减轮SPECK算法的不可能差分分析

Impossible Differential Cryptanalysis of Reduced-round SPECK

SPECK系列算法是2013年由美国国家安全局提出的轻量分组密码算法。算法整体为变形的Feistel结构,轮函数为模整数加法、循环移位和异或的组合,即所谓的ARX模块。在不可能差分研究方面,目前仅有LEE等人给出了SPECK 64算法的一些6轮不可能差分特征。该文进一步找到了SPECK 32/64算法和SPECK 48/96算法的一些6轮不可能差分特征,并在其前面添加1轮后面添加3轮,给出了对两个算法的10轮不可能差分分析。

SPECK is a family of lightweight block ciphers proposed in 2013 by researches from National Security Agency （NSA） of USA. The algorithm adopts a modified Feistel construction that applies a combination of addition, rotation and XORing （the so-called ARX structure）. Up to now, nothing is done on the impossible differential cryptanalysis of the SPECK family except that some 6-round impossible differential characteristics are found by LEE et al. In this article, some 6-round impossible differential characteristics of SPECK 32/64 and SPECK 48/96 are found and a 10-round impossible differential cryptanalysis on these two ciphers is presented by adding one round forward and three rounds backward.