Image watermarking for identity protection

Abstract

Identity protection is an indispensable feature of any information security system. A person’s or an organisation’s identity, i.e., personal information, can exist in physically printed and digital forms. It serves the vital purposes of verifying the owners, defending their copyrights, and protecting them from imposters. Numerous security mechanisms are being developed to achieve those goals, a prominent one of which is watermarking. Watermarking safeguards different media types, such as audio files, images, and videos. However, image watermarking is the focus of this thesis. Watermarking in images has two main purposes. The first is to curtail images’ illegal distribution by providing them with copyright protection, and the second is to maintain their integrity by making them verifiable. A successful image watermarking scheme must address three main requirements. First, the watermark in the host signal (original image) must be imperceptible. No deformities perceivable by the human visual system can be present. Second, the watermark must be secured against unauthorised modifications. Third, a watermarking scheme should have high capacity, i.e., be able to embed large watermark(s). However, those three requirements are closely correlated, and changing one can significantly affect the others. For instance, high capacity or embedding large watermarks can improve security but degrade imperceptibility. In other words, the smaller the watermark, the better the imperceptibility but the weaker the security. Thus, balancing those requirements is a significant challenge in the field. This research study aimed to develop image watermarking that achieves a better equilibrium between the aforementioned watermarking requirements than existing state-of-theart watermarking methods. In that study, several image watermarking methods were developed to achieve that aim: 1. A dual watermarking scheme for identity protection; 2. A novel multipurpose watermarking scheme capable of protecting and authenticating images with tamper detection and localisation abilities; 3. A single watermark-based scheme for both protection and authentication of identities. Overall, the thesis has made significant contributions to the image watermarking field. The novel methods developed during this research result in watermarked images that not only achieve an excellent balance between the aforementioned watermarking requirements but also surpass the performance of ones produced via state-of-the-art methods. Moreover, the developed watermarking approaches can be potentially employed to safeguard the copyright of images and help maintain their integrity.

Date of Award	2023
Original language	English