docs: private final void setExpiration(long expirationInMinutes) {
  	expirationInMilliseconds = System.currentTimeMillis()+ expirationInMinutes * 60 * 1000;
          signature = null;
          if (userData != null) {
              encryptedBytes = null;
              userData.addAttribute("expire", Long.toString(expirationInMilliseconds));
          } else {
              encryptedBytes = null;
          }
      }