The Improbable Differential Attack: Cryptanalysis of Reduced Round CLEFIA

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Tezcan C.

11th International Conference on Cryptology in India, Hyderabad, Pakistan, 12 - 15 December 2010, vol.6498, pp.197-209 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 6498
  • Doi Number: 10.1007/978-3-642-17401-8_15
  • City: Hyderabad
  • Country: Pakistan
  • Page Numbers: pp.197-209
  • Keywords: Cryptanalysis, Improbable differential attack, CLEFIA
  • Middle East Technical University Affiliated: Yes


In this paper we present a new statistical cryptanalytic technique that we call improbable differential cryptanalysis which uses a differential that is less probable when the correct key is used. We provide data complexity estimates for this kind of attacks and we also show a method to expand impossible differentials to improbable differentials. By using this expansion method, we cryptanalyze 13, 14, and 15-round CLEFIA for the key sizes of length 128, 192, and 256 bits, respectively. These are the best cryptanalytic results on CLEFIA up to this date.