Optimistic protocols for fair exchange
Proceedings of the 4th ACM conference on Computer and communications security
Optimal efficiency of optimistic contract signing
PODC '98 Proceedings of the seventeenth annual ACM symposium on Principles of distributed computing
Formal Analysis of Multi-Party Contract Signing
CSFW '04 Proceedings of the 17th IEEE workshop on Computer Security Foundations
Resolve-Impossibility for a Contract-Signing Protocol
CSFW '06 Proceedings of the 19th IEEE workshop on Computer Security Foundations
A dolev-yao-based definition of abuse-free protocols
ICALP'06 Proceedings of the 33rd international conference on Automata, Languages and Programming - Volume Part II
Efficient and secure protocol in fair certified E-mail delivery
WSEAS Transactions on Information Science and Applications
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A multi-party contract signing protocol allows a set of participants to exchange messages with each other with a view to arriving in a state in which each of them has a pre-agreed contract text signed by all the others. "Optimistic" such protocols allow parties to sign a contract initially without involving a trusted third party T. If all signers are honest and messages are not arbitrarily delayed, the protocol can conclude successfully without T's involvement. Signers can ask T to intervene if something goes amiss, for example, if an expected message is not received. Two multi-party contract signing protocols have been proposed so far. One solution to this problem was proposed by Garay and MacKenzie (DISC'99) based on private contract signatures, but it was subsequently shown to be fundamentally flawed (it fails the fairness property). Another more efficient protocol was proposed by Baum-Waidner and Waidner (ICALP'00). It has not been compromised, but it is based on a non-standard notion of a signed contract. In this paper, we propose a new optimistic multi-party contract signing protocol based on private contract signatures. It does not use a non-standard notion of a signed contract and has half the message complexity of the previous solution.