From owner-freebsd-questions@FreeBSD.ORG  Thu Sep 13 16:31:59 2007
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Subject: Re: /dev/random question
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On Thu, 13 Sep 2007 17:36:30 +0200
Roland Smith <rsmith@xs4all.nl> wrote:

> On Thu, Sep 13, 2007 at 04:56:26PM +0200, Per olof Ljungmark wrote:
> > Hi,
> > 
> > Could someone on the list point me to a document that explains the 
> > functionality of /dev/random in FreeBSD in a little more depth than
> > the man page? In other OS's I've looked at random and urandom are
> > different, here it's a symlink (talking about RELENG-6 onwards).
>  
> FreeBSD uses the yarrow algorithm, as mentioned in random(4). See 
> http://en.wikipedia.org/wiki/Yarrow_algorithm
> http://www.schneier.com/yarrow.html

Yarrow is reseeded with interrupt entropy, and is supposedly good
enough not to require the amount of entropy to be tracked.
So /dev/random need not block, and there's no need for a separate
non-blocking device.