Cryptology ePrint Archive: Report 2016/209

Automatic Differential Analysis of ARX Block Ciphers with Application to SPECK and LEA

Ling Song and Zhangjie Huang and Qianqian Yang

Abstract: In this paper, we focus on the automatic differential cryptanalysis of ARX block ciphers with respect to XOR-difference, and develop Mouha et al.'s framework for finding differential characteristics by adding a new method to construct long characteristics from short ones. The new method reduces the searching time a lot and makes it possible to search differential characteristics for ARX block ciphers with large word sizes such as $n=48,64$. What's more, we take the differential effect into consideration and find that the differential probability increases by a factor of $1.4\sim 8$ for SPECK and about $2^{10}$ for LEA when multiple characteristics are counted in. The efficiency of our method is demonstrated by improved attacks of SPECK and LEA, which attack 1, 1, 4 and 6 more rounds of SPECK48, SPECK64, SPECK96 and SPECK128, respectively, and 2 more rounds of LEA than previous works.

Category / Keywords: Differential cryptanalysis, automatic search, ARX, SPECK, LEA

Original Publication (with minor differences): ACISP 2016

Date: received 25 Feb 2016, last revised 3 Jul 2017

Contact author: songling at iie ac cn

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Version: 20170704:014535 (All versions of this report)

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