流密码典型分析方法及实例

Typical Methods and Examples of Stream Cipher Analysis

流密码的设计与分析在现代密码学中占有重要地位。简要介绍了流密码分析的基本原理和模型,主要包括:折中攻击、猜测和决定攻击、相关攻击、最佳仿射攻击、代数攻击和边信道攻击。然后基于Mathematica平台,使用简易密钥流发生器为测试对象,对其中的折中攻击、猜测和决定攻击及相关攻击进行了仿真实现。通过实验,揭示了流密码算法的一个重要设计原则:避免内部状态演变的线性性以及输出序列统计性质的偏向性。最后对流密码分析方法给予了总结和展望。

The design and analysis of stream cipher plays an important role in modern cryptology. This paper briefly reviews the basic principle and model of stream cipher analysis, mainly including TMD tradeoff attack, guess-and-determine attack, correlation attack, BAA attack, algebraic attack and side-channel attack. Then simulations of TMD tradeoff attack, guess-and-determine attack and correlation attack are performed by using Mathematical kit software, with results and a part of codes appended. The tests reveal an important design principle： it is critical to avoid the linear evolvement of internal state and eliminate the biased statistical properties of keystream. Finally some conclusions and prospects of stream cipher analysis are provided.