International Journal of Advance Computational Engineering and Networking (IJACEN)
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Statistics report
Aug. 2020
Submitted Papers : 80
Accepted Papers : 10
Rejected Papers : 70
Acc. Perc : 12%
Issue Published : 87
Paper Published : 1231
No. of Authors : 3095
  Journal Paper

Paper Title
LFSR Based Stream Cipher (Enhanced A5/1)

In GSM cellular standard, A5 family of stream ciphers are used for providing user security over wireless communication and for this, three standards namely A5/1, A5/2 and A5/3 algorithms are stipulated. Initially, these algorithms were kept secret, but once disclosed, many cryptographic weaknesses were revealed and several cryptanalytic attacks were proposed ,particularly in A5/1. The major weaknesses in A5/1 are due to the use of fixed feedback polynomial based LFSR, weak clocking mechanism, insignificant taps of register structure, non-invertible clocking mechanism and frequent resetting. In this paper, a new enhanced LFSR based stream cipher for A5 family has been proposed that includes variable tapping mechanism, variable feedback polynomial and new clocking scheme with increased number of LFSRs and increased length of each LFSR. The proposed scheme uses four LFSRs of length 30, 32, 29 and 37 instead of three as used in other works, two of which are used for mutating of the main back-bone LFSR while the fourth LFSR mutates the final output. The mutation apparently induces variable feedback polynomial effect in the back-bone LFSR. This mutation is further randomized with a new clocking mechanism, where the clocking bit, generated by XOR-ing of two bits taken from two LFSRs, decides whether the LFSR output will be included in final output or not. The proposed algorithm has been simulated by using MATLAB and its randomness properties have been tested using ‘Randomness Test Suit’ given by National Institute of Standard and Technology (NIST), USA. The results shows that the proposed scheme is robust and resistive to the cryptographic attacks as compared to the conventional A5/1 stream cipher. It generates cryptographically better binary sequence than the A5/1 stream cipher of GSM with comparable complexity. Keywords- Stream cipher, A5/1, GSM standard, LFSR, Mutation, Randomness Test Suit

Author - Amandeep Singh Bhal, Zhilmil Dhillon

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| Published on 2014-12-02
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