I've watched a video about Meet passkeys and I have a question. After key agreement have happened, the two devices connect to a relay server picked by the phone. I understand that the key agreement local part uses Bluetooth. After then, the FIDO CTAP operation does not use Bluetooth? Does it uses Transmission Control Protocol? What happens if I turn off Bluetooth, after the key agreement is finished? Can you explain in more detail how FIDO CTAP operates and how client and authenticator exchange information after two devices connect to a relay server?

I understand that during the CTAP process with a Passkey, a key agreement takes place when scanning the QR code and sending Bluetooth advertisements. Is the Diffie-Hellman algorithm used for the key agreement during this process?

I initiated the Passkey CTAP process after establishing an internet connection on my smartphone (authentication device) using Wi-Fi. Once the client PC and the smartphone established a TCP connection and were in the midst of the CTAP process, I attempted to switch the internet connection to a different Wi-Fi network or transition to mobile data. As a result, I was unable to log in with the Passkey. (There was no observable change on the client PC screen; it did not transition to a success/failure screen, leading me to believe that no packets were transmitted.) I initially thought that performing a network handover after the TCP connection might have caused the connection to be severed, resulting in the absence of packet transmission. However, I discovered that if I established the authentication device's internet connection using mobile data and then, in the middle of the CTAP process, turned off the mobile data to automatically switch back to Wi-Fi, the Passkey login process succeeded. What is the reason behind this outcome? Can you explain the technical factors that contribute to this behavior?