## 4 Experimental Evaluation--RIOTA's Implementation and Cork as a UNO
### Results
#### 4.4.2. Cork as Unique Object  
As defined in Section 2, for an object be considered as a UNO, it must satisfy the following requirements: disorder, operability, and Unclonability. The disorder requirement is simple to achieve, since the information used for recognition purposes are binary descriptors extracted from the detected keypoints on the image of the cork stopper. Therefore, the \"fingerprint\" is only based on the unique disorder of the surface of cork stoppers. The operability requirement includes several prerequisites: (i) the time needed to calculate the object's fingerprint; (ii) the repeatability of measurements; (iii) the robustness to aging and environmental conditions; and (iv) the measurement equipment should be economically viable. Regarding point (i), this approach only takes an average time of 6.9 ms to detect and extract the \"fingerprint\" from one image of a cork stopper. This time is spent just one time per image on two occasions: when registering the image in the database (enrollment phase), and when querying the database (verification phase). Although the matching time needs further improvements as discussed previously in Section 4.4.1, the detection/extraction time is adequate for this application. The repeatability of measurements, point (ii), by using different camera sensors, was demonstrated in the tests performed (repeatable features test, and cork database test) and proven by the achieved results. The non-overlapping in Figure 6, the score displayed in Figure 4, and the intra-distance (\(\mu_{intra}\)) that expresses the notion of average noise on the measurements demonstrate that cork stoppers can be measured repeatedly (using an image as representation of the measure). Relative to point (iii), in Reference [57], the authors have performed aging tests exposing cork to extreme environmental conditions following the standard ASTM (American Society for Testing and Materials) G154-12a [58]. The authors state that cork does not suffer large changes when exposed to extreme environmental changes even in the face atmospheric factors such as light and humidity. Although the focus of this study is the mechanical properties (e.g., elasticity, damping, etc.) and not the variation of the visual appearance of cork, this can be used as a good indicator that the visual aspect of the cork possesses a certain degree of robustness to aging and environmental conditions. Besides, in this application, the cork stoppers are not exposed to these hard environmental conditions. Moreover, the wine experts from a large bottling company in Portugal have guaranteed that beyond some possible color changes in the cork the physical structure does not change over the years. Therefore, it is expected that the illumination device minimizes these color changes allowing the method to successfully recognize a cork stopper. However, full cork stopper aging tests according to standard ASTM G154-16 [58] may be necessary to correctly support the aforementioned sentence. Lastly, point (iv), the measurement device should be economically viable. Since no special components are used in the illumination device (the setup comprises two 3D printed parts, six Consumer Of the Shelf (COTS) white LEDs, and a smartphone COTS macro lens) it is not expected that the production cost of this device will make it impossible to use. \"The rule of thumb\" of anti-counterfeiting systems states that an anti-counterfeiting device should not be more expensive than the product its protecting. Despite not having calculated a real cost for the illumination device, it is not expected that the cost of mass-producing this device would exceed the cost of expensive/premium wine bottles and/or spirits or even the cost of regular wine/spirits bottles that use cork stoppers. Moreover, the same illumination device can be used to validate several wine bottles. Finally, the unclonable requirement was demonstrated in two different ways.