Today, the Internet is a worldwide broadcasting capability, a mechanism for information dissemination and a medium for collaboration and interaction between individuals and their computers without regard for geographic location. With the rapid evolution of digital networks, digital libraries and World Wide Web (WWW) services, the convenient broadcasting or exposition of digital products on the global network leads easily to illegal copying, modifying and retransmission. The Internet has spawned many copyright issues involving multimedia content distribution. Let’s say an owner would like to sell or distribute a work to legal/registered users only. If the work were subsequently copied/redistributed illegally, how could the owner find who was responsible? Cryptographic techniques provide an effective solution for securing the delivery process and controlling the use of the contents that an user has obtained. However, with flawless transmission through the network, the contents after decryption are exactly the same as the original data. The contents can be copied perfectly infinite times. A user can also manipulate the contents. Digital watermarking (Arnold, Schmucker, & Wolthusen, 2003; Katzenbeisser & Petitcolas, 2000) offers a way to counter copyright piracy on global networks that are not solvable by cryptography. It provides proof and tracking capabilities to illegal copying and distribution of multimedia information. Most existing digital watermarking schemes are based on some assumptions for watermark detection and extraction. Some schemes require the previous knowledge of watermark locations, strengths or some thresholds. In some algorithms, the watermark is estimated with the help of the original watermark information. To ensure the robustness and invisibility of the watermark, the optimum embedding locations are usually different for different images. For a large image database, it could be a disadvantage to require watermark location and strength information for watermark detection and extraction. A large amount of information then needs to be stored. On the Internet, an owner would like to distribute multimedia data by signing different watermarks to different users in order to prevent illegal redistribution of the data by a legal user. In this scenario, watermark detection and extraction algorithms requiring information of either watermark embedding locations and strengths or the original watermark should fail, since one does not know exactly which watermark is embedded in a particular copy of the watermarked image. To this end, we present a new blind watermarking scheme (Yu, Sattar, & Ma, 2002; Yu & Sattar, 2003, 2005) based on Independent Component Analysis (ICA) (Hyvarinen, 1999; Hyvärinen & Oja, 1999; Lee, 1998) for color images, which can overcome existing problems of watermark detection and extraction as described above. The new ICA-based scheme is found to be efficient in the application of data tracking/tracing for multimedia distribution through the Internet against other digital watermarking schemes. By adopting this ICA-based watermarking scheme, an efficient multimedia distribution framework/protocol for copyright protection can be accomplished. This article is organized as follows: The watermark embedding and extraction algorithms for color image watermarking using the new ICA-based scheme are presented next, followed by a discussion and comments on the results, security issues, summary and future works.
An Improvement Technique Based on Structural Similarity Thresholding for Digital Watermarking