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Date:      Thu, 6 Sep 2012 10:18:24 -0700
From:      David O'Brien <obrien@FreeBSD.org>
To:        RW <rwmaillists@googlemail.com>
Cc:        Arthur Mesh <arthurmesh@gmail.com>, freebsd-security@freebsd.org
Subject:   Re: svn commit: r239569 - head/etc/rc.d
Message-ID:  <20120906171824.GC14757@dragon.NUXI.org>
In-Reply-To: <20120903005708.7082f230@gumby.homeunix.com>
References:  <201208221843.q7MIhLU4077951@svn.freebsd.org> <5043DBAF.40506@FreeBSD.org> <20120903005708.7082f230@gumby.homeunix.com>

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On Mon, Sep 03, 2012 at 12:57:08AM +0100, RW wrote:
> The more significant problem is that initrandom dumps some very
> low-grade entropy into /dev/random before the entropy file (see below).
> Since /dev/random has very limited buffering, and processes the buffers
> in a timed loop,

Arthur and I are aware of that.  I believe this behavior of our yarrow
implementation is poorly documented.


> IMO the order should be reversed or the low-grade
> stuff should be piped through sha256. 

We considered that.  Arthur wanted to do it sooner, but I'm concerned
about impact of multiple sha256 invocations on a large amount of data
on low-end MIPS.

I did some measurements on one of our lower-end Octeon MIPS devices and
lowest-end ARM devices.  My concerns are based on the Octeon MIPS result.
I have zero concern for ARM devices [based on my very limited access to
ARM devices].

[I don't have the results anymore thus they aren't supplied here]

-- 
-- David  (obrien@FreeBSD.org)



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