It's not so much selling votes, as to discourage voter intimidation: The husband forces his wife, the boss forces his subordinates, the local mafia forces their victims to vote a particular way.
I don't know the rules in the USA, but in the UK it is generally forbidden to stream yourself voting or take a photo in the polling station. Maintaining the secrecy of ballots is high priority.
Someone might still privately take that picture of their ballot paper, after all there's a private voting booth; the officials wouldn't know. You're allowed to say you made a mistake and ask for a replacement ballot paper, so you could show your boss the version they want to see, and then vote differently.
Except we allow postal voting pretty much willy nilly, especailly in areas where intimidation can happen
So in Germany postal voting is secured against selling votes.
It's not about selling, which would be easy to detect like all large conspiracies. It's about subtle coercion that postal voting can enable.
Lack of postal votes makes the ballot less fair and representative, because it affects people with systematic bias in relevant sub-populations (wealth, working conditions, age, health, etc) and areas.
In areas where intimidation can happen... for going to the polling station. (All the intimidator has to do is post menacing guards, soldiers, etc. outside the station or on the routes to it. There are plenty of news reports of this happening in some countries. I'm not aware of this in the UK though.)
So the question is whether you get a more fair and representative vote outcome by allowing postal voting, or by disallowing it.
The balance of trade-offs has led to UK policy allowing postal votes, encouraging each individual to fill out and seal their vote in private, and use statistical and other investigation methods to look for signs of fraud, while maintaining a high standard of secret ballots when voting in person.
That might not be the balance that works best in other countries. In the UK it is said by the Electoral Commission that there is no evidence that postal voting has changed electoral outcomes to date, but some attempts at large scale fraud were discovered and prevented.
It's quite easy to see how a secret ballot can be not secret if the (typically patriarch) says "lets fill the forms out together and I'll take them all in"
Most vote countings are public. I can go to my polling place, cast my vote, check that nobody tampers with the box, watch how they count every vote correctly, ensure that the written tallies are correct, and then verify that the central system tallies match with those I counted.
Also, you're assuming the system is perfectly implemented. In reality, such a system will be complex, will have many more pieces than the ZK system itself (and those pieces will have vulnerabilities), and will require users to do more which will also be prone to errors and vulnerabilities.
I don't understand the insistence on electronic voting for elections. It's less transparent to laypeople, offers small benefits and adds significant complexity both in the implementation and use.
Political machines exploiting nursing homes, pushing absentee ballots on the elderly, etc are already problematic, and allowing field GOTV teams to collect this type of data in mass is would make expanding these operations in size and scope.
You’d also create the new problem of hyper-partisan people crying about voter fraud. You’ll have a bunch of lunatics running around with fake ballot receipts to push whatever narrative they are trying to push.
In my state, it’s illegal to take pictures of ballots at the poll, and there are bipartisan poll inspectors that will shut that down if it happens.
It's a trade off. I want to be able to prove that my vote was counted. How can I trust that my voice was actually heard by the system?
>as nobody else can verify what you voted for.
You can mitigate this problem by giving people a way to fake any vote outcome. The voter knows how to verify their actual vote, but someone else would not be sure if what they verified was real or fake. Also I doubt this type of buying votes with verification is that big of an actual thing. You can trivially do it with paper voting to by just asking them to stream themself voting or by taking a picture of their ballot.
>You either have to blindly trust the system
Having someone else count votes without the ability for you yourself to count votes and check to see if your vote was included is the opposite of blindly trusting the system.