Slid pairs in the initialisation of the A5/1 stream cipher
Ali Alhamdan, Harry Bartlett, Ed Dawson, Leonie Ruth Simpson, Kenneth Koon‐Ho Wong · QUT ePrints (Queensland University of Technology) · 2013
A5/1 is a shift register based stream cipher which uses a majority clocking rule to update its registers. It is designed to provide privacy for the GSM system. In this paper, we analyse the initialisation process of A5/1. We demonstrate a sliding property of the A5/1 cipher, where every valid internal state is also a legitimate loaded state and multiple key-IV pairs produce phase shifted keystream sequences. We describe a possible ciphertext only attack based on this property.