改进 DES 子密钥使用顺序的算法研究

通过对DES算法进行分析,针对DES易受穷举搜索等方法攻击的缺陷,提出基于分组与哈希函数的改进方案.该改进方案首先将明文与密钥进行异或,然后根据分组结果或者哈希表查找比较次数,结合仿射变换决定子密钥的使用顺序,最后利用RSA加密子密钥的使用顺序.该改进方案因为输入明文的不同而引起子密钥的使用顺序不同,使得每次破解都需要16!次穷举,从而提高穷举搜索与选择明文攻击的难度,提高DES算法的安全性.

Research of Improving the Algorithm of DES Subkey Usage Order

The data encryption standard (DES) is liable to suffer from exhaustive attack. Through DES algorithm analysis, this paper puts forward two improved schemes based on grouping and Hash function to solve the defect. First, exclusive OR (XOR) is performed on the plaintext and the key. Then, according to the grouping result or the comparison times in Hash table lookup, and combined with affine transformation, the improved algorithms determine the subkey order. Finally, RSA is used to encrypt the subkey order. With the proposed algorithms, different input plaintexts cause different subkey orders, so every crack needs 16! exhaustive searches. Consequently, the ability to resist exhaustive attack and chosen plaintext attack is improved and the security of DES algorithm is enhanced.