From: Sandy Harris <sandyinchina@gmail.com>
To: "Theodore Ts'o" <tytso@mit.edu>,
Stephan Mueller <smueller@chronox.de>,
Jeff Epler <jepler@unpythonic.net>,
linux-crypto@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH] Entropy generator with 100 kB/s throughput
Date: Sun, 10 Feb 2013 14:27:00 -0500 [thread overview]
Message-ID: <CACXcFmm6Xfc_W06DNQ=d0wmGgqFLsUuzCnEivVzoFmKmTNv1GA@mail.gmail.com> (raw)
In-Reply-To: <20130210185002.GA10801@thunk.org>
On Sun, Feb 10, 2013 at 1:50 PM, Theodore Ts'o <tytso@mit.edu> wrote:
> On Sun, Feb 10, 2013 at 01:46:18PM +0100, Stephan Mueller wrote:
>>
>> However, the CPU has timing jitter in the execution of instruction. And
>> I try to harvest that jitter. The good thing is that this jitter is
>> always present and can be harvested on demand.
>
> How do you know, though, that this is what you are harvesting?
> ...
> And what's your proof that your entropy source really is an entropy
> source?
One paper that seems to show there is some randomness in
such measurements is McGuire, Okech & Schiesser
"Analysis of inherent randomness of the Linux kernel",
http://lwn.net/images/conf/rtlws11/random-hardware.pdf
They do two clock calls with a usleep() between, take the
low bit of the difference and pack them unmixed into
bytes for testing. Their tests show over 7.5 bits of entropy
per byte, even with interrupts disabled. The same paper
shows that simple arithmetic sequences give some
apparent entropy, due to TLB misses, interrupts, etc.
There are lots of caveats in how this should be used and
it is unclear how much real entropy it gives, but is seems
clear it gives some.
My own program to feed into random(4) is based on
such things:
ftp://ftp.cs.sjtu.edu.cn:990/sandy/maxwell/
HAVEGE also uses them
http://www.irisa.fr/caps/projects/hipsor/
& there is a havegd daemon for Linux
http://www.issihosts.com/haveged/
random(4) also mixed in timer data at one point,
which seems the correct thing for it to do. Later
I heard something about that code having been
removed. What is the current status?
next prev parent reply other threads:[~2013-02-10 19:27 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-08 22:04 [RFC][PATCH] Entropy generator with 100 kB/s throughput Stephan Mueller
2013-02-09 18:06 ` Theodore Ts'o
2013-02-10 1:57 ` Jeff Epler
2013-02-10 12:46 ` Stephan Mueller
2013-02-10 15:53 ` Jeff Epler
2013-02-10 18:50 ` Theodore Ts'o
2013-02-10 19:27 ` Sandy Harris [this message]
2013-02-10 19:32 ` Stephan Mueller
2013-02-10 21:59 ` Sandy Harris
2013-02-11 0:05 ` Theodore Ts'o
2013-02-10 12:25 ` Stephan Mueller
2013-02-21 14:07 ` Phil Carmody
2013-02-21 14:17 ` Stephan Mueller
2013-02-21 17:46 ` Sandy Harris
2013-02-21 20:30 ` Theodore Ts'o
[not found] ` <CAFtRNNzcUpxT3R6ttUJ0c-7QTVRxbwRVq6bPqvkSL93vbstT4g@mail.gmail.com>
2013-02-22 11:14 ` Nick Kossifidis
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CACXcFmm6Xfc_W06DNQ=d0wmGgqFLsUuzCnEivVzoFmKmTNv1GA@mail.gmail.com' \
--to=sandyinchina@gmail.com \
--cc=jepler@unpythonic.net \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=smueller@chronox.de \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).