Receipt-Free Universally-Verifiable Voting with Everlasting Privacy

Abstract. We present the first universally verifiable voting scheme that can be based on a general assumption (existence of a non-interactive commitment scheme). Our scheme is also the first receipt-free scheme to give “everlasting privacy ” for votes: even a computationally unbounded party does not gain any information about individual votes (other than what can be inferred from the final tally). Our voting protocols are designed to be used in a “traditional ” setting, in which voters cast their ballots in a private polling booth (which we model as an untappable channel between the voter and the tallying authority). Following in the footsteps of Chaum and Neff [7,16], our protocol ensures that the integrity of an election cannot be compromised even if the computers running it are all corrupt (although ballot secrecy may be violated in this case). We give a generic voting protocol which we prove to be secure in the Universal Composability model, given that the underlying commitment is universally composable. We also propose a concrete implementation, based on the hardness of discrete log, that is slightly more efficient (and can be used in practice)