Interconnect-Based PUF With Signature Uniqueness Enhancement

Physical unclonable function (PUF) is an important security primitive, which generates unique signatures as fingerprints for each chip. This article first presents a novel interconnect-based PUF (iPUF). The proposed iPUF utilizes the manufacturing process variability of interconnect lines to introduce crosstalk variations for generating PUF signatures. By leveraging the variations of passive interconnects, iPUF minimizes the usage of active CMOS components, providing an increased resiliency against environmental variations and aging. Initiated by a linear feedback shift register (LFSR), iPUF sequentially generates 1-bit signature at each clock cycle, making it more efficient compared with ring-oscillator PUF. Second, two schemes for signature uniqueness enhancement of sequential PUFs are proposed. The self-masking scheme windows the sequential signature with an m-bit mask trained by the PUF's own initial sequential signature. Meanwhile, the bit-filtering scheme screens the randomness of each bit within the sequential signature by exploiting several sub-iPUFs and selects the bits with high randomness. To verify the performance of iPUF, Monte Carlo simulations of 500 samples, with variations following industrial data, are conducted in different operating corners. The uniqueness of the given sample set approaches 48.63% with a 10-bit mask. With ±10% supply voltage, 0 °C-100 °C temperature variations, as well as one year of unaccelerated aging, iPUF's reliability values, are as high as 96.09%, 99.06%, and 99.63%, respectively. For verification, 50 dies of iPUF chips are manufactured with a 55-nm technology node. Silicon results demonstrate that iPUF generates 1024-bit signatures with satisfied uniqueness (48.03%) while exhibiting good reliability (90.07%) under 120-mV voltage variations. Finally, iPUF's robustness against various attacks is also proven.