Abstract:
Solving nonlinear systems of Boolean equations is NP-hard.
Nevertheless, certain classes of such systems can be solved by efficient algorithms.
There are theoretical and applied reasons for studying these classes and designing
corresponding efficient algorithms.
The paper proposes an approach to solving the systems of quadratic equations
over two-element field. The method makes use of the quadratic functions'
representation by their affine normal forms, i. e., in a sense, of their
piecewise affine approximation. So, the initial nonlinear instance comes to
a number of linear equations systems of the same variables. The paper
also discusses possible ways to reduce the complexity of the proposed method.
Keywords:Boolean function, system of quadratic Boolean equations, vector space partition, flat, local affinity, affine normal form, algebraic cryptanalysis.