International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 14 May 2015

Bing Sun, Xin Hai, Lei Cheng, Zhichao Yang, Wenyu Zhang
ePrint Report ePrint Report
Feistel structure is among the most popular choices for designing ciphers. Recently, 3-round/5-round integral distinguishers for Feistel structures with non-bijective/bijective round functions are presented. At EUCRYPT 2015, Todo proposed the Division Property to effectively construct integral distinguishers for both Feistel and SPN structures. In this paper, firstly, it is proved that if a subset X of F_2^n has the division property D_k^n, the number of elements in X is at least 2^k, based on which we can conclude that if a multi-set X has the division property D_n^n, it is in some sense equivalent to either F_2^n or the empty set. Secondly, let d be the algebraic degree of the round function F of a Feistel structure. If d\\le n-1, the corresponding integral distinguishers are improved as follows: there exists a 3-round integral distinguisher with at most 2^n chosen plaintexts and a 4-round integral distinguisher with at most 2^{2n-2} chosen plaintexts. These results can give new insights to both the division property and Feistel structures.

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