| Summary: | Unique Objects (UNOs) are relevant for real-world applications such as anti-counterfeiting systems. In this work, cork is demonstrated as a UNO, part of the Physical Unclonability and Disorder (PUD) system. An adequate measurement kit (illumination device) and recognition method are also devised and evaluated. Natural hills and valleys of the cork are enhanced using the illumination device and the overall robustness of the recognition application inherent to UNOs is presented. The lighting device is based on grazing light and the recognition task is based on a local feature detector and descriptor called ORB - Oriented FAST (Features from Accelerated Segment Test) and Rotated BRIEF (Binary Robust Independent Elementary Features). The performance evaluation utilizes a private cork database (1500 photos of 500 cork stoppers) and three public iris databases. In the tests carried out on the illumination device, the results clearly show the success of capturing stable/repeatable features needed for the recognition task in the cork database. This achievement is also reflected in the perfect recognition score achieved in the cork database, in the intra-distance measure <inline-formula> <math display="inline"> <semantics> <msub> <mi>μ</mi> <mrow> <mi>i</mi> <mi>n</mi> <mi>t</mi> <mi>r</mi> <mi>a</mi> </mrow> </msub> </semantics> </math> </inline-formula>, which gives the notion of average noise between measures, and in the inter-distance <inline-formula> <math display="inline"> <semantics> <msub> <mi>μ</mi> <mrow> <mi>i</mi> <mi>n</mi> <mi>t</mi> <mi>e</mi> <mi>r</mi> </mrow> </msub> </semantics> </math> </inline-formula> which provides hints about the randomness/uniqueness of a cork. Regarding the recognition application, its effectiveness is further tested using the iris databases. Regardless of the fact that the recognition algorithm was not designed for the iris recognition problem, the results show that the proposed approach is capable of competing with the techniques found in the literature specially designed for iris recognition. Furthermore, the evaluation shows that the three requirements that constitute a UNO (Disorder, Operability, and Unclonability) are fulfilled, thus supporting the main assertion of this work: that cork is a UNO.
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