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Sudoku Protects Photographers from Copyright Pirates

SudokuImages, photos and graphics on the Internet are very easy to be picked and used by plagiarists and those who may ignore copyright rules. Photographers and others usually add a watermark to their works to reduce the risk of their images being lifted for use by others without permission. However, in some cases, those intent on leeching an image can simply crop the watermark.

With the proliferation of digital multimedia contents on the web, content creators and service providers need robust techniques to protect their copyright. Digital watermarking is a commonly used method to embed specific information into the media to be protected, for example, you can add a company’s logo or product serial number into the image. Such information can be extracted later and used to detect forgery or unauthorized usage as well as to prove provenance and authenticity. More importantly, digital watermark should not disrupt or distort the display of the original image, thus it has to be used in rightful place and be imperceptible in use.

Recently, Shamsul Khalid and co-workers from the Universiti Tun Hussein Onn Malasia, explain how a valid 9 x 9 Sudoku solution – comprising a pixelated second image – can be used to create the watermark. The water mark is evenly distributed within an image and hence, it resists automated cropping and noise additions by bots or other software that can scrape images from the web and add them in an illicit database for unlicensed distribution or resale to other sites that want to store a range of unique images but don’t wish to pay for the privilege. This method utilizes the permutations of columns and rows in Sudoku solutions to generate and detect an invisible digital watermark that is overlaid on an image with random distribution. Even if the image pirates crop some parts of the image, chances are that sufficient of the watermark will remain elsewhere in the image so that the complete watermark can be retrievable provided that the correct and precise Sudoku solution is provided.

The initial tests from the group demonstrated that with 81 9 x 9 Sudoku solutions they were able to defeat more than 94 percent of cropping attempts. Currently, the researchers are implementing a stronger solution – a 256 16 x 16 Sudoku while in comparison, the previously best anti-cropping watermark only achieved 75 percent resistance. In addition, the Sudoku method doesn’t require investigators or the authorities to have access to the original works. Based on the relationship between partially recovered and full watermarks, this approach will be able to discern whether a pirated image has the watermark from the copyright owner or not.

Source: Eurekalert!