IACR News item: 29 January 2015
Handan Kılınç, Alptekin Küpçü
ePrint ReportWe construct an asymptotically optimal (for the complete topology) multi-party fair exchange protocol that requires a constant number of rounds, in comparison to linear, and O(n^2) messages, in comparison to cubic, where n is the number of par- ticipating parties. We enable the parties to efficiently exchange any item that can be efficiently put into a verifiable escrow (e.g., signatures on a contract). We show how to apply this protocol on top of any SMPC protocol to achieve a fairness guarantee with very little overhead, especially if the SMPC protocol works with arithmetic cir- cuits. Our protocol guarantees fairness in its strongest sense: even if all n − 1 other participants are malicious and colluding, fairness will hold.
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