Curve25519 is a state-of-the-art Diffie-Hellman function suitable
for a wide variety of applications.
Given a user's 32-byte secret key, Curve25519 computes the user's
32-byte public key. Given the user's 32-byte secret key and another
user's 32-byte public key, Curve25519 computes a 32-byte secret
shared by the two users. This secret can then be used to authenticate
and encrypt messages between the two users.
