Patent ID: 7760884
Filing Date: 2010-07-20
Classification: H04L

Abstract:
1. A cryptographic method for a transaction whereby a first entity generates, by means of an RSA private key, a proof verifiable by a second entity by means of an RSA public key associated with said private key, said public key comprising a public key exponent and a modulus, the method comprising the steps of: generating, on a processor at the first entity, a first element of proof by using a generic number raised to a first power, modulo the modulus, having a first exponent equal to the public key exponent multiplied by a random integer kept secret by the first entity, whereby calculation of said first element of proof is executable independently of the transaction; generating, at the first entity, a second element of proof related to the first element of proof and dependent on a common number shared by the first and second entities specifically for the transaction; and verifying, at the second entity, that the first element of proof is related through a relationship with a second power, modulo the modulus, of a generic number having a second exponent equal to a linear combination of at least part of the common number and of the public key exponent multiplied by the second element of proof wherein the second element of proof is generated by the first entity by subtracting, from the random integer, the private key multiplied by the common number, wherein the linear combination equal to the second exponent comprises a positive unitary coefficient for the common number and a positive unitary coefficient for the public key exponent multiplied by the second element of proof, and wherein, in the verified relationship, the first element of proof is considered with a unitary exponent power.