Optimistic protocols for fair electronic exchange

Abstract

Society has relied on Trusted Parties (TPs for short) for a long time to facilitate commerce fair exchange transactions. And because of the deep involvement of TPs in every single transaction, it is very resource-consuming and expensive. While on the other hand optimistic fair exchange protocols with invisible TPs offer a more hands-off and cheaper service so that they provide enormous opportunities in communications and financial networks. In the past twenty years optimistic fair exchange protocols have attracted much attention in cryptographic community, and it is believed that they are quite suited to be applied in communication networks such as Internet. Optimistic fair exchange protocol is different from the traditional exchange protocol in the sense that it is in an all-or-nothing manner. All parties involved in an exchange protocol could get what they desire, or none of them will. It will rely on an invisible trusted party, which only participate in dispute transactions, not at all in honest transactions and still guarantees the fairness of all transactions. In this project, I am going to design and implement one application of the optimistic fair exchange protocol -Fair Certified Email (CEM for short)-through studying an optimistic fair exchange protocol proposed by Silvio Micali in 2003[4]. Also a traditional fair exchange protocol proposed by Manuel Blum [1] in 1983 will be studied. By comparing these two protocols, we can see how significant improvements have been achieved in fair exchange realm in the past twenty years and by implementing the CEM application, a better and deeper view of this protocol will be gained. At the end of this project, future improvements will be suggested.