13.01.2017 19:51, Emil Velikov пишет:
From: Emil Velikov <emil.veli...@collabora.com>
At the moment we support 5+ different implementations each with varying
amount of bugs - from thread safely problems [1], to outright broken
implementation(s) [2]
In order to accommodate these we have 150+ lines of configure script and
extra two configure toggles. Whist an actual implementation being
~200loc and our current compat wrapping ~250.
Let's not forget that different people use different code paths, thus
effectively makes it harder to test and debug since the default
implementation is automatically detected.
To minimise all these lovely experiences, import the "100% Public
Domain" OpenBSD sha1 implementation. Clearly document any changes needed
to get building correctly, since many/most of those can be upstreamed
making future syncs easier.
It can hurt performance. OpenSSL implementation is optimized for all
thinkable architectures and it will use hardware SHA-1 instructions on
newer CPUs. From
https://github.com/openssl/openssl/blob/master/crypto/sha/asm/sha1-x86_64.pl
:
> Current performance is summarized in following table. Numbers are
> CPU clock cycles spent to process single byte (less is better).
>
> x86_64 SSSE3 AVX[2]
> P4 9.05 -
> Opteron 6.26 -
> Core2 6.55 6.05/+8% -
> Westmere 6.73 5.30/+27% -
> Sandy Bridge 7.70 6.10/+26% 4.99/+54%
> Ivy Bridge 6.06 4.67/+30% 4.60/+32%
> Haswell 5.45 4.15/+31% 3.57/+53%
> Skylake 5.18 4.06/+28% 3.54/+46%
> Bulldozer 9.11 5.95/+53%
> VIA Nano 9.32 7.15/+30%
> Atom 10.3 9.17/+12%
> Silvermont 13.1(*) 9.37/+40%
> Goldmont 8.13 6.42/+27% 1.70/+380%(**)
Quick benchmark on my Haswell of the OpenBSD implementation compiled
with GCC5 -O2: ~8 cycles per byte on 32-bit, ~7 cycles per byte on
64-bit. But Haswell is a very powerful CPU, on weaker CPUs the
difference would be probably larger, especially on new CPUs that have
SHA instruction set.
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