Digital Watermarking Based On Chaos Theory

The advance of network and the promotion of information technology have been making the use of digital multimedia information become rather widely. The use, storage, copy and transaction of this information is more convenient for people. The multimedia technology and the technology of digital transaction can simply and quickly give us lots of enjoyment, but they also bring in many problems, such as information security, piracy, copyright disputes and so on. In current, with the development of ability of computer, the traditional technology of encryption has been unable to meet the demand for information security, digital watermarking, which is a important branch of information hiding, provides a good complement for traditional encryption, is a hot field that the international academics is concentrate on. It provides a very useful measure for protection of multimedia information, copyright and product anti-counterfeiting.Two watermarking-encryption methods have been proposed in this paper according to the characteristic of Chaos system's pseudo-random and being sensitive to initial number. One is making gray image watermarking encrypted by using chaos sequence and the Fractional Fourier Transform (FRFT). The other is making binary image watermarking encrypted by using chaos sequence only. Meanwhile combining chaos-encryption and Arnold scramble either making the decryption of watermarking more difficult, or dispersing the sudden errors, and in a certain extent guaranteeing the security of watermarking.The theory and applications of the discrete wavelet transform (DWT) have been introduced simply. In one hand, according to the feature of watermark, in order to complete the embedding of watermark we choose different areas and embedding strengths. In the other hand, combining DWT and the Singular Value Decomposition (SVD), modifying the singular value of the domain of wavelet makes the watermark embedded according to the stability and the security against geometric distortion of image's singular value. According to the feature of different wavelet domains, watermark has been embedded for several times in order to enhance the watermark's security. The strategy of extracting the watermark is"choosing two from three", and then choosing the best extracting watermark by comparing their normalized correlation coefficients.The results of simulate experiment show that the algorithms in this paper are simple, convenient and invisible. And they are robustness against JPEG compression, added noises attack, filtrations attack, image rescale, image sharpening as well as other common image processing methods, they are also have good effects against image crop and the other geometric attacks.