Yeah. You just need a noisy channel. Radiation is really overkill. You probably could use quantum tunneling on a silicon chip to produce a reliably random noise source small enough for a an port. The issue, however becomes the computer itself. It isn't hard to muck up a serial port so that you wouldn't even know you aren't getting the true data. On Tuesday, October 22, 2013, Cathal Garvey wrote:
If the particle flux is high enough for it to be usefully rich in random data, you could just hash the image output and use the hash outputs as an entropy source.
However, you'd want to be careful that you: A) Use a good hash, and perhaps double-hash to be paranoid B) Try to measure and correct/alarm for the flux of your radioisotope as it decays, though depending on the isotope perhaps this isn't important.
Thinking all the thoughts on this channel through, I'm beginning to wonder if the easiest answer isn't just a vibrating surface covered in sand with a camera pointed at it, hashing the output. :)
On 22/10/13 16:15, Ted Smith wrote:
On Tue, 2013-10-22 at 00:07 -0700, Andy Isaacson wrote:
On Fri, Oct 18, 2013 at 11:42:21AM -0400, Sandy Harris wrote:
On Thu, Oct 17, 2013 at 12:56 PM, grarpamp <grarpamp@gmail.com<javascript:;>> wrote:
Problem is, apparently no one is solving it, so round and round it goes...
Now if someone would just sell a completely open discrete logic serial port hw entropy source for under $50... that would end a lot of the talk. Even with a more costly radiation source rather than other phenomena you'd still likely make good profit ...
If you have an audio device free or can add one and are using Linux, I'd say Turbid is the obvious solution: http://www.av8n.com/turbid/paper/turbid.htm
Open source, available for over a decade, well thought out and well documented. It even has a proof, using only some quite mild assumptions, that it gives almost perfect entropy in the output. What's not to like?
It's super frustrating that Turbid assumes you are going to reverse-engineer the amplifier stage of your sound card in order to set some difficult-to-understand parameters which apparently can completely break it's ability to extract entropy if set incorrectly. (See the installation instructions in section 12 of the paper linked above.)
It would be much better for it to have a default set of parameters (or an autotuned parameter engine) that have a very high likelihood of giving acceptable results upon "apt-get install turbid" on some arbitrary hardware.
I mean, seriously. The Turbid authors appear to assume that every person who installs Turbid is going to build a custom Y-audio cable and put a voltmeter (set to the correct mode of course!) on the outputs of their sound card. WTF?
It's fine if conservative, default settings result in Turbid getting only 100 bits of entropy per second rather than 100 Kbit/sec. Mix it into /dev/urandom and call it a day.
-andy
A while ago, a friend and I bought a smoke detector and a webcam, hacked them together, and built this: http://www.inventgeek.com/Projects/AlphaRad/OverView.aspx
It actually works; when you view the webcam you can see the little points of light where an alpha particle hits the sensor.
However, there wasn't really any software to support it as an RNG, so it's just sitting around.
Is it possible to make an entropy source out of something like that? If so, it was a really simple (less than two hours IIRC) build, and it cost about $40.
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