I can't see a way of that working without breaking down somehow:

- If every time you vote you get a receipt for that vote that can be checked if it's still valid then you can send that receipt to the buyer and he can then check that your vote is still according to his purchase - If you can only check that the receipt was registered but not if it's still valid you can't check that your vote was correctly counted because you don't know if the vote has been changed after in multiple possible ways - If you can check that the vote actually is for candidate A at any time you can sell that access to the buyer for him to confirm - If the only way to avoid all this is to also cast an actually secret vote on election day the buyer now just needs to make sure you don't go to the polling place. Posting spotters at the door is not too hard.

I don't see a way for you to actually be able to confirm your vote was counted and not having at the same time the ability to sell your vote in a verifiable way. Perfect verification isn't needed either. If you're selling your vote to the mob you'll have second thoughts about failing to deliver. If you make the process easier "honest" sellers will create the market.

> Note that frauding vote buyers this way is also possible in most election systems that have non-digital preliminaries.

Most I know are actually harder because you only get the single mail-in ballot so you can't do the double or triple voting. If you can show up on the day and invalidate your mail-in then part of same can be done. Depending on how the invalidation of the mail-in is done it can be even sketchier. But I don't consider mail-in and absentee paper votes to have enough security guarantees either way. Paper ballots, in a box, counted by adversaries is the gold standard. Everything else has a high burden of proof.

Screencaps are trivial to counterfeit. Every computer has a screen cap editor.

Someone with a paper ballot can photograph their ballot with a phone of spycam, to prove their vote to a buyer.

Iceland doesn’t have e-voting, but they do have absentee voting. You can vote as often as you want during the absentee ballot, and your most recent will count (or none if you also show up during election day). If you need to physically be present to make sure your agent does’t show up during election day, buying enough vote to sway any election is going to be hard. I suppose if you are a part of a larger organization, you can post several spotters around every voting station. But that will increase the chance of them being spotted and spoofed by the police.

> I suppose if you are a part of a larger organization, you can post several spotters around every voting station. But that will increase the chance of them being spotted and spoofed by the police.

It's easy enough to deploy spotters without being found out. Just deploy spotters as exit pollers, they're already part of any modern election :)

Exit polls are not done everywhere, and in some countries they are even illegal. Just make soliciting around poll stations is illegal and the problem is solved.

Eliminating exit polls seems like a really bad idea. They're one of the only ways to validate an election system that doesn't depend on the system itself. When you have wild discrepancies, particularly in some precincts, you know to investigate. And it seems you'd want that particularly when you've implemented a complex electronic voting system.

And thinking about it some more the Estonian system seems perfect for vote selling. You just provide your ID card and PIN in the last day of early voting and get it back the day after the election. The buyer can vote in your name and hold your ID card to make sure you can't vote in the booth.

You might be right about the exit polls. Perhaps this can only be applied in countries that have strong independent monitors (which Estonia should have being an EU member). Regarding vote selling, I don’t know how it is in Estonia, but in Iceland voter ID is pretty lax. You can provide an ID in the form of passport, drivers license, bank issued debit cards, etc. As a buyer I have no way of knowing if I'm witholding all possible IDs from my agent since they might have several debit cards from several banks, more then one passport (through dual-citizenship), etc.

It should be noted that ID+PIN is not just for the elections: it covers all of the e-services from online health records to online banking, also including digitally signing documents in your name. So I would assume that people wouldn't trust their ID+PIN to strangers.

This is exactly how the Estonian voting system works.