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

TL;DR

This paper introduces a new guess-and-determine attack on the A5/1 stream cipher used in GSM phones, significantly reducing the attack complexity while maintaining a high success rate.

Contribution

The paper presents a novel attack method on A5/1 with lower complexity and practical implementation details, improving on previous cryptanalysis techniques.

Findings

Attack complexity reduced to 2^(48.5) from 2^(64)

Success rate of 100% in experiments

Requires approximately 5.65GB storage

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.