Improving the reliability of RO PUF using frequency offset

Physical unclonable function (PUF) is a promising hardware security primitive that can be applied to various security related areas. The ring oscillator (RO) PUF is one of the most popular PUFs that can generate the volatile key by comparing the frequency between ROs. Previous RO PUFs incur unacceptable hardware overheads to improve the reliability in order to eliminate the effect of environment factors. In this paper, we propose a frequency offset algorithm (FOA) to enhance the reliability and low the hardware overhead. The key idea is to make the frequency difference larger than a given threshold by offsetting the frequencies of RO pairs. Experimental results show that our proposed FOA method has the better reliability and lower hardware overhead than the temperature-aware cooperative (TAC). Especially, our proposed method can achieve the 100% utilization of ROs.