What is faraday-usb-signer?

Faraday USB Signer is firmware for a small piece of hardware that acts as an offline signing device for XRPL, the network behind the XRP cryptocurrency. It runs on an ESP32-S3 microcontroller with a built in touchscreen, and its whole purpose is to keep a wallet's private seed completely isolated from any computer or network. The device never connects to WiFi or Bluetooth. Instead, an unsigned transaction is sent to it over a plain USB cable from a companion desktop app. The device displays the transaction's details on its own screen, field by field, so the person holding it can actually see what they are about to approve, rather than trusting whatever a connected computer claims the transaction says. Approving requires physically holding down a touch control, after which the device signs the transaction internally and sends the signed result back over the same USB connection, still without the seed itself ever leaving the hardware. The firmware only works with the XRPL mainnet, and it only recognizes a fixed, limited list of transaction types, such as payments, trading offers, and account settings changes. Anything outside that list is refused. Communication between the device and the computer follows a simple text based protocol over a serial connection, with clear messages for submitting a transaction, acknowledging it, and returning either a signed result or a rejection. To build and install this firmware, a person needs the specific touchscreen hardware it targets and a tool called PlatformIO, then runs a couple of command line steps to compile the code and flash it onto the device. It is meant to be used together with a separate desktop companion application that builds the transactions in the first place. The code is shared publicly but only for non commercial use, and security issues are meant to be reported privately rather than posted as public bug reports.