流密码Grain-128密钥恢复攻击及改进

KEY RECOVERY ATTACK ON STREAM CIPHER GRAIN-128 AND ITS IMPROVEMENT

流密码Grain-128是Grain v1算法的密钥增长版本。为探讨流密码Grain-128的安全性,指出Grain-128密钥流生成器的3个布尔函数的设计缺陷,在此基础上给出流密码Grain-128一种基于密钥流生成器中间内部状态的密钥恢复攻击。该攻击的计算复杂度和空间复杂度都为O(256)。为了抵抗该攻击,对Grain-128密钥流生成器的设计进行了改进。安全性分析表明,改进后的流密码Grain-128能够抵抗所提出的密钥恢复攻击。

Stream cipher Grain-128 is the key-growth version of Grain v1 algorithm. In order to probe the security of stream cipher Grain-128,we pointed out three design weaknesses of Boolean function in regard to Grain-128 key-stream generator. Based on that,we presented a key recovery attack on the stream cipher Grain-128,which is based on the internal state in key-stream generator. The computational complexity and spatial complexity of attack are all O（ 254）. In order to resist the key recovery attack,we improved the design of Grain-128key-stream generator. Security analysis showed that the improved stream cipher Grain-128 I was able to resist the proposed key recovery attacks.