In this model we specify the ideally fair functionality as allowing parties to ``invest resources'' in return for outputs, but in such an event offering all other parties a fair deal. (The formulation of fair dealings is kept independent of any particular functionality, by defining it using a ``wrapper.'') Thus, by relaxing the notion of fairness, we avoid a well-known impossibility result for fair multi-party computation with corrupted majority; in particular, our definition admits constructions that tolerate arbitrary number of corruptions. We also show that, as in the UC framework, protocols in our framework may be arbitrarily and concurrently composed.
Turning to constructions, we define a ``commit-prove-fair-open'' functionality and design an efficient resource-fair protocol that securely realizes it, using a new variant of a cryptographic primitive known as ``time-lines.'' With (the fairly wrapped version of) this functionality we show that some of the existing secure multi-party computation protocols can be easily transformed into resource-fair protocols while preserving their security.
Category / Keywords: cryptographic protocols / Secure multi-party computation, universal composability, fair exchange, timed commitments Date: received 12 Oct 2005 Contact author: mmp at cs uiuc edu Available formats: Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation Version: 20051019:181533 (All versions of this report) Discussion forum: Show discussion | Start new discussion