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2007
Springer

A Hardware-Assisted Realtime Attack on A5/2 Without Precomputations

11 years 7 months ago
A Hardware-Assisted Realtime Attack on A5/2 Without Precomputations
Abstract. A5/2 is a synchronous stream cipher that is used for protecting GSM communication. Recently, some powerful attacks [2,10] on A5/2 have been proposed. In this contribution we enhance the ciphertext-only attack [2] by Barkan, Biham, and Keller by designing special-purpose hardware for generating and solving the required systems of linear equations. For realizing the LSE solver component, we use an approach recently introduced in [5,6] describing a parallelized hardware implementation of the Gauss-Jordan algorithm. Our hardware-only attacker immediately recovers the initial secret state of A5/2 - which is sufficient for decrypting all frames of a session - using a few ciphertext frames without any precomputations and memory. More precisely, in contrast to [2] our hardware architecture directly attacks the GSM speech channel (TCH/FS and TCH/EFS). It requires 16 ciphertext frames and completes the attack in about 1 second. With minor changes also input from other GSM channels (e.g...
Andrey Bogdanov, Thomas Eisenbarth, Andy Rupp
Added 07 Jun 2010
Updated 07 Jun 2010
Type Conference
Year 2007
Where CHES
Authors Andrey Bogdanov, Thomas Eisenbarth, Andy Rupp
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