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Date: Thu, 27 Mar 2014 16:03:28 +0100
From: Torsten Duwe <duwe@lst.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>, "Theodore Ts'o" <tytso@mit.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        Heiko Carstens <heiko.carstens@de.ibm.com>,
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Subject: Re: [PATCH v2 02/03]: hwrng: create filler thread
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References: <20140321142950.GI1763@lst.de> <20140321143342.GK1763@lst.de> <533375C1.5060904@mit.edu> <158d2776-1ea4-4f32-a9e9-0488047e6b70@email.android.com> <CALCETrUa_y6nGAtHmKkMwfTttXEabXCWPsXv==RrJN0_T3imZA@mail.gmail.com> <5333AD63.9030808@zytor.com>
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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