Reasoning details

  1. How to prove we're over 18: Passport, Driver's License, Social security card?
  2. Look at server's policy. Check credentials.
    • Passport copy? Must be deleted after 7 days
    • Electronic driver's license credential? Must be deleted after 8 days
    • Social security card? Must only be given out to social security entities
  3. Maximize privacy, minimize linkability.
    • Management of pseudonyms
    • Passport, Driver's license
  4. Client to server:
    • Here's proof that I have a driver's license.
    • Please forget this after 8 days.
  5. Server to client: Got it!