Blind watermarking of colour images based on visual cryptography and Schur decomposition

Digital watermarking systems based on Third-party Authentication Authorities (TPA) provide exceptional usability and efficacy in copyright protection. Yet, they encounter security and trust issues. A digital blind watermarking technique for color photos integrating Schur decomposition and Visual Cryptography (VC) is presented to improve watermark robustness and TPA's security. Watermark data is first preprocessed using (2, 2) VC to create two shared images. Using this method, two shared images must be superposed to recover the original watermark. The numerical stability of Schur decomposition strengthens the watermark's resistance against geometric attacks. Tests validate the system's enhanced security and resistance to common threats.