Exploiting Routing Asymmetry for APUF Implementation in FPGA: A Proof-of-Concept

Implementing Arbiter PUF in an FPGA requires identical logic and symmetrical routing to ensure the delay differences are due to process variations. As the FPGA routing tools optimise for performance and not for symmetry, the FPGA CAD flow requires interventions like manual routing and the use of hard macros. These measures require a designer to work at a lower level of abstraction than RTL which can be tedious and error prone. Furthermore, they require an extensive knowledge of the FPGA fabric which may not be available owing to their proprietary nature. Considering these challenges, we investigate the possibility of an arbiter PUF implementation within the FPGA CAD flow by leveraging the routing asymmetry instead of eliminating it. Preliminary characterisation of a proof of concept APUF model demonstrated uniformity of 49.4 % and reliability of 96.3 %.