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More and more digital services provide capability of distributing digital content to end-users through high-band networks, such as satellite systems. In such systems, Digital Right Management has become more and more important and is encountering great challenges. Digital watermarking is proposed as a possible solution for the digital copyright tracking and enforcement. The nature of DRM systems puts high requirements on the watermark's robustness, uniqueness, easy detection, accurate retrieval and convenient management. We have developed a series of feature-based watermarking algorithms for digital video for satellite transmission. In this paper, we will first describe a general secure digital content distribution system model and the requirements of watermark as one mechanism of DRM in digital content distribution applications. Then we will present a few feature-based digital watermarking methods in detail which are integrated with a dynamic watermarking schema to protect the digital content in a dynamic environment. For example, a watermark which is embedded in the DFT feature domain is invariant to rotation, scale and translation. Our proposed DFT domain watermarking schemas in which exploit the magnitude property of the DFT feature domain will allow both robust and easy watermark tracking and detection in the case of copyright infringement using cameras or camcorders. This DFT feature-based watermarking algorithm is able to tolerate large angle rotation and there is no need to search for possible rotated angles, which reduces the complexity of the watermark detection process and allows fast retrieval and easy management. We will then present a wavelet feature-based watermark algorithm for dynamic watermark key updates and key management, and we will conclude the paper with the summary, pointing our future research directions.
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