Colorblind Friend Proof Example

A example scenario of a Interactive Proof.

Scenario

We attempt to prove to our colorblind friend that two balls are different colors.

1. Friend $(V)$ takes the balls, and hides them behind their back
2. Friend shows you a ball. now you seen this
3. Friend shuffles the balls in some sense, chooses one of the balls and shows you it
4. Friend asks “Have i switched the balls?”
5. Because we can tell the balls from color, we can always answer this question
6. Repeat 128 times, this is to validate that guessing is Negligible.

Properties

1. Designated Verifier : This proof only convinces your friend
2. Zero Knowledge : Your friend learns nothing except that the balls are different (they dont learn which ball was red, and which was green)