Creating digital fingerprints on commercial field programmable gate arrays

In this paper, we discuss the method of creating a circuit identifier, or digital fingerprint, for field programmable gate arrays (FPGAs). The proposed digital fingerprint is a function of the natural variations in the semiconductor manufacturing process that cannot be duplicated or forged. The proposed digital fingerprint allows the use of any arbitrary of nodes internal to the circuit or the circuit outputs as monitoring locations. Changes in the signal on a selected node or output can be quantified digitally over a period of time or at a specific instance of time. Two monitoring methods are proposed, one using cumulative observation of the nodes and the other samples the nodes based on a signal transition. Two monitoring methods were validated on a small sample of twenty Xilinx^reg Virtex-II Pro FPGAs, where both methods successfully created unique identifiers for each FPGA. In addition, the effects of temperature and voltage fluctuations are also discussed.