1Sharif University of Technology. Department of electrical engineering
2Department of Electrical Engineering Sharif University of Technology
3Sharif University of Technology
An Optimistic fair exchange (OFE) protocol is a protocol for fairly exchanging items between two parties. For the first time in 2008, Huang et al. introduced the concept of ambiguous OFE in which the partial signature is ambiguous but the full signature is not. Qu et al. in 2012, proposed a shceme with ambiguity for the full signature but not for the partial one. We solve the problem of both schemes by proposing the first efficient protocol that has ambiguity in both partial and full signature. At the same time, by using a traceable ring signature (TRS), we achieve the accountability property. We should highlight that our accountable OFE protocol is the first one secure in the standard model.
optimistic fair exchange, traceable ring signature, ambiguity, accountability.