Diffretial Cryptanalysis of CAST-256 Reduced to Nine Quad-Rounds(Special Section on Fundamentals of Information and Communications)

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概要

• 論文の詳細を見る

• The block cipher CAST-256 based on CAST-128 was a candidate algorithm for the AES round 1. In this paper we present a first result of a differential attack on CAST-256 reduced to 9 quad-rounds. One of the three round functions of CAST-256 has differential characteristics, for which a non-zero inputxor results in a zero outputxor, with high probability. This type of characteristic is the most useful for differential attack. We also show that CAST-256 has weak keys with respect to differential attack. Thus CAST-256 reduced to 9 quad-rounds can be attacked using 2^<123> chosen plaintexts in the case of differentially weak keys. The time complexity is about 2^<100> encryptions. Immunity to differential cryptanalysis of CAST-256 is not necessarily improved compared with CAST-128. Only 5 rounds of CAST-128 can be attacked using a similar differential characteristic.

• 社団法人電子情報通信学会の論文
• 2001-04-01

著者

• Kaneko Toshinobu

  Science University of Tokyo

• SEKI Haruki

  TAO, or Telecommunications Advancement Organization

• Seki Haruki

  Tao Or Telecommunications Advancement Organization

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• An Efficient Interpolation Attack(Special Section on Cryptography and Information Security)
• Improved Higher Order Differential Attack and Its Application to Nyberg-Knudsen's Designed Block Cipher
• Diffretial Cryptanalysis of CAST-256 Reduced to Nine Quad-Rounds(Special Section on Fundamentals of Information and Communications)

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