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Hey! I independently came up with the Where’s Waldo protocol right here on Hacker News!

https://news.ycombinator.com/item?id=15323790




Oh wow! It looks like you attempted to avoid the problem with the original Waldo solution (namely, that's it not completely zero-knowledge since you can't fool outsiders.)

I'm not 100% sure I understand your protocol though. You're putting a fake picture that has Waldo in it beneath the cardboard? So that you can always punch a hole to reveal Waldo? How does that prove anything?

I'm not sure what I'm missing here.


The idea is that a prover puts the original page at some random position behind the screen. The verifier randomly decides to force you to punch the hole or remove the screen, but not both. The possibility of doing the latter is what weeds out frauds who try to cheat by not using the original page (or inserting fake Waldos).


Well his example does break down since it is supposed to have a protocol, and the prover could fake it by showing him a fake waldo. To make it a ZKP, The person requesting the proof would need to know exactly what waldo looks like (possibly reconfiguring/redrawing him himself), but doesn't know where he is. He hands the prover the new picture, and he proves it by showing the cutout with the exact rendition of the new waldo. Repeat n times with new waldos to reduce the likelihood of getting a lucky guess. I'm not sure but I think this sounds closer.


The model of the WW problem assumes you know what Waldo looks like (but not where he is), so that part is taken care of.

Under the protocol I gave, you can’t cheat by using a fake Waldo, because each time there’s a fifty percent chance the prover will ask you to remove the screen, which would reveal you’re not using (only) the original page.

(Keep in mind you do the protocol many times with a new position in each one.)


I see, that makes more sense


Late follow-up: I didn't read carefully; I actually came up with a different protocol that improves upon it and makes it actually zero-knowlege, by only being convincing to the verifier, and which prevents you from cheating with a fake Waldo.




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