The Security Power of the Ballot Box

Abstract

We show that any function F can be securely evaluated by a protocolwith ballots and a ballot box. That is, N mutually suspicious players,each player possessing a secret input, can use ballots and a ballotbox to jointly evaluate F on their secret inputs so that (no matterhow many players may collude and deviate from their prescribed instructions, and no matter how long they compute!) each player learnsexactly the output of the function with the same privacy and correctnessas if all players privately handed their secret inputs to a trustedparty, who privately evaluates F and privately returns the outputs toeach player.Our protocol is (1) efficient, (2) enjoys perfect privacy, (3) guarantees perfect correctness, (4) is universally composable, and (5)is collusion-free even for games with secret actions.