In the setting of secure multiparty computation, a set of mutually distrustful parties wish to securely compute some joint function of their private inputs. The computation should be carried out in a secure way, meaning that the properties privacy, correctness, independence of inputs, fairness and guaranteed output delivery should all be preserved. Unfortunately, in the case of no honest majority -and specifically in the important two-party case -it is impossible to achieve fairness and guaranteed output delivery. In this paper, we show how a legal infrastructure that respects digital signatures can be used to enforce fairness in two-party computation. Our protocol has the property that if one party obtains output while the other does not (meaning that fairness is breached), then the party not obtaining output has a digitally signed cheque from the other party. Thus, fairness can be "enforced" in the sense that any breach results in a loss of money by the adversarial party.
Lindell REF constructs a framework that can be adopted by any two-party functionality with the property that either both parties receive the output, or one party receives the output while the other receives a digitally-signed check (i.e., monetary compensation).
Legally-Enforceable Fairness in Secure Two-Party Computation ∗
CT-RSA
Computer Science