Cryptology ePrint Archive: Report 2021/656

Automated Search Oriented to Key Recovery on Ciphers with Linear Key Schedule: Applications to Boomerangs in SKINNY and ForkSkinny

Lingyue Qin and Xiaoyang Dong and Xiaoyun Wang and Keting Jia and Yunwen Liu

Abstract: Automatic modelling to search distinguishers with high probability covering as many rounds as possible, such as MILP, SAT/SMT, CP models, has become a very popular cryptanalysis topic today. In those models, the optimizing objective is usually the probability or the number of rounds of the distinguishers. If we want to recover the secret key for a round-reduced block cipher, there are usually two phases, i.e., finding an efficient distinguisher and performing key-recovery attack by extending several rounds before and after the distinguisher. The total attacked number of rounds is not only related to the chosen distinguisher, but also to the extended rounds before and after the distinguisher. In this paper, we try to combine the two phases in a uniform automatic model.

Concretely, we apply this idea to automate the related-key rectangle attacks on SKINNY and ForkSkinny. We propose some new distinguishers with advantage to perform key-recovery attacks. Our key-recovery attacks on a few versions of round-reduced SKINNY and ForkSkinny cover 1 to 2 more rounds than the best previous attacks.

Category / Keywords: secret-key cryptography / Key recovery, SKINNY, ForkSkinny, Rectangle attack, MILP

Original Publication (in the same form): ToSC 2021, issue 2

Date: received 19 May 2021, last revised 27 May 2021

Contact author: qinly at tsinghua edu cn,xiaoyangdong@tsinghua edu cn,xiaoyunwang@tsinghua edu cn,ktjia@tsinghua edu cn,univerlyw@hotmail com

Available format(s): PDF | BibTeX Citation

Version: 20210527:113405 (All versions of this report)

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