure. For MANET, possessing highly limited resources, Symmetric key algorithms are more efficient and viable as compared to asymmetric key algorithms while transmitting messages via network due to less power consumption. Due to technological advancement MANET is getting more and more accessible to common man, but the most alarming challenge that MANET is facing is the security issue. In this paper we introduce an enhanced approach of selective encryption algorithm for achieving better data protection. First we are giving an overview of selective encryption algorithm, and proposing an enhanced selective encryption algorithm based on symmetric key. By implementing the proposed method, the process of message encryption can be made more uncertain and overhead may be reduced, thereby making the encryption procedure more efficient. We will carry out a set of simulation experiments on ns2 simulator in future to validate our proposed method.

Keywords- Mobile ad hoc network; encryption; decryption; cryptosystem; cipher text; symmetric key.

I. INTRODUCTION

The formal definition of cryptography says the art of protecting information by transforming it (encrypting it) into an unreadable format called as cipher text. Only those who possess a secret key can decipher (decrypt) the message into plain text. Encrypted messages can be broken by cryptanalysis also called as code breaking although modern cryptography techniques are virtually unbreakable. For encryption of data, cryptography employs two styles symmetrical and asymmetrical encryption.

The keys are same for both encryption and decryption process in symmetric algorithm while they are different in asymmetric algorithms. Symmetric encryption, also known as secret key encryption, is the oldest and best-known technique for data protection. A secret key, which can be a number, a word, or just a string of random letters, is applied to the text of a message to change the content in a particular way. This might be as simple as shifting each letter by a number of places in the alphabet. As long as both sender and recipient know the secret key, they can encrypt and decrypt all messages that use this key.

In this article, II section discusses the updated related work of data protection approaches. The III section gives the security issues for MANET. Section IV illustrates the

contribution of selective encryption algorithm for data security. Next section will discuss the proposed method, designed to enhance the security for MANET. Finally the paper concludes with future scope.

Figure 1. An example of symmetrical algorithm

II. LITRATURE REVIEW

Youngling et al [1] present a probabilistic selective encryption algorithm which utilizes the advantages of the probabilistic methodology that aims to acquire additional uncertainty. While sending messages, the sender will randomly produce a value to designate the encryption percentage, which represents how many messages will be encrypted among the transmitted messages.

They compared their probabilistic approach with toss a coin method, in toss a coin every alternate word was encrypted which needed 50 % encryption of message. But in probabilistic selective encryption a random encryption ratio, er is generated for each run, which decides what percentage of message is to be encrypted, because of the uncertainty of value of er, randomness is increased, and a probability variable is used for making decision whether a particular message of whole data, should be encrypted or not.

Pseudo Random Generator is combined with the Random Generator to form a hybrid generator by Witjaksono et al.

2012 Fourth International Conference on Computational Intelligence, Modelling and Simulation

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DOI 10.1109/CIMSim.2012.16

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[2]. This hybrid resultant can enhance the randomness and reliability for generation of key in crypto-system.

Uthariaraj and Prakash [3] use symmetric key for developing an n-way cryptosystem. This multicrypt system uses a hierarchical structure for managing nodes that forms the network. They also helped in introducing functions that are significant for key management for e.g. rekeying, key revocation. This is helpful in reducing the overhead of key exchange.

Cao and Zhou [4] use the properties of public-key based certificate. The approach examine digital signature by employing self-certificate. Here registration to the authority is done by any user, using the public key and hash function. Then after the authority will compute and issue one guarantee G to authenticate the signer’s signature.

Dang and Boa [5] make use of both block cipher and stream cipher, Block cipher’s advantage is being used for protecting secret key distribution and stream cipher contributes in encrypting the pain text. Because of this combined approach, the resulting cryptosystem is broad and fast.

Lee and Keromytis [6] propose changes in receiver of a cryptosystem. They suggested a dual receiver, which decrypts a cipher text, after having separate keys from first and second user.

Zhou and Yang [7] propose a blind signature method. Here a trusted signer can generate blind signature, and verify the signature, with having no knowledge about the message. The approach uses hyper-elliptic curve encryption.

Liu et al. [8] provide a video encryption scheme for Advanced Video Coding (AVC) code C, in which encryption is done only for residue data and motion vector, as the selected data are sensitive, and demand for encryption.

Zou et al. [9] present a selective encryption algorithm for MPEG video transmission, which is a 2-way approach. Here, each frame is sliced to m slices, each slice is implemented with XOR operation and then selective encryption is done for resultant slice, which ultimately speed the encryption procedure.

Talele et al. [10] present a comparison of different MPEG encryption algorithms. The various points of view considered for comparison are security level, encryption speed, string size. The emphasis is given to encryption speed in real-time communication environment, such as on demand video conferencing.

