Research Of Image Watermarking And Steganography Algorithm In Compressed Domain

With the development of network and multimedia techniques, the creation and distribution of e-works become more and more easily, however, pirated copies and content tampers of digital works also become more and more popular. Digital watermarking technique as a countermeasure for copyright protection and content authentication has attracted many eyes from academic and industrial world during the last decade. Especially in recent years, the research of watermarking methods paid more attention to practicability and current multimedia standard. Among the various problems to be solved in watermarking world, effective compressed domain scheme is the most challenging issue.The JPEG compressed domain watermarking scheme and steganography algorithm are focus of this paper. The main work is described as follows:(1) A fragile watermarking scheme in compressed domain is proposed in this paper. The self-embedding watermarking technique is applied, and the operations of embedding and extracting the watermark are all in the compressed domain. The decoded DCT coefficients are used directly to embed the watermark, which avoids a large of computation on full decoding and re-encoding process. Therefore, the proposed algorithm has a low complexity and a high extracting speed. Furthermore, thanks to the high sensitivity on initial values and the good randomness of the chaotic system, the very accurate localization is not only realized for the malicious tampers to JPEG images, but also discriminate whether the watermark is modified or not.(2) The typical F5 steganography algorithm is improved. In F5 steganography algorithm, the histogram of steganographic image using F5 method has same properties with original image, that is, the bigger the absolute value of DCT domain coefficient, the less it appears, the less decrement of it's arisen times. However, the corresponding value of each DCT domain coefficient is modified at all, moreover the statistical characteristic of block effect is also changed, which may be utilized by attacker for steganographic analysis. The statistical value of quantized DCT domain coefficients is utilized and the statistical characteristic of image is considered in our improved F5 steganography scheme. The coefficients are self-adaptive modified and the security of the improved scheme is enhanced.