> you can't get out of the fact that things can be anonymous (no one can know how you voted) or verifiable (people can prove that you only voted once) but not both.
Actually, I think there might be a way to get both. I've been thinking about this while building my app SoWasIt.
The idea:
A public chain records that "user X voted at time T" (like a digital voter roll). It's immutable and public. "user X" could contain voter Id, name, like on a signing sheet.
The vote itself (the choice) is stored separately, with a random UUID generated. Privately during the vote, no timestamp, no incremental id, no link to the voter. The UUID is sent back to the voter who will use it to verify his vote integrity.
At the end, all votes are published in batches (anonymous UUID + choice in clear). Ideally in an immutable chain so it can't be altered later (and ideally for me on my app )
=> You can verify your vote by looking for your UUID in the final table.
=> You can verify that the number of votes matches the number of voters (public chain count = final table size)
=> you can verify the counting for each candidate
=> You can't link a UUID to a voter unless you have both the UUID and the voter's identity, which only the voter knows.
It's not perfect, you still need to trust that the system doesn't secretly store the link between voter and UUID, or have a man-in-the-middle system to intercept votes whil it's processed. And to not add fake voters: That's why you need to publish something like voter cards ids, so that anyone can go to the administration, check that a specific voter actually exists.
So no, it's not impossible to have both anonymity and verifiability – it's just hard, and it shifts the trust to other parts of the system. But that's politics, not just tech
Anyway, in my humble opinion, people manage to cheat with traditional paper vote (mostly because citizens don't care enough to spend time lokking after the ballot box till the end), electronic can only make things worse.
And as the French comedian Coluche once said: "If voting really changed anything, it would have been banned a long time ago."