Review on Credential Systems in Anonymizing Networks

A credential system is a system in which users can obtain credentials from organizations and reveal possession of these credentials. This system is called anonymous when transactions carried out by the same user cannot be linked. In this paper we are describing few such credential systems. Nymble is a credential system in which servers themselves can blacklist misbehaving users, and thus blocks users but keeps their anonymity intact. Pseudonym systems permit users to communicate with many organizations secretly with the use of pseudonyms. An anonymous credential system is based on the strong RSA assumption and the decisional Diffie-Hellman assumption. It allows a user to unlinkably demonstrate possession of a credential as many times as necessary without involving the issuing organization. Traceable signatures extend group signatures to address various basic traceability issues beyond merely identifying the anonymous signer of a rogue signature. Dynamic accumulators allow capable membership revocation in anonymous setting. Verifier local revocation is the approach of membership revocation in the group signatures. In this revocation method only verifiers are concerned, and signers have no involvement. Keywords– Credential Systems, Pseudonymous system, Nymble, Anonymous credential system, Dynamic accumulator, Traceable Signature, Verifier local revocation.