GSM network and its privacy- the A5 stream cipher

Abstract: This paper shows the basic mechanisms of the GSM cellular network to protect security and privacy. The A5 stream cipher is described in detail in both variations A5/1 and A5/2, with a short introduction of the required A8 cipher and the similar A3 cipher. A summary of major cryptanalysises on the A5 cipher is presented, followed by ideas and personal opinions about the practical approach of attacks