A device including a microprocessor and a secure non-volatile memory is disclosed. The microprocessor is used for executing unsecure and secure application programs. The microprocessor includes a secure execution mode initialized logic circuit and an authorized public private key register. The initialized logic circuit provides the initialization of the secure execution mode in the microprocessorand checks the enabling parameter that is decrypted by the unsymmetrical private key algorithm in order to instruct the microprocessor to initialize the secure execution mode. The authorized public private key register is used for storing an authorized public private key which decrypts the enabling parameter. The enabling parameter is encrypted by the unsymmetrical private key algorithm and the authorized private key corresponding to the authorized public private key. The secure non-volatile memory stores the secure application program. The data transmission between the microprocessor and thesecure non-volatile memory in the private bus is separated from the system bus and the corresponding system bus resources in the microprocessor.