step crypto nacl sign command group uses public-key cryptography to sign and
verify messages. The implementation is based on NaCl's crypto_sign function.
NaCl crypto_sign is crypto_sign_edwards25519sha512batch, a particular
combination of Curve25519 in Edwards form and SHA-512 into a signature scheme
suitable for high-speed batch verification. This function is conjectured to meet
the standard notion of unforgeability under chosen-message attacks.