Re: On /dev/random devices

From: Benjamin Goldberg (goldbb2@earthlink.net)
Date: 04/02/03 

From: Benjamin Goldberg <goldbb2@earthlink.net>
Date: Wed, 02 Apr 2003 15:42:11 -0500

NuncEstBibendum wrote:
>
> Thanks everybody for your answers. What I find
> confusing is that it is not at all obvious that there
> is a dependency of the /dev/random thruput on external
> events. That is, other /dev/random implementations block
> when their entropy pool gets depleted, but start churning
> out data again when external events (e.g. mouse movement)
> kick in.
>
> The Solaris implementation seems to be impervious
> to such a thing. I would have expected for its entropy
> pool to fill up more quickly in the presence of a larger
> number of external events, but that doesn't seem to be
> the case. Hence my beffudlement concerning the nature of
> the entropy gathering techniques used for this particular
> device under Solaris.
>
> Like I said before, any info that anyone can
> provide about this will be much appreciated.

Maybe I didn't phrase my response correctly.

It's not that it's magically getting more -- it simply doesn't keep
track of how much it has, and nor does it ever decide "oh, I've run out
of entropy; I should stop sending data to whomever is reading until I
get more."

The Solaris implementation simply *ignores* the fact that it has run out
of entropy. It just gives and gives and gives... Similarly to how most
machines' "/dev/urandom"s work. 

-- 
$a=24;split//,240513;s/\B/ => /for@@=qw(ac ab bc ba cb ca
);{push(@b,$a),($a-=6)^=1 for 2..$a/6x--$|;print "$@[$a%6
]\n";((6<=($a-=6))?$a+=$_[$a%6]-$a%6:($a=pop @b))&&redo;}
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