The domain becomes part of authentication
With passwords, the user decides where to type the secret, so a convincing lookalike can steal it. A passkey uses public-key cryptography and relying-party binding. The wrong origin cannot obtain the right assertion.
The service stores a public key while the private key remains on an authenticator or within protected platform sync. A database leak no longer exposes a shared secret that can be replayed as a normal sign-in.
Strong sign-in, weak recovery
The migration fails if an attacker can bypass a passkey through an old SMS code or a lightly verified support request. Recovery is another authentication route and belongs in the same threat model.
Let users register multiple authenticators, see understandable device names, and receive alerts when a new passkey is added. Removing the last strong factor deserves especially careful confirmation.
- Offer passkey enrollment immediately after a successful trusted sign-in.
- Explain the outcome without requiring users to learn cryptographic terminology.
- Test lost devices, platform changes, and cross-device flows.
- Measure recovery abuse as closely as primary login attacks.
Treat adoption as a journey
Measure enrollment and sign-in success by platform before tightening fallback paths. Passwords may remain during transition, but each fallback needs an owner and a retirement plan.
Passkeys improve the whole system only when support and recovery preserve the phishing-resistant boundary. A strong front door does little if the side entrance still trusts a reusable secret.