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International Conference on Communications, Circuits and Systems

A gradual and optimistic fair exchange protocol

Tian Lan, Zhiguang Qin, Yang Zhao, Hu Xiong, Li Liu

Published Jul 1, 2007• 2 citations
Publisher

Abstract

For electronic items without generability or revocability, previous optimistic exchange protocols can't guarantee strong fairness. Gradual protocols assume equal computing power. And online-TTP (Third Trusted Party) protocols often suffer from communication bottle-neck. A gradual and optimistic fair exchange protocol is presented in this paper to solve the problem. Secrets are gradually exchanged with partially validation by recipients, while the probability of detecting cheats increases. Fairness doesn't depend on equal computational power assumption. TTP isn't involved unless dispute appears. The protocol provides stronger fairness than optimistic or gradual schemes.

DOI
10.1109/icccas.2007.6251604

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For electronic items without generability or revocability, previous optimistic exchange protocols can't guarantee strong fairness. Gradual protocols assume equal computing power. And online-TTP (Third Trusted Party) protocols often suffer from communication bottle-neck. A gradual and optimistic fair exchange protocol is presented in this paper to solve the problem. Secrets are gradually exchanged with partially validation by recipients, while the probability of detecting cheats increases. Fairness doesn't depend on equal computational power assumption. TTP isn't involved unless dispute appears. The protocol provides stronger fairness than optimistic or gradual schemes.
An exchange protocol is a protocol that allows two or more parties to exchange electronic information. Bao et al. proposed a multi-party fair exchange protocol based on an offline TTP. Participants in this protocol have to trust the initiator of the exchange in addition of the TTP. In this paper we present an improved optimistic multi-party fair exchange protocol in which participants do not have to trust anyone except for the TTP. Moreover, the communication overhead of our protocol is not increased.
An Optimistic fair exchange (OFE) protocol is a good way for two parties to exchange their digital items in a fair way such that at the end of the protocol, both of them receive their items or none of them receives anything. In 2008, Huang et al. presented an efficient OFE protocol, but there is a security problem in their scheme. If the trusted third party (TTP) is dishonest and colludes with the verifier, the TTP can complete the transaction without getting signer's agreement. To solve this problem, we propose an OFE protocol in which there is a tracing algorithm to detect the party who completes the transaction. Furthermore, we obtain the accountability property introduced by Huang et al. in 2011, more efficiently and in the standard model while their protocol is in the random oracle model. We prove the security of our scheme under the chosen-key model and multi-user setting in the standard model.
In this paper, we propose a new practical fair exchange protocol allowing the exchange of an electronic item against a signature. The protocol is based on the Guillou-Quisquater scheme and assumes the existence of a trusted third party that is involved in the protocol only in the setup phase and when one of the parties does not follow the protocol or some technical problems occur during the execution of the protocol. The interesting feature of the protocol is the low communication and computational costs required by the parties. Moreover, in case of problems during the main protocol, the trusted third party acts transparently. 1
Based on a short signature scheme and discrete logarithm problem,a new fair exchange protocol with the off-line semi-Trusted Third Party(TTP) is proposed.The off-line semi-TTP intervenes into the protocol in case of trouble,which makes the fair exchange optimistic.The off-line TTP need not be completely trusted,since it can get neither signature exchanged when disputation is solved.Because this protocol is based on short signature,which needs low storage and little communication,it can be used in low-bandwidth communication and low-storage environments.
This paper presents an optimistic protocol based on the scheme of public verifiable secret share for distributed fair exchange. A distributed third party is designed to guarantee the fairness of exchange. Comparing to traditional trusted third party, this distributed third party is not fixed but dynamically selected by the players of exchange. This solution can effectively remove the risk of single point of failure and defend compromising attacks. The results of protocol analysis show that the protocol guarantees strong fairness and effectiveness of up to one-half malicious participants in distributed third party.