Image processing.

Phase-encoded nanostructures such as quick response (QR) codesmade of metallic nanoparticles are suggested to be used in security and authentication applications. We present a polarimetric optical method able to authenticate random phase-encoded QR codes. The system is illuminated using polarized light, and the QR code is encoded using a phase-only random mask. Using classification algorithms, it is possible to validate the QR code from the examination of the polarimetric signature of the speckle pattern. We used Kolmogorov–Smirnov statistical test and Support Vector Machine algorithms to authenticate the phase-encoded QR codes using polarimetri