  Nano artifact metrics exploit unique physical attributes of nanostructured
matter for authentication and clone resistance, which is vitally important in
the age of Internet-of-Things where securing identities is critical. However,
high-cost and huge experimental apparatuses, such as scanning electron
microscopy, have been required in the former studies. Herein, we demonstrate an
optical approach to characterise the nanoscale-precision signatures of silicon
random structures towards realising low-cost and high-value information
security technology. Unique and versatile silicon nanostructures are generated
via resist collapse phenomena, which contains dimensions that are well below
the diffraction limit of light. We exploit the nanoscale precision ability of
confocal laser microscopy in the height dimension, and our experimental results
demonstrate that the vertical precision of measurement is essential in
satisfying the performances required for artifact metrics. Furthermore, by
using state-of-the-art nanostructuring technology, we experimentally fabricate
clones from the genuine devices. We demonstrate that the statistical properties
of the genuine and clone devices are successfully exploited, showing that the
liveness-detection-type approach, which is widely deployed in biometrics, is
valid in artificially-constructed solid-state nanostructures. These findings
pave the way for reasonable and yet sufficiently secure novel principles for
information security based on silicon random nanostructures and optical
technologies.
