Patent ID: 7650494

Claim:
A method of enabling a second party to prove to a third party the existence of an association between the second party and a first party, the first party being associated with a first element of a first algebraic group, the second party being associated with a second element of a second algebraic group, the second element being formed from an identifier string of the second party using a hash function, and there being a computable bilinear map for the first and second elements, wherein the method comprises: a second-party computer entity, acting on behalf of the second party, performing the steps of: receiving a shared secret provided by the first party as the product of a first secret and the second element; computing first, second and third verification parameters, wherein the first verification parameter is a product of a second secret and said shared secret, the second verification parameter is a product of the second secret and the second element and the third verification parameter is a product of the second secret and the first element; and outputting the first, second and third verification parameters for use by the third party, wherein the first, second, and third verification parameters enable the third party to verify the association between the first and second parties by performing checks that use the first, second, and third verification parameters and public information.