[curves] FourQ

[Trevor Perrin]

There's an updated paper and new code for MSR's FourQ curve:

http://eprint.iacr.org/2015/565

http://research.microsoft.com/en-us/projects/fourqlib/

I tossed the numbers into the spreadsheet at [1], but the paper has a
better performance analysis across several platforms.

What do people think?

Without using the endomorphisms the performance is better than 25519,
and then endomorphisms are close to a 2x speedup.  And if unencumbered
use of the endomorphisms is just ~4 years away [2], that's not that
long, in the scheme of things.


Trevor

[1] https://docs.google.com/spreadsheets/d/1SO3NGX-EgIZ1slw9uExb5FoeFy5TVkuA2lEutP6roYI/edit#gid=0

[2] https://moderncrypto.org/mail-archive/curves/2014/000133.html