Fair Exchange of Digital Signatures with Offline Trusted Third Party

Abstract

In this paper we show how fair exchange of digital signatures can be made possible without a separate verifiable encryption. This means that the fair exchange protocol can be established based on an existing signature algorithm without modification, except that the users need to get a ticket from an off-line trusted third party to enable the fair exchange. The trusted third party is needed to make a judgment only when there is a dispute. Explicit protocols based on different digital signature algorithms are proposed.