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.sub.1 having coordinates (X.sub.1, Y.sub.1); using m and P.sub.1, generating a point u; sending the pair (u, P.sub.1) as a digital signature to a receiver computer system; in said reciever computer system; using u, generating a point Q having coordinates (X, Y); using P.sub.1, generating a point P.sub.2 having coordinates (X.sub.2, Y.sub.2); without using Y.sub.1 and Y.sub.2, testing the equality P.sub.1 +P.sub.2 =Q; identifying a signature as not authentic when the equality P.sub.1 +P.sub.2 =Q is not satisfied.