Software protection methods and apparatus

Details Software protection methods and apparatus Software protection methods and apparatus

1982-05-21

1985-06-25

Cangialosi, Sal

Telegraphy

Systems

Printing

178 2209, 364200, H04L 900

Patent

active

045255997

ABSTRACT:
Methods and apparatus are disclosed for inhibiting the unauthorized copying of ROM-resident computer software or the like, for example, the audio-visual display of an electronic video game. A protection circuit including encryption/decryption means is coupled between the microprocessor and the ROM-memory and is operable in a first mode to properly encrypt/decrypt the program information according to a first algorithm and in a second mode to prevent proper encryption/decryption. The address-data buses are monitored by the protection circuit to detect an invalid program event, such as may occur when a microprocessor emulator is used to attempt an unauthorized copying or "dumping" of the program information. Upon detection of the invalid program event or "trap condition", the protection circuit switches to its second operating mode thereby to prevent copying of the decrypted program information.

REFERENCES:
patent: 3996449 (1976-12-01), Attanasio et al.
patent: 4120030 (1978-10-01), Johnstone
patent: 4168396 (1979-09-01), Best
patent: 4183085 (1980-01-01), Roberts et al.
patent: 4246638 (1981-01-01), Thomas
patent: 4278837 (1981-07-01), Best
patent: 4306289 (1981-12-01), Lumley
patent: 4319079 (1982-03-01), Best
patent: 4446519 (1984-05-01), Thomas
IBM Technical Disclosure Bulletin, vol. 21, No. 2, (7/78), Guruge, pp. 836-837.

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