High Fidelity Security Mesh Monitoring using Low-Cost, Embedded Time Domain Reflectometry

Security Meshes are patterns of sensing traces covering an area that are used in Hardware Security Modules (HSMs) and other systems to detect attempts to physically intrude into the device’s protective shell. State-of-the-art solutions manufacture meshes in bespoke processes from carefully chosen materials, which is expensive and makes replication challenging. Additionally, state-of-the-art monitoring circuits sacrifice either monitoring precision or cost efficiency. In this paper, we present an embeddable security mesh monitoring circuit constructed from low-cost, standard components that utilizes Time Domain Reflectometry (TDR) to create a unique fingerprint of a mesh. Our approach is both low-cost and precise, and enables the use of inexpensive standard Printed Circuit Boards (PCBs) as security mesh material. We demonstrate a working prototype of our TDR circuit costing less than 10 € in components that achieves both time resolution and rise time better than 200 ps—a 25x improvement over previous work. We demonstrate a simple classifier that detects several types of advanced attacks such as probing using an oscilloscope probe or micro-soldering attacks with no false negatives.