Improved Meet-in-the-Middle Attacks on Reduced-Round Camellia-192/256

Camellia is one of the widely used block ciphers, which has been selected as an international standard by ISO/IEC. In this paper, we focus on the key-recovery attacks on reduced-round Camellia-192/256 with meet-in-the-middle methods. We utilize multiset and the differential enumeration methods which are popular to analyse AES in the recent to attack Camellia-192/256. We propose a 7-round property for Camellia-192, and achieve a 12-round attack with 2 encryptions, 2 chosen plaintexts and 2 128-bit memories. Furthermore, we present an 8-round property for Camellia-256, and apply it to break the 13-round Camellia-256 with 2 encryptions, 2 chosen ciphertexts and 2 128-bit memories.