Subject: Re: [PATCH] API for true Random Number Generators to add entropy
	(2.6.11)
From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Reply-To: johnpol@2ka.mipt.ru
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Pavel Machek <pavel@ucw.cz>, Andrew Morton <akpm@osdl.org>,
       James Morris <jmorris@redhat.com>, linux-kernel@vger.kernel.org,
       linux-crypto@vger.kernel.org, cryptoapi@lists.logix.cz,
       Jeff Garzik <jgarzik@pobox.com>, David McCullough <davidm@snapgear.com>
In-Reply-To: <20050329104627.GD19468@gondor.apana.org.au>
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Organization: MIPT
Date: Tue, 29 Mar 2005 15:42:05 +0400
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On Tue, 2005-03-29 at 20:46 +1000, Herbert Xu wrote:
> On Tue, Mar 29, 2005 at 02:50:28PM +0400, Evgeniy Polyakov wrote:
> >
> > Without ability speed this up in kernel, we completely [ok, almost]=20
> > loose all RNG advantages.
>=20
> Well if you can demonstrate that you're getting a higher rate of
> throughput from your RNG by doing this in kernel space vs. doing
> it in user space please let me know.

Quote from VIA RNG crypto analysis:

"Bitrate. The RNG generates output at significantly
higher rates than most PC-based randomness resources.
Raw bits are produced at rates of 30 to 50 Mbits/sec,
and whitened bits were observed at rates of 4 to 9
Mbits/sec. Variations in output rates depend on the
RNG configuration and the oscillator rates. PRNGs
seeded with the Nehemiah RNG should be able to
easily sustain output in excess of 2 Mbits of entropy per
second, which should eliminate blocked PRNG reads in
virtually all applications."


While raw bits reading from hw_random on the fastest=20
VIA boards can exceed 55mbits per second=20
[above quite was taken from VIA C3 Nehemiah analysis],=20
it is not evaluated in rngd and is not written=20
back to the /dev/random.

David provided his patch exactly because of
"Adding this can dramatically improve the performance of=20
/dev/random on small embedded systems which do not=20
generate much entropy."
and it works.

--=20
        Evgeniy Polyakov

Crash is better than data corruption -- Arthur Grabowski

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