Cryptology ePrint Archive: Report 2016/1115

Impossible Differential Cryptanalysis of Reduced-Round SKINNY

Mohamed Tolba and Ahmed Abdelkhalek and Amr M. Youssef

Abstract: SKINNY is a new lightweight tweakable block cipher family proposed by Beierle $et$ $al$. in CRYPTO 2016. SKINNY-$n$-$t$ is a block cipher with $n$-bit state and $t$-bit tweakey (key and tweak). It is designed to compete with the recent NSA SIMON block cipher. In this paper, we present impossible differential attacks against reduced-round versions of all the 6 SKINNY's variants, namely, SKINNY-$n$-$n$, SKINNY-$n$-2$n$ and SKINNY-$n$-3$n$ ($n=64$ or $n=128$) in the single-tweakey model. More precisely, we present impossible differential attacks against 18, 20 and 22 rounds of SKINNY-$n$-$n$, SKINNY-$n$-2$n$ and SKINNY-$n$-3$n$ ($n=64$ or $n=128$), respectively. These attacks are based on the same 11-round impossible differential distinguisher. To the best of our knowledge, these are the best attacks against these 6 variants of the cipher in the single-tweakey model.

Category / Keywords: Cryptanalysis, Impossible differential attacks, Tweakable, Block ciphers, SKINNY.

Date: received 25 Nov 2016, last revised 13 Mar 2017

Contact author: m_tolba at encs concordia ca

Available format(s): PDF | BibTeX Citation

Version: 20170313:144020 (All versions of this report)

Short URL: ia.cr/2016/1115

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