Re: [PATCH] sha256: add support for Nettle

"brian m. carlson" [off-list ref] writes:

When it does not make any semantic difference, it is preferrable to
add a new thing after existing things.  But this sequence is meant
to list them in the order of preference when multiple choices are
availble, so it is OK to prepend nettle IF our intention is to favor
it over all others.

I am OK with that design choice, and I think the first paragraph of
the proposed log message adequately justifies why, but I'd prefer to
see it a bit more explicitly stated in the log message.

For SHA-256, we currently have support for OpenSSL and libgcrypt because
these two libraries contain optimized implementations that can take
advantage of native processor instructions.  However, OpenSSL is not
suitable for linking against for Linux distros due to licensing
incompatibilities with the GPLv2, and libgcrypt has been less favored
by cryptographers due to some security-related implementation issues.

Let's add another option that's compatible with the GPLv2, which is
Nettle.  It also has recently gained support for Intel's SHA-NI
instructions, which compare very favorably to other implementations.
For example, using this implementation and SHA-1 DC on a machine with
SHA-NI, hashing a 2 GiB file with SHA-1 takes 7.582 seconds, while
hashing the same file with SHA-256 takes 2.278 seconds.

Perhaps "Let's add another option ..., which is Nettle, and give it
preference over all others when multiple libraries are availalble"
or something along that line?

Not really ;-)

+
+#include <nettle/sha2.h>