高容错伪随机扰码的快速盲恢复

Fast blind restore of LFSR sequences with high error tolerance

首先通过组合枚举方法寻找伪随机扰码序列的反馈多项式,然后利用基于卷积码的快速相关攻击方法对线性反馈移位寄存器(LFSR)的初态进行盲恢复。攻击过程分为两个关键步骤,第一步是快速找出尽可能多的校验方程,以构造具有强纠错能力的超低码率的卷积码,第二步是实现超低码率的快速Viterbi译码。本文提出并实现了离线(offline)查找与在线(online)译码分工组合的方案。经过大量的实验仿真,本文描绘出了各种参数之间的关系图。

This paper presents how to search the LFSR (the linear Feedback Shift Register) feedback polynomials through combination and enumeration, and how to blindly restore the initial states of LFSR through fast correlation attack based on convolutional codes. Two key steps are involved in the attack process. One is to quickly look for as much check equations as possible. The other is to realize the Viterbi decoding for the convolutions with very low rate. The divide-combine algorithm of offline search and the online decoding is present and realized in this paper. Based on experiment and simulation, the relation graph of various parameters is also depicted.