Vote&Check: Secure Postal Voting with Reduced Trust Assumptions

Postal voting is a frequently used alternative to on-site voting.Traditionally, its security relies on organizational measures, andvoters have to trust many entities.In the recent years, several schemes have been proposed to addverifiability properties to postal voting, while preserving vote privacy. Postal voting comes with specific constraints. We conduct a systematic analysis of this setting and we identify a list of generic attacks, highlighting that some attacks seem unavoidable. This study is applied to existing systems of the literature. We then propose Vote&Check, a postal voting protocol which provides a high level of security, with a reduced number of authorities. Furthermore, it requires only basic cryptographic primitives, namely hash functions and signatures. The security properties are proven in a symbolic model, with the help of the ProVerif tool.