Privacy-preserving gait biometrics via synchronous mechanical and bioelectrical co-sensing and ciphertext-domain inference

Abstract

Gait information is rooted in muscle contraction dynamics and neuromuscular regulation, and represents a reliable biometric. However, mechanical and bioelectrical signals acquired using conventional wearables are prone to replication and forgery during storage and transmission. Moreover, the degradation of recognition performance under standard encryption can occur due to limited feature dimensionality and fidelity. In this study, we present a spatiotemporally synchronous strain-surface electromyography (sEMG) co-sensing system (S-SESS), which co-locates and phase-aligns kinematic and neuromuscular signals from the gastrocnemius to deliver secure gait recognition. The strain sensing unit achieves a low hysteresis (1.6% at 100% strain) and high cyclic fidelity (> 10,000 cycles) using hierarchical supramolecular aggregates with multiple hydrogen bonds and dynamic π-π stacking that ensure precise phase tracking. The adaptive sEMG unit exhibits high interfacial conformity, suppresses motion artifacts, and achieves a signal-to-noise ratio (SNR) greater than 40 dB. The bimodal features are locally encrypted using the Advanced Encryption Standard-128 (AES-128) algorithm and processed directly in the ciphertext domain via a dedicated ByteEmbedded Temporal Convolutional Network (ByteEmbedded-TCN). This directly maps ciphertext streams into byte-embedded sequences and leverages causal and dilated convolutions to construct multi-scale receptive fields for temporal alignment and classification. The end-to-end framework achieves 89.7% ± 1.2% gait identification accuracy under encryption. The findings of this study provide a privacy-preserving wearable paradigm for trustworthy identity authentication.

Keywords

Low hysteresis / gait recognition / multimodal sensors / flexible wearable electronics / machine learning

References

[1] Zeng L.,Shen P.,Zhu X.,Tian X.,Chen C.. A review of privacy-preserving biometric identification and authentication protocols Comput. Secur. 2025 150 104309

[2] Alrawili R.,Alqahtani A. A. S.,Khan M. K.. Comprehensive survey: Biometric user authentication application, evaluation, and discussion Comput. Electr Eng. 2024 119 109485

[3] Nonnekes J.,Goselink R. J. M.,Růžička E.,Fasano A.,Nutt J. G.,Bloem B. R.. Neurological disorders of gait, balance and posture: a sign-based approach Nat. Rev. Neurol. 2018 14 183 9

[4] Li J.,Zhang S.,Zhong J..et al. Laser-induced graphene-assisted patterning and transfer of silver nanowires for ultra-conformal breathable epidermal electrodes in long-term electrophysiological monitoring Adv. Funct. Mater. 2025 35 2504481

[5] Dong X.,Fan F.,Chen L..et al. Mechanical interlocking enhanced hybrid electrode for long-term epidermal biopotential monitoring in clinical applications Chem. Eng. J. 2026 527 171609

[6] Xiao M.,Luo Y.,Chen H..et al. Conformal bioadhesive hydrogel-based multimodal wristband for accurate, mobile, and real-time sign language translation and human-machine interactions Adv. Funct. Mater. 2025 36 e22153

[7] Álvarez-aparicio C.. Guerrero-higueras, Á. M.; González-santamarta, M. Á.; Campazas-vega, A.; Matellán, V.; Fernández-llamas, C. Biometric recognition through gait analysis Sci. Rep. 2022 12 14530 PMC9406276

[8] Wang Q.,Guan H.,Wang C..et al. A wireless, self-powered smart insole for gait monitoring and recognition via nonlinear synergistic pressure sensing Sci. Adv. 2025 11 eadu1598 PMC12002114

[9] Sun R.,Wu P.,Li P..et al. Bio-inspired triboelectric nanogenerator as a self-powered gait recognition sensor for legged robots Sci. China Mater. 2025 68 1542 51

[10] Jani A. B.,Bagree R.,Roy A. K.. Design of a low-power, low-cost ECG & EMG sensor for wearable biometric and medical application. In 2017 IEEE SENSORS, Glasgow, UK, October 29-November 1, 2017; IEEE, 2017; pp 1-3

[11] Huang X.,Zheng H.,Zhou Z.,Sheng Y.. Gait recognition based on a-mode ultrasound and inertial sensor fusion systems. In Intelligent Robotics and Applications, ICIRA 2024, Xi'an, China, July 31-August 2, 2024; Lan, X., Mei, X., Jiang, C., Zhao, F., Tian, Z., Eds.; Springer: Singapore, 2025; pp 192-205

[12] Chen Y.,Liu Z.,Wang Z..et al. Bioinspired robust gas-permeable on-skin electronics: armor-designed nanoporous flash graphene assembly enhancing mechanical resilience Adv. Sci. 2024 11 2402759 PMC11234450

[13] Shi X.,Song D.,Hu W..et al. A sweat absorbing skin electrode for electrophysiology during exercise Adv. Funct. Mater. 2024 34 2314775

[14] Liu Y.,Chen S.,Shi L..et al. Water-enhanced adhesive interface for high-quality physiological signal monitoring in skin-device integration Adv. Funct. Mater. 2025 36 e16396

