Multi-party fair exchange protocol with an Off-line Semi-Trust Third Party

A multi-party fair exchange protocol is a cryptographic protocol allowing several parties to exchange electronic items in such a way that everyone gives an item away if and only if it receives an item in return. In this paper, we present a new multi-party fair exchange protocol with an Off-line Semi-Trust Third Party (OSTTP). The new protocol can ensure strong fairness and the OSTTP can't get the exchanged secrets without conspiring with any participants.