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USER’S GUIDE
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Change Code
Perhaps most importantly, the user should reprogram
portions of the Secure Microcontroller that deal with se-
curity. For example, if the microprocessor is performing
DES, the user can change DES keys. Any security sys-
tem can be broken with enough time and resources. By
altering the security features, this threat can be mini-
mized.
External Circuits
A variety of external circuits can support secure opera-
tion. For example, the DS2400 is a unique 48–bit Silicon
Serial Number. If it is installed with the microprocessor, it
can be read when the system is first powered up, then
stored inside the Secure Microcontroller. This serializes
the system. If the software ever finds a different serial
number (or missing number) from the stored one, it can
refuse to work. This would mean that the microproces-
sor had been moved.
Tamper Protection
Using a variety of tamper sensors in conjunction with the
DS5002 makes the system very difficult to crack. These
circuits vary from simple switches to light, temperature,
pressure, or oxygen sensors. When the physical secu-
rity is violated, the SDI pin is activated and the memory
contents are destroyed.