[15] He Y.,Cheng Y.,Yang C.,Guo C. F.. Creep-free polyelectrolyte elastomer for drift-free iontronic sensing Nat. Mater. 2024 23 1107 14

[16] He J.,Huang J.,Li R..et al. Hysteresis-free and dynamically resilient strain sensor enabled by interfacial coordination Sci. Adv. 2026 12 eaea2450 PMC12757069

[17] Yang J. C.,Mun J.,Kwon S. Y.,Park S.,Bao Z.,Park S.. Electronic skin: recent progress and future prospects for skin-attachable devices for health monitoring, robotics, and prosthetics Adv. Mater. 2019 31 1904765

[18] Ohm Y.,Pan C.,Ford M. J.,Huang X.,Liao J.,Majidi C.. An electrically conductive silver-polyacrylamide-alginate hydrogel composite for soft electronics Nat. Electron. 2021 4 185 92

[19] Sun T.,Feng B.,Huo J..et al. Artificial intelligence meets flexible sensors: emerging smart flexible sensing systems driven by machine learning and artificial synapses Nano-Micro Lett. 2023 16 14 PMC10643743

[20] Song Y.,Liu Y.,Qi T.,Li G. L.. Towards dynamic but supertough healable polymers through biomimetic hierarchical hydrogen-bonding interactions Angew. Chem. Int. Ed. 2018 57 13838 42

[21] Jeon I.,Cui J.,Illeperuma W. R. K.,Aizenberg J.,Vlassak J. J.. Extremely stretchable and fast self-healing hydrogels Adv. Mater. 2016 28 4678 83

[22] Liu K.,Cheng L.,Zhang N..et al. Biomimetic impact protective supramolecular polymeric materials enabled by quadruple H-bonding J. Am. Chem. Soc. 2020 143 1162 70

[23] Jin Y.,Wang R.,Tang D..et al. AI-enabled adaptive eutectogel skin for effective motion monitoring with low signal artifacts Adv. Funct. Mater. 2025 35 2424965

[24] Jiang W. J.,Zhong F. Y.,Zhou L. S.,Peng H. L.,Fan J. P.,Huang K.. Chemical dual-site capture of NH₃ by unprecedentedly low-viscosity deep eutectic solvents Chem. Commun. 2020 56 2399 402

[25] Guo X.,Zhang S.,Patel S..et al. A skin-mimicking multifunctional hydrogel via hierarchical, reversible noncovalent interactions Sci. Adv. 2025 11 eadv8523 PMC12083530

[26] Xiang H.,Li X.,Wu B.,Sun S.,Wu P.. Highly damping and self-healable ionic elastomer from dynamic phase separation of sticky fluorinated polymers Adv. Mater. 2023 35 2209581

[27] Yu T.,Zhang L.,Dou X..et al. Mechanically robust hydrogels facilitating bone regeneration through epigenetic modulation Adv. Sci. 2022 9 2203734 PMC9661832

[28] Zhu R.,Zhu D.,Zheng Z.,Wang X.. Tough double network hydrogels with rapid self-reinforcement and low hysteresis based on highly entangled networks Nat. Commun. 2024 15 1344 PMC10864390

[29] Li W.,Wang X.,Liu Z..et al. Nanoconfined polymerization limits crack propagation in hysteresis-free gels Nat. Mater. 2023 23 131 8

[30] Yang K.,Li Q.,Tian S..et al. Highly stretchable, self-healing, and sensitive e-skins at -78 °C for polar exploration J. Am. Chem. Soc. 2024 146 10699 707

[31] Sun H.,Lee H. H.,Blakey I..et al. Multiple hydrogen-bonded complexes based on 2-ureido-4[1H]-pyrimidinone: a theoretical study J. Phys. Chem. B. 2011 115 11053 62

[32] Fengler C.,Keller J.,Ratzsch K. F.,Wilhelm M.. In situ RheoNMR correlation of polymer segmental mobility with mechanical properties during hydrogel synthesis Adv. Sci. 2021 9 2104231 PMC8811812

[33] Dong J.,Liu H.,Lim T..et al. Viscoelastic adhesive, super-conformable, and semi-flowable liquid metal eutectogels for high-fidelity electrophysiological monitoring ACS Appl. Mater. Interfaces 2024 16 34732 42

[34] Liu P.,Pei D.,Wu Y.,Li M.,Zhao X.,Li C.. Dynamic and mechanically robust and ultrafast healable ionogel for nerve fiber-inspired signal transmitter J. Mater. Chem. A. 2022 10 25602 10

[35] Noda I.. Generalized two-dimensional correlation method applicable to infrared, Raman, and other types of spectroscopy Appl. Spectrosc. 1993 47 1329 36

[36] Yang J.,Chang L.,Deng H.,Cao Z.. Zwitterionic eutectogels with high ionic conductivity for environmentally tolerant and self-healing triboelectric nanogenerators ACS Nano 2024 18 18980 91

[37] Lata K.,Saini S.. Hardware software co-simulation of an AES-128 based data encryption in image processing systems for the internet of things environment. In 2020 IEEE International Symposium on Smart Electronic Systems (iSES) (Formerly iNiS), Chennai, India, December 14-16, 2020; IEEE, 2020; pp 260-4