Nope, no tunnel or anything. When you touch the yubikey, it does some math on-device and "types" out a long string that can be mathematically validated with the

Nope, no tunnel or anything. When you touch the yubikey, it does some math on-device and "types" out a long string that can be mathematically validated with the shared secret the site stored when you set it up. It's an open standard, so you can read all about it: https://webauthn.guide/ https://webauthn.guide/