Design of enhanced pseudo-random sequence generator usable in GSM communication

Divulgence of A5 family of stream ciphers disclosed a number of cryptographic faults, especially in A5/1, and several cryptographic attacks were also proposed. This paper proposes an improved Linear Feedback Shift Register based stream cipher for A5 family which comprises variable tapping scheme, a new clocking mechanism, a non-linear combination function and key-generation mechanism with increased number of LFSRs and their length. Based on the feedback, period of polynomial changes randomly in this algorithm. Randomness of this proposed algorithm has been tested through “Randomness Test Suit” and it is simulated on MATLAB. Result unveils improvement in randomness of key-stream and creation of a better binary sequence in comparison to A5/1 stream cipher of comparable complexity.