Think built-in authenticators like touch ID or face ID. What they do is that they authenticate you via biometrics, and then unlock a private key stored on your

Think built-in authenticators like touch ID or face ID. What they do is that they authenticate you via biometrics, and then unlock a private key stored on your device that will sign a challenge. The challenge is only relevant for some situation, so that you can't replay it. Essentially, signing is a zero-knowledge proof that you know your private key, associated with some metadata.