Finding Higher Order Differentials of MISTY1

Yukiyasu TSUNOO  Teruo SAITO  Takeshi KAWABATA  Hirokatsu NAKAGAWA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E95-A   No.6   pp.1049-1055
Publication Date: 2012/06/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E95.A.1049
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Cryptography and Information Security
block cipher,  CRYPTREC,  higher order differential attack,  MISTY1,  NESSIE,  

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MISTY1 is a 64-bit block cipher that has provable security against differential and linear cryptanalysis. MISTY1 is one of the algorithms selected in the European NESSIE project, and it is recommended for Japanese e-Government ciphers by the CRYPTREC project. In this paper, we report on 12th order differentials in 3-round MISTY1 with FL functions and 44th order differentials in 4-round MISTY1 with FL functions both previously unknown. We also report that both data complexity and computational complexity of higher order differential attacks on 6-round MISTY1 with FL functions and 7-round MISTY1 with FL functions using the 46th order differential can be reduced to as much as 1/22 of the previous values by using multiple 44th order differentials simultaneously.