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Optimization for the Algebraic Method and Its Application to an Attack of MISTY1
Yasuo HATANO Hidema TANAKA Toshinobu KANEKO
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E87A
No.1
pp.1827 Publication Date: 2004/01/01
Online ISSN:
DOI:
Print ISSN: 09168508 Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security) Category: Symmetric Cipher Keyword: MISTY1, higher order differential attack, algebraic method, linear dependency, probabilistic attack equation,
Full Text: PDF(458.6KB)>>
Summary:
In this paper, we describe a technique for optimizing the algebraic method that is applied to higher order differential attack. The higher order differential attack is a wellknown attack on block ciphers, in which we derive an attack equation to determine a round key from a property of a higher order differential of a target block cipher. The algebraic method is a linearization of the attack equation and determines the true key by a method such as Gaussian elimination. Our technique is based on linear dependency and can reduce the complexity of that method. We also describe a technique that allows the algebraic method to be used as an attack equation that holds probabilistically. We demonstrate this method by attacking a fiveround MISTY1 and show that it needs 2^{21.6} chosen plaintexts and 2^{28.0} encryption times. The computer simulation took about two minutes to complete.

