linux-kernel - Re: [PATCH v2 1/2] hwrng: iproc-rng200

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Message-ID: <dleftjr1vf2cqf.fsf%l.stelmach@samsung.com>
Date:   Wed, 20 May 2020 11:10:32 +0200
From:   Lukasz Stelmach <l.stelmach@...sung.com>
To:     Stephan Mueller <smueller@...onox.de>
Cc:     Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Markus Elfring <elfring@...rs.sourceforge.net>,
        Matthias Brugger <mbrugger@...e.com>,
        Stefan Wahren <wahrenst@....net>, linux-crypto@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v2 1/2] hwrng: iproc-rng200 - Set the quality value

It was <2020-05-20 śro 08:23>, when Stephan Mueller wrote:
> Am Dienstag, 19. Mai 2020, 23:25:51 CEST schrieb Łukasz 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 numbers 
> post-processing with the statistical tools does NOT give any idea about the 
> entropy rate. Thus, all that was calculated is the proper implementation of 
> the post-processing operation and not the actual noise source.
>
> What needs to happen is that we need access to raw, unconditioned data from 
> 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=v5.6
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/hw_random/core.c?h=v5.6#n251

Kind regards,
-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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