PostHeaderIcon Discover IC code

The most widely used non-invasive discover IC code include playing around with the supply voltage and clock signal. Under-voltage and over-voltage IC code discover could be used to disable protection circuit or force a processor to do the wrong operation. For these reasons, some security processors have a voltage detection circuit, but this circuit cannot react to fast transients. Power and clock transients can also be used in some processors to affect the decoding and execution of individual instructions.

Another possible IC code discovery uses current analysis. We can measure with an analog-to-digital converter the fluctuations in the current consumed by the device. Drivers on the address and data bus often consist of up to a dozen parallel inverters per bit, each driving a large capacitive load. They cause a significant power-supply short circuit during any transition. Changing a single bus line from ‘0’ to ‘1’ or vice versa can contribute in the order of 0.5–1mA to the drain current right after the clock edge. So a 12-bit ADC is sufficient to estimate the number of bus bits that change at anyone time. SRAM write operations often generate the strongest signals.

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