密码算法旁路立方攻击改进与应用

Side Channel Cube Attack Improvement and Application to Cryptographic Algorithm

立方攻击的预处理阶段复杂度随输出比特代数次数的增长呈指数级增长,寻找有效立方集合的难度也随之增加。该文对立方攻击中预处理阶段的算法做了改进,在立方集合搜索时,由随机搜索变为带目标的搜索,设计了一个新的目标搜索优化算法,优化了预处理阶段的计算复杂度,进而使离线阶段时间复杂度显著降低。将改进的立方攻击结合旁路方法应用在MIBS分组密码算法上,从旁路攻击的角度分析MIBS的算法特点,在第3轮选择了泄露位置,建立关于初始密钥和输出比特的超定的线性方程组,可以直接恢复33 bit密钥,利用二次检测恢复6 bit密钥。所需选择明文量221.64,时间复杂度225。该结果较现有结果有较大改进,恢复的密钥数增多,在线阶段的时间复杂度降低。

The complexity of the pre-processing phase of the cubic attack grows exponentially with the number of output bit algebras, and the difficulty of finding an effective cube set increases. In this paper, the algorithm of preprocessing stage in cubic attack is improved. In the cube set search, from random search to target search,a new target search optimization algorithm is designed to optimize the computational complexity of the preprocessing stage. In turn, the offline phase time complexity is significantly reduced. The improved cubic attack combined with the side-channel method is applied to the MIBS block cipher algorithm. The algorithm characteristics of MIBS are analyzed from the perspective of side-channel attack. The leak location is selected in the third round, and the overdetermined linear equations from initial key and output bit are established, which can directly recover 33 bit key. Then the 6 bit key can be recovered by quadric-detecting. The amount of plaintext required is 221.64, time complexity is 225. This result is greatly improved compared with the existing results, the number of keys recovered is increased, and the time complexity of the online phase is reduced.