## Cryptology ePrint Archive: Report 2012/360

Multiple Differential Cryptanalysis using \LLR and $\chi^2$ Statistics

Céline Blondeau and Benoît Gérard and Kaisa Nyberg

Abstract: Recent block ciphers have been designed to be resistant against differential cryptanalysis. Nevertheless it has been shown that such resistance claims may not be as tight as wished due to recent advances in this field. One of the main improvements to differential cryptanalysis is the use of many differentials to reduce the data complexity. In this paper we propose a general model for understanding multiple differential cryptanalysis and propose new attacks based on tools used in multidimensional linear cryptanalysis (namely \LLR and $\CHI$ statistical tests). Practical cases are considered on a reduced version of the cipher PRESENT to evaluate different approaches for selecting and combining the differentials considered. We also consider the tightness of the theoretical estimates corresponding to these attacks.

Category / Keywords: block cipher, multiple differential cryptanalysis, statistical test, data complexity

Date: received 25 Jun 2012, last revised 16 Jul 2012

Contact author: celine blondeau at aalto fi

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