PT Symmetry-Enabled Physically Unclonable Functions for Anti-Counterfeiting RF Tags

We present the concept and design of physically unclonable function (PUF)-based cryptographic key generation, which exploits the uniqueness of electromagnetic signatures of radio frequency (RF)-transponder tags derived from random physical variations during manufacturing. When the RF tag is inductively coupled to a designated readout circuitry, forming the higher-order parity-time (PT) symmetry, high sensitivity, and high entropy near the system's divergent exceptional point (DEP) can maximize the difference in temporal/spectral responses among tags. Our results show that due to the DEP singularity, PUF keys generated by converting the temporal response into binary sequences can exhibit excellent encryption performance in terms of randomness, uniqueness, encoding capacity, and resilience to machine learning (ML)-based modeling attacks. This RF PUF technique may pave the way toward ultra-lightweight, low-cost, and efficient hardware security solutions for wireless identification and authentication in various applications, including but not limited to the security of near-field connectivity and telematics infrastructure, wireless access control, authentication protocols for Internet-of-Things (IoTs), and anti-counterfeiting labels for goods, foods, and drugs.