Algorithm Of Digital Multi-Watermarking Based On Chaos And DWT

The digital media has become more and more important along with the booming development of network and data communication technology. At the same time, copyright protection of digital media is becoming a problem. As an important measure, digital watermarking technology provides a novel way to solve this problem. In recent years, many different schemes have been proposed, but all of them are single watermarking. However, in many applications they need multi-watermarking. So the paper proposes a kind of multi-watermarking schemes, which has the important theory and the practical significance. Contents of the paper have two parts as shown.(1)A digital multi-watermarking based-on chaotic sequence was researched. Chaotic sequence is a type of pure pseudo-random sequences. It has characters of simple form, extremely sensitive to initial condition, irreversible and white noise. The locations of watermarking embedded are determined by chaotic sequence, so that they are random, however, security and anti-attack ability are enhanced. And a mapping table was designed, when the first watermarking is embedded, the key K₁ is needed, then according to K₁ to select the second watermarking in mapping table, K₁ and the second watermarking in mapping table is one correspondence, when the second watermarking is embedded, K₂ is also needed. When watermarks are extracted, first, the second watermarking is extracted according to K₂, then in accordance with the second watermarking to select the key K₁ in mapping table, at last, the first watermarking is extracted according to K₁. As long as not all the two keys is right, watermarks will not be able to extracted rightly, so watermarks are protected.(2)A digital multi-watermarking based-on chaotic sequence and Discrete Wavelet Transform (DWT) was researched. In a digital multi-watermarking algorithm based on chaotic sequence, its robustness is low against cropping attacks, so the algorithm is improved. In the watermark embedding domain, choosing DWT that in line with HVS, and researching a type of digital multi-watermarking based on chaos and DWT, also and taking into account the watermarking robustness and the quality of vision image with watermarking, original image make the three wavelet decomposition, frequency coefficients of image are separately embedded a watermarking.