摘要： 提出一种针对序列密码的改进的快速相关攻击算法。将序列密码的攻击问题转化为线性分组码的译码问题，采用最大似然译码方法进行译码。利用Walsh变换进一步优化算法的计算复杂度。对算法中的穷搜索比特数和校验方程重量2个关键参数的选取进行探讨，从理论上推导出校验方程重量与算法攻击成功概率之间的解析关系，为选取参数提供了依据。仿真结果表明，该算法性能优于之前的快速相关攻击算法。

关键词: 序列密码, 快速相关攻击, Walsh变换

Abstract: An improved algorithm of fast correlation attack on stream cipher is proposed. The attack of stream cipher is regarded as the decoding of linear block code, and the linear block code is decoded by the ML-decoding strategy. With the Walsh transform, the computing complexity of this algorithm is reduced sharply. The selection of two important parameters of the algorithm, that are the number of the exhaustively searched initial bits and the weight of parity-check, are further studied. The analytic relation between the weight of parity-check and the probability of success attack is deduced. These discussions of parameter selection provide a better guidance for practical application. Simulations results show that the new algorithm performs better than previous algorithms.

Key words: stream cipher, fast correlation attack, Walsh transform

中图分类号: 

• TP309