Statistical cryptanalysis of block ciphers as channel communication

摘要：分组密码是通信基础设施中不可缺少的组成部分，但对于分组密码的设计和分析却缺乏统一的原则。因此，不可能轻易地表征好密码和坏密码，并且设计好的密码是困难的。虽然对这个问题的一般处理确实存在，并提供了有价值的见解，但很难将特定攻击的个别处理和特定密码设计结合成一个总体理论，还有很多工作要做。这个项目研究了一大类被称为统计密码分析的攻击，它利用明文、密钥和密文之间的概率关系来确定密钥。该研究扩展了统计密码分析的现有通信信道模型-其中低容量信道将密钥的编码符号传递给对手-已经非常成功地用于设计对流密码的攻击，但并未广泛用于分组密码密码分析。该项目利用的一个关键见解如下：现有的密码分析模型不提供研究相关密钥攻击和统计攻击组合的方法。PI观察到，相关秘密在信息泄露通道上形成代码，提高了对手的通信效率。使用这种方法，该项目获得了攻击效率的一般结果-尽可能通过实验验证-以及相关的密码设计标准。通过与当地高中尚蒂伊学院建立合作关系，PI教授密码学模块，该项目为K-12教育做出了贡献，并激励高中生学习数学、工程和计算机科学。

Abstract: Block ciphers are indispensable components of the communication infrastructure, yet few unifying principles for their design and analysis exist. As a result, it is not possible to easily characterize good and bad ciphers, and the design of good ciphers is difficult. While notable general treatments of the problem do exist and have contributed valuable insights, it has been difficult to combine the individual treatments of specific attacks and specific cipher designs into an overarching theory, and much remains to be done.This project studies a large class of attacks known as statistical cryptanalysis, which exploits probabilistic relationships among the plaintext, key and ciphertext to determine the key. The research extends existing communication channel models of statistical cryptanalysis---where low capacity channels carry encoded symbols of the key to the adversary---which have been used very successfully to design attacks on stream ciphers, but are not as widely used for block cipher cryptanalysis. A key insight exploited by the project is as follows: existing cryptanalytic models do not provide a means of studying the combination of related-key attacks and statistical attacks. The PI observed that related secrets form codes over information leakage channels, improving adversary communication efficiency. Using this approach, the project obtains general results on attack efficiency---experimentally verified as far as possible---and related cipher design criteria. Through an established r elationship with local high school Chantilly Academy, where the PI teaches cryptography modules, the project contributes to K-12 education, and inspires high school students to study mathematics, engineering and computer science.