Multiplier-adder in the Galois fields, and its use in a digital signal processing processor

Claim 1

A multiplier-adder in one of the Galois fields up to CG(2 N ) where N is a predetermined integer, having three multiple inputs intended to receive the coefficients of polynomial operands A, B and C of degree m-1 less than N for the polynomial operation P in the Galois field of degree m, CG(2 m ):P=(A*B)+C, where * and + are respectively multiplication and addition, performed Modulo G, in the Galois field CG(2 m ) of generator polynomial G, and a data input for applying parameters, for this generator polynomial, comprising: a decoder (10) constituted from a line of N elementary identical cells CD j , arranged in order from j=0 to N-1, receiving the coefficients of the generator polynomial G(N:O) and transmitting the coefficients of this polynomial without the one having the highest degree G(N-1:0) and a polynomial with a significant coefficient derived by the logical combination of the generator polynomial marking the degree m of the chosen Galois field, DG(N-1:0); a computing matrix (20) constituted from p lines of identical elementary computing cells for performing the polynomial computation of p steps, the cells of the last line supplying the terms of degrees 0 to m-1 of the resulting polynomial P, characterized in that, for a computation in p=2N-1 steps, the computing matrix comprises 2N-1 lines from i =0 to 2(N-1) and N columns of j=0 to N-1 of cells CM i ,j connected in a tree structure, the non-connected inputs receiving logic "0" levels, each elementary computing cells MC i ,j comprising: five vertical inputs connected to the vertical outputs of the preceding cell of the same column, receiving the terms of degree j, G(j), DG(j) and B(j) of the generator polynomial, of the degree polynomial, and of the polynomial B, the term of degree i-j of the polynomial A, where i is the index of the matrix line and i=0 to 2(N-1), and the term of degree j of an intermediate result z i-1 (j) where i is the index of matrix column and j=0 to N-1, two lateral inputs receiving from the cell of the column of inferior rank of the same line the term of degree j-1 of the intermediate result z i-1 (j-1) and the term of degree (i+1-j), A(i+1-j) of the polynomial A, two lateral outputs to be applied to the cell of superior rank of the same line supplying the term of degree j of the intermediate result z i-1 (j) and the term of degree i-j, A(i-j) of the polynomial A.