SYSTEM AND METHOD FOR PREVENTION AGAINST ILLEGAL ALTERNATION OF PROGRAM CODE AND RECORDING MEDIUM WITH RECORDED CONTROL PROGRAM THEREOF

摘要

PROBLEM TO BE SOLVED: To provide an illegal alteration prevention system for a program code which can execute a ciphered program code at high speed.;SOLUTION: When a data processor is in execution, a high-speed deciphering means 16 deciphers the ciphered program code by using a cipher key that a cipher key computing means 12 as well as a deciphering means 14 executed when the data processor 1 is initialized and performs the deciphering faster than the deciphering means 14. An illegal operation detecting means 15 detects whether or not the operation of the program code is analyzed by a software debugger, etc. When the illegal operation detecting means 15 detects the program code being analyzed, the data processor 1 does not use the program code deciphered in following processing, and uses a ciphered dummy program or quits the processing.;COPYRIGHT: (C)2002,JPO