A Hybrid Watermarking Scheme for Increasing Watermark Capacity and Security

Imperceptible and robust watermarking schemes have been vastly used recently as powerful tools to guard the copyright protection, rightful ownership, and content authentication. This paper introduces a secure hybrid digital image watermarking algorithm based on bi-dimensional empirical mode decomposition (BEMD); redundant discrete wavelet transform (RDWT); discrete cosine transform (DCT) and singular value decomposition (SVD). A watermark is scrambled by Arnold transform to boost up its secrecy and robustness. The main purpose of this scheme is to increase the embedding watermark capacity and encryption while keeping it robust against different types of attacks. The number of changing pixel rate (NPCR) and the unified averaged changed intensity (UACI) are two most common quantities used to estimate the strength of watermark image encryption algorithms/ciphers with reference to differential attacks. A high NPCR/UACI score is usually explicated as a high resistance to differential attacks, as well as higher PSNR evaluation metrics. Experimental using PSNR, WDR, MSE, NC and BCR metrics on different host images (Lena, Barbara, and Boat) and the cameraman as the watermark image show that the presented scheme is rich in terms of imperceptibility, capacity, security and robustness. This has been also highlighted by comparing its performance against other stateof-the-art schemes.