Zero Knowledge Proof — A popular Explanation

To easily understand Zero-Knowledge Proof, there is a very classic example of Alibaba. Alibaba is able to prove to the thieves that he knows the magical word without disclosing it. Recently, when watching Stanford professor Dan Boneh’s lecture videos, I found another vivid example that describes Zero-Knowledge Proof:

https://youtu.be/V0JdeRzVndI?t=1972

Professor Dan is a Cryptography expert. If you are not familiar with him, you can check out his main page on Stanford University Website:

https://crypto.stanford.edu/~dabo/

Professor Dan tries to introduce Zero-Knowledge Proof to kindergarten children, using the game — “Where is Waldo” — as shown in the video.

Where is Waldo is a classic board game, asking the player to find a specific character — Waldo — in a picture full of crowded people. Such as the image shown below:

How to use Zero-Knowledge Proof to prove that you know where Waldo is?

First, you will need a pair of scissors. Next, turn around and cut out the Waldo figure from behind your back, so the challangers don’t see it. Then tear apart the rest of the board. And Give the Waldo figure to the challangers. This perfectly proves that you know Waldo’s location without exposing it. The knowledge used in this example is called “Waldo’s location”.