| 摘要 |
PURPOSE:To increase difficulty in analyzing and prevent a copy from being taken even if there is a jump instruction by coding and decoding instructions with various conversion values. CONSTITUTION:Codes corresponding to instructions are stored in a memory device. When successive instructions I3, I4, and I8 are executed, an OR gate 3 outputs 0 to send a signal 35 to an adding circuit 24, and when the jump instruction I5 is executed, the gate 23 outputs 1 to send out a signal 36. In this case, if the contents of a key register 22 are already 07 at the stage of the execution of the instruction I3, the contents of the register are increased in the order of 08 and 09 on the execution of the instructions I3 and I4 and become 00 at the time of the execution of an instruction I5 and then 01 on the execution of the instruction I8. Thus, instruction codes are converted and decoded according to the output of the register 22. |
