drupal_get_token('arg1')

$private_key = Drupal::service('private_key')->get();
// Get a drupal CSRF token. (The actual service is called 'csrf_token').
$token_generator = Drupal::csrfToken();
$token = $token_generator->get();

// Check that the token is valid.
if ($token_generator->validate($token)) {
}