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 execution, both of them receive their items or none of them receive anything. In an OFE protocol there is a semi-trusted third party, named arbitrator, which involves in the protocol if it is necessary. But there is a security problem when a...

Privacy-preserving optimistic fair exchange (POFE) is a kind of protocols which aim to solve the fairness problem in the exchange of digital signatures between two parties and in the meanwhile protect their privacy. In POFE, no one else including the semi-trusted third party in charge of arbitration can confirm an exchange even after resolving a dispute. In this paper we present a black-box con...

In this paper we propose an optimistic two-party fair exchange protocol which does not rely on a centralized trusted third party. Instead, the fairness of the protocol relies on the honesty of part of the neighbor participants. This new concept, which is based on a generic verifiable secret sharing scheme, is particularly relevant in networks where centralized authority can neither be used on-l...

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 exe...

In PODC 2003, Park et al. [32] first introduce a connection between fair exchange and sequential two-party multi-signature scheme and provide a novel method of constructing fair exchange protocol by distributing the computation of RSA signature. This approach avoids the design of verifiable encryption scheme at the expense of having cosigner store a piece of prime signer’s secret key. Dodis and...

In PODC 2003, Micali presented a fair electronic exchange protocol for contract signing with an invisible trusted party [17]. The protocol was filed as a US patent No 5666420 in 1997 [16]. In the protocol, two mutually distrusted parties exchange their commitments to a contract in a fair way such that either each of them can obtain the other’s commitment, or neither of them does. The protocol i...

Ring signatures, introduced by Rivest, Shamir and Tauman, attest the fact that one member from a ring of signers has endorsed the message but no one can identify who from the ring is actually responsible for its generation. It was designed canonically for secret leaking. Since then, various applications have been discovered. For instance, it is a building block of optimistic fair exchange, dest...

In an Optimistic Fair Exchange (OFE) for digital signatures, two parties exchange their signa-tures fairly without requiring any online trusted third party. The third party is only involved whena dispute occurs. In all the previous work, OFE has been considered only in a setting where both ofthe communicating parties are individuals. There is little work discussing about the fair ex...

We present an efficient and fair protocol for secure two-party computation in the optimistic model, where a partially trusted third party T is available, but not involved in normal protocol executions. T is needed only if communication is disrupted or if one of the two parties misbehaves. The protocol guarantees that although one party may terminate the protocol at any time, the computation rem...