关键词: 滤波生成器 非线性滤波函数 等价函数 自相关函数

Abstract:

In this paper, we consider a special kind of filter generators. For these filter generators, the input bits of the filter functions are less than the degree of LFSRs. According to the particularities of this kind of filter generators and the properties of LFSRs, we construct an equivalent system. By a nalyzing the relationships between the input states of the filter function and the states of LFSR in the equivalent system, we get a number of linear equations and an example is described to attack this kind of filter generators in section four.

Key words: filter generator, nonlinear filter function, equivalent function, autocorrelation function