Abstract: An attack on a reduced-round version of Crypton algorithm is presented, which is based on the dedicated Square attack. This paper defines a -set for the Crypton algorithm, and proves in detail that all the 16 byte positions in the output of a -set after 4-round of Crypton encryption are balanced, and this balancedness can be used to attack the 4-round Crypton algorithm. When the way is used to attack 6-round cipher algorithm, it improves the method to guess keys, and gets rid of the parts which are repeatedly calculated so that the time complexity of attacking the 6-round Crypton algorithm is reduced to 250.

Key words: Crypton algorithm, Square attack, balancedness

摘要： 基于原始的Square攻击对低轮的Crypton算法进行分析。针对Crypton算法构造一个 -集，证明该 -集经过4轮的Crypton算法后在16个字节上都是平衡的。该平衡性可以被用于对4轮的Crypton算法进行分析，当该方法扩展到分析6轮的算法时，将密钥猜测进行改进，去掉重复计算的部分，6轮的Crypton算法攻击时间复杂度降可低到250。

关键词: Crypton算法, Square攻击, 平衡性

CLC Number: 

• TP309