International Association for Cryptologic Research

International Association
for Cryptologic Research


Ping Li


Impossible Differential Cryptanalysis on E2
E2 is a 128-bit block cipher which employs Feistel structure and 2-round SPN in round function. It is an AES candidate and was designed by NTT. In the former publications, E2 is supposed no more than 5-round impossible differential. In this paper, we describe some 6-round impossible differentials of E2. By using the 6-round impossible differential, we first present an attack on 9-round reduced version of E2-256 without IT Function(the initial transformation) and FT-Function(the Final transformation) function.
Impossible Differential Cryptanalysis of CLEFIA
This paper mainly discussed the impossible differerential crypt- analysis on CLEFIA which was proposed in FSE2007. New 9-round impossible differentials which are difrererent from the previous ones are discovered. Then these differerences are applied to the attack of reduced-CLEFIA. For 128-bit case, it is possible to apply an impossible differen-tial attack to 12-round CLEFIA which requires 2^110.93 chosen plaintexts and the time complexity is 2^111. For 192/256-bit cases, it is possible to apply impossible differential attack to 13-round CLEFIA and the chosen plaintexts and time complexity are 2^111.72 and 2^158 respectively. For 256-bit cases, it needs 2^112.3 chosen plaintexts and no more than 2^199 encryptions to attack 14-round CLEFIA and 2^113 chosen plaintexts to attack 15-round 256-bit CLEFIA with the time complexity less than 2^248 encryptions.
Enumeration of Balanced Symmetric Functions over GF(p)
It is proved that the construction and enumeration of the number of balanced symmetric functions over GF(p) are equivalent to solving an equation system and enumerating the solutions. Furthermore, we give an lower bound on number of balanced symmetric functions over GF(p), and the lower bound provides best known results.