Optical authentication of nano-scale artifacts using their interference images under white light illumination

Abstract

In the age of the Internet of Things, physical security framework of edge devices connected to the Internet is essential. Accordingly, higher security and higher authenticity are strongly required to prevent unauthorized invasion via irregular devices. On the other hand, artifacts comprising nano-scale structures that are smaller than the fabrication resolutions of general technologies are technically difficult to duplicate. Thus, the addition of such artifacts to each edge device or its components can be considered to ensure security and authenticity because the nano-scale artifact metrics are self-defined based on their higher clone resistance. However, reading out and evaluating physical identities of such artifacts requires the use of advanced setups and techniques. Therefore, they are not preferred in widespread practical applications. In this study, we propose and demonstrate an optical approach as another readout method for nano-scale physical identity based on a simpler setup and technology. Furthermore, the performance of experimental authentication using the identity of nano-scale artifacts was quantitatively verified. Our experimental setup operates by following a white light interferometry sensing. Generally, white light interferometry aids in obtaining numerous interference images by changing the distance between the target and the detection setup precisely to reconstruct a height distribution image with nano-scale resolution. However, in our application, reconstruction of the height distribution image is not necessarily required, while a single interference image is expected to be defined as identity of the target artifact. Subsequently, certain interference images were used to calculate the false match and non-match rates to qualitatively evaluate the authentication performance of the proposed method. Furthermore, the dependence of the performance on the spatial resolution and corresponding data size of the interference images was experimentally investigated. The results of these experiments pave the way for a practical and reliable method for the physical security of nano-scale artifacts based on general optical technology.