Towards robust hidden watermarking using multiple quasi-circles

Digital watermarking is the process of embedding a pattern or an icon into an image to establish legal ownership to protect the copyrights of the image in a publicly accessible image database. In this paper, we propose three robust watermarking schemes. One of our schemes, Diagonal Insersion (DI), modifies the Fourier coefficients of the middle frequencies of the input image, according to a binary string. Another scheme, Randomized Multiple Circles (RMC), is based on a technique proposed by Licks [8] which embeds a binary string by modifying the Fourier coefficients along concentric circles. We introduce a random perturbation into the radius of the circles to protect the waterwark from removal (cryptographic attack). A hybrid technique (HY) is also proposed to combine DI and RMC. These methods are robust against various attacks, such as geometric transformation, filtering, cropping and histogram equalization. Some experiemental results are also reported.