Security circuit for protecting data stored in an internal memor

Details Security circuit for protecting data stored in an internal memor Security circuit for protecting data stored in an internal memor

1991-07-18

1994-12-27

Robertson, David L.

Cryptography

Key management

Having particular key generator

380 3, 235382, G11C 700

Patent

active

053773438

ABSTRACT:
A security circuit for protecting data stored in an internal memory of a microcomputer has a first memory for storing an externally applied security code and a latch circuit for latching a key code in order to read data stored in the internal memory. A comparator determines whether or not the security code in the first memory and the key code in the latch circuit are in agreement and outputs comparison results for storage in a second memory. A read control circuit uses the comparison results stored in the second memory as the basis for prohibiting reading of data in the internal memory when the security code and the key code are not in agreement, and for using an externally applied output control signal as the basis to control reading of data stored in the internal memory when there is agreement.

REFERENCES:
patent: 4654829 (1987-03-01), Jiang et al.
patent: 4757533 (1988-07-01), Allen et al.
patent: 4864542 (1989-09-01), Oshima et al.
Intel 2716 Data Sheet as reproduced In "Microcomputer Hardware Handbook", ELCOMP Publishing, 1982, pp. 244-247.
Pp. 2-4 and 3-10 of FASTCARD III users manual, Thesys Memory Products Corporation, Jul. 1985.
Bursky, "Protect Your EEPROOM Data and Gain More Flexibility," Electronic Design, vol. 36, No. 12, pp. 43, 44, 46 & 48 (May 1988).
DeFrancesco et al., "Intelligent Non-Volatile Memory for Smart Cards," IEEE Transactions on Consumer Electronics, vol. CE-32, No. 3, pp. 604-607.

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