不可能差分分析时间复杂度通用计算公式的改进

研究Boura等和Derbez分别提出的不可能差分分析时间复杂度计算公式，根据实际攻击过程优化密钥排除的步骤，给出不可能差分分析实际攻击的时间复杂度计算的改进公式，进而利用两个分组密码算法模型将改进后公式计算的实际结果分别与Boura等的公式和Derbez的公式的计算结果进行对比，结果表明Boura等的公式计算结果既可能高于优化公式的实际分析计算的结果，也可能低于优化公式的实际分析计算的结果，而在轮子密钥独立时改进后公式的实际计算结果是Derbez公式的计算结果的2-1.2倍。
The previous formulas of the time complexity of impossible differential cryptanalysis proposed by Boura et al. and Derbez were researched respectively. By studying the filtration of round subkeys during the attacking procedure carefully, an improved formula estimated the real time complexity of impossible differential cryptanalysis was proposed. On this basis, the impossible differential attacks were mounted on two models of block ciphers and the time complexities by three formulas were calculated. The results show that the time complexity computed by Boura′s formula can be higher or lower than the real time complexity, and the real time complexity is 2-1.2 times as big as the time complexity calculated by Derbez′s formula if the round subkeys are independent of each other.