Efficient and random oracle-free conditionally anonymous ring signature

Abstract

Compared to conventional ring signature schemes, conditionally anonymous ring signatures allow to revoke the anonymity of actual signer without the group manager's help if necessary. When the actual signer intends to confirm his role, it can be proved by a confirmation algorithm. In addition, any user, who is in a ring but not signer, can claim this through a disavowal algorithm. There were several proposals which were proved secure in random oracles. In other words, the security of such schemes depends on the randomness of hash functions. Recently, Zeng et al. proposed a generic construction of conditionally anonymous ring signature scheme without random oracles. Their scheme relies on NIZKs and pseudorandom functions, which render it to be inefficient. This paper proposes a practical ring signature scheme with traceability without random oracles in the common reference string model. © 2012 Springer-Verlag.