New results on impossible differential cryptanalysis of reduced AES

  • Authors:
  • Wentao Zhang;Wenling Wu;Dengguo Feng

  • Affiliations:
  • State Key Laboratory of Information Security, Graduate University of Chinese Academy of Sciences, Beijing, P.R. China;State Key Laboratory of Information Security, Institute of Software, Chinese Academy of Sciences, Beijing, P.R. China;State Key Laboratory of Information Security, Institute of Software, Chinese Academy of Sciences, Beijing, P.R. China

  • Venue:
  • ICISC'07 Proceedings of the 10th international conference on Information security and cryptology
  • Year:
  • 2007

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Abstract

In this paper, we present some new results on impossible differential cryptanalysis of reduced AES, which update the best known impossible differential attacks on reduced AES. First, we present some new attacks on 6-round AES (for all the three key length). Second, we extend to 7-round AES, also for all the three key variants. Especially for 128-bit keys, the best known results can attack up to 7 rounds using square attack and collision attack respectively, but their complexity are both marginal either on data or on time (ie. require nearly the entire codebook, or close to key exhaustive search). In this sense, our attack is the first non-marginal one on 7-round AES with 128-bit keys. Thirdly, we extend to 8 rounds for 256-bit keys, which is also non-marginal compared with the best non-related-key attacks so far. Finally, we give an improvement of the 7-round attack for 192-bit keys in R.C.W. Phan's paper, which makes the time complexity reduced greatly.