Sound card as a random number source ??

[Mark M.]

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On Wed, 27 Nov 1996, Pavel Korensky wrote:

> when I read about hardware random number generators in this mailing list, I got
> one idea. Maybe it sounds crazy, but is it possible to use soundcard
> (SoundBlaster for example) as a source for really random numbers ?
> What if I connect the input line of the soundcard with some external source of
> noise, like FM receiver or Dolby Surround decoder (with built-in white noise
> generator) or tape recorder with blank (erased) tape. It is possible to sample
> the sound (noise) and use the sampled values as a random numbers ? And how much
> random is this source ? 

The LSBs of a recording of white noise or static should be pretty random.
This should not be your only source of entropy as it's very easy for an
attacker to bias the signals.  If a one-way hash is applied to the output, it
does make it much more difficult for an attacker to predict or influence the
RNG.

Mark
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