ACS Nano 11, 12772–12779 (2017)

A physically unclonable function (PUF) of a semiconducting device acts as its digital fingerprint, created as a result of manufacturing randomness. Silicon-based PUFs provide a CMOS-compatible solution, but their fabrication requires extensive post-processing associated with increased security vulnerability of computing systems. Nanomaterials that exhibit randomness of nucleation during large-scale growth may prove to be promising cost-effective security primitives. A. Alharbi et al. now report unclonable cryptographic primitives obtained via standard chemical vapour deposition of a few-layer transition metal dichalcogenide (TMD), MoS2.

During the growth, multiple layered islands are simultaneously formed on a continuous MoS2 monolayer. Using statistical analysis of the surface coverage, the authors confirm the natural randomness of the speckle distribution. Next, a small region of the film is used to fabricate a physical security primitive consisting of 32 × 64 pixel dense arrays. Owing to the arbitrary thickness distribution of the film features and the thickness-sensitive excitonic emission of MoS2, on photoexcitation the primitive exhibits a unique optical response of the array into a binary cryptographic key. Such unclonable TMD-based primitives can be readily scaled to large-area manufacturing. OB