linux-kernel - Re: [PATCH v2 02/03]: hwrng: create filler thread

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Message-ID: <20140327150328.GB18563@lst.de>
Date:	Thu, 27 Mar 2014 16:03:28 +0100
From:	Torsten Duwe <duwe@....de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Theodore Ts'o <tytso@....edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Arnd Bergmann <arnd@...db.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Satoru Takeuchi <satoru.takeuchi@...il.com>,
	ingo.tuchscherer@...ibm.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hans-Georg Markgraf <MGRF@...ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Joe Perches <joe@...ches.com>, Greg Price <price@....edu>
Subject: Re: [PATCH v2 02/03]: hwrng: create filler thread

On Wed, Mar 26, 2014 at 09:47:31PM -0700, H. Peter Anvin wrote:
> On 03/26/2014 06:11 PM, Andy Lutomirski wrote:
> > Also, in the /dev/random sense,
> > most hardware RNGs have no entropy at all, since they're likely to be
> > FIPS-approved DRBGs that don't have a real non-deterministic source.
> 
> Such a device has no business being a Linux hwrng device.  We already
> have a PRNG (DRBG) in the kernel, the *only* purpose for a hwrng device
> is to be an entropy source.

That's also my understanding. The shot noise from a Schottky-diode seems
to be quite popular, for example.

> TPMs, in particular, should almost certainly be massively derated based
> on what little we know about TPM.

Backdoors, anyone? :-)

	Torsten

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