23. The method of claim 16 , further comprising: the user generating one or more pseudonyms for registration at the RP and the IdP using a pseudonym system, wherein the pseudonym system is operable to create an unbounded number of pseudonyms based on a fixed number of cryptographic keys.
23. The method of claim 16 , further comprising: the user generating one or more pseudonyms for registration at the RP and the IdP using a pseudonym system, wherein the pseudonym system is operable to create an unbounded number of pseudonyms based on a fixed number of cryptographic keys. 24. The method of claim 23 , further comprising: the user linking or denying linkage between two pseudonyms generated using the pseudonym system in zero knowledge.