This is an implementation of EdDSA in Java. Structurally,
it is based on the ref10 implementation in SUPERCOP
(see https://ed25519.cr.yp.to/software.html).
There are two internal implementations:
* A port of the radix-2^51 operations in ref10 - fast and
constant-time, but only useful for Ed25519.
* A generic version using BigIntegers for calculation - a
bit slower and not constant-time, but compatible with
any EdDSA parameter specification.
