It's called hybrid transport, and the old name for it was caBLE. Yubico has a nice explainer here: https://developers.yubico.com/WebAuthn/Concepts/Hybrid_Flows/

It's called hybrid transport, and the old name for it was caBLE. Yubico has a nice explainer here: https://developers.yubico.com/WebAuthn/Concepts/Hybrid_Flows/High_assurance_hybrid_flows/ https://developers.yubico.com/WebAuthn/Concepts/Hybrid_Flows... It's not fundamentally different than other transports for other roaming authenticators like a USB key; the QR code sets up a BLE connection between both devices and presents the authenticator with a challenge for it to sign and log in the originating device.