Reconfigurable Multilevel Optical PUF by Spatiotemporally Programmed Crystallization of Supersaturated Solution.

Physical unclonable function (PUF) is emerging as an alternative to information security by providing an advanced level of cryptographic keys with non-replicable characteristics, yet the cryptographic keys of the conventional PUFs are not reconfigurable from the ones assigned at the manufacturing stage and the overall authentication process slows down as the number of entities in the dataset or the length of cryptographic key increases. Herein, we present a supersaturated solution-based PUF (S-PUF) that utilizes stochastic crystallization of a supersaturated sodium acetate solution to allow a time-efficient, hierarchical authentication process together with on-demand rewritability of cryptographic keys. By controlling the orientation and the average grain size of the sodium acetate crystals via a spatiotemporally programmed temperature profile, S-PUF now includes two global variables, i.e., angle of rotation and divergence of the diffracted beam, in addition to the speckle pattern to produce multilevel cryptographic keys, and these variables function as prefixes for the classification of each entity for a fast authentication process. At the same time, the reversible phase change of sodium acetate enables repeated reconfiguration of the cryptographic key, which is expected to offer new possibilities for a next-generation, recyclable anti-counterfeiting platform. This article is protected by copyright. All rights reserved.