One way to do it would be to present the user with the number but not give them a physical / digital certificate of the UUID. If they are all public, the conspi

One way to do it would be to present the user with the number but not give them a physical / digital certificate of the UUID. If they are all public, the conspirator trying to buy votes cannot trust that their client isn't just looking up UUIDs and giving them a different one. You can write your identifier down, but you could also go online and look up any other identifier you want and use that one instead. The public ledger results could be timestamped so you can correlate your vote with the on chain results, but given a large enough election thousands of votes should be coming in every <unit of time the ledger uses> and you could pick any one that voted the way your sponsor wanted to claim to be your own. It is only a problem if results don't come in in real time I think. Trying to photograph the display would be just as much of a problem as taking a picture of your ballot today. The broad point is to convey the UUID in the only untrustable memory store, the human brain.