A Physically Unclonable Bio-Signal Encoder for Privacy-Preserving IoMT Applications

Next-generation Internet of Medical Things (IoMT) must balance efficient local decision-making with strong privacy protection for remote monitoring and diagnosis. However, the resource constraints of IoMT devices make this difficult. This paper introduces a novel bio-signal encoder within the hyperdimensional computing (HDC) framework. It leverages inherent transistor variations for physically unclonable encoding. This technique is called variation-based analog entropy (VAE). VAE reduces memory footprint and power consumption while enhancing security. It offers a scalable, energy-efficient solution that addresses IoT’s resource limitations while ensuring secure, intelligent healthcare applications.The VAE cell achieves high entropy robustness (30.23-57.76 dB signal-to-noise ratio) with only a 10-transistor footprint. It reduces HDC vector dimensions by 14.3× and improves accuracy by 2%. Compared to an SRAM baseline, it shrinks encoder area by 1.3-4.4× and cuts leakage power by 327×. Custom analog circuits for entropy management eliminate data conversion, boosting energy efficiency to 48.5 nJ per query. Evaluations on experimentally collected bio-fluid data demonstrate classification accuracy of 94.9 % and 97.6 % in 5-class and 3-class viscosity sensing, respectively. This highlights the potential of the system for IoMT applications. Furthermore, the VAE significantly enhances security, lowering attacker-restored data peak SNR by 16 dB, and making unauthorized recovery indistinguishable.