Re: Extracting random data from static, for /dev/random



bmearns <mearns.b@xxxxxxxxx> writes:

I have a radio plugged into my soundcard, tuned to static. This should
be a good source of randomness, right? I know of course it's not all
random data, as confirmed with rngtest. I was looking at the lavarnd
project, they use an algorithm they're calling DigitalBlender (tm) to
"extract" the random data and throw away the rest.

Are there any tools that can do the same thing on an arbitrary input
stream that I could use with my audio static? I thought rngd would do
it, but that just tests the randomness and throws it away if it fails,
instead of extracting what ever is random.

One thing you can do is to take the input and hash it. Eg, take in 2048 bits and
has to 1024 bits (eg MD5) This means that if the input has at least 1024 bits of
randomness, the output of MD5 should also have roughly that much randomness.


I've tried audio-entropyd (aed), but it keeps failing the randomness
tests as well, so isn't giving me any extra entropy.

Any advice would be great, my entropy pool is getting exhausted more
and more often these days.

Don't use /dev/random, use /dev/urandom, which does not exhaust. Yes, it uses a
PRNG but continuously seeded with whatever randomness it can find, giving you a
continuous stream of cryptographically good PRNG even when the physical randomness
runs out.

Thanks,
-Brian
.



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