Paper 2003/135

Collision Attack on Reduced-Round Camellia

Wen-Ling Wu and Deng-Guo Feng

Abstract

Camellia is the final winner of 128-bit block cipher in NESSIE. In this paper, we construct some efficient distinguishers between 4-round Camellia and a random permutation of the blocks space. By using collision-searching techniques, the distinguishers are used to attack on 6,7,8 and 9 rounds of Camellia with 128-bit key and 8,9 and 10 rounds of Camellia with 192/256-bit key. The 128-bit key of 6 rounds Camellia can be recovered with $2^{10}$ chosen plaintexts and $2^{15}$ encryptions. The 128-bit key of 7 rounds Camellia can be recovered with $2^{12}$ chosen plaintexts and $2^{54.5}$ encryptions. The 128-bit key of 8 rounds Camellia can be recovered with $2^{13}$ chosen plaintexts and $2^{112.1}$ encryptions. The 128-bit key of 9 rounds Camellia can be recovered with $2^{113.6}$ chosen plaintexts and $2^{121}$ encryptions. The 192/256-bit key of 8 rounds Camellia can be recovered with $2^{13}$ chosen plaintexts and $2^{111.1}$ encryptions. The 192/256-bit key of 9 rounds Camellia can be recovered with $2^{13}$ chosen plaintexts and $2^{175.6}$ encryptions.The 256-bit key of 10 rounds Camellia can be recovered with $2^{14}$ chosen plaintexts and $2^{239.9}$ encryptions.