Differential and Linear Cryptanalysis of a Reduced-Round SC2000

We analyze the security of the SC2000 block cipher against both differential and linear attacks. SC2000 is a six-and-a-half-round block cipher, which has a unique structure that includes both the Feistel and Substitution-Permutation Network (SPN) structures. Taking the structure of SC2000 into account, we investigate oneand two-round iterative differential and linear characteristics. We present two-round iterative differential characteristics with probability 2 and two-round iterative linear characteristics with probability 2. These characteristics, which we obtained through a search, allowed us to attack four-anda-half-round SC2000 in the 128-bit user-key case. Our differential attack needs 2 pairs of chosen plaintexts and 2 memory accesses and our linear attack needs 2 known plaintexts and 2 memory accesses, or 2 known plaintexts and 2 memory accesses.