Apparatus and method for inhibiting analysis of a secure circuit
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United States of America Patent
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Aug 24, 2004
Grant Date -
N/A
app pub date -
Apr 26, 1991
filing date -
Apr 26, 1991
priority date (Note) -
Expired
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Abstract
A secure circuit is protected from reverse engineering by sensing radiation to which the circuit is normally not exposed, but which is present in its analysis. The circuit is modified in response to such radiation so that it is not compromised by subsequent analysis. The secure circuit can be implemented as a volatile memory having a power supply circuit that is interrupted in response to radiation exposure. Alternately, a circuit used to burn out the secure circuit, or to reprogram the circuit in the case of a programmable memory, could be actuated by the radiation exposure. Reprogramming mechanisms include an operational amplifier with its input state controlled by a photodiode, a random access memory cell with inherently photosensitive transistors, and a photosensitive transistor switch connecting a multi-vibrator to a memory address line.
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