A Low-Power Hybrid Ro Puf With Improved Thermal Stability For Lightweight Applications

Ring oscillator (RO)-based physical unclonable function (PUF) is resilient against noise impacts, but its response is susceptible to temperature variations. This paper presents a low-power and small footprint hybrid RO PUF with a very high temperature stability, which makes it an ideal candidate for lightweight applications. The negative temperature coefficient of the low-power subthreshold operation of current starved inverters is exploited to mitigate the variations of differential RO frequencies with temperature. The new architecture uses conspicuously simplified circuitries to generate and compare a large number of pairs of RO frequencies. The proposed nine-stage hybrid RO PUF was fabricated using global foundry 65-nm CMOS technology. The PUF occupies only 250 mu m(2) of chip area and consumes only 32.3 mu W per challenge response pair at 1.2 V and 230 MHz. The measured average and worst-case reliability of its responses are 99.84% and 97.28%, respectively, over a wide range of temperature from -40 to 120 degrees C.