An Efficient e-Commerce Fair Exchange Protocol That Encourages Customer and Merchant to Be Honest

A new e-Commerce fair exchange protocol is presented in this paper. The protocol is for exchanging payment with digital product (such as computer software) between customer (C) and merchant (M). It makes use of Trusted Third Party (TTP) but its use is kept to minimum when disputes arise. In this respect it is an optimistic fair exchange protocol. A new idea, in which if the parties are willing to exchange then they are encouraged to be honest, is originated in this protocol. The protocol has the following features: (1) It comprises four messages to be exchanged between C and M in the exchange phase; (2) It guarantees strong fairness for both C and M so that by the end of executing the protocol both C and M will have each other’s items or no one has got anything; (3) It allows both parties (C and M) to check the correctness of the item of the other party before they send their item; (4) It resolves disputes automatically online by the help of the Trusted Third Party (TTP); and (5) The proposed protocol is efficient in that it has a low number of modular exponentiations (which is the most expensive operations) when compared to other protocols in the literature.