  In this paper we describe the volunteer computing project SAT@home, developed
and maintained by us. This project is aimed at solving hard instances of the
Boolean satisfiability problem (SAT). We believe that this project can be a
useful tool for computational study of inversion problems of some cryptographic
functions. In particular we describe a series of experiments performed in
SAT@home on the cryptanalysis of the widely known keystream generator A5/1. In
all experiments we analyzed one known burst (114 bits) of keystream produced by
A5/1. Before the cryptanalysis itself there is a stage on which the
partitioning of the original problem to a family of subproblems is carried out.
Each of subproblems should be easy enough so that it could be solved in
relatively small amount of time by volunteer's PC. We construct such
partitioning using the special technique based on the Monte Carlo method and
discrete optimization algorithms for special predictive functions. Besides this
in the paper we describe the technique for reducing inversion problems of
cryptographic functions to SAT.
