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Séminaire des équipes de recherche

Bicliques in Block Cipher Cryptanalysis: New Results on AES

Séminaire organisé par l'équipe-projet CASCADE.

A 10h30, entrée libre.

  • Date : 1/07/2011
  • Place : École Normale Supérieure, Salle INFO 5 - Niveau -1 - NIR
  • Guest(s) : Christian Rechberger (ENS, Chaire France Telecom pour la sécurité des réseaux de télécommunications)
  • Organiser(s) : Equipe-projet CASCADE

Since Rijndael was chosen as the Advanced Encryption Standard (AES), improving upon 7-round attacks on the 128-bit key variant or upon 8-round attacks on the 256-bit key variant is considered to be one of the most difficult challenges in the cryptanalysis of block ciphers for more than a decade.

We present a novel technique of block cipher cryptanalysis using so-called bicliques. This allows us to obtain for the first time results on a higher number of rounds, yet the advantage over brute-force search may become small.
In contrast to most shortcut attacks settings on AES versions, we do not need any related-keys. Our approach is practically verified to a large extent, yet its full implementation needs prohibitively large computational resources and hence does not threaten the practical use of AES in any way.

This is joint work with Dmitry Khovratovich.

Keywords: CASCADE Cryptographie ENS Séminaire Paris - Rocquencourt