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. 25. The method of claim 23 , further comprising: the user generating a temporary pseudonym based on the second pseudonym; the user interactively proving possession of the second pseudonym to the RP using the temporary pseudonym; and the user expunging linkage between the temporary pseudonym and the second pseudonym.