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New Linear Cryptanalytic Results of Reduced-Round of CAST-128 and CAST-256

  • Meiqin Wang
  • Xiaoyun Wang
  • Changhui Hu
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5381)

Abstract

This paper presents a linear cryptanalysis for reduced round variants of CAST-128 and CAST-256 block ciphers. Compared with the linear relation of round function with the bias 2− 17 by J. Nakahara et al., we found the more heavily biased linear approximations for 3 round functions and the highest one is 2− 12.91. We can mount the known-plaintext attack on 6-round CAST-128 and the ciphertext-only attack on 4-round CAST-128. Moreover the known-plaintext attack on 24-round CAST-256 with key size 192 and 256 bits has been given, and the ciphertext-only attack on 21-round CAST-256 with key size 192 and 256 bits can be performed. At the same time, we also present the attack on 18-round CAST-256 with key size 128 bits.

Keywords

Linear Cryptanalysis Block Cipher CAST-128 CAST-256 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Meiqin Wang
    • 1
  • Xiaoyun Wang
    • 1
  • Changhui Hu
    • 1
  1. 1.Key Laboratory of Cryptologic Technology and Information Security, Ministry of EducationShandong UniversityJinanChina

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