Differential cryptanalysis of S-Functions

[Ruslan Kiyanchuk]

There is a tool for differential cryptanalysis of S-functions by Nicky Mouha
on ECRYPT site: http://www.ecrypt.eu.org/tools/s-function-toolkit

The documentation for that framework explains the analysis of xor, addition
modulo 2^n and few other transformations but it is not clear for me how to
apply the analysis to the whole stream cipher (or for LFSR only).

As I understand one has to initialize the adjacency matrix for the analysed S-
function (which represents the transformation). In order to accomplish that
the transformation has to be described bitwise. It is not clear for me what
should be done in order to use the toolkit for differential cryptanalysis of a
simple LFSR.

I would appreciate any explanation, thanks.