cvs commit: src/sys/modules/random Makefile src/sys/dev/random randomdev.h randomdev_soft.c randomdev_soft.h yar

Nate Lawson nate at
Mon Apr 12 15:35:08 PDT 2004

On Sun, 11 Apr 2004, Mark Murray wrote:
> Nate Lawson writes:
> > > Still, opinion seems to be in favour of further postprocessing, so I'll
> > > do it.
> > I haven't looked at the FreeBSD PRNG yet but why not seed Yarrow?
> Yarrow's entropy accumulation and PRNG generator parts are disconnected
> (that is part of its point), so there is no connection between the
> number of bytes harvested and the number of bytes supplied. This
> makes a very long armoured pipeline between accumulation and issue,
> which seems like overkill when the suppied entropy is 99% OK (far
> better than Yarrow currently ever gets, BTW).
> [...]
> Yarrow is unsuitable for this purpose; it is a great generator when
> you have a low-entropy environment and you need to protect against
> attackers having potential knowledge of the inputs.

* XSTORE is an unprivileged operation, users can call it all they want.

* If your hardware fails undetectably somehow (101010101...), a
single-source PRNG also fails.  If we seed our existing PRNG which
accepts multiple sources, it doesn't.

I think Jacques said it best.  All I'm asking is that we use a
well-reviewed PRNG and as many entropy sources as possible, including this
nice VIA part.


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