Firmware Update

AT -

To update the device’s firmware, enter Configuration mode as described in Configuration section above. Instead of steps 4 and 5, copy the new firmware image to ME-CONFIG. Follow the rest of the procedure from step 6.

If the LED turns off after a few seconds of fast blinking, the update has been successful. If it indicates an error, the current firmware has remained intact.

Note The file with extension .bin and the most recent timestamp will be considered as a candidate. The actual running firmware is stored internally, so you can safely remove or overwrite these .bin files.

For security reasons, Mycelium Entropy only accepts firmware images that have been cryptographically signed. By default, only Mycelium signatures are trusted. Should you desire to flash your own firmware, or third party firmware that you trust, you must add the corresponding public key to settings.txt. Even then, your device will request confirmation from you with a 4-blink warning code. Press the button on the device to authorise the update.

This extra confirmation is a necessary protection measure against malware. A malicious program can quietly copy rigged firmware to the device and sneak its signing key into settings.txt, but it cannot press the button for you.

Summary of the security checks:
  1. Is the new firmware in a correct format and signed using 256-bit ECDSA?

    • If not, reject it with error 7.

  2. Is the public part of the signing key listed in settings.txt?

    • If not, reject the update with error 6.

  3. Is the signature valid?

    • If not, reject the update with error 6.

  4. Is the signature made with the Mycelium signing key?

    • If not, request confirmation (warning code 4) and await button press.

  5. Update the firmware.

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