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From:   Lukasz Stelmach <l.stelmach@samsung.com>
To:     Stephan Mueller <smueller@chronox.de>
Cc:     Matt Mackall <mpm@selenic.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ray Jui <rjui@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        bcm-kernel-feedback-list@broadcom.com,
        Kukjin Kim <kgene@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Markus Elfring <elfring@users.sourceforge.net>,
        Matthias Brugger <mbrugger@suse.com>,
        Stefan Wahren <wahrenst@gmx.net>, linux-crypto@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-samsung-soc@vger.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH v2 1/2] hwrng: iproc-rng200 - Set the quality value
Date:   Wed, 20 May 2020 11:10:32 +0200
In-Reply-To: <1748331.j7eDFAdTc1@tauon.chronox.de> (Stephan Mueller's
        message of "Wed, 20 May 2020 08:23:59 +0200")
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It was <2020-05-20 =C5=9Bro 08:23>, when Stephan Mueller wrote:
> Am Dienstag, 19. Mai 2020, 23:25:51 CEST schrieb =C5=81ukasz Stelmach:
>
>> The value was estimaded with ea_iid[1] using on 10485760 bytes read from
>> the RNG via /dev/hwrng. The min-entropy value calculated using the most
>> common value estimate (NIST SP 800-90P[2], section 6.3.1) was 7.964464.
>
> I am sorry, but I think I did not make myself clear: testing random numbe=
rs=20
> post-processing with the statistical tools does NOT give any idea about t=
he=20
> entropy rate. Thus, all that was calculated is the proper implementation =
of=20
> the post-processing operation and not the actual noise source.
>
> What needs to happen is that we need access to raw, unconditioned data fr=
om=20
> the noise source that is analyzed with the statistical methods.

I did understand you and I assure you the data I tested were obtained
directly from RNGs. As I pointed before[1], that is how /dev/hwrng
works[2].

If I am wrong, do show me the code that processes the data from a HW RNG
before copying them to user provided buffer[3].

[1] https://lkml.org/lkml/2020/5/15/252
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree=
/Documentation/admin-guide/hw_random.rst?h=3Dv5.6
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree=
/drivers/char/hw_random/core.c?h=3Dv5.6#n251

Kind regards,
=2D-=20
=C5=81ukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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