Hardware: Romu board, USB Type-A port, WebAuthn-compatible browser (Chrome, Firefox).
Firmware: Use the open-source 'Fido2-STM32' firmware adapted for RP2354 or a community port. The RP2354A offers TrustZone to isolate cryptographic keys.
Configuration: Enable secure boot to protect the firmware. Configure debug pads to disable developer mode after initial flash.
Enrollment: Plug in the Romu. Go to a WebAuthn-supporting site (e.g., GitHub). Click 'Add security key'. Romu should be detected.
Interaction: Press the physical Romu button to confirm registration. The RGB LED should blink blue during key generation.
Verification: Try to log in. Romu should request tactile confirmation. The private key remains stored in the RP2354's secure zone.
Deep Dive: Implement a locally stored encrypted PIN to add an extra layer of security (physical 2FA).