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Sudoku Saves Photographers From Copyright Theft

A new watermarking technology based on Sudoku puzzles has been developed by computer scientists in Malaysia to thwart image thieves.

| September 10, 2013 | In the Lab

Asian Scientist (Sep. 10, 2013) - A new watermarking technology based on a system akin to the permutation rules used to solve the numeral puzzles known as Sudoku has been developed by computer scientists in Malaysia.

Images, photos and graphics on the web are easy pickings for plagiarists and those who might ignore copyright rules. Photographers and others often add a watermark to their images to reduce the risk of their images being lifted for use on others' sites without permission. However, those intent on leeching an image might simply crop the watermark in some cases.

With the proliferation of digital multimedia content on the internet, content owners and service providers commonly use digital watermarking to embed specific information into the media to be protected, such as a company's logo or product serial number.

Such information can later be extracted and used to detect forgery and unauthorized usage and to prove authenticity and provenance. Importantly, a digital watermark must not distort or disrupt display of the image when used in its rightful place and so needs to be imperceptible in use.

Now, researchers in Malaysia have used a valid 9x9 Sudoku solution - comprising a pixelated second image - to create a watermark so that it is evenly distributed within an image.

The system, described in a paper published in the International Journal of Grid and Utility Computing, resists attempts to "crop" the watermark in more than nine times out of ten cases.

The approach uses the permutations of rows and columns in Sudoku solutions to create and detect an invisible digital watermark that is overlaid on an image with a random distribution. If the image pirate crops part of the image, then the chances are that enough of the watermark will remain elsewhere in the image that the complete watermark might be retrievable provided that the precise and correct Sudoku solution is given.

The team's initial tests showed that with 81 9x9 Sudoku solutions they could defeat more than 94% of attempts at cropping. They are currently implementing 256 16x16 Sudoku, which they suggest will be even stronger.

The best "anti-cropping" watermarks used previously achieved only 75% resistance. Moreover, the Sudoku approach does not require investigators or the authorities to have access to the original image. Based on the relationship between full and partially recovered watermarks, the Sudoku approach will be able to discern whether a pirated image has the copyright owner's watermark.

The article can be found at: Khalid et al. (2013) Anti-Cropping Digital Image Watermarking Using Sudoku.


Source: Inderscience; Photo: Photos by Mavis/Flickr/CC.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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