The distribution and playback of digital images and other multimedia products are easily and fast done. Thus, its processing in order to achieve satisfactory copyright protection is a challenging problem for the research community. Encrypting the data only offers protection as long as the data remains encrypted, since once an authorized but fraudulent user decrypts it, nothing stops him from redistributing the data without having to worry about being caught. A watermarking scheme, which embeds some owner information (mark) into host images, is regarded as a possible solution to this problem. Nevertheless, digital watermarking is not strong enough to offer protection against illegal distributors. In this environment, digital fingerprinting techniques provide a good solution to dissuade illegal copying. To make such distribution systems work securely, the embedded marks in those system must be resistant to powerful attacks such as common image processing operations, lossy image compression, geometric transforms, combination addition of random noise (errors) and/or collusion attacks.
The work presented in this paper consists on the development of an empirical and portable JAVA platform where digital video (in MPEG2 format) can be protected against redistribution by dishonest users. The platform allows to verify at a practical level the strength properties of digital watermarking and fingerprinting marks. More precisely, it can be used to compare the performance of different watermarking algorithms (spread-spectrum and QIM). Moreover, it also offers the capability of embedding different digital fingerprinting codes, and verify its behaviour.
In this paper, the influence of the estimated perceptual mask from the watermarked image is analyzed with the purpose of decreasing the probability of error in detection. We concentrate on a well known perceptual model that has been applied to 8x8 block-wise DCT coefficients. A new procedure based on extracting the mask of the original image from the watermarked image is developed. A closed form solution is derived to estimate the coefficients of the original image. The mask in then computed from these coefficients. The model can also be recursively estimated. Results show that the proposed solution outperforms those solutions based on not considering at all the perceptual mask in detection or on applying the same procedure that was used when embedding the watermark but using the watermarked image instead of the original image.
This work concentrates on the problem of watermarking embedding and blind optimum detection in full-frame DCT domain using channel-state knowledge concepts. Minimum length sequences are used to embed the watermark information in the color components. Each chip of the sequence is inserted in a random-like fashion in those coefficients that ensure imperceptibility, robustness and a very low probability of error in detection. As it will be shown the power of the watermark has to be distributed among the symbols not only considering imperceptibility but also to improve the detection process. Furthermore, two solutions are proposed to improve the robustness against cropping operations.