A 154 F 2 Bistable Physically Unclonable Function With Independent Responses Based on Dynamic Division Multiplexing Technique
Gang Li, Junjie Zhou, Pengjun Wang, Xuejiao Ma, Bo Chen, Xilong Shao · IEEE Transactions on Very Large Scale Integration (VLSI) Systems · 2025
Physically unclonable functions (PUFs) have significant potential in the field of information security applications. To reduce the area of PUF cells and improve the utilization of the PUF entropy source, a dynamic division multiplexing bistable PUF with independent output response is proposed. Initially, a bistable PUF model is constructed by dividing traditional cross-coupled bistable PUF cells. The pull-up (pull-down) network employs large transistor sizes to minimize process variations, while the pull-down (pull-up) network, as the main PUF entropy source, utilizes the minimum transistor size to maximize random process variations. Subsequently, a cross-coupled twin cell with a symmetrical structure and shared word lines is designed, and a PUF cell array is composed ofntwin cells. Finally, the PUF cell array is dynamically configured using the output signal from a decoder. In this configuration, a single selected cell (with large deviation) and$n-1$unselected cells connected in parallel (with negligible deviation) collectively form a bistable PUF circuit for dynamic division multiplexing. The proposed PUF can operate in two independent modes, each of which can generate a 2304-bit feature key. The design is fully customized using the Taiwan Semiconductor Manufacturing Company (TSMC) 65-nm process, and the area (feature size) of a twin cell is only$1.32~\mu $m2(308 F2). Chip test results demonstrated that the proposed PUF achieved the entropy of 0.9999 (0.9997), the uniqueness of 49.9% (49.7%), and the reliability of 99.1% (97.7%) in the Ncell PUF (NC-PUF) [Pcell PUF (PC-PUF)] mode, respectively.