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Séminaire des équipes de recherche

Rethinking IDEA

Séminaire organisé par l'équipe-projet CASCADE.

A 10h30, entrée libre.

  • Date : 4/07/2011
  • Place : École Normale Supérieure, Salle INFO 5 - Niveau -1 - NIR
  • Guest(s) : Orr Dunkelman (Weizmann Institute)
  • Organiser(s) : Equipe-projet CASCADE

IDEA is a 64-bit block cipher with 128-bit keys introduced by Lai and Massey in 1991. IDEA is one of the most widely used block ciphers, due to its inclusion in several cryptographic packages, such as PGP. Since its introduction in 1991, IDEA has withstood extensive cryptanalytic efforts, but no attack was found on the full (8.5-round)
variant of the cipher.

In this talk, we will discuss the various attacks on IDEA: The early differential and linear attempts, impossible differential attacks, the Demirci-Selcuk-Ture attack, and some of the newer attacks which are based on the Biryukov-Demirci relation.

Finally, we shall introduce a new and simple attack on 6-round IDEA which uses 20 known plaintexts and has a time complexity of 2^112.
This attack is currently the best known attack on IDEA (in the single-key model).

Keywords: CASCADE Cryptographie ENS Séminaire Paris - Rocquencourt