[RFC PATCH] Add SHA1 support

Sebastian Andrzej Siewior rsync at ml.breakpoint.cc
Thu Feb 20 21:34:53 UTC 2020

On 2020-02-20 20:06:39 [+0100], Markus Ueberall wrote:
> On 2020-02-09 23:19, Sebastian Andrzej Siewior wrote:
> > [...]
> > My primar motivation to use SHA1 for checksumming (by default) instead
> > of MD5 is not the additional security bits but performance. On a decent
> > x86 box the SHA1 performance is almost the same as MD5's but with
> > acceleration it outperforms MD5.
> > 
> > The other alternative would be to go for xxHash64 [0] which has the
> > superior performance but provides a non-cryptographic hash so I though
> > SHA1 would be better here.
> > [...]
> With respect to *both* speed and security, wouldn't BLAKE3 be a better,
> modern alternative if we're looking at checksumming?
> It's "[r]eleased into the public domain with CC0 1.0. Alternatively, it is
> licensed under the Apache License 2.0".  And the performance (see the chart
> at https://github.com/BLAKE3-team/BLAKE3) is *impressive* ...

I'm still not sure if rsync requires a cryptographic hash _or_ if a
strong hash like xxHash64 would be just fine for the job.

> Kind regards, Markus


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