循环移位对Rijndael密码安全性的影响

目前针对新一轮高级加密标准(AES)Rijndael密码的最有效攻击算法仍是由设计者提出的Square攻击。文献1]中指出Square攻击是一种选择明文攻击，攻击强度不依赖于S盒、列混合矩阵和密钥扩散准则的选取。本文提出的逆序Square攻击算法是一种选择密文攻击方法，对5、6轮的Rjjndael密码的攻击优于Square攻击，对RD-256的攻击较原算法复杂度降低2^3，Square攻击对RD-192的攻击优于逆序攻击。如果改变密码循环移位的方向或密钥扩展算法中的循环移位方向则逆序攻击对5、6轮RD-128的攻击复杂度较Square攻击降低2^8，对7轮RD-192的攻击优于Square攻击，而在许多文献中将改变后的行移位方向默认为原算法移位的方向。

The relation between cyclic shift structure and Rijndael's safety

The best-known attack against Rijndael is still the one presented by the designers called Square attack. In the paper 1], the author said Square attack is s a chosen plaintext attack and is independent of the specific choices of ByteSub, the multiplication polynomial of MixColumn and the key schedule. In this paper we present a new kind of attack called inverse Square attack, which is a kind of chosen cipher text attack and better than Square attack. This paper also show that if only the moving direction of the ShiftRow transformation or key schedules RotByte transformation be inversed, the complexity of our attack will be 28 factor bellow than the Square attack.