Efficient optimistic N-party contract signing protocol

Abstract

Contract signing is a fundamental service in the environment of theelectronic commerce. It is a kind of fair exchange of values: a signature on atext contract for another signature on the same text. We present a fair protocolthat requires the existence and possible involvement of a TTP (trusted thirdparty), but it only intervenes in case of exception (it plays a subsidiary role).The protocol is the best solution to the date in terms of efficiency. We presentand analyse a two-party and three-party version of the protocol, and we outlinean N-party version. Finally, it is very simple and easy to understand. If we thinkthat at the end some conflicts will be solved in courts, it is a non worthlesscharacteristic.