The proof is bound to a cryptographic key stored in a tamper-resistant module (as in a phone). See https://educatedguesswork.org/posts/age-verification-id/#dev

The proof is bound to a cryptographic key stored in a tamper-resistant module (as in a phone). See https://educatedguesswork.org/posts/age-verification-id/#device-binding https://educatedguesswork.org/posts/age-verification-id/#dev... for some more detail.