An apparatus including a microprocessor and a secure non-volatile memory. The microprocessor executes non-secure application programs and a secure application program. The microprocessor has secure execution mode initialization logic and an authorized public key. The secure execution mode initialization logic provides for initialization of a secure execution mode within the microprocessor. The secure execution mode initialization logic employs an asymmetric key algorithm to decrypt an enable parameter directing entry into the secure execution mode. The authorized public key is used to decrypt the enable parameter, the enable parameter having been encrypted according to the asymmetric key algorithm using an authorized private key that corresponds to the authorized public key. The secure non-volatile memory stores the secure application program, where transactions over the private bus between the microprocessor and the secure non-volatile memory are isolated from the system bus and corresponding system bus resources within the microprocessor.