Research Of Multiple Digital Watermarking Technology

With the rapid development of computer network technology and multimedia technology,and the growing of illegal copy and dissemination of digital works,it becomes very important to protect the multimedia information. So as a major branch of information hiding technique, digital watermarking has brought much attention of researchers, and research results are also emerging in endlessly. With the intensive study of digital watermarking application,single watermark can't solve the problems of multiple copyrights and copyright certification of digital products at different stages of the publication,distribution,sale and so on.Multiple watermarking technology emerges as the times require.Multiple digital watermarking can be used to track the transmission of digital products, multiple authentication and copyright protection of digital works. So it has practical value and broad application prospects.Multiple watermarking algorithms for image authentication and copyright protection are studied in this paper. By analyzing the current watermarking algorithms, two multiple digital watermarking algorithms are proposed.(1)By the researching of the spread spectrum theory in communications and the chaotic systems firstly, combining the masking effect of human visual system ,a multiple watermarking algorithm based on DCT and spread spectrum is proposed. First, the two watermarks are encrypted by Arnold transform and chaotic sequence. After this,the first watermark is modulated by m-sequence,then they are embedded in middle frequency coefficients of DCT domain,using different strategies. The algorithm has better security and robustness , larger capacity,in the same time can realize blind detection.(2)In the analysis of existing digital watermarking authentication technology,combining the noise visible function model, a watermarking algorithm based on DWT and chaotic system is proposed. According to the characteristics of DWT,the two watermarks are embedded in different components of three-level wavelet decomposition. The strength of robust watermark is decided by the NVF of embedding aeras.The watermarked image has better visual quality and the transparency of the watermark is good. The semi-fragile watermark is generated by a chaotic system and embedded in the wavelet component using odd-even quantization. The algorithm of generating semi-fragile watermark has lower computational complexity compared with HASH. Experimental results show that the robust watermark can resist common image processing operations and the semi-fragile watermark can detect and localize the tamper areas.