[ianmiers]

if you just sent Mick down the left path and he came out the right, then a video would conclusively show he knew the password.

And this is why "How to explain zero-knowledge protocols to your children" is probably the worst way to explain zero-knowledge protocols to anyone. Its not explaining what a zero-knowledge proof is or how it works. It's explaining what a simulator is when proving a protocol is zero-knowledge . Oh, and the explanation only works for interactive protocols.