Low Data Complexity Differential-Algebraic Attack on Reduced Round DES

Abstract

At IMA 2007 Courtois and Bard present low-data complexity attacks on up to 6 rounds of DES by software algebraic attack methods and SAT solvers. With current methods it appears that 8 rounds of DES should be able to resist such attacks [10]. An explicit challenge with a price was proposed: break 8 rounds of DES in less than a week on one PC with maximum 2 gigabytes of RAM and given at most 16 chosen plaintexts.
In this paper we propose a new attack which is trying to achieve this objective as much as possible. Presented method combines two, already known techniques, namely differential cryptanalysis and algebraic attacks. More specifically, it shows how to use relations arising from differential characteristics to speed up and improve key-recovery algebraic attacks against reduced block cipher DES