How do FIDO2 and WebAuthn enable passwordless logins?

FIDO2 and WebAuthn enable passwordless authentication by allowing users to log in using cryptographic key pairs instead of passwords. Instead of sending a password to a server, your device locally verifies your identity using biometrics or a PIN

 

How FIDO2 and WebAuthn Work

1. User Registers a Device (Passkey Creation): When signing up, the user registers a device (phone, laptop, or security key). A public-private key pair is generated. The private key stays securely on the user’s device. The public key is stored on the server, shared with the website’s server, and associated with your account

2. Login Request is Initiated: The user enters their username or email to start the login process.

3. Authentication Challenge is Sent: The server sends a cryptographic challenge to the user’s device via WebAuthn.

4. User Verifies Identity: Your device prompts you to verify your identity locally using a biometric scan (fingerprint/face) or a device PIN.

5. Cryptographic Verification: The signed response is sent back to the website. The server uses your previously stored Public Key to verify the signature.

6. Access is Granted: If the signature is valid, the user will be logged in without even entering a password.

 

Benefits of FIDO2 and WebAuthn

1. Phishing-resistant authentication – credentials cannot be reused or tampered with

2. Stronger security – No server secrets

3. Seamless user experience – fast login with biometrics or passkeys

4. Device-based trust – authentication tied to user devices