Cyberattack‐Resistant Cholesteric Liquid Crystal‐Based Physical Unclonable Function Keys

Physical unclonable functions (PUFs) are the new paradigm for the development of anticounterfeiting devices. Optical PUFs, which use the properties of light and how it interacts with materials to create unique identifiers, are attractive due to their high complexity. Cholesteric liquid crystals (CLCs), with their peculiar optical properties, are excellent candidates for optical PUF fabrication. Here, we present new fabrication methods to easily obtain complex random optical patterns, resembling human fingerprints, in CLC microspheres by exploiting temperature variations or mechanical stresses. Both methods enable large‐scale production of unclonable identifiers, easy to be encapsulated in polymeric thin films to create flexible anticounterfeiting labels. The authentication procedure of the labels is performed through image recognition algorithms. Through this procedure, an additional security feature is added. Each set of labels is used to generate a signature of the set itself. The signature represents a further and strong encoding level that guarantees the security of the labels against cyberattacks.