Stefan recently came up with a simple way of explaining E2E (receipt-based) voting systems. He said, imagine if your ballot was attached to a string, and at the end of the string was a tag, and on the tag was some (pseudonymous) identifier.

You put the ballot in the ballot box, but leave the string and tag hanging out. Eventually, as people cast their ballots, the strings and ballots become all jumbled up. The next day you could come back and find your tag. You can see your string disappear into the ballot box (and into a knotted ball). But is your ballot still attached to the other end?

The election authority conducts a zero-knowledge proof to demonstrate the strings are all still in one piece by showing the jumble of strings in sections. At each section you can visually inspect that the strings are in one piece, but cannot (simultaneously) tell where they come from or where they go.

So if you can find your tag, and if across the entire length of strings you do not see any cuts, it’s proof your ballot is still in the ballot box somewhere.

I’ve been calling this the “tea-pot” model for (I hope) obvious reasons: