Rational Secure Computation: New Definitions and Constructions

Abstract

Cryptography and Game Theory are two fascinating areas of modern computing, and there have been numerous works since the early 2000s to bridge these. While cryptography provides mechanisms to detect deviations, game theory typically uses monetary utilities to accomplish the same. While cryptography assumes that parties are either purely honest or malicious, game theory treats parties as rational agents governed by their utility functions. The specific problem we consider in this work is that of enabling secure computation when parties behave rationally. We make the following contributions: 1) We provide a rigorous definition of security that overcomes gaps in prior definitions as well as takes an “entropic” view of utilities, 2) We place rational security in the hierarchy of traditional security for two-party computation, and finally, 3) We construct a protocol for two-party computation that is rationally secure as per our definition for a class of functions called NCC functions