在流密码体制下,RC4算法经过密钥初始化部分后所得的内部状态不是均匀分布的.为此,证明了算法密钥流第1个输出字分布的不均匀性,其等于186的概率为0.003 892 5.利用该输出字分布的不均匀性,给出改进的RC4区分攻击,攻击所需的数据为224 Byte,区分优势为0.84.通过实验验证了该区分攻击的有效性.%This paper proves the probability distribution of the first output byte which is not uniform when the inner state is not uniform proved by fluhrer after the KSA of RC4, its probability equal to 186 is 0.003 892 5. Using the obtained results, the paper proposes a new and practical distinguishing attack on RC4. The data complexity of the new attack is 224 Byte and the distinguishing advantage is 0.84. Experimental result shows the validity of the distinguishing attack.
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