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Modified A5/1 Based Stream Cipher For Secured GSM Communication


Nur Hafiza Zakaria, Kamaruzzaman Seman, Ismail Abdullah


Vol. 11  No. 2  pp. 223-226


A5/1 is the stream cipher algorithm used in GSM communication in order to provide over the air communication privacy. The objective of this paper is to modify the algorithm of the existing A5/1 stream cipher in order to improve the security of GSM communication. Several statistical tests such as frequency test, serial test, runs test, long runs of ones test, and linear complexity test were used to test the strength of the algorithm. Two proposed modified A5/1 algorithms successfully passed all the basic statistical tests.


component, stream cipher, keystream generator, linear feedback shift register (LFSR), non-linear feedback shift register (NLFSR), clocking, least significant bit (LSB), cryptanalysis