Download PDFOpen PDF in browserImproved Integral Cryptanalysis on Reduced-Round Piccolo15 pages•Published: August 21, 2025AbstractPiccolo is a 64-bit block cipher proposed by Shibutani et al. in 2011, supporting 80-bit and 128-bit keys. In higher order differential cryptanalysis, computer experiments have verified that Piccolo has a 6-round characteristic using the 32-nd order differential, which was theoretically extended to a 7-round characteristic using the 48-th order differential. The integral attack is cryptanalysis, similar to a higher order differential cryptanalysis. An investigation of integral characteristics by establishing the Mixed Integer Linear Programming (MILP) model based on bit-based division property has revealed the existence of a 7-round integral characteristic using a 63-rd order differential, and a search using the Satisfiability Problem (SAT) has found a same-round integral characteristic using the 56-th order differential. In this paper, we introduce the integral property based on the frequency distribution, clarify the reason for the 5-round integral characteristic using the 16-th order differential we found by computer experiment, and derive the integral characteristics by applying the round extension.Then, we show that if the property can be used in the attack equation, the key can be identified more efficiently than the conventional method. We also present the experimental results of a key recovery attack against the reduced-round Piccolo. Keyphrases: block cipher, cryptanalysis, higher order differential attack, integral attack, piccolo In: Akira Yamada, Huy Kang Kim, Yujue Wang and Tung-Tso Tsai (editors). Proceedings of the 20th Asia Joint Conference on Information Security, vol 106, pages 99-113.
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