A New Guess-and-Determine Attack on the A5/1 Stream Cipher

Abstract: In Europe and North America, the most widely used stream cipher to ensure privacy and confidentiality of conversations in GSM mobile phones is the A5/1. In this paper, we present a new attack on the A5/1 stream cipher with an average time complexity of 2^48.5, which is much less than the brute-force attack with a complexity of 2^64. The attack has a 100% success rate and requires about 5.65GB storage. We provide a detailed description of our new attack along with its implementation and results.