Abstract

There is encryption algorithms used in GSM. This is for to encrypt the information when transmit from mobile station to base station during communication. As stated that A5/1 is strong algorithm but it cryptanalysis by cryptanalysts. This paper modified concept to improve A5/1 encryption algorithm by consideration of feedback combining function of LFSRs (Linear feedback shift register) use in A5/1 and modified version of A5/1 is fast and easy to implement. This is proved by the comparison of existing A5/1 and modified A5/1 with novel key stream generator using pseudorandom binary sequence. Basic security of A5/1 analysis by statistical tests given by national institute of standards and technology (NIST) in order to ensure the quality of bit stream produced by the generator.

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