Differential Attack on Five Rounds of the SC2000 Block Cipher

The SC2000 block cipher has a 128-bit block size and a user key of 128, 192 or 256 bits, which employs a total of 6.5 rounds if a 128bit user key is used. It is a CRYPTREC recommended e-government cipher. In this paper we describe two 4.75-round differential characteristics with probability 2-126 of SC2000 and seventy-six 4.75-round differential characteristics with probability 2-127 . Finally, we present a differential cryptanalysis attack on a 5-round reduced version of SC2000 when used with a 128-bit key; the attack requires 2125.68 chosen plaintexts and has a time complexity of 2125.75 5-round SC2000 encryptions. It suggests for the first time that the safety margin of SC2000 with a 128-bit key decreases below one and a half rounds. Key words: Cryptology, Block cipher, SC2000, Differential cryptanalysis

• Type: Journal
• Year: 2009
• Where: CISC
• Authors: Jiqiang Lu
• Keywords: 128-bit Key, CISC 2009, Cryptology, SC2000, User Key