@spec derive_public_key(key()) :: key() | :error

Derive the public key from a secret key

@spec derive_shared_secret(key(), key()) :: key() | :error

Derive a shared secret for a secret and public key

Given our secret key and our partner's public key, returns a shared secret which can be derived by the partner in a complementary way.

@spec generate_key_pair() :: {key(), key()}

Generate a secret/public key pair

Returned tuple contains {random_secret_key, derived_public_key}