Verifiable postal voting

This proposal aims to combine the best properties of paper-based and end-to-end verifiable remote voting systems. Ballots are delivered electronically to voters, who return their votes on paper together with some cryptographic information that allows them to verify later that their votes were correctly included and counted. We emphasise the ease of the voter's experience, which is not much harder than basic electronic delivery and postal returns. A typical voter needs only to perform a simple check that the human-readable printout reflects the intended vote. The only extra work is adding some cryptographic information into the same envelope as the human-readable vote. The proposed scheme is not strictly end-to-end verifiable, because it depends on procedural assumptions at the point where the ballots are received. These procedures should be public and could be enforced by a group of observers, but are not publicly verifiable afterwards by observers who were absent at the time.