Robust and Versatile Biodegradable Unclonable Anti‐Counterfeiting Labels with Multi‐Mode Optical Encoding Using Protein‐Mediated Luminescent Calcite Signatures

Abstract Physical unclonable functions (PUFs) are emerging as a cutting‐edge technology for enhancing information security by providing robust security authentication and non‐reproducible cryptographic keys. Incorporating renewable and biocompatible materials into PUFs ensures safety for handling, compatibility with biological systems, and reduced environmental impact. However, existing PUF platforms struggle to balance high encoding capacity, diversified encryption signatures, and versatile functionalities with sustainability and biocompatibility. Here, all‐biomaterial‐based unclonable anti‐counterfeiting labels featuring multi‐mode encoding, multi‐level cryptographic keys, and multiple authentication operations are developed by imprinting biomimetic‐grown calcites on versatile silk protein films. In this label, the inherent non‐clonability comes from the randomized characteristics of calcites, mediated by silk protein during crystal growth. The successful embedding of photoluminescent molecules into calcite lattices, assisted by silk protein, allows the resulting platform to utilize fluorescence patterns alongside birefringence for high‐capacity encoding. This design facilitates easy and rapid authentication through Hamming distance and convolutional neural networks using standard cameras and portable microscopes. Moreover, angle‐dependent polarization patterns enable multi‐level key generation, while multi‐spectral fluorescence signals offer multi‐channel keys. The developed anti‐counterfeiting labels combine biodegradability, green manufacture, easy authentication, high‐level complexity, low cost, robustness, patternability, and versatility, offering a practical and high‐security solution to combat counterfeiting across various applications.