Realization and analysis of high performance physical unclonable functions based on ring oscillators

Physical Unclonable Functions (PUFs) are powerful techniques that are proposed recently to address security related problems. They have a wide range of applications including cryptographic key generation and storage, authentication, identity generation, and intellectual property protection. PUFs off er new, low cost, and secure solutions in these areas with their ability to generate chip speci fic signatures on the fly. In the scope of the thesis study, quality metrics for the robustness and uniqueness properties of PUF circuits are derived. Confi dence interval and confi dence level concepts are adapted to PUF performance evaluation for the reliability of the results. Theoretical background of Ring Oscillators (ROs) is studied to analyze the eff ect of the number of stages and measurement time in RO-PUFs. Depending on the theoretical calculations, optimum number of stages and measurement time are determined and the theory is validated via experimental analysis. Then, ordering based RO-PUFs, which aim to maximize the robustness and entropy extraction, are discussed and dynamic programming is adapted for achieving lower complexity in the grouping step. Next, systematic analysis of the bit error probability in ordering based RO-PUFs is performed and area usage vs. robustness tradeo is presented. Implementation and analysis of error correction codes to maintain the robustness in ordering based RO-PUFs are also discussed. In addition to these, two challenge-response pair enhancement methods for ordering based RO-PUFs are introduced. Finally, e ffects of aging on ordering based RO-PUFs and compensation mechanisms are presented.