Differential cryptanalysis of eight-round SEED

Block Cipher SEED is one of the standard 128-bit block ciphers of ISO/IEC together with AES and Camellia (Aoki et al., 2000, ISO/IEC 18033-3, 2005; Korea Information Security Agency, 1999; National Institute of Standards and Technology, 2001) [1], [4], [5] and [6]. Since SEED had been developed, there is no distinguishing cryptanalysis except a 7-round differential attack in 2002 [7]. For this, they used the six-round differential characteristics with probability 2−1242−124 and analyzed seven-round SEED with 2126 chosen plaintexts. In this paper, we propose a new seven-round differential characteristic with probability 2−1222−122 and analyze eight-round SEED with 2125 chosen plaintexts. The attack requires about 2122 eight-round encryptions. This is the best-known attack on a reduced version of SEED so far.

Research highlights
► We suggest a new seven-round differential characteristic.
► We analyze eight-round SEED with this seven-round differential characteristic.
► This is the best-known attack on a reduced version of SEED so far.