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From:   Stephan Mueller <smueller@chronox.de>
To:     Alexander Dahl <ada@thorsis.com>
Cc:     linux-crypto@vger.kernel.org
Subject: Re: jitterentropy_rng on armv5 embedded target
Date:   Fri, 08 May 2020 14:30:47 +0200
Message-ID: <6708214.Ppv1U3N1OP@tauon.chronox.de>
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References: <2567555.LKkejuagh6@ada> <8028774.qcRHhbuxM6@tauon.chronox.de> <2904279.2zIEgBPu8l@ada>
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Am Freitag, 8. Mai 2020, 14:26:41 CEST schrieb Alexander Dahl:

Hi Alexander,

> Hello,
> 
> Am Freitag, 8. Mai 2020, 14:22:02 CEST schrieb Stephan Mueller:
> > Am Freitag, 8. Mai 2020, 14:17:25 CEST schrieb Alexander Dahl:
> > > Okay and DRBG has nothing to do with /dev/random ?
> > 
> > Nope, it is used as part of the kernel crypto API and its use cases.
> > 
> > > Then where do the random
> > > numbers for that come from (in the current or previous kernels without
> > > your
> > > new lrng)?
> > 
> > The DRBG is seeded from get_random_bytes and the Jitter RNG.
> 
> Oh, I was not precise enough. I wanted to know where /dev/random gets its
> numbers from. As far as I understood now: not from DRBG? (Which is
> sufficient knowledge for my current problem.)

Interrupts, HID events, block device events, external sources.

For a full analysis, see [1]

[1] https://bsi.bund.de/SharedDocs/Downloads/EN/BSI/Publications/Studies/
LinuxRNG/LinuxRNG_EN.pdf


Ciao
Stephan