Department of Microelectronic Engineering, National Kaohsiung Marine University,Department of Information Management, Cheng-Shiu University,Department of Electronics Engineering, Cheng-Shiu University,
New methods for digital image watermarking based on the characteristics of vector quantization (VQ) are proposed. In contrast with the conventional watermark embedding algorithms to embed only one watermark at a time into the original source, we present several algorithms, including embedding one binary watermark, three binary watermarks, and the grey-level watermark, for copyright protection. The embedding and extraction processes are efficient for implementing with the conventional VQ techniques, and they can be accomplished in parallel to shorten the processing time. After embedding, the embedder would output one watermarked reconstruction image and secret keys associated with the embedded watermarks. These secret keys are then registered to the third party to preserve the ownership of the original source in order to prevent the attackers from inserting counterfeit watermarks. Simulation results show that under no attacks, the embedded watermarks could be perfectly extracted. If there are some intentional attacks such as VQ or JPEG compression, image cropping, spatial filtering, or geometric attacks in our simulation, all the watermarks could survive to protect the copyrights. Therefore, we are able to claim the robustness, usefulness, and ease of implementation of our algorithm.