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

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Date:   Fri, 15 May 2020 12:59:45 +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 1/2] hwrng: iproc-rng200 - Set the quality value

It was <2020-05-15 pią 11:10>, when Stephan Mueller wrote:
> As I mentioned, all that is or seems to be analyzed here is the
> quality of the cryptographic post-processing. Thus none of the data
> can be used for getting an idea of the entropy content.
>
> That said, the ent value indeed looks too low which seems to be an
> issue in the tool itself.
>
> Note, for an entropy assessment commonly at least 1 million traces
> from the raw noise source are needed.

I've got 1MiB from each source. Of course I used raw data from /dev/hwrng
for tpm, exynos and rng200.

| Source       | ea_iid -i | ea_iid -c (h') |      ent |
|--------------+-----------+----------------+----------|
| /dev/random  |  7.875064 |       0.998166 | 7.999801 |
| /dev/urandom |  7.879351 |       0.998373 | 7.999821 |
| tpm-rng      |  7.880012 |       0.998118 | 7.999828 |
| exynos-trng  |  7.435701 |       0.947574 | 7.991820 |
| rng200       |  7.883320 |       0.998592 | 7.999824 |

> See for examples on how such entropy assessments are conducted in the LRNG 
> documentation [1] or the Linux /dev/random implementation in [2]

Thanks a lot, I am reading.

I will try to write somthing clever as soon as I parse and understand
these documents (and do other stuff too). Thank you very much for your help.

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

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