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Distributed Multimedia Systems

Identity-based optimistic fair exchange with transparent signature recovery

Shahrokh Saeednia, Olivier Markowitch, Yves Roggeman

Published Jan 1, 2003• 3 citations
OpenAlex

Abstract

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

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IEEE Transactions on Information Forensics and Security•Feb 3, 2011•27 citations
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
A fair exchange scheme is a protocol by which two parties Alice and Bob exchange items or services without allowing either party to gain advantages by quitting prematurely or otherwise misbehaving. To this end, modern cryptographic solutions use a semi-trusted arbitrator who involves only in cases where one party attempts to cheat or simply crashes. We call such a fair exchange scheme optimistic. When no registration is required between the signer and the arbitrator, we say that the fair exchange scheme is setup free. To date, the setup-free optimist fair exchange scheme under the standard RSA assumption was only possible from the generic construction of [12], which uses ring signatures. In this paper, we introduce a new setup-free optimistic fair exchange scheme under the standard RSA assumption. Our scheme uses the GQ identity-based signature and is more efficient than [12]. The construction can also be generalized by using various identity-based signature schemes. Our main technique is to allow each user to choose his (or her) own “random” public key in the identitybased signature scheme.
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.
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.
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.
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.
Optimistic fair exchange (OFE) protocols are useful tools for two participants to fairly exchange items with the aid of a third party who is only involved if needed. A widely accepted requirement is that the third party's involvement in the exchange must be transparent, to protect privacy and avoid bad publicity. At the same time, a dishonest third party would compromise the fairness of the exchange and the third party thus must be responsible for its behaviors. This is achieved in OFE protocols with another property called accountability. It is unfortunate that the accountability has never been formally studied in OFE since its introduction ten years ago. In this paper, we fill these gaps by giving the first complete definition of accountability in OFE where one of the exchanged items is a digital signature and a generic (also the first) design of OFE where transparency and accountability coexist.