36.4 A Physically Unclonable Function Combining a Process Mismatch Amplifier in an Oscillator Collapse Topology

Physically unclonable functions (PUFs) have been actively investigated as a promising solution for low-cost secure authentication in Internet of Things (IoT) applications. A PUF should generate unique challenge-response pairs (CRPs) which need to be determined solely by process variations (which are unpredictable) with strong immunity to supply and temperature changes. A PUF requires intrinsically stable and reliable operation while keeping area small and power consumption low. Approaches using metastability can provide efficient operation with fast response [1], but they suffer from high sensitivity to noise, supply and temperature changes. To achieve better stability, circuits for amplification of process skew effects have been adopted in PUF cells. The two-transistor amplifier [2], NAND-gate [3] and current-starved inverter [4] have been proposed as static amplifiers for detection of process mismatch, achieving further improved stability, as well as fast response. However, these approaches mostly rely on the process variation of the first stage amplifier. Therefore, they eventually result in an inconsistent output affected by transient noise when the process variation of the first stage amplifier is small.