Logic block used to check instruction buffer configuration

Details Logic block used to check instruction buffer configuration Logic block used to check instruction buffer configuration

2004-05-21

2008-12-23

Peeso, Thomas R (Department: 2132)

Electrical computers and digital processing systems: support

Data processing protection using cryptography

Computer instruction/address encryption

C713S193000, C713S194000

Reexamination Certificate

active

07469344

ABSTRACT:
A CPU is provided with an ability to modify its operation in accordance with an encryption key. When a program is compiled, the program is modified in order that execution may be performed with the CPU with its operation modified. In order to execute program instructions, the buffer interdependencies must match that expected by the compiler. This makes analysis of the program operation extremely difficult. The instruction buffer on a keyed microprocessor contains logic which is able to route a subset of the instruction bits on the microprocessor. This selects destination logic gates in the microprocessor which eventually reach a programmable instruction decoder and an instruction buffer interdependency checking logic block.

REFERENCES:
patent: 5339419 (1994-08-01), Chan et al.
patent: 5724425 (1998-03-01), Chang et al.

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