Passkey (FIDO2 / WebAuthn)

A phishing-resistant login standard in which a biometric (fingerprint or face) is checked locally on the user's device and never leaves it; the server receives only a cryptographic assurance that the check passed. It is biometric authentication — a one-to-one "does this credential belong to this body?" check — not proof of personhood's one-to-many uniqueness check. A trust-the-authenticator model: it binds a credential durably to a body, cheaply, within that trust boundary. Part of the identity family.