class RbNaCl::HMAC::SHA512256

def compute_authenticator(authenticator, message)
  state = State.new
  self.class.auth_hmacsha512256_init(state, key, key.bytesize)
  self.class.auth_hmacsha512256_update(state, message, message.bytesize)
  self.class.auth_hmacsha512256_final(state, authenticator)
end