Stabilizing Techniques for Secure On-chip Key Generation Based on RO-PUF

Abstract

Based on intrinsic physical characteristics of devices, Physically Unclonable Functions (PUFs) provide the high reliability while maintaining the sufficient uniqueness. However, in the practical implementation based on PUFs, the extracted bit-string normally exhibits the unavoidable small fluctuation. Hence, PUFs can be used for the application of chip identification, but not suitable for the application that strictly requires an exact generated number. In this work, we propose several techniques to stabilize the generated value based on the existing Ring Oscillator (RO)-PUF circuit so that the stable unique number can be directly used for high-profile hardware security applications. In detail, we design a specialized on-chip key generation circuit that repeatedly samples the RO frequency values for statistical analysis and dynamically phases out the unstable bits, resulting in a unique and stable output bit-string. The experiments are conducted for the actual data measured from Xilinx Artix-7  FPGA devices. The generated key is proven to be relatively stable and can be readily used for the emerging security applications.