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Fair Contract Signing Protocol Based on Short Signature

Luo Wen-jun, Tong Ling, Zufeng Fu, Changgen Peng

Published Jul 1, 2010• 1 citation
Publisher

Abstract

Based on Zhang's short signature scheme without random oracles and k+1-square roots assumption, a new fair contract signing protocol with the off-line semi-Trusted Third Party is given because the disadvantages of existed fair contract signing protocol. The off-line semi-TTP intervenes into the protocol in cases where one party attempts to cheat or simply crashes to make the fair exchange optimistic. The off-line TTP need not be completely trusted, since the TTP can get neither exchanged signature when dispute is mediated. 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.

DOI
10.1109/itcs.2010.69

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Based on Zhang's short signature scheme without random oracles and k+1-square roots assumption, a new fair contract signing protocol with the off-line semi-Trusted Third Party is given because the disadvantages of existed fair contract signing protocol. The off-line semi-TTP intervenes into the protocol in cases where one party attempts to cheat or simply crashes to make the fair exchange optimistic. The off-line TTP need not be completely trusted, since the TTP can get neither exchanged signature when dispute is mediated. 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.
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.
A fair contract-signing protocol allows two potentially mistrusted parities to exchange their commitments (i.e., digital signatures) to an agreed contract over the Internet in afairway, so that either each of them obtains the other's signature, or neither party does. Based on the RSA signature scheme, a new digital contract-signing protocol is proposed in this paper. Like the existing RSA-based solutions for the same problem, our protocol is not only fair, but also optimistic, since the trusted third party is involved only in the situations where one party is cheating or the communication channel is interrupted. Furthermore, the proposed protocol satisfies a new property-abuse-freeness. That is, if the protocol is executed unsuccessfully, none of the two parties can show the validity of intermediate results to others. Technical details are provided to analyze the security and performance of the proposed protocol. In summary, we present the first abuse-free fair contract-signing protocol based on the RSA signature, and show that it is both secure and efficient.
Fair exchange of digital signatures is an important tool for signing digital contracts, e-payment and other electronic commerce actions. An ID-based scheme of fair exchange of digital signature is proposed in this paper. The protocol relies on a trusted third party, but is “optimistic”, in that the third party is only needed in cases where one player attempts to cheat or simply crashes. The proposed scheme has properties of short signature, low computation and verification cost. It can realize exchange of digital signatures fairly and efficiently. A key feature of our scheme is that it is identity-based, which needs no certificates and has a simple key management. To our best knowledge, this is the first identity-based scheme of fair exchange of digital signatures.
Today in the field of security there are various protocols and authentication techniques that makes an application in the network more secure and free from various attacks in the network. There are various applications which require exchange of data between parties. A fair exchange is required since the chances of attacks have been greatly increased. Hence a new protocol has been implemented for the fair exchange of data between parties called contract signing protocol. Although there are various techniques applied for the security of these contract signing protocols such as using RSA [1]. This protocol use RSA to generate digital signature for the authentication of fair exchange between two parties, also in this technique instead of using single TTP (Trusted Third Party) and the trust can be distributed on multi TTP's. But the protocol implemented here in these techniques has less security issues and the chances of attack are more and also by using multiple TTP's storage cost is increased. Hence to overcome these limitations we propose an efficient and secure protocol of contract signing using OTPK (One Time Private Key). This technique requires less storage cost since there is no need to store any key at any end.
Based on the verifiably encrypted signature scheme without random oracles recently proposed by Gorantla et al.,a new scheme of optimistic fair exchange of digital signatures is proposed in this paper.The two players firstly exchange their verifiably encrypted signature on agreed-upon messages then their ordinary signature after the verification of each other's verifiably encrypted signature.If one of them executes the protocol dishonestly,the other can resort to a trusted third party so as to get the purpose of fair exchange of signatures.The proposed scheme has properties of short signature,low computation and verification cost.It can realize exchange of digital signatures fairly and efficiently.