The team behind Trezor has announced an accessory for the Raspberry Pi that will turn it into a, somewhat chunky, Trezor wallet. Trezor is a dongle-sized computer that can be used to hold private keys and sign transactions. The project is still in its early days and its developers have made it open source so that anyone can build their own implementation of a Trezor wallet.
The Raspberry Pi Shield is a circuit board that is added to the Raspberry Pi that presents the same interface as a Trezor wallet device. That is, two hardware keys and a small OLED screen. From the photos on the Trezor website, the Shield directly connects to the Raspberry Pi's general purpose input/output (GPIO) pins.
The Raspberry Pi has been popular with hobbyists and educators, as it is an extremely low cost computer (around £30) that provides complete access to its hardware. The bank of GPIO pins on the Raspberry Pi circuit board are a way to directly access the system, rather than going through its USB ports, and this is how Trezor have effectively created a circuit board sandwich without a need for untidy USB cables.
Raspberry Pi comes without an operating system, and requires users to install an operating system, usually a Linux distribution, onto an SD card. Hobbyists and hackers hoping to make a Raspberry Pi Trezor wallet will need to pick a distribution (e.g. Raspbian) and then go on to install the Trezor software.
The problem with keeping your bitcoins on your computer is that your system may be infected by malware designed to steal your wallet. Trezor is made to be used with a desktop bitcoin client, it stores the private keys of your wallet, rather than having them stored on a PC.
When you start a bitcoin transaction on your desktop client, the details of that (unsigned) transaction are sent through to Trezor, which then signs the transaction with the private keys stored in its memory. Then the signed message is returned to your PC which then transmits that message onto the bitcoin network for mining nodes to confirm.
Of course, having a Raspberry Pi sized Trezor wallet will not be as comfortable or convenient as the embedded device that the company behind Trezor is producing. However, it is useful for enthusiasts, developers and hackers to try out.
Trezor described the Raspberry Pi shield to us as:
This is a board containing an OLED display, two buttons and a special chip which acts as a USB HID device. By itself the board is pretty useless but if you put it on a Raspberry Pi and run our software, you'll get a device that behaves exactly like TREZOR. Of course, it does not meet the physical security or comfort of the real product, but it's a great way for hackers or enthusiasts to learn how to develop TREZOR compatible applications (e.g. software wallets), understand how TREZOR works under the hood or to create custom applications. This board is aimed for casual hackers and tinkerers who have a Raspberry Pi computer and understand Linux and Python.