Why would you need to include the email address? Just the token should be enough, shouldn't it? Handing out a valid certificate is proof already, you can leave

Why would you need to include the email address? Just the token should be enough, shouldn't it? Handing out a valid certificate is proof already, you can leave the common name empty as long as it's signed by the right authority. This approach does make it rather trivial to clone certificates and spread them, though. All it takes is one kid on their parents' computer dumping a p12 file and the entire school is suddenly bypassing age filters. Another problem is that colluding websites/trackers (i.e. those "first party" trackers that will use things like CNAMEs to trick browsers into executing their tracker code) can use the public key you use to authenticate your age to track you across websites. Your public key will also be non-repudiable unless your CA often makes you reauthenticate and publishes your private key after expiry (similar to how Signal does this, except less secure).