Abstract
Due to the development and availability of printing and scanning devices, the number of forged/counterfeited valuable documents and product packages is increasing. Therefore, different security elements (holograms, inks, papers) have been suggested to prevent these illegal actions. In this thesis, we focus on printed security elements that give access to a high security level with an easy implementation and integration. We present how to generate several novel security elements that aim to protect valuable documents and packaging against unauthorized copying process. Moreover, these security elements allow us to store a huge amount of hidden information.The main characteristic of these security elements is their sensitivity to the print-and-scan process. This sensitivity stems from the use of specific textured patterns. These patterns, which are binary images, have a structure that changes during the printing, scanning and copying processes. We define new specific criteria that ensures the chosen textured patterns to have the appropriate property. The amount of additional information encoded in the patterns increases with the number of patterns used.Additionally, we propose a new weighted mean squared error measure to improve the robustness of module detection for any high density barcodes. Thanks to this measure, the recognition rate of modules used in standard high density barcodes after print-and-scan process can be significantly increased. Finally, we experimentally study several effects: the physical print-and-scan process, separation of scanner noise from printer noise and changes of colors after print-and-scan process. We conclude, from these experimental results, that the print-and-scan process cannot be considered as being a Gaussian process. It has been also highlighted that this process is neither white nor ergodic in the wide sense.