42轮SHACAL-2新的相关密钥矩形攻击

New related-key rectangle attack on 42-round SHACAL-2

利用SHACAL-2密码算法轮变换的特点,构造了一个新型的34轮区分器。基于该区分器和部分密钥分别猜测的技术,针对40轮、42轮简化SHACAL-2分别给出了新的攻击方法。研究结果表明:利用2个相关密钥,对40轮SHACAL-2进行相关密钥矩形攻击其数据复杂度约为2235选择明文数据量,计算复杂度约为2432.6次加密;而对42轮SHACAL-2进行相关密钥矩形攻击其数据复杂度约为2235选择明文数据量,计算复杂度约为2472.6次加密。与已有的结果相比较,这些新分析所需的数据复杂度和计算复杂度均有明显的降低。

A new 34-round related-key rectangle distinguisher was constructed by exploiting the properties of the round transform of SHACAL-2. Moreover, two new relate-key rectangle attacks on 40-round and 42-round reduced SHACAL-2 were presented by using both the distinguisher and a technique of key-byte guessing. It is shown that related-key rectangle attacks with only 2 related keys on 40-round and 42-round reduced SHACAL-2 all require data complexity of about 2235 chosen plaintexts and time complexity of about 2^432.6 encryptions on 40-round reduced SHACAL-2, and 2^472.6 encryptions on 42-round reduced SHACAL-2, respectively. The presented results are better than previous published cryptanalytic results on reduced SHACAL-2 in terms of both the data complexity and the time complexity.