论文部分内容阅读
Biryukov等人在FSE 2015首次将多重集的中间相遇攻击应用于Feistel结构,并给出TWINE-128算法目前最好的分析结果.基于Biryukov等人的工作,本文详细介绍了TWINE算法的中间相遇攻击的自动检测算法.该算法分为三个步骤.(1)区分器的自动检测算法,结合算法结构,搜索出全部区分器.然后,对搜索出的区分器逐个用步骤(2)、(3)进行筛选.(2)在线阶段涉及轮密钥的自动定位算法,在区分器的头部和尾部添加轮数,分别推导出区分器的头部δ集解密到明文,区分器的尾部加密到密文,需要猜测的轮密钥.(3)待求轮密钥向等价主密钥的自动转换算法,选取主密钥或者密钥调度算法生成的某一个128比特的中间变量作为等价主密钥WK[r](r为轮数),猜测WK[r]的部分半字节,并推导相应的轮密钥取值,若步骤(2)中需要的所有轮密钥都可推导出来,攻击成立.程序结果可手动验证,在δ集特性不变的情况下,我们发现,除Biryukov等人采用的区分器外,还存在其他区分器,可对25轮的TWINE-128算法进行中间相遇攻击,复杂度不变.因为运算规则的定义与加密算法的具体细节无关,本文给出的自动检测算法可适用于S盒是一一映射的广义Feistel结构的分组密码算法.
Biryukov et al. First applied the mid-encounter of multiple sets to the Feistel structure at FSE 2015, and gave the best analysis result of the TWINE-128 algorithm at present. Based on the work of Biryukov et al., This paper introduced the middle encounter attack of TWINE algorithm The algorithm is divided into three steps: (1) automatic detection of the discriminator algorithm, combined with the algorithm structure, search out all the differentiators.Then, the search of the discriminator one by one with steps (2), (3 ). (2) The online phase involves the round key automatic positioning algorithm, adding the numbers of rounds at the head and the tail of the discriminator, respectively deriving the discriminator’s δ set of header to be decrypted to the plain text, and encrypting the tail of the discriminator to Ciphertext, round key to be guessed. (3) The round-robin key to be converted to the equivalent master key automatic conversion algorithm, select the master key or key scheduling algorithm to generate a 128-bit intermediate variable as the equivalent The master key WK [r] (r is the number of rounds), guesses the partial nibbles of WK [r] and derives the corresponding round key value. If all the round keys needed in step (2) Out, the attack set up.Program results can be manually verified, in the δ set of features the same circumstances, We find that in addition to the differentiators used by Biryukov et al., There are other differentiators that can attack 25-round TWINE-128 algorithms in the middle with the same degree of complexity because the definition of arithmetic rules has nothing to do with the details of the encryption algorithm , The automatic detection algorithm given in this paper can be applied to the block cipher algorithm of S-box which is a one-to-one mapping generalized Feistel structure.