文章基本信息

标题：Observations of Skipjack-like Structure with SP/SPS Round Function
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作者：Ting Cui ; Chenhui Jin ; Guoshuang Zhang 等
期刊名称：Journal of Universal Computer Science
印刷版ISSN：0948-6968
出版年度：2013
卷号：19
期号：16
页码：2453-2471
出版社：Graz University of Technology and Know-Center
摘要：Impossible differential cryptanalysis is an important tool for evaluating the security level of a block cipher, and the key step of this cryptanalysis is to find the longest impossible differential. This paper focuses on retrieving impossible differentials for m-cell Skipjack-like structure with SP/SPS round function (named Skipjack_SP and Skipjack_SPS resp.). Up to now, known longest impossible differentials in m-cell Skipjack-like structures is m² rounds. In this paper, we provide some new m² rounds impossible differentials for these two structures. Further, we prove that if P layer is chosen from binary matrices, we can always retrieve m² + 1 rounds impossible differentials for these two structures, and m² + 2 rounds impossible differentials for Skipjack_SP. Moreover, if P layer satisfies some satiable conditions, we may further obtain m² + 2 rounds impossible differential for Skipjack_SPS. Our results show that we should choose P layer carefully when employing these two structures.