A method and apparatus for establishing product items unique identity for purpose of anti-counterfeiting or anti-theft is disclosed. It employs a fluorescent taggant embedded in product item, template, digitally based Encoder and Decoder. The taggant comprising plurality of fluorescent entities which in turn may comprise such distinct geometric and spectral optical characteristics-attributes as relative locations, emission/absorption spectra, polarization degrees and post luminanc delay and duration times. Such uniqueness is determined by the presence of a combination of a wide variety of fluorescent materials used during the application. The set of fluorescent entities are result of a random process and form a product item's fingerprint. The said template is a particular digitized representation of a taggant. The Encoder may comprise a camera, LED array based activator, configured to follow a particular illumination sequence and computation unit. The said camera further comprises at least two polarizing filters and template generator and the respective controllers. The Decoder may comprise at least one camera identical to the of the Encoder, at least one template/taggant readers and a computation unit, which may be shared with the said Encoder. Product item identity is based on the fluorescent taggant uniqueness, with the later embedded into the product in a non separable way. After the extracted attribute values assiciated with the taggant, are digitized. Digitazing comprises mixing with chaff (spurious) patterns of the same format, error correction, transformation in a non invertible and compression and encryption. This forms a template, embedded in the product in a readable form. The decoding comprises feature extraction of taggant, reading template and decrypting, its content, error correction, decompression. Then the extracted and the decoding results are cross-matched in order to identify the product item. Irreproducibility of a plurality of fluorescent entities and high degree of security of its digital representation due to encryption, high variability of LED patterns and non-invertible transformation is a basis of a chaosmetric anti-counterfeiting solution disclosed in the present invention.