Synchronous sampling of internal state for investigation of digital systems
OwnerColin Patrick O'Flynninventor
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Abstract
Methods and apparatus are provided for sampling an indicator of the internal state of an embedded system or integrated circuit, where the indicator is sampled in a manner synchronous to the internal clock of the embedded system or integrated circuit. The resulting samples can be used for determining secret data within the embedded system or integrated circuit, detecting failures, or detecting counterfeit devices.
Claims18
An apparatus for performing synchronous acquisition of an indicator of an internal state of a device under test, said device under test not configured to communicate said internal state on digital communication channels of said device under test, the apparatus comprising:
- a clock generator configured to retrieve clock data from a clock configured to execute instructions on the device under test;
- a probe configured to produce an analog signal representing an internal state of the device under test;
- an analog to digital converter coupled to the probe and configured to generate a plurality of digital samples representing the magnitude of said analog signal by performing sampling operations at times indicated by the clock generator;
- and
- a digital processing unit configured to receive the plurality of digital samples from the analog to digital converter.
A method for performing synchronous acquisition of an indicator of an internal state of a device under test executing processor instructions, said internal state being not available over digital communication channels of the device under test, the method comprising:
- determining temporal locations of clock transitions of a clock retrieved from the device under test, said clock being used by the device under test to determine the temporal location of processor instruction execution;
- and
- generating samples of the indicator of the internal state of the device under test at a plurality of sampling points, wherein said sampling points have a known or constant temporal relation to the clock transitions.
A computer-readable storage medium that is not a transient signal, the computer readable medium having stored thereon instructions that, when executed by one or more processors, cause an apparatus to at least perform the following:
- communicate with a device under test, wherein said device under is performing operations in response to communications with an apparatus or third party;
- and
- determine locations of clock transitions of a clock retrieved from the device under test, wherein the device under test is performing said operations under control of said clock;
- and
- by use of said clock transitions, cause a plurality of samples to be taken of an indicator of an internal state of said device under test, the location of said plurality of samples having a known or constant temporal relationship to the location of said clock transitions.
Dependencies are inferred from the claim text.