Class A Digital Watermarking Algorithm Based On Fractional Fourier Transform Of The Chirp

Digital watermarking is a new and effective digital encryption technique, and the basic idea is to embed secret information into the digital data in order to protect the property rights of the owners. This technique can make up the drawbacks of traditional cryptography, which makes it being one of the hot-point techniques in the multimedia information protection field. The perceptual invisibility and robustness is the most important properties considered in the domain. Chirp-typed watermark is presented recently and can be used as robust watermark structure because of the characteristics of chirp signal. This dissertation is supported by the subject of the National Natural Science Foundation of China (No.60472044): "The theory and application of image digital watermarking based on fractional Fourier transform". This dissertation focuses on the chirp-typed digital watermarking algorithm which based on fractional Fourier transform, and the main innovations and contributions are:1. The energy distribution of the image at different fractional Fourier transform has analyzed and verified by simulations. In this paper, the simulations show the energy distribution of the image at different fractional Fourier domain, which show that the energy distribution of the image will present concentration. This conclusion gives the reference for choosing best projection plane and threshold.2. An algorithm of the single chirp and multiple chirps watermarking based on fractional Fourier transform is proposed, and the simulation is given. The simulation results have shown that, compared with Radon-Wigner distribution, FRFT computation can be realized by using FFT and thus the complexity is much small, and the algorithm is robust to cropping and noise attacking in a certain extent, and also robust to other image processing.3. Since there are different time-frequency planes of fractional Fourier transform, a new watermarking scheme in fractional Fourier domain is proposed. Here, multiple two-dimensional chirp signals are also used as watermarks, which are...