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After reading your post I understand that the challenge to show the picture is to test for a fake picture (one with only Waldo for example), so that makes more
by cmehdy 5y ago
After reading your post I understand that the challenge to show the picture is to test for a fake picture (one with only Waldo for example), so that makes more sense to me. Bob is just allowed to make sure the hidden image that Alice uses is the original (and she can still cheat when Bob choses the other option but the probabilities of succeeding the tricks become vanishingly small with tries, which is the point).
And I assume the screen is meant to always cover the picture (i.e. MUST be much larger than the picture) and only Alice can know the actual coordinates of the picture behind the larger screen (otherwise Bob can infer the position of the Waldo), right?
It is also possible that I have not understood something from your interesting proof there.
Thanks for sharing the discussion about the finer points of ZKP being only between Alice and Bob.
- SilasX 5y agoThat's correct. Ideally you'd want a screen with double the dimensions so that you can designate a portion of it with uniform probability of any location having Waldo. And my model has it so that (for the second challenge) Bob learns the position of Waldo relative to the screen, but not the position of Waldo relative to the page, which is what we mean by "finding Waldo". And, of course, on that challenge, Bob would not get to learn the position of the page relative to the screen (which would allow him to "find Waldo").