System for securing a data processing system and method of operation

A system (10) and a method for securing an integrated circuit each have at least three modes of security. A first mode of security is a normal mode of operation wherein access to data which is internal to the integrated circuit is not limited. The normal mode of security may be readily changed to a revocable security mode or an irrevocable security mode. In the revocable security mode, the data stored internal to the integrated circuit package portion (11) is not accessible from external to the integrated circuit. The revocable mode may be changed to either the normal mode of operation or the irrevocable mode of operation by a user-defined key. The irrevocable security mode offers security similar to the revocable security mode. The difference is that the irrevocable security mode cannot be exited once entered. Only destructive techniques, such as depotting, have a possibility of changing the irrevocable security mode.