The Study, Based On Fractional Fourier Transform Digital Watermarking Technology

It is likely due to the protection of copyright issue for a greater growth of interest about watermarking techniques. In recent years, digital watermarking technique, a new method for copyright protection, has become one of hot techniques in multimedia information security field and has been great concern in the international academic community. Transform domain digital watermarking algorithm is one of study focuses. Fractional Fourier Transform(FRFT) is a new tool for time-frequencyanalysis, which has some excellent properties for some time-verity signals.This paper focuses on digital watermark algorithm which based on fractional Fourier transform.The main content is as following.Firstly, the energy distribution of the image at different fractional Fourier transform is analysised and verified by simulations. Simulation results show that fractional Fourier transform has dual characteristics of time-frequency domain. Images are changing with transform order change between in (0,1) in the time-frequency domain. The transform order greater shows more frequency-domain characteristics. Simulation results also show that fractional Fourier transform has characteristics of energy aggregation, The greater transform order makes more energy to gather in the central region of the image.Secondly, a random sequence watermark algorithm is presented in fractional Fourier transform domain and two order (p1,p2) keys are added in FRFT transform in order to enhance algorithm security. Two different random sequences are added to real and imaginary parts of the coefficient of the FRFT, which enhances the security of the algorithm, too.Thirdly, a more popular digital image watermark algorithm is presented which is based on random sequence watermark algorithm in FRFT domain. In order to increase the security, a chaotic sequence is used to modulate the watermark firstly. And the watermark signal is embedded in sub-major component in a compromise between robustness and visibility.Finally, simulation experiments of two algorithms are carried out, results demonstrate that the watermark is invisible and robust against some attacks, such as crop, common noise and JPEG compress. It also has certain counteractant ability against a comprehensive attack.