Optimistic Fair Exchange of Ring Signatures
An Optimistic Fair Exchange (OFE) protocol is an effective tool helping two parties exchange their digital items in an equitable way with assistance of a trusted third party, called arbitrator, who is only required if needed. In previous studies, fair exchange is usually carried out between individual parties. When fair exchange is carried out between two members from distinct groups, anonymity of the signer in a group could be necessary for achieving better privacy. In this paper, the authors consider Optimistic Fair Exchange of Ring Signatures (OFERS), i.e. two members from two different groups can exchange their ring signatures in a fair way with ambiguous signers.