In this paper, we propose a lightweight authentication and identification protocol based on different phosphorescent Strontium aluminate color labels. The excitation sources are pulsed UV LEDs emitting at 365 nm and 385 nm, causing different RGB-dependent time responses of the label that are measured using a smartphone recording at 30 FPS. The rise and decay time responses as measured by the red (R), green (G) and blue (B) pixels were separately analyzed and were found to follow a power law with individual parameters depending on the excitation wavelength, pulse duration and duty cycle, which serve as security features and are suitable for authentication purposes in IoT applications. Our solution uses simple cryptographic functions such as HMAC and XOR. We performed a security analysis of our protocol to prove its resistance to known attack vectors. The proposed scheme has minimal computation and communication costs and can be deployed on resource-constrained Internet of Things devices.

Optical magnetic field sensors employ diverse operating principle and sensing media, including magneto-optic crystals, glasses, fibers, and liquids, and range from relatively simple to highly complex and costly systems. In this paper, we report on the development of a fiberized, low-cost polarimetric magnetic field/current sensor based on spectral interrogation. To double the sensitivity, we propose a hybrid configuration combining a fluorescent magneto-optic bismuth silicon oxide (Bi12SiO20) crystal, which exhibits a high, spectrally dependent intrinsic optical activity, with a transparent magneto-optic glass (MOG) exhibiting no optical activity. While a conventional spectrometer tracks three spectral minima, the smartphone-based setup tracks two, which is sufficient for multi-parameter sensing and absolute temperature compensation. Using a 2D smartphone spectrometer, we demonstrate simultaneous spectral interrogation of multiple distinct sensors and demonstrate that this multi-channel topology can be effectively expanded into a 3D vector magnetometer. We also introduce a demodulation protocol that tracks spectral shifts by the separately analyzing the raw red, green and blue (RGB) smartphone pixels, thereby eliminating grayscale-induced distortion. The proposed hybrid BSO-MOG schemes enable the development of affordable, self-compensated current-sensor networks and 3D vector magnetometers using low-cost white LEDs, sheet polarizers, transmission diffraction gratings, and plastic optical fibers.