Fair Exchange in the Blockchain (Draft)

A.W. Roscoe, Bangdao Chen, Wang Lei.
Chieftin Lab

Fair exchange is an important primitive in transactions where the parties do not completely trust one another. It is well known to be impossible to implement this with 100% assurance without a trusted third party. The blockchain is a sort of trusted third party built out of many untrusted parties, and a very popular target for systems involving peer-to-peer (i.e. without passing via central authorities) transactions. In this paper we show a number of different ways in which fair exchange can be implemented.