Counterfeit Detection Based on Unclonable Feature of Paper Using Mobile Camera

This paper studies the authentication problem of specific pieces of paper using mobile imaging devices. Prior work showing high matching accuracy has used the normal vector field, which serves as a unique, microscopic, physically unclonable feature of paper surfaces, estimated by consumer grade scanners. Industrial cameras were also used to capture the appearance of the surface rendered after the normal vector field based on the laws of optics under a semi-controlled lighting condition. In comparison, past explorations based on mobile cameras were very limited and have not had substantial success in obtaining consistent appearance images due to the uncontrolled nature of the ambient light. We show in this paper that images captured by mobile cameras can be used for authentication when the camera flashlight is exploited for creating a semi-controlled lighting condition. We have proposed new algorithms to demonstrate that the normal vector field of paper surface can be estimated by using multiple camera-captured images of different viewpoints. Perturbation analysis shows that the proposed method is robust to inaccurate estimates of camera locations, and a matching accuracy of 10^-4 in equal error rate can be achieved using 6 to 8 images under a lab-controlled ambient light environment. Our findings can relax the restricted imaging setups and enable paper authentication under a more casual, ubiquitous setting with a mobile imaging device, which may facilitate duplicate detection of paper documents and counterfeit mitigation of merchandise packaging.