Ma et al. [11] provide a selective algorithm which is for light weight media data. The encryption process is divided into 2 stages in the first stage, the plain text is partially encrypted by block cipher method, in second stage, and the rest of the data is encrypted using plain text. The ratio of first stage and second stage is modified, for adjustment of encryption speed.

Massoudi et al. [12] provide a list of evaluation standard for JPEG 2000 compressed image transfer. These are cryptographic security, encryption ratio, format compliance, compression friendliness and so on.

III. SECURITY ISSUES IN MANET

Following are the challenges that MANET faces while transmitting the data from one node to another [13]:

i. No predefined edges: As the nodes are of moving in nature, it is hard to define a précised boundary for the network, this result in the attacks such as the attacks include eavesdropping impersonation; tempering, replay and Denial of Service [14] attack.

ii. Malicious nodes inside the network: As the nodes are dynamically changing, it is hard to detect the behaviour of the node, if it is malicious or not.

iii. No centralized administration: In MANET the network cannot be monitored by a central control, so detection of attack becomes challenging.

iv. Scarcity of energy resources in MANET: The resources which are responsible for the transmission of data in wireless network possess limited energy that must be preserved. It is difficult to save energy of resources while transmitting data in MANET.

IV. SELECTIVE ENCRYPTION ALGORITHM

A. Concept of Selective Encryption

The concept of selective encryption was independently introduced by Spanos and Maples [15], and Li et al [16], for the purpose of reducing the amount of encrypted MPEG data in a video sequence while at the same time providing an acceptable security level.

Selective encryption is a new trend in content protection. It aims at reducing the amount of data to encrypt while achieving a sufficient and inexpensive security.

Figure 2. Schematic diagram of selective encryption algorithm[1]

B. Secure Key Allocation

Public key algorithm need more computational power, which is a limitation in wireless devices, so secure key distribution is more appropriate for this technique. The above figure 2 illustrates the secret key distribution in selective key encryption for wireless network.

Let us denote the initiating node as X and receiving node as Y. [1]. If an initiating node X node R, it will notify node Y about the public key which is with X, for the authentication between them. After that the receiving node Y

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assigns a secret key to the node X for performing encryption/decryption. For distributing the secret key securely, X encrypts this secret key using the public key of node S before sending it. Besides, there is different secret key generation by Y for different initiating nodes. This ensures that each sender has a unique secret key for communicating with the receiver and all information is encrypted using the corresponding secret key.

Figure 3. Schematic diagram of key distribution[1]

The above figure illustrates the procedure of secret key distribution between a pair of nodes. The message’s sender composes a communicating request message req which contains not only its identifier IDS, but also its public key PKS, for the purpose of their later mutual authentication. Once the receiver gets such a communication request, a secret key (symmetric key) SKS will be generated by the receiver and encrypted using the public key PKS of the requester, which is included in the communicating request message.

V. PROPOSED SELECTIVE ENCRYPTION ALGORITHM FOR

TEXT MESSAGES

In this section, we will explain the proposed selective encryption algorithm step by step. Our emphasis will be on improving the encryption process in terms of processing time and security. Our main aim is not only to send data on the wireless network from one node to another, but also to secure the data from hackers. In ad hoc networks all nodes are capable of performing all tasks on their own. Generally the links between the wireless nodes are always bidirectional.

Proposed Algorithm Step 1. Input Wi

Step 2. For each Wi, where i=1 to n Check if Wi � D If yes go to step 4 Else go to step 3

Step 3. Encrypt Wi using public key algorithm and send the message to network.

Step 4. Send the message to network without encryption.

Wi means words present in the message. Mi is the message to be encrypted. D is the database of all commonly used

words like articles, conjunctions etc And i is the iteration variable

A. Advantages of proposed method over previous work

This paper gives an algorithm which is better in terms of security and reliability when compared to [1] by following reasons:

i. The part of data which is encrypted by referring to encryption ratio er, need not encrypt all the sensitive data, that are present in the message and thus provide loopholes for attackers. While our approach, ensures that the sensitive data (infrequent words) are getting encrypted, and thus ensures the security of message during transmission.

ii. The text data possess parts of speech, such as articles, preposition, conjunction, modals and interjection in majority and encryption of these words, increases the overhead of encryption process, and not required also but our approach removes encryption effort for overall message.

Figure 4. Flow chart of proposed selective encryption algorithm

VI. CONCLUSIONS

Nowadays wireless network demand a secure method for data transmission. This paper provides an enhanced approach of selective encryption algorithm for text data transfer via MANET. The approach provides the advantages of selective encryption by encrypting only those data that are sensitive, and must be encoded and sending the less sensitive data as it is. As a result the overhead of whole process is reduced, and security of data is ensured, by providing a reliable model for data transmission. The proposed algorithm will be implemented in ns2 simulator and will be compared with other methods of data encryption.

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