Lights and Security Technologies are connected in a deep and diverse way. To stimulate the reader’s curiosity, five very interesting commentary articles that make up this special issue are introduced by arranging their short abstracts side-by-side form a security researcher's personal point of view.

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Nano-artifact metrics exploits the unique physical attributes of nanostructured matter for authentication. The crucial point is how to read and utilize nanostructured matter. This article cites work on optical nano-artifact metrics using a white-light interferometric measurement.

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Lasers are widely used in criminal investigations. Fingerprints are one of the most important clues among forensic samples taken in the field. Although fingerprints are detected on various substrates, fingerprints cannot be visualized in some cases when the fluorescence of the substrate is strong. Therefore, we performed fingerprint visualization with a pulsed laser by time-resolved spectroscopy. We also examined the aging of fingerprints and fingerprint components. The fingerprints were visualized using various lasers such as UV, visible, IR, ns-pulsed, fs-pulsed, and CW. In addition, the application of lasers to forensic samples other than fingerprints was described in this paper.

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Fault injection attack is a serious threat to the security of embedded devices. In fault injection attacks, an adversary applies physical stress to a target embedded device, causes a computational fault, and exploits the faulty computational result to break the system’s security. A laser is an effective way of applying such physical stress, and laser fault injection attacks have been scrutinized over the last decade. This paper, which explains and describes laser fault injection attacks to researchers and practitioners in the laser field, covers the following three main topics: (i) general physical attacks on embedded systems, (ii) the mechanism through which a laser injection causes a computational fault, and (iii) sensor-based countermeasures that detect an attempt of fault injection attacks.

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We overview the recent progress in fast physical random number generation with complex photonics and investigate the bandwidth enhancement of chaos in three unidirectionally-coupled semiconductor lasers as a source of fast random number generation. We use a photonic integrated circuit and a field programmable gate array to implement real-time random number generation and introduce a statistical method to evaluate the entropy source of physical random number generation.

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Embedding coded data to a target using micro-fabrication technology to hide secret data is one of the most familiar techniques. However, there is a universal paradox that an attacker can also demonstrate similar performance of the fabrication. In this paper, we propose nano-optical metrics, which is the functional fusion of optical security and nanophotonics. Because nanophotonics have been defined as a novel technology based on optical near-field interactions between light and material, they are difficult to counterfeit. A basic procedure to retrieve nanoscale features of hidden data interactions is proposed using nonscanning probe microscopy, and experimentally demonstrated through practical retrievals. Furthermore, the definition of the feature quantities of retrieved results is shown and its applicability for nano-optical metrics is experimentally demonstrated.

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We investigated the relationships of the sensitivity of laser microphones to the oscillation mode of LDs using two types of them. A VCSEL has a side mode power ratio that ranges from 12 to 66 %, and for DFB-LD the side mode power ratio that is less than 5 %. The sensitivity is affected by the side modes and decrease more greatly with an increase of the side mode power ratio. When it exceeds 50%, the sensitivity of the laser microphone decreases greatly. Although the sensitivity of a laser microphone using VCSEL is 1.87 mV/Pa at most, the one using DFB-LD is 2.12 mV/Pa. We conclude that, the side oscillation mode negatively affects to the sensitivity, which increases with an LD that has a lower side mode and higher laser power. Therefore, DFB-LD is suitable for laser microphones.

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