Coercion-Resistant Electronic Elections

We introduce a model for electronic election schemes that involves a more powerful adversary than previous work. In particular, we allow the adversary to demand of coerced voters that they vote in a particular manner, abstain from voting, or even disclose their secret keys. We define a scheme to be coercion-resistant if it is infeasible for the adversary to determine if a coerced voter complies with the demands.A first contribution of this paper is to describe and characterize a new and strengthened adversary for coercion in elections. (In doing so, we additionally present what we believe to be the first formal security definitions for electronic elections of any type.) A second contribution is to demonstrate a protocol that is secure against this adversary. While it is clear that a strengthening of attack models is of theoretical relevance, it is important to note that our results lie close to practicality. This is true both in that we model real-life threats (such as vote-buying and vote-canceling), and in that our proposed protocol combines a fair degree of efficiency with an unusual lack of structural complexity. Furthermore, previous schemes have required use of an untappable channel throughout. Ours only carries the much more practical requirement of an anonymous channel during the casting of ballots, and an untappable channel during registration (potentially using postal mail).This extended abstract is a heavily truncated version of the full paper available at http://eprint.iacr.org/2002/165.