New Attacks Against Reduced-Round Versions of IDEA

In this paper, we describe a sequence of simple, yet efficient chosen-plaintext (or chosen-ciphertext) attacks against reduced-round versions of IDEA (with 2, 2.5, 3, 3.5, and 4 rounds) which compare favourably with the best known attacks: some of them decrease considerably the time complexity given the same order of data at disposal while other ones decrease the amount of necessary known- or chosen-plaintext pairs under comparable time complexities. Additionally, we show how to trade time and memory for some of the known-plaintext attacks of Nakahara et al. Key words: Block ciphers, IDEA, Demirci-Biryukov relation.

• Type: Conference
• Year: 2005
• Where: FSE
• Authors: Pascal Junod
• Keywords: Comparable Time Complexities, Cryptography, FSE 2005, Reduced-round Versions, Time Complexity