Raspberry Pi Pico Random Number Generator

A basic random number generator that generates numbers from enviromental noise with the onboard DAC of the Raspberry Pi Pico. The project uses the Raspberry Pi Pico USB dev_lowlevel as a starting point. The Pico RNG is not meant to be FIPS 140-2 compliant as a stand-alone device by any means. However it does supply the Linux Kernel with random bits that is used with the appropriate entropy to achieve FIPS 140-2 compliant random numbers. Maybe one day the next gen Pico's will include an onboard crypto module.

Project Goals

• Raspberry Pi Pico firmware generates random numbers as a USB Endpoint.
• Linux Kernel Module (aka driver) provides random numbers to the Kernel.
• Driver can transmit random numbers on demand to the system and/or user processes via a character device.

Prerequisites

• Raspberry Pi Pico development environment. See Raspberry Pi Pico Getting Started Documentation
• Linux Kernel development headers

Building

The entire project uses CMake to keep with Rasberry Pi Pico's development environment and project setup instructions.

# Create build directory
mkdir build

# Change to the build directory
cd build

# Run cmake
cmake ..

# Run make
make

Install

The driver can be installed from the build directory using the traditional insmod command.

# Assumes CWD is 'build/'
# debug will enable debug log level
# timeout will set the usb endpoint timeout. Currently defaults to 100 msecs
sudo insmod driver/pico_rng.ko [debug=1] [timeout=<msec timeout>]

The Pico firmware is installed thorugh the normal process as outlined in the Raspberry Pi Pico Development Documentation.

• Unplug the Pico from the host.
• Plug the Pico into the host while holding the 'boot' button.
• Mount the Pico sudo mount /dev/sdb1 /mnt. Note /dev/sdb1 could be different you. Use sudo dmesg to find out what device the Pico shows up as on your system.
• Copy the uf2 file to the Pico sudo cp firmware/pico_rng.uf2 /mnt.
• Umount the pico sudo umount /mnt.

Testing

You can test Pico RNG firmware with the pico_rng_test.py script.

# Running with --performance will measure the devices' KB/s.
# if the kernel module has been installed, then the test tool will use /dev/pico_rng otherwise python's libusb implementation will be used.
sudo firmware/pico_rng_test.py [--performance]

You can also test the Kernel's random number pool that contains random numbers from the Pico

Remove

sudo rmmod pico_rng

License

This project is licensed under the BSD 3-Clause "New" or "Revised" License - see the LICENSE.md file for details

References

• https://github.com/raspberrypi/pico-examples/tree/master/usb/device/dev_lowlevel