Attacking the combination generator

TL;DR

This paper introduces a highly efficient attack on the combination generator, exploiting autocorrelation properties of the filtering function using classical cryptanalytic tools, revealing vulnerabilities even in systems designed to resist other attacks.

Contribution

The paper presents a novel attack method on the combination generator leveraging autocorrelation, applicable under common design assumptions, using classical cryptanalytic techniques.

Findings

The attack is highly efficient against the combination generator.

It requires only classical tools like Walsh transform and correlation analysis.

The attack exploits autocorrelation properties of the filtering function.

Abstract

We present one of the most efficient attacks against the combination generator. This attack is inherent to this system as its only assumption is that the filtering function has a good autocorrelation. This is usually the case if the system is designed to be resistant to other kinds of attacks. We use only classical tools, namely vectorial correlation, weight 4 multiples and Walsh transform.