Reconfigurable Multilevel Optical PUF by Spatiotemporally Programmed Crystallization of Supersaturated Solution

Abstract

Physical unclonable functions (PUFs) are emerging as an alternative toinformation security by providing an advanced level of cryptographic keyswith non-replicable characteristics, yet the cryptographic keys of conventionalPUFs are not reconfigurable from the ones assigned at the manufacturingstage and the overall authentication process slows down as the number ofentities in the dataset or the length of cryptographic key increases. Herein, asupersaturated solution-based PUF (S-PUF) is presented that utilizesstochastic crystallization of a supersaturated sodium acetate solution to allowa time-efficient, hierarchical authentication process together with on-demandrewritability of cryptographic keys. By controlling the orientation and theaverage grain size of the sodium acetate crystals via a spatiotemporallyprogrammed temperature profile, the S-PUF now includes two globalparameters, that is, angle of rotation and divergence of the diffracted beam, inaddition to the speckle pattern to produce multilevel cryptographic keys, andthese parameters function as prefixes for the classification of each entity for afast authentication process. At the same time, the reversible phase change ofsodium acetate enables repeated reconfiguration of the cryptographic key,which is expected to offer new possibilities for a next-generation, recyclableanti-counterfeiting platform.