一种PUFFIN类SPN型分组密码的积分攻击

An Integral Attack on PUFFIN and PUFFIN-like SPN Cipher

PUFFIN是一个具有64bit分组长度、128bit密钥的SPN型分组密码,为评估其安全性,从比特的层面分析其平衡性,构造了PUFFIN的5轮积分区分器,并利用高阶积分的思想将5轮区分器扩展为6轮,然后对8轮PUFFIN密码进行攻击。8轮攻击的数据复杂度为221,时间复杂度为234,空间复杂度为220。结果表明,8轮PUFFIN密码对于给出的攻击是不免疫的。对于线性层为置换的PUFFIN类SPN型分组密码,证明了至少存在3轮积分区分器,并给出了寻找该区分器的方法。

PUFFIN is a block cipher with 64-bit block size and 128-bit key size. For evaluating its security,the balance at bit-level was analyzed. A 5-round integral distinguisher was constructed and then extended to a 6-round one based on the theory of higher order integral. By using the 6-round distinguisher,8-round attack was performed. For 8-round attack,the data complexity,time complexity and space complexity were,and respectively. The result shows that PUFFIN reduced to 8 rounds is not immune to the integral attack. Besides,the cipher with SPN-structure and permutation-linear layer which at least has 3-round integral distinguisher is proved. The result also indicates the method for finding the distinguisher.