Secure Auctions in the Presence of Rational Adversaries

Sealed bid auctions are used to allocate a resource among a set of interested parties. Traditionally, auctions need the presence of a trusted auctioneer to whom the bidders provide their private bid values. Existence of such a trusted party is not an assumption easily realized in practice. Generic secure computation protocols can be used to remove a trusted party. However, generic techniques result in inefficient protocols, and typically do not provide fairness -that is, a corrupt party can learn the output and abort the protocol thereby preventing other parties from learning the output. At CRYPTO 2009, Miltersen, Nielsen and Triandopoulos [MNT09], introduced the problem of building auctions that are secure against rational bidders. Such parties are modeled as self-interested agents who care more about maximizing their utility than about learning information about bids of other agents. To realize this, they put forth a novel notion of information utility and introduce a game-theoretic framework that helps analyse protocols while taking into account both information utility as well as monetary utility. Unfortunately, their construction makes use a of generic MPC protocol and, consequently, the authors do not analyze the concrete efficiency of their protocol. In this work, we construct the first concretely efficient and provably secure protocol for First Price Auctions in the rational setting. Our protocol guarantees privacy and fairness. Inspired by [MNT09], we put forth a solution concept that we call Privacy Enhanced Computational Weakly Dominant Strategy Equilibrium that captures parties' privacy and monetary concerns in the game theoretic context, and show that our protocol realizes this. We believe this notion to be of independent interest. Our protocol is crafted specifically for the use case of auctions, is simple, using off-the-shelf cryptographic components. Executing our auction protocol on commodity hardware with 10 bidders, with bids of length 10, our protocol runs to completion in 0.141s and has total communication of 30KB.