How do you mathematically prove that a system is using 'data minimization' without storing the original PII (personally identifiable information) on your local servers?

To prove you are using data minimization without storing personal information, you use a method called zero-knowledge proofs. This is a mathematical way for one person to prove to another that they know a secret or a fact without actually showing the secret itself. Imagine you have a locked box with a key inside. Instead of giving your friend the key, you show them that you can open the box to prove you have it....