Paper 2014/704

A 128-bit Block Cipher Based on Three Group Arithmetics

Shenghui Su and Shuwang Lü and Daqiang Dong

Abstract

Enlightened by the IDEA block cipher, the authors put forward a symmetric key cryptosystem called REESSE3+ based on three group arithmetics: addition modulo 2 (bit XOR), addition modulo 2 ^ 16, and multiplication modulo 2 ^ 16 + 1. Different from IDEA, REESSE3+ uses a 128-bit block, a 256-bit key, and a renovative round function. The authors describe the REESSE3+ cipher algorithm in the graph, and expound the encryption subkeys, encryption operation, decryption subkeys, and decryption operation. Further, demonstrate the correctness of the REESSE3+ cipher algorithm, and analyze the security of REESSE3+ from four aspects. The measures for assuring the security of REESSE3+ cover those for assuring the security of IDEA, which indicates that the ability of REESSE3+ in resisting differential cryptanalysis should be at least equivalent to that of IDEA. Moreover, experiments show that a mini-version of REESSE3+ is immune to differential cryptanalysis, thus it may be expected that REESSE3+ is secure against differential attack after 8 rounds.

Note: The content has no essential change.