Gimli/Xoodoo密码算法的不可能差分分析

Impossible Differential Cryptanalysis on Gimli/Xoodoo Ciphers

大状态轻量级分组密码Gimli和Xoodoo具备逻辑门较少﹑低功耗和快速加密等诸多优点,备受业界关注。Gimli和Xoodoo算法均基于384 bit置换,大状态增加了对其安全性分析的困难性。该文通过引入AND、OR操作与S盒之间的等价表示,构建了Gimli和Xoodoo不可能差分区分器自动化搜索模型。进一步,为了验证不可能差分区分器的正确性,提出基于“二分法”的不可能差分区分器矛盾点检测新方法。结果表明:该文搜索并验证得到Gimli算法10轮不可能差分区分器以及Xoodoo算法4轮不可能差分区分器。特别地,Gimli算法不可能差分区分器轮数较已有结果提高了3轮。

Gimli and Xoodoo are large state lightweight block ciphers that have many advantages such as fewer logic gates,low power consumption and fast encryption,and have attracted much attention on the industry.Both are based on 384 bit permutation,while the large state can lead to the increase of difficulty of security analysis.In this paper,the equivalent representations of the AND,OR and S-boxes operations are introduced.And the automatic search model of the impossible differential distinguisher of Gimli and Xoodoo are constructed.Furthermore,a new technique based on"bisection method"is proposed to detect the contradiction for the impossible differential distinguisher,which is used to verify the correctness of the distinguisher.The results show that the impossible differential distinguishers of 10-round Gimli and 4-round Xoodoo are obtained and verified in this paper.Especially,the new impossible differential distinguisher of Gimli is increased by 3 rounds compared with the existing results.