SD-PUF: Spliced Digital Physical Unclonable Function

Digital circuit physical unclonable function (PUF) have been attracting attentions for the merits of resilience to the environmental and operational variations that analog PUFs suffer from. Existing state-ofthe-art digital circuit PUFs, however, are either hybrid of analog-digital circuits which are still under the shadow of vulnerability, or impractical for real-world applications. In this work, we propose a novel highly non-linear and secure digital PUF (D-PUF) and the spliced version SDPUF. The fingerprints are extracted from intentionally induced VLSI interconnect randomness during lithography process, as well as a post silicon shuffling process. Strongly skewed CMOS latches are used to ensure the immunity against environmental and operational variations. Crucially, a highly non-linear logic network is proposed to effectively spread and augment any subtle interconnect randomness, which also enables strong resilience against machine learning attacks. On top of it, the expandable architecture of the proposed logic network empowers a novel post silicon shuffle-splice mechanism, where multiple randomly selected D-PUFs are spliced to be one SD-PUF, pushing the statistical security to a much higher level, while significantly reducing the mask cost per PUF device. It also decouples the trustworthy demands enforced to the foundries or other third party manufacturers. Our proposed PUFs demonstrate close to ideal performance in terms of statistical metrics, including 0 intra Hamming Distance. Various stateof-the-art machine learning models show prediction accuracies almost no better than random guesses when attacking to the proposed PUFs. We also mathematically prove the probability of existence of identical SD-PUF pair is significantly lower than that of D-PUF pair, e.g., such probability of an SD-PUF spliced by 30 D-PUFs is 2.3⇥10 22, which is 19 order magnitude lower than that of D-PUF. Benefited from the proposed shuffle-splice mechanism, the mask cost per SD-PUF is also reduced by 300⇥ than that of D-PUF.