针对流密码HC-256'的区分攻击

Distinguishing Attack on Stream Cipher HC-256′

流密码HC-256'是eSTREAM计划候选密码HC-256的改进算法,至今未见关于HC-256'的安全性分析结果。该文提出了一种针对HC-256'的线性区分攻击,利用不同的非线性函数代替内部状态更新函数来寻找偶数位置上密钥流生成序列的弱点,通过线性逼近HC-256'的内部状态构造区分器。分析结果表明,需要约2 281bit,就能以0.9545的区分优势对密钥流进行区分。同时,该攻击为解决Sekar等人在2009年IWSEC会议上提出的问题进行了有益的探索。

Stream cipher HC-256＇ is an improved algorithm of HC-256 which is proposed as a candidate to the eSTREAM project.Until now,there has not any cryptanalysis on HC-256＇.In this paper,a linear distinguishing attack on HC-256＇ is presented.This method uses different nonlinear functions instead of state update functions to exploit the weaknesses in the even positions output bits of the keystream generation sequence.By linear approximation to the internal state bits,a distinguisher is built.The result shows that there needs about 281 2 bit keystream with advantage 0.9545 to distinguish HC-256＇ form random sequence.Thereby,this is a beneficial attempt to solve a problem which is given by Sekar et al in IWSEC 2009.