curve25519-donna is an implementation of the Curve25519 ECDH key-exchange algorithm by Dan J Bernstein.
curve25519 is a "256-bit strength" elliptical curve (equivalent to NIST P-256) with 32-byte secret/public keys.
It is very fast, easy to implement securely in software, and fully public-domain.
Downloaded 2/10/2016 from https://github.com/floodyberry/curve25519-donna
Filenames containing VALVE are *not* entirely public domain - see individual files for details.