Cryptology ePrint Archive: Report 2014/448

Differential Attacks on Reduced SIMON Versions with Dynamic Key-guessing Techniques

Ning Wang and Xiaoyun Wang and Keting Jia and Jingyuan Zhao

Abstract: SIMON is a family of lightweight block ciphers which are designed by the U.S National Security Agency in 2013. It has totally 10 versions corresponding to different block size $2n$ and key length $l_k$, named as SIMON$2n/l_k$. In this paper, we present a new differential attack by considering the sufficient bit conditions of the previous differential paths. Based on the bit conditions, we successfully propose a new type of dynamic key-guessing technique which greatly reduces the key space guessed. Our attacks work on the reduced SIMON of all 10 suggested versions, which improve the best previous results by 2 to 4 rounds. For verification, we implemented a practical attack on 19-round SIMON32 in a PC, and the experimental data confirm the correctness of the attack, which also fit the theoretical complexity and success rate very well. It is remarked that, our cryptanalysis only provides a more accurate security evaluation, and it does not mean the security problem of the whole SIMON family

Category / Keywords: SIMON, lightweight block cipher, bit condition, differential attack, dynamic key-guessing

Date: received 10 Jun 2014, last revised 26 May 2015

Contact author: wangning2012 at mail sdu edu cn

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Version: 20150527:032435 (All versions of this report)

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