Cryptology ePrint Archive: Report 2010/661

Security Evaluation of MISTY Structure with SPN Round Function

Ruilin Li and Chao Li and Jinshu Su and Bing Sun

Abstract: This paper deals with the security of MISTY structure with SPN round function. We study the lower bound of the number of active s-boxes for differential and linear characteristics of such block cipher construction. Previous result shows that the differential bound is consistent with the case of Feistel structure with SPN round function, yet the situation changes when considering the linear bound. We carefully revisit such issue, and prove that the same bound in fact could be obtained for linear characteristic. This result combined with the previous one thus demonstrates a similar practical secure level for both Feistel and MISTY structures. Besides, we also discuss the resistance of MISTY structure with SPN round function against other kinds of cryptanalytic approaches including the integral cryptanalysis and impossible differential cryptanalysis. We confirm the existence of 6-round integral distinguishers when the linear transformation of the round function employs a binary matrix (i.e., the element in the matrix is either 0 or 1), and briefly describe how to characterize 5/6/7-round impossible differentials through the matrix-based method.

Category / Keywords: secret-key cryptography / Block ciphers, MISTY structure, SPN, Practical security, Differential cryptanalysis, Linear cryptanalysis, Integral cryptanalysis, Impossible differential cryptanalysis

Date: received 29 Dec 2010, last revised 17 Jan 2012

Contact author: securitylrl at gmail com

Available format(s): PDF | BibTeX Citation

Note: The practical security evaluation for such block cipher construction against linear cryptanalysis is added.

Version: 20120117:144521 (All versions of this report)

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