I was arguing about this with someone when they pointed out that in Australian Senate elections, it's trivially easy to make your vote unique. There are many candidates and you can order them however you like, so you can vote a particular way among the candidates that are actually competitive, and then order the rest of the candidates in some improbable way to make your vote unique. Then when the database gets published later someone can verify that you voted how you said you would.

So the Australian Senate is currently vulnerable to vote buying, for what it's worth.