Research On The Application Of The Concurrent Signatures In The Fair Exchange Protocal

Electronic commerce is the Internet-based exchange of tangible or intangible merchandise between two or multi party, so the fair exchange protocols take important part in the electronic commerce. Fair exchange protocols play an important theoretical role in the realization of the fair exchange in the electronic commerce and they are considered indispensable in security study. At present, mostly fair exchange protocols are based on the trusted third party, but trusted third party has many disadvantage, so how to design fair exchange protocols without trusted third party become an important topic in the electronic commerce security field. In 2004, Chen et. proposed concurrent signature, and using concurrent signature can design fair exchange protocols without trusted third party, and improve the protocols' efficiency.This thesis mainly researches on the concurrent signatures and their application in the fair exchange protocols. The primary research is summarized as follows:1.This thesis proposes the rational definition of fairness, and introduce the modular analysis for fair exchange protocols.2.This thesis exhaustively introduces the algorithm, protocol and security of three representational two-party concurrent signatures(Concurrent Signature, Perfect Concurrent Signature and improved Perfect Concurrent Signature). Ph.D Li introduces the concept of the accountability of concurrent signature, and indicates that current concurrent signatures are all have non-accountability, so he proposes a novel concurrent signature which is accountability. This thesis designs a fair exchange protocol without trusted third party that can use to exchange tangible merchandise based on the accountable concurrent signature.3.This thesis introduces the multi-party concurrent signature, and take the accountability into the multi-party concurrent signature.This thesis analyses the multi-party concurrent signature, prove that it is not accountable, and designs a method to attract it. For that, this thesis improves the multi-party concurrent signature and proposes a protocol to solve the problem of signing a multi-party agreement without trusted third party.4.This thesis introduces the conception of exchange on the single-unit circuit. The communications volume of the multi-party concurrent signature on the unit loop is only O(n), so this thesis proposes a novel multi-party concurrent signature on the unit loop based on Li's concurrent signature.