Blind watermarking technique for topographic map data
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ORIGINAL PAPER
Blind watermarking technique for topographic map data Haowen Yan & Jonathan Li
Received: 9 June 2010 / Accepted: 20 September 2011 / Published online: 1 October 2011 # Società Italiana di Fotogrammetria e Topografia (SIFET) 2011
Abstract A blind watermarking technique for protecting topographic data from illegal use is proposed, taking into account four rules, i.e., usability, invisibility, robustness, and blindness. The technique firstly determines two feature layers and selects the key points from each layer as watermark embedding positions; then it shuffles the watermark and embeds the watermark in the two layers, respectively. To detect the watermark, a similar process for obtaining the feature layers and the key points in the watermark embedding process is carried out first; then the coordinates of the key points are detected to extract the embedded watermark; finally, the similarity degrees of the two versions of the extracted watermark is calculated, by which the conclusion on whether the data contains the watermark is made. Our experiments show that the technique can resist the attacks from data format change, random noise, similarity transformation, and data editing to some extent. Keywords Blind watermark . Topographic data . Key point . Similarity degree
Introduction Topographic map data is of great value because the acquisition of such data is a high-cost process. Consequently, it cannot be freely used without the owner’s permission. Nevertheless, the rapid development of computer comH. Yan (*) : J. Li Department of Geography & Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada e-mail: [email protected]
munication and Internet techniques make it easy to duplicate and distribute digital data via networks, which troubles the data owners for protecting the data from piracy. Digital watermarking provides a viable solution for this dilemma. A digital watermark is an imperceptible but identifiable digital signal or mode embedded in the host data, while it does not affect the host data’s usability (Ahmed 2004). There are four important rules that should be obeyed in any successful watermarking techniques (Cox and Miller 2002; Zhou et al. 2006). First of all, the embedded watermark should not degrade the quality of the host data. Secondly, the watermark should be perceptually invisible to data users to maintain its protective secrecy. Next, the technique must be robust enough to resist common data processing attacks and not be easily removable by illegal users, but only the data owners ought to be able to extract the watermark. Finally, the watermark should be blind if it is difficult for the data users to obtain the original data and the original watermark. Not only have the techniques of digital watermarking received a great deal of attention to ensure copyright protection for video, audio, and image data, but also it has become a hot issue in the community of geoscience for protecting vector geospatial data from piracy. Generally, there are two categories of w
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