Python prototype for EdDSA variants Ed25519-SHA-512, Ed4417-SHA-512/832, Ed448-SHA-512/912, Ed521-SHA-512/1056 specified in http://ed25519.cr.yp.to/eddsa-20150704.pdf
This implementation does not include protection against side-channel attacks.
Very slow!
Warning, Ed4417-SHA-512/832, Ed448-SHA-512/912, Ed521-SHA-512/1056 poorly tested (no test vectors available at this time).