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IET Information Security

Efficient abuse‐free fair contract‐signing protocol based on an ordinary crisp commitment scheme

Alawi A. Al‐Saggaf, Lahouari Ghouti

Published Jul 25, 2014• 9 citations
Publisher

Abstract

A mathematical framework for conventional commitment schemes is proposed. Digital contract‐signing protocols represent an important application of the proposed framework, where usually two mistrusted parties wish to exchange their commitments in a fair way. Building on a variant of the proposed framework, an efficient contract‐signing protocol over the Internet is developed. The latter protocol is ‘optimistic, fairness and abuse‐free’. Detailed security and performance analyses are provided. The performance analysis reveals an important computational aspect of the proposed protocol which requires only ‘four rounds’ to complete unlike existing protocols. Moreover, the communication and computational costs are relatively small. Given these theoretical and practical features, the proposed contract‐signing protocol is not only of theoretical interest, but it also enjoys practical merits which make it very suitable for electronic transactions requiring online signature exchange.

DOI
10.1049/iet-ifs.2012.0277

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A mathematical framework for conventional commitment schemes is proposed. Digital contract‐signing protocols represent an important application of the proposed framework, where usually two mistrusted parties wish to exchange their commitments in a fair way. Building on a variant of the proposed framework, an efficient contract‐signing protocol over the Internet is developed. The latter protocol is ‘optimistic, fairness and abuse‐free’. Detailed security and performance analyses are provided. The performance analysis reveals an important computational aspect of the proposed protocol which requires only ‘four rounds’ to complete unlike existing protocols. Moreover, the communication and computational costs are relatively small. Given these theoretical and practical features, the proposed contract‐signing protocol is not only of theoretical interest, but it also enjoys practical merits which make it very suitable for electronic transactions requiring online signature exchange.
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.
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.
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.
we propose a new efficient protocol. which allows a pair of potentially mistrusting parties to exchange digital signatures over the Internet in a fair way. The protocol relies on an off-line Trusted Third Party (TTP). which does not take part in the exchange unless any of the parties behaves improperly or other faults occur. Efficiency of the protocol is achieved by using a cryptographic primitive, called designated confirmer signatures. The confirmer commitment schemes and ordinary signatures are combines to form the confirmer signatures. The security of the protocol is analyzed and the fairness of it is guaranteed.
If two parties want to sign a contract C over a communication network, they must “simultaneously” exchange their commitments to C Since simultaneous exchange is usually impossible in practice, protocols are needed to approximate simultaneity by exchange partial commitments in a piece by piece manner The party of secondly sending commitments may have a slight advantage; a “fair” protocol must keep this advantage within acceptable limits The protocol for signing a contract is improved based on the research result of secure multiparty computation In this protocol, the parties obliviously transfer the signed bit and the committed bit; the other parties can prove the validity of this bit based on the confirming sub protocol, but he can't gain more information about the whole signature by accumulating the signed bit or the committed bit After the parties exchange the whole signed information, they declare the commitment about the signature respectively, and gain the whole signature of the other party At this moment, the party doesn't care about the advance quit of the other party, because he has gained the whole signed information Finally, it is proved that this protocol is quit fairness
ABSTRACT A fair exchange protocol allows two entities to exchange digital signatures over open networks in a fair way, so that either each entity obtains the other's signature or neither entity does. Fair exchange protocol plays an important role in electronic commerce in the case of exchanging digital contracts. In this paper, we propose a fair exchange protocol based on identity‐based verifiably encrypted signatures. Our protocol involves an offline trusted third party which is only required when one entity attempts to cheat or crashes. The underlining identity‐based verifiably encrypted signature scheme is proven secure under the computational Diffie–Hellman assumption and is the first identity‐based verifiably encrypted signature scheme provably secure against existential unforgeable under adaptive chosen message and identity attacks in the standard model. Copyright © 2012 John Wiley & Sons, Ltd.