So you don't trust your operating system's random number generator and you have blisters on your hands from flipping coins to create bitcoin private keys. All your dice have worn out at the corners and every deck of cards you own is severely dog-eared.
Whether you need a quantum-tinfoil hat to protect you from malignant hidden non-local variables, or you want a slow but steady stream of truly random bits generated on your Raspberry Pi then you may and may not need a hardware random number generator.
This is a toy project and should not be taken seriously. I am not a cryptographer and although I have tried to make the minimum number of assumptions, a die-rolling or coin-flipping machine would have fewer complexities and potential attack vectors.
A paranoid person must assume that processor manufacturers and kernel
developers are highly vulnerable to infiltration or coercion by military
intelligence and other state actors, so feeding this into /dev/random may not
be enough; for this you must trust your OS and CPU's RNG.
That said, you should exercise even more caution if you choose to use the raw values themselves. From what I understand the safest way to use this tool is to consider each row a single bit of information, select a column and compare its direction from the observed average to decide whether it represents a 0 or a 1.
- Don't mess with the device while it is recording, it may skew the output.
- Consider each row of output to only have one bit of entropy. A value on the same row is part of the same event and may share information; a frame number declares that the X and Y values are not off the screen; the angle of the radiation source may mean that the brightness of an event may leak information about its position, or a given X position may make a Y position more likely.
- Don't generate random numbers on a machine that has been or will be connected to the Internet and do not keep them for longer than is necessary.
You will need...
- 1 machine running Linux.
- The cheapest Linux-compatible webcam money can buy.
- 1 ionization smoke detector containing americium-241.
- Any screwdriver except the sexist pink one that you're not allowed to use.
- A glue gun.
- Tin / aluminium foil.
- Insulation / gaffer / BDSM tape.
Unscrew the webcam and remove the lens from the sensor. Open the smoke detector, remove the housing around the radiation source and then the source itself. This is a thin sheet of film with americium-241 embedded in it and is facing at the ion detector. Do not inhale, burn or otherwise let this get into your body, it's not good for you. Affix the radiation source to the webcam sensor and glue it in place. Cover the rest of the electronics in glue to prevent shorts and then wrap the thing in several layers of foil (probably not necessary but I'm paranoid) and then tape it up. Easy-peasy.
Assuming video4linux works with your webcam it should show up as /dev/video0
or /dev/video1 if you already have a webcam. Install uvcview
(apt-get install guvcview) or some other webcam viewer and you should observe
a black screen with a pixel flashing in a random location every 10-20 seconds.
Run ./configure to check for dependencies and create the FIFO queue (needed
because "streamer" actually lacks streaming output support). You should only
need to apt-get install streamer python, but pypy or jython are
recommended for speed/power use (the fastest available interpreter will be
selected by ./configure)
Finally, run ./capture to dump the data out to CSV. If you're trusting then
this can be used to feed your system's random pool, just
./capture > /dev/random.
If you don't trust your system's random pool, and you really shouldn't unless
you compiled your kernel from source, have audited the source yourself and are
running it on a simulated processor that you understand, then you can pipe the
output into filter.py. The following command will create a random 256-bit
hexadecimal string:
./capture | ./filter.py --column=2 --length=32
Even the most cynical layman can audit every step to confirm that the random bits are indeed coming from the universe and nobody else has seen them:
- Confirm that no white flashes appear on the webcam via streamer before you attach the radiation source.
- Confirm that flashes do appear in streamer after attaching it.
- Confirm that your own observations match the observations in the CSV output
- Confirm that the final output data matches your observations
- Run it on a machine with no writable disks, Internet connection, network cards and inside a Faraday cage to ensure that you are the only person who has ever seen the generated random sequence.
Todo list and bugs are being held on the project's GitHub issue Tracker
Copyright (c) 2013 Gaz Davidson gaz@bitplane.net
Licensed under the WTFPL with one additional clause:
- Don't blame me.