Research On Abuse-Free Three-Party Contract Singing Protocols

An important issue in electronic commerce is how to exchange electronic dataamong potentially distrusted parties in an efficient and fair manner. Exanples of suchexchanges include signing of electronic contracts, certified e-mail delivery and fairpurchase of goods over communication networks such as the Internet.Blum et al first introduce the concept of electric contract signing, which can beseen as a special case of fair exchange signatures on one text involed two or moreparties. In the contract signing, supposing Bob and Carol are two potential competitorswho will sign a contract with Alice. If Alice can convince Carol that Bob would like tosign a contract m with her, she may obtain a better contract m’ from Carol. In this sense,a contract signing protocol without the property of abuse-free is unfair to Bob.Therefore, abuse-freeness is a necessary condition to achieve fairness. In order to solvethe problem, Garay et al. first introduced the notion of abuse-free contract signing,which ensures neither party can prove to others that he is capable of choosing whetherto validate or invalidate the contract in any stage of the protocol. How to designefficient abuse-free contract signing protocols is a hot and difficult issue in currentacademic research.We use the notion of Verifiable Encryption of Chameleon Signatures (VECS) todesign an abuse-free three-party contract singing protocol. Our protocol enjoys theproperties of completeness, fairness of the parties, abuse-freeness, accountability, andinvisibility of the third party, and achieves high-efficiency contract signing forthree-party. Furthermore, our signing protocol enjoys the distinguishing property ofeverlasting secrecy about the contract against the third party. That is, the third partycannot know any useful information of the contract in any stage if the protocol, whichprevents him from illegally selling the commercial secret to any interested party.