Ag/Ag ₂ S Nanoparticle‐Based In‐Materio Lightweight Cryptographic System for IoT Edge Security

In Internet of Things (IoT) edge environments, securing sensor data with minimal computational overhead is increasingly important, as conventional software‐based cryptographic methods require significant computational resources and remain vulnerable to cyber‐physical attacks such as side‐channel attacks. In this study, we demonstrate an in‐materio lightweight cryptographic scheme that leverages the nonlinear response and short‐term memory of Ag/Ag ₂ S nanoparticle devices to directly encrypt analog signals without relying on any external computational resources. By sequentially processing electrocardiogram signals through a series of nanoparticle devices, the encrypted outputs exhibit enhanced complexity and statistical randomness and pass the NIST SP 800‐22 randomness tests. Decryption is performed using step‐by‐step inverse conversion models constructed with echo‐state networks, enabling the reconstruction of the original signal with 91% accuracy while preserving the intrinsic device dynamics. These results establish a computation resource‐free physical‐layer encryption approach based on nanomaterial behavior and highlight its potential as a practical and computationally efficient security mechanism for next‐generation IoT edge systems.