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Re: memxor

From: Simon Josefsson
Subject: Re: memxor
Date: Tue, 12 Apr 2011 15:50:45 +0200
User-agent: Gnus/5.110016 (No Gnus v0.16) Emacs/23.2 (gnu/linux)

Nikos Mavrogiannopoulos <address@hidden> writes:

> On 04/12/2011 03:12 PM, Simon Josefsson wrote:
>>>> I had 10% speed-ups in a web server that used gnutls with the optimized
>>>> version of memxor. That is because CBC encryption mode uses XOR heavily.
>>>> 10% is enormous speed-up considering that this is a very small part of
>>>> the encryption process.
>>> OK, that is sufficient rationale for having this faster memxor function in
>>> gnutls.
>> I'm surprised the gnulib memxor ends up being used by GnuTLS at all.
>> Nikos, shouldn't the Nettle implementation be used instead?  Is this a
>> question of the GnuTLS (gnulib) memxor symbol replacing the memxor that
>> is shipped with Nettle?  Maybe the solution is to fix the Nettle
>> namespace.
> GnuTLS uses gnulib memxor, because it might be compiled either with
> nettle or libgcrypt.

But the performance critical uses of memxor is only through Nettle,
isn't it?  And by accident Nettle ends up using the gnulib memxor
instead of its own.  That could be fixed by either changing Nettle's
namespace, or do an '#define memxor gl_memxor' inside GnuTLS.

Hm.  Looking at both master and 2.12.x I can't find any direct calls to
memxor at all in the GnuTLS code.  Where is it used?  So maybe it is
only via Nettle.


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