Digital Watermarking Technology Based On Fractional Fourier Transformation

As an emerging and rapidly developing interdisciplinary, digital watermarking technology has become a hot research in the field of information security. As the digital watermark data is permanently embedded in the host that can be identified with the nature of digital information, and it does not interrupt the availability of host data, the digital watermark provides a potential and effective solution program for such issues of multi-media products in interconnection network as copyright protection. There are lots of digital watermarking methods, which use optical systems to achieve the watermarking technology is a new attempt.Fractional Fourier optics is a new branch of optical information technology which is formed by the fractional Fourier transform in mathematics to introduce into the formation of modern optics. It is the Fourier optics development and extension, it retained the nature and characteristics of original Fourier transform, and also increased the nature and characteristics of the new which the Fourier transform does not have, while the fractional order has become a new freedom of motion. Through it we can use a new perspective to examine the propagation and imaging of light, information processing and other issues, and it provides us with a new tool to resolve these related issues. Fractional Fourier optics will be more and more new applications.As there is a close relationship between the fractional Fourier transform with Fresnel diffraction, so it provides the possibility for people to use coherent optical processing system to achieve the fractional Fourier transform. In 1993, Lohmann explained the internal relations between fractional Fourier transform with Fresnel diffraction, then designed the corresponding optical device, thereby it has been given the new research methods in fractional Fourier transform.On the basis of analysis and discussion the digital watermarking technology of the system model and implementation method, we explore the feasibility study of using of optical information processing system to carry out digital watermarking. Optical information processing has the capacity of high speed, parallel processing and simple devices, and information can be hidden in parameters such as phase or spatial frequency, so using optical information processing to deal with information hiding operation related to optical images is a very valuable method in study.This article has the following main elementsFirst, this paper presents a watermarking algorithm based on transform domain, mainly watermarking algorithm in fractional Fourier transform spectrum domain. Fractional Fourier transform can be expressed in both spectrum of spatial and frequency domain, so relative to the frequency domain algorithm, its applicability is more flexible. When the transformation stage times smaller, the amplitude of the spectrum is dispersive, and it will be better resistance to attack. While class times and its transformation can be used as the decryption key, the watermark security will be improved.Second, In the latter part of this article, we carried out computer simulation according to the relevant algorithms to verify the feasibility of the digital watermarking system. We argument the feasibility and reliability of image hiding based on Fourier transform from the perspective of simulation methods.In the end, the embedded watermark effect was tested, such as the geometric attack, noise jamming, different types of image contrast and other embedded test. Through the study it implies that the algorithm based on transform domain has stronger robustness and anti-jamming capability.