Computing the biases of parity-check relations
Cryptography and Security
2009-04-29 v1
Abstract
A divide-and-conquer cryptanalysis can often be mounted against some keystream generators composed of several (nonlinear) independent devices combined by a Boolean function. In particular, any parity-check relation derived from the periods of some constituent sequences usually leads to a distinguishing attack whose complexity is determined by the bias of the relation. However, estimating this bias is a difficult problem since the piling-up lemma cannot be used. Here, we give two exact expressions for this bias. Most notably, these expressions lead to a new algorithm for computing the bias of a parity-check relation, and they also provide some simple formulae for this bias in some particular cases which are commonly used in cryptography.
Cite
@article{arxiv.0904.4412,
title = {Computing the biases of parity-check relations},
author = {Anne Canteaut and Maria Naya-Plasencia},
journal= {arXiv preprint arXiv:0904.4412},
year = {2009}
}