Browse Prior Art Database

Computer Program Protection

IP.com Disclosure Number: IPCOM000076824D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Lengyel, EJ: AUTHOR [+2]

Abstract

A proprietary computer program, which is intended for use on only a specific processor central processing unit (CPU), may be protected as follows. The first instruction in the program will be a special instruction, added to the CPU, which compares an identifier ID in the program to a hardwired ID in the CPU. The comparison may be based on identity or on another specific relationship between the IDs.

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Computer Program Protection

A proprietary computer program, which is intended for use on only a specific processor central processing unit (CPU), may be protected as follows. The first instruction in the program will be a special instruction, added to the CPU, which compares an identifier ID in the program to a hardwired ID in the CPU. The comparison may be based on identity or on another specific relationship between the IDs.

An invalid compare will terminate the program. If the comparison is correct, an instruction field BR-TO will be decoded, using the CPU ID as a key, to determine the address of the next instruction to be executed. This instruction may also be in code, with the CPU ID being the decoding key, but subsequent instructions will be in normal form and will not require special decoding.

On CPUs which do not accept the special instruction, the program will not start. Because the CPU ID is needed to decode the BR-TO address, the protection cannot be defeated by replacing the special instruction with a no- operation instruction. Merely changing the program ID will not permit the program to be run on another CPU, because the BR-TO address requires the proper CPU ID for decoding. Thus, such a program will run only on the CPU which was used to assemble it.

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