1. A method for creating and authenticating a digital signature comprising the steps of: in a sender computer system; generating a random integer m; using m, generating a point P 1 having coordinates (X 1, Y 1 ); using m and P 1, generating a point u; sending the pair (u, P 1 ) as a digital signature to a receiver computer system; in said receiver computer system; using u, generating a point Q having coordinates (X, Y); using P 1, generating a point P 2 having coordinates (X 2, Y 2 ); without using Y 1 and Y 2, testing the equality P 1 &plus;P 2 &equals;Q; identifying a signature as not authentic when the equality P 1 &plus;P 2 &equals;Q is not satisfied.