A Watermarking Encryption Method Of Fractional Order Fourier Holography

With the rapid development of science and technology,people can use wireless electronic devices to obtain images,audio and other digital products on the Internet.However,the security of digital product has become an urgent problem for copyright holders.In the field of information security,digital watermarking technology has attracted the attention of scholars because of its good concealment and security,but the traditional digital watermarking embeds less information and has limited ability to resist external attacks.In order to solve this problem,digital holographic watermarking technology emerged.In the process of hologram generation,it will carry the encryption ability but also have a lot of information.If it is transmitted or embedded directly without any operation,it will cause network jam,reception delay,carrier image quality damage and other problems.Therefore,this thesis studies digital holographic watermarking algorithm from the following aspects:(1)The traditional methods for generating holograms include optical path construction,Fourier transform construction and fractional Fourier transform construction,etc.However,it is too complicated to construct optical path,and holographic elements containing image information should be exposed one by one to complete the printing of holographic body view.Since the Fourier transform cannot represent the local time-frequency characteristics of the non-stationary signal well,the fractional Fourier can reflect the information of time and frequency domain simultaneously and the holographic watermark has more stable performance against external attack.(2)Because whale algorithm itself is easy to fall into local optimum,the compression rate of the hologram compression model generated by whale algorithm is low,so the cross factor of genetic algorithm is introduced to optimize whale algorithm and the whale optimized genetic algorithm is used to improve wavelet transform to obtain the improved hologram compression model,which is combined with particle swarm compression model and whale compression model By contrast,the compression ratio of the holographic watermark image is significantly improved.(3)The existing watermarking algorithm combining discrete cosine transform with matrix singular value cannot resist the geometric attack from the outside,while the fractional Fourier transform can act on the digital holographic watermarking image in both time and frequency domain,so this problem can be effectively solved.Therefore,a holographic watermarking algorithm based on fractional Fourier transform and matrix singular value is proposed to realize a digital holographic watermarking algorithm with stronger resistance to geometric attacks.Compared with the watermark embedding algorithm based on the combination of DCT and singular value of matrix,the proposed algorithm can resist salt and pepper noise,gaussian filter,mean filter,clipping attack and sharpening attack.