evalimine

This has been solved, and it's really simple actually. I wrote about it in another comment, but I'll quickly go over the technology here as well. When a citizen votes, the vote is encrypted with the government public key. The vote is then put into a container and is signed with the citizens private key. The vote gets sent to the voting-system servers and is then stored until counting day. Once the voting period has ended the encrypted votes are pulled out of the signed containers and the signed containers themselves are destroyed, this anonymizes the votes. Only then are the encrypted votes decrypted with the government private key. We keep the signed containers around the encrypted vote to make sure no-one can be forced to e-vote. Every citizen can vote as many times as they want during the e-voting period and only the last vote counts.

Estonian reporting in. Our internet voting system has solved this problem. The votes secrecy is guaranteed by allowing citizens to vote multiple times and only the last vote is counted. No-one is obligated to vote on the internet and a paper system works in parallel. If you cast your vote on the internet AND with a paper ballot as well, the paper ballot is counted. This guarantees no-one can be forced to vote, as they can simply vote again in the 7 day e-voting period. Each vote is encrypted and signed, but in two different containers. The goverment public key is used to encrypt the vote. That container is then wrapped into another that is signed with the citizens private key. Before counting, the double-casts are filtered out and the votes are anonymized by removing the signed wrapper. And, it's open source: https://github.com/vvk-ehk/ev