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 an improved guess-and-determine attack on the A5/1 stream cipher with an average time complexity of 2^48.5, which is much less than any known guess-and-determine attack. The attack has a 100% success rate and requires a small amount of memory. We provide a detailed description of our new attack along with its implementation results.
Highlights
The most widely used stream cipher to ensure privacy and confidentiality of communications in GSM mobile phones in Europe and North America is the A5/1
We present an improved guess-and-determine attack on the A5/1 stream cipher with an average time complexity of 248.5, which is much less than any known guessand-determine attack
We describe an improved guess-and-determine attack on the A5/1 stream cipher
Summary
The most widely used stream cipher to ensure privacy and confidentiality of communications in GSM mobile phones in Europe and North America is the A5/1. The A5/1 was developed in 1987 when GSM was not considered for use outside of Europe. The description of the A5/1 was initially kept secret. Its design was disclosed in 1999 by reverse engineering (Briceno, Goldberg, & Wagner, 1999). The GSM organization later confirmed the disclosed algorithm (Biryukov, Shamir, & Wagner, 2001)
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