linux-kernel - Re: [PATCH resend 0/2] random: Use DRBG sources

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Message-ID: <20140414161359.GD29351@lst.de>
Date:	Mon, 14 Apr 2014 18:13:59 +0200
From:	Torsten Duwe <duwe@....de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Theodore Ts'o <tytso@....edu>, Greg Price <price@....EDU>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH resend 0/2] random: Use DRBG sources

On Mon, Apr 14, 2014 at 08:49:58AM -0700, Andy Lutomirski wrote:
> [Resent because I forgot to email lkml.  This also surreptitiously
>  fixes a silly typo on a patch description.]
> 
> This is my attempt to come up with a workable way to use so-called
> entropy sources like a TPM to feed /dev/urandom.

Ahem, The TPM RNGs are true HWRNGs, but they are very limited.
Their main purpose is to generate enough bits so that the TPM
can generate a genuine key pair after a few seconds.

Why do you want to put those valuable true random bits into urandom?

> Arguably we should be feeding the input pool as well, but if the

Yes.

> /dev/random algorithm is correct, this shouldn't matter.  I don't want
> sensible use of TPMs for /dev/urandom to block on a long debate about
> /dev/random, so these patches have no effect on /dev/random.

That confuses me a bit.

	Torsten

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