流密码Grain v1的密钥恢复攻击及其改进

Key Recovery Attack on Stream Cipher Grain v1 and Its Improvement

为探讨流密码Grain v1的安全性,通过研究Grain v1密钥流生成器的结构,指出了Grain v1密钥流生成器设计的3个弱点,在此基础上提出了一种基于中间状态的流密码Grain v1的密钥恢复攻击.该攻击的计算复杂度和空间复杂度分别等价于Grain v1密钥流生成器的计算复杂度和空间复杂度.为了抵抗所提出的攻击,对Grain v1密钥流生成器的设计进行了改进.安全性分析表明,改进设计能够抵抗所提出的密钥恢复攻击.

In order to probe into the security of the stream cipher Grain v1,three design weaknesses of the Grain v1 key-stream generator were pointed out by studying its structure.Based on the above work,a key recovery attack on the stream cipher Grain v1 with an intermediate state was proposed.Time complexity and memory complexity of the proposed attack are equal to the time complexity and memory complexity of the Grain v1 key-stream generator respectively.In order to resist the proposed attack,an improvement on the Grain v1 key-stream generator was made.The security analysis shows that the improved generator is secure against the proposed key recovery attack.