On some algorithms for constructing low-degree annihilators for Boolean functions

V. V. Baev

Diskretnaya Matematika, Tome 18 (2006) no. 3, pp. 138-151

Résumé

The algebraic method is widely used in analysis of filter generators of pseudo-random sequences. It is based on obtaining low-degree Boolean equations in bits of the initial states of the generator. The problem to obtain such equations reduces to finding low-degree annihilators for the filtering Boolean function. The presence of nonzero low-degree annihilators decreases the complexity of determining the initial state of the generator by means of its output. In this research we deal with the problem to find all low-degree annihilators for a Boolean function defined as a polynomial in several variables. We propose two new algorithms which solve this problem. Their complexities are bounded above by polynomials of the number of variables of the function and of the number of monomials in the polynomial which defines the function. We also consider the application of these algorithms to realising the algebraic method by three known scenarios which yield low-degree equations.