ANALYSIS OF RESISTANCE BLOCK CIPHERS AGAINST ALGEBRAIC CRYPTANALYSIS
This paper is devoted to the investigation of GOST algorithm with regard to its resistance against algebraic cryptanalysis. The general idea of algebraic analysis is based on the representation of initial encryption algorithm as a system of multivariate quadratic equations, which define relations between a secret key and a cipher text. Extended linearization method is evaluated as a method for solving the nonlinear system of equations. The research has shown that 32-round GOST is described by a system of 5 376 quadratic equations, which characterize dependencies between inputs and outputs of S-blocks. The total number of variables is 2 048 and the system contains 9 472 monomials.