Stabilizing On-chip Secure Key Generation Using RO-PUF

Based on intrinsic physical characteristics of devices, Physical Unclonable Functions (PUFs) have high reliability while maintaining sufficient uniqueness. However, in the reality, the PUF extracted bit-string normally exhibits unavoidable small fluctuation and can be used for chip identification but not for the application that strictly required an exact generated number. In this work, we proposed a method that on-chip stabilizes the generated value based on the existing RO-PUF circuit. 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 RO frequency values for statistical analysis and dynamically phases out the unstable bits, resulting in a unique and stable output bit-string. The experiment has been conducted for actual data measured from FPGA devices. The generated key has been proven to be relatively stable and can be readily used for security applications such as section key generation for data encryption, hard-write digital token generation, or trusted computing.