一种优化DES算法

An Optimizing DES Algorithm

论文简要介绍DES算法及其实现上影响速度的原因。对S-盒代替和P-盒置换进行了分析和优化,将其合并为SP-盒。将S-盒代替表和P-盒置换表进行了分析和优化,将其合并为SP-盒变换表。这一优化并未改变DES的计算结果,因而并未改变DES的安全性。同时,取消了原算法S-盒代替中对S-盒输入的与和移位操作;取消了P-盒置换的与和移位操作。将原来的S-盒输入,即,SP-盒的输入作为索引,直接从SP-盒变换表中取得SP-盒的输出,即,原来的P-盒置换的输出。因而,节省了CPU的计算时间,提高DES的实现速度。

At first,this paper introduces the algorithm of DES(Data Encryption Standard)and the reason of its low cal-culating speed.Then it analyzes and optimizes the substitution of S-box and replacement of P-box,then combine both operations to generate SP-box;analyzes and optimizes the table of substitution of S-box and the table of replacement of P-box,and combines both tables to generate the table of SP-box.The optimizing process does not change the calculating result so that the security of DES is not changed.At the same time ,cannels the AND and SHIFT opertions in S-box and P-box.According to the index which is the original input of S-box,that is,the input of SP-box,we can directly get the output of SP-box from the table of SP-box,that is,the original output of P-box.So the time of calculating of CPU is saved and the calculating speed of DES is higher than that of its origin.