| 摘要 |
PURPOSE:To prevent the foul use of software via another computer despite a copying action carried out without notice by allowing the software to run through a specific computer only and leaving no decoded program in an external file or a main memory. CONSTITUTION:An instruction of an original software is partly ciphered by the software of a central processing unit. The instructions to be ciphered are ciphered by means of a key synthesized with an identification symbol ID and an instruction address (n) by rotation, etc., and then outputted to a main memory 10. An instruction executing device 1 decides the address (n) of the instruction to be executed next in order to decode the ciphered software. Then the device 1 extracts the relevant instruction out of the memory 10 and delivers it to an instruction decoder 3. The decoder 3 sends the instruction to a decoder 4 if the instruction code part of said instruction is coded. The decoder 4 decodes the instruction from the symbol ID and the address (n) and sends it back to the decoder 3. The decoder 3 decodes the instruction and sends it to an instruction executing device 2. The device 2 executes the received instruction. |
