The Taub Faculty of Computer Science Events and Talks

We study a model of secure computation in which deviating parties are forced to pay monetary penalties, without relying on a trusted party to provide an ideal bank functionality. Our protocols work in a hybrid model where parties have access to claim-or-refund or multilock ideal functionalities, which can be efficiently realized in (a variant of) Bitcoin. In this talk we present three results: 1. Compilation of any secure multiparty computation protocol into a protocol that enforces fairness with penalties, meaning that all corrupt parties who abort on receiving output are forced to pay a mutually predefined monetary penalty. 2. Protocol for {\em secure cash distribution with penalties}, a variant of secure computation in which the inputs and outputs of the parties are also comprised of money. Our protocol allows dropout-tolerant realizations of digital games in which money changes hands, in the sense that any party who drops out in the middle of the game is forced to pay a penalty to all other parties. This implies that it is feasibile to play real poker rather than just mental poker, in the absence of a trusted referee. 3. Amortization of the cost over multiple executions of secure computation with penalties, in an optimistic setting. Specifically, we design a protocol that implements $n$ instances of secure computation with penalties where the total number of claim-or-refund calls is independent of $n$, as long as all parties are honest.