摘要
Bogdanov等人在2011年亚密会上提出了一种新的针对分组密码的密钥恢复攻击,称为biclique攻击,该攻击方法在构造biclique结构的基础上结合了中间相遇攻击的思想,可以有效降低攻击的时间复杂度和数据复杂度.此后这一方法被广泛用于分组密码的安全性分析.mCrypton作为一种新的能够在资源有限的硬件环境下高效运行轻量级分组密码,其安全性备受关注.本文首先介绍了biclique攻击的一般方法,并给出了一个d维biclique的完整定义.接着,我们说明了如何通过分析密码的密钥扩展算法,找出两条较短的且相互独立的差分路径,进而完成biclique结构的构造并利用该biclique结构进行全轮攻击.在此基础上,我们给出轻量级分组密码mCrypton-64的算法描述,并利用biclique攻击对其进行分析.mCrypton-64整体采用了SP结构,其分组长度为64比特,密钥长度为64比特,其加密过程包括非线性替换、比特置换、行列换位和密钥加.最后,我们针对mCrypton-64的密钥扩展算法找到了两条相互独立的差分路径,进而构造出一个11~12轮的4维biclique,利用它对全轮mCrypton-64进行了攻击,攻击的数据复杂度为2^(32),计算复杂度为2^(63.115),均好于已有的结果.
A new key-recovery attack on block ciphers was proposed by Boganov et al in ASIACRYPT 2011, called biclique attack. This attack can effectively reduce time and data complexity by combining the idea of meet-in-the-middle attack on the basis of constructing biclique structure. Since then, biclique attack has widely been used in the security analysis of block ciphers. mCrypton as a new light-weight block cipher can operate efficiently in hardware environment of limited resources, however its security is a great concern. In this paper, we first introduce a general method of biclique attack and provide a complete definition of d-dimensional biclique. Then, we demonstrate how to construct a biclique and how to attack a full-round block cipher by searching for two short and independent differentials and analyzing the key expansion algorithm of the cipher. Next, we describe the light-weight block cipher mCrypton-64. mCrypton-64 is an SP Network, whose block size and key length are both 64 bits. The encryption function of mCrypton-64 includes 4 operations, they are non-linear substitution, bit permutation, column-to-row transposition and key addition. Last, we construct two independent differentials for mCrypton-64, and construct a 4-dimensional biclique of round 11~12, which is used to attack the full-round mCrypton with data complexity of 2^(32) and computing complexity of 2^(63.115), both of them are better than the current known results.
出处
《密码学报》
CSCD
2016年第6期564-572,共9页
Journal of Cryptologic Research
