A method for determining r error detection bits of a word of m bits to be coded, including the step of calculating the product of a vector with m components representative of said word of m bits to be coded and of a parity check matrix. The parity check matrix includes a pattern matrix that may be repeated in said parity check matrix, and said pattern being chosen so that a sum modulo 2 of any two columns of said sub-matrix does not give as a result another column of said sub-matrix. Another method determines a syndrome using r error detection bits determined by the above method.