Ziyad Altarawneh , Mutaz Al-Tarawneh International Journal on Engineering Applications (I.R.E.A.), Vol. 9, N. 5 ISSN 2281-2881 September 2021 .     Abstract – Nano-scale Physical Unclonable Functions (PUFs) have recently emerged as promising hardware solutions for next-generation secure digital systems. In this context, the utilization of nano-scale Quantum dot Cellular Automata (QCA) technology provides power efficient and high-performance implementations of digital systems relative to their CMOS counterparts. In this paper, three different 8-bit PUF designs are introduced and implemented based on QCA technology. The proposed designs are constructed using different arrangements of a proposed area-efficient random seed. Simulation results show that the proposed structures surpass existing designs in terms of their structural cost, energy dissipation and latency while achieving adequate PUF performance metrics. The proposed designs have achieved up to 81%, 77% and 73% improvement in cell count, area and energy dissipation, respectively. The proposed designs can serve as building blocks for secure hardware systems and can be extended to implement larger PUF designs. Keywords: QCA Technology, Secure Systems, Physical Unclonable Functions, Nano-Technology.     Keywords: QCA Technology, Secure Systems, Physical Unclonable Functions, Nano-Technology