Stability has always been one of the major limitations that constraints Physical Unclonable Function (PUF) from being put in widespread practical use. In this paper, we propose a weak PUF and a strong PUF that are both completely stable with 0% intra-distance. These PUFs are called Locally Enhanced Defectivity Physical Unclonable Function (LEDPUF). A LEDPUF is a pure functional PUF which eliminates the instability of conventional parametric PUFs, therefore no helper data, fuzzy comparator, or any kinds of correction schemes are required. The source of randomness is extracted from Directed Self Assembly (DSA) process, and connections that are permanently closed or opened are formed randomly. The weak LEDPUF is constructed by forming arrays of DSA random connections, and the strong LEDPUF is implemented by using the weak LEDPUF as the key of a keyed-hash message authentication code (HMAC). Our simulation and statistical results show that the entropy of the weak LEDPUF bits is close to ideal, and the inter-distances of both weak and strong LEDPUFs are about 50%, which means that these LEDPUFs are not only stable but also unique.
['Wei-Che Wang', 'Yair Yona', 'Suhas N. Diggavi', 'Puneet Gupta']
LEDPUF: Stability-guaranteed physical unclonable functions through locally enhanced defectivity