Lecture Notes in Computer Science vol:3108 pages:98-109
ACISP 2004 date:July 13-15, 2004
This paper presents a dedicated known-plaintext attack on up to four rounds of the IDEA cipher, that trades-off a small number of known data blocks (114) for a larger time complexity (2(114)). This attack is also applied to up to 2.5-round MESH block ciphers, but are not more effective than previously known attacks. An advantage of this attack compared to previous known-plaintext attacks on IDEA/MESH is that no assumptions on the key value are required. Chosen-plaintext and chosen-plaintext-adaptively-chosen-ciphertext attacks can reach the full 8.5-round IDEA, and up to 5.5-round MESH ciphers, but always under weak-key assumptions.