Re: Random Hiss from Mac mike

["W. Kinney" <kinney@bogart.Colorado.EDU>]

Andrew Spring writes:

> I've been looking at using the Mac's Sound Input Manager for hardware RNG.
[...]
> In the simplest case, where the microphone is not attached, the signal
> consists of  long runs of '0x80's alternating with '0x7f's.  Now, I have no
> problem transforming this into uniformly distributed RN's : just hash the
> buffer with MD5.
[...]
> Does anybody have any experience/advice in this area?

Yeah, I played with this idea a while ago and eventually gave up on it, 
exactly because of those long runs of 0x80's and 0x7f's. I'm not sure
how you estimate 0.65 bits of entropy per byte sampled when you have long
strings of repeating bytes like that. 

The thing is that event timings (the Time Manager allows you microsecond
resolution) and mouse position measurements give you so much more entropy
than the sound port that it's hardly worth it, IMO.

                                  -- Will