linux-kernel - Re: [PATCH 3/3] crypto: exynos - Reseed PRNG after generating 2^16 random bytes

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Message-ID: <6915204.SlqusmoAzB@tauon.chronox.de>
Date:   Tue, 05 Dec 2017 14:52:31 +0100
From:   Stephan Mueller <smueller@...onox.de>
To:     Łukasz Stelmach <l.stelmach@...sung.com>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>, robh+dt@...nel.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Kukjin Kim <kgene@...nel.org>, linux-crypto@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        m.szyprowski@...sung.com, b.zolnierkie@...sung.com
Subject: Re: [PATCH 3/3] crypto: exynos - Reseed PRNG after generating 2^16 random bytes

Am Dienstag, 5. Dezember 2017, 13:35:58 CET schrieb Łukasz Stelmach:

Hi Łukasz,

> Reseed PRNG after reading 65 kB of randomness. Although this may reduce
> performance, in most casese the loss is not noticable.

Please add to the log that you also increase the timer-based reseed to 1 
second?!

Another suggestion: maybe you want to add a comment to the reseed function to 
indicate it is for enhanced backtracking resistance. Otherwise a lot of folks 
would scratch their head why such code exists in the first place. :-)

Other than that:

Reviewed-by: Stephan Mueller <smueller@...onox.de>

Ciao
Stephan