分组密码算法的密钥编排方案研究

密码算法是信息安全的基石。分组密码算法在实际中应用广泛，其设计和安全评估一直是密码学者研究热点。但对于其中重要的组成模块- - 密钥编排方案的研究则相对较少。近年来利用密钥编排方案弱点的攻击的频繁出现，表明我们在过去过多地忽视了密钥编排方案在攻击中的作用。相应的，在设计安全合理的密钥编排方案方面也存在大量空白。 本项目主要研究分组密码的密钥编排方案对算法安全性的影响，从密钥编排方案的角度，特别是密钥编排与算法轮函数的相关性出发，精确刻画密钥编排方案的弱点导致实际攻击的一般规律。在此基础上，获得更准确有效的密码算法安全性分析手段，设计并实现能自动检测密钥编排方案弱点的工具，对现有的主流分组密码进行检测分析。针对未来算法效率和安全性需求的发展趋势，提出密钥编排方案应满足的条件和设计准则。在保证算法执行效率的基础上，构造更加安全有效的密钥编排方案，为分组密码算法的设计提供更为安全合理的科学依据。

Cryptographic algorithms play fundamental roles in information security. Among all cryptographic algorithms, block ciphers are widely used in the field of practical security. Design and cryptanalysis of block ciphers have been a hot research topic over decades. However, as one of the significant modules in block ciphers, key schedules have not received enough attention in the cipher design. Many recently found attacks are based on the weaknesses of key schedules, reminding us of the fact that the effect of key schedules on the attacks was overly neglected in the past， and showing the need for scientific design principles that can help to avoid weaknesses in the key schedule. In this project, we will explore what the roles a key schedule play in the cryptanalytic techniques, and the principles of how the weaknesses of key schedules work in the attacks. Especially, we will investigate the relationship between the key-schedule and the cipher round-function. With such knowledge, we can obtain more precise and efficient methods for analyzing security of cryptographic algorithms, develop efficient software tools to detect flaws in key schedules. Moreover, we will be dedicated to find necessary and sufficient design principles for key schedules, and study how to design more secure but low cost key schedules, so that to provide scientific foundation for the design of secure and efficient block-cipher algorithms.