MD4差分路径的自动化构造算法

Automatic Algorithm to Construct Differential Path in MD4

通过考察MD4算法及其差分路径自动化构造算法的原理,分析了差分路径自动化构造中发挥影响的各因素,对原算法进行了改进。改进算法通过充分考虑第32比特位差分的特殊性,有效控制自动化构造过程中相应的进位扩展次数,并利用了MD4本身的结构缺陷,构造得到了新的差分路径。相对于原算法,生成的差分路径含有更少的充分条件。

By studying the theory of MD4 and the automatic algorithm to construct difference, influ- ence factors in the construction process are analysed and the original algorithm is improved. In the improved algorithm,the particularity of difference in the 32th bit is fully considered to control the length of carry expansions more effectively. Besides,the weakness of MD4 structure is also used to construct the new differential path which has less sufficient conditions compared with differential paths generated by the original algorithm.