Date: Mon, 10 Feb 2014 16:07:44 -0500
From: =?utf-8?B?SsO2cm4=?= Engel <joern@logfs.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>, "Theodore Ts'o" <tytso@mit.edu>,
        Stephan Mueller <smueller@chronox.de>,
        Linux Kernel Developers List <linux-kernel@vger.kernel.org>,
        "Maciej W. Rozycki" <macro@linux-mips.org>,
        Ralf Baechle <ralf@linux-mips.org>, dave.taht@gmail.com,
        John Crispin <blogic@openwrt.org>, andrewmcgr@gmail.com,
        Thorsten Glaser <tg@mirbsd.de>, sandyinchina@gmail.com
Subject: Re: [RFC PATCH 0/5] CPU Jitter RNG
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On Tue, 4 February 2014 12:39:28 -0800, H. Peter Anvin wrote:
> 
> USB and the Ethernet PHY frequently do still have their own crystals,
> for reasons not entirely clear to me.  However, what all of these have
> in common is that they are way out in the periphery.

Storage might be another source.  We have had add_disk_randomness()
forever.  Flash also takes quite variable timings for writes and
erases.  Even if the timings are not random, they certainly change
from block to block and depending on wear.

I am less certain about reads.  But one can run a few experiments and
see how consistent the timings are.

Jörn

--
Linux is more the core point of a concept that surrounds "open source"
which, in turn, is based on a false concept. This concept is that
people actually want to look at source code.
-- Rob Enderle
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