client_session_keys(binary(), binary(), binary()) ::
  {:ok, binary(), binary()} | {:error, atom()}

keypair() :: {:ok, binary(), binary()} | {:error, atom()}

publickeybytes() :: pos_integer()

secretkeybytes() :: pos_integer()

seed_keypair(binary()) :: {:ok, binary(), binary()} | {:error, atom()}

seedbytes() :: pos_integer()

server_session_keys(binary(), binary(), binary()) ::
  {:ok, binary(), binary()} | {:error, atom()}

sessionkeybytes() :: pos_integer()