Cyber-Physical System Integrity and Security with Impedance Signatures
Many safety-critical domains, such as aerospace, agriculture, automotive, electronics, and medical, assemble systems using parts procured from a distributed supply chain. A costly issue faced by these industries and others is the inability to reliably detect counterfeit components that may compromise final products and systems because of inferior build quality or otherwise subpar specifications.
Current attempts to mitigate the use of counterfeit parts in such systems include Original Component Manufacturer (OCM) authentication and labeling using serial numbers, barcodes, or QR codes to ensure authentic parts. These methods have at least two critical shortcomings: 1) identifiers are easily removed, transferred, modified, or destroyed, and 2) fail to assess the structural quality of a part to ensure its authenticity, increasing the probability that counterfeit parts remain undetected.
Recent work investigating the assessment of damage and structural integrity in manufactured components supports the use of piezoelectric transducers as interfaces to determine the condition of a part and whether it should be used in a system.
These efficient, low-cost devices convert mechanical stress induced on a part into an electrical signal representing the physical state of the part, including mass, stiffness, and geometry.
The electrical signal exhibited by a part can be captured quickly by an impedance analyzer and stored as an impedance identity: a mapping of a part’s electrical impedance over each step of a range of excitation frequencies (the “Impedance Identity”). The Impedance Identity uniquely identifies a single instance from many instances of the same type of part. A key feature is that if specific physical properties of a part are invisibly modified (in the case of a lookalike, counterfeit part), the Impedance Identity of that part changes in a detectable way, so the part integrator can take appropriate action. In one case, yes, the part is acceptable for use in production; in the other, no, the part should not be used but instead discarded or rerouted for further inspection.