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arXiv 0905.3682math.CO
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随机排列的统计与周期分组密码的分析

Statistics of Random Permutations and the Cryptanalysis Of Periodic Block Ciphers

Nicolas T. Courtois, Gregory V. Bard, Shaun V. Ault

摘要:

分组密码旨在在计算上与适当域和范围的随机排列不可区分。但是随机排列的性质是什么呢?借助于指数生成函数和普通生成函数,我们导出了一系列密码学界感兴趣的集合。这些都遵循强循环结构定理的排列,并在渲染严格的两个攻击Keeloq,在广泛使用的分组密码是有用的。这些攻击以前有启发式近似的成功概率。此外,我们描绘了一个攻击(大致)百万倍迭代的随机排列。特别是,我们创建了一个区别攻击,即密码的迭代次数等于一个特别选择的高度合数是可破解的,但仅仅少一轮就安全得多。然后,我们将其扩展到“Triple-DES”风格构造中的密钥恢复攻击,但使用AES-256并迭代中间密码(大约)一百万倍。希望这些结果将展示指数和普通生成函数的效用,并鼓励它们在密码分析研究中的使用。

英文摘要:

A block cipher is intended to be computationally indistinguishable from a random permutation of appropriate domain and range. But what are the properties of a random permutation? By the aid of exponential and ordinary generating functions, we derive a series of collolaries of interest to the cryptographic community. These follow from the Strong Cycle Structure Theorem of permutations, and are useful in rendering rigorous two attacks on Keeloq, a block cipher in wide-spread use. These attacks formerly had heuristic approximations of their probability of success. Moreover, we delineate an attack against the (roughly) millionth-fold iteration of a random permutation. In particular, we create a distinguishing attack, whereby the iteration of a cipher a number of times equal to a particularly chosen highly-composite number is breakable, but merely one fewer round is considerably more secure. We then extend this to a key-recovery attack in a "Triple-DES" style construction, but using AES-256 and iterating the middle cipher (roughly) a million-fold. It is hoped that these results will showcase the utility of exponential and ordinary generating functions and will encourage their use in cryptanalytic research.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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