How Does Peggy Prove Her Age, Without Giving Away Her Age?

The method defined in this article is here, and is well known in the literature. So let’s have a bit of fun with it, in order that we can illustrate why we should move to a world where we do not send out our core data, but just prove that we know things.

Introduction

In this modern world, we give away far too much data, and much of the data that is passed is untrusted (and lacks verification). In a future blockchain-focused world, we should be able to verify and trust all of our transactions and thus build a more trustworthy world.

So how do we prove something, without giving away our data? Now let’s met Peggy, who is having a problem. She looks young and keeps getting rejected from pubs, even though she is 19 years old. So Peggy turns up at the “Crypto Nights” bar, but the bar has very strict on age requirements and Victor, who guards the door, makes sure that everyone is 18 or over.

So Peggy says that she is over 18, but Victor asks for proof of her age. “Well, I don’t want to tell you! You will go an tell everyone how old I am!”, she says, and Victor replies, “Well you are not getting in!”.

So Peggy, with her angry face on, says to Victor, “Whom would you trust to verify that I am old enough?”, and Victor, with an equally angry face…