linux-kernel - Re: Entropy Pool Contents

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Date:	Mon, 27 Nov 2006 11:16:19 -0500
From:	Phillip Susi <psusi@....rr.com>
To:	G.Ohrner@...t.rwth-aachen.de
CC:	linux-kernel@...r.kernel.org
Subject: Re: Entropy Pool Contents

Gunter Ohrner wrote:
> IMHO something really fishy's going on there. If I explicitely write data
> into the pool, it shouldd not stay at "zero", from wwhat I understood about
> how /dev/*random work.
> 

<snip>

> I'm mainly wondering why writing stuff to /dev/*random does not change the
> entropy from zero to at least any low non-zero value...
> 

I ran into this the other day myself and when I investigated the kernel 
code, I found that writes to /dev/random do accept the data into the 
entropy pool, but do NOT update the entropy estimate.  In order to do 
that, you have to use a root only ioctl to add the data and update the 
estimate.  I am not sure why this is, or if there is a tool already 
written somewhere to use this ioctl, maybe someone else can comment?

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