The copyright and protection of innovation is not only restricted to audio, video, books and software, it can sometimes concern the images. Protecting images is not obvious, considering the wide spread of images especially after the appearance of Internet. Images are used in different areas (products, banners, logos …etc.) and sometimes it’s crucial to protect images from illegal usage same as audio or video contents. Images can also be used in more critical areas such marking a currency or signing a certificate. Those, it is important to add a security layer to the image and make sure that it’s reproduction won’t provide the same amount of relevant data. I am considering here the usage of stamps or marking the currency, we have all heard about illegal or fraudulent currency re-production which caused the lost of millions if not more.
Digital watermarking is defined as inserted bits into a digital image, audio or video file that identify the copyright information; the digital watermarking is intended to be totally invisible unlike the printed ones, bits are scattered in different areas of the digital file in such a way that they cannot be identified and reproduced, otherwise the whole goal of watermarking is compromised.
(Cox et.al, 2007) defined watermarking as “the practice of imperceptibly altering a work to embed a message about that work”. Another definition which confirms the application and area of usa of watermarking has been provided in the 3rd international workshop, by Cox and Kalker as “data hiding as promising technic for information assurance” (Cox et.al, 2005).
Depending on the importance of image’s support, watermarking technics might vary, from the casual inspection to the more advanced ones which might require powerful method to investigate and analyse their authenticity, different companies have applied watermarking technics to mark the authenticity of their products and avoid illegal re-production. We can think of different technics and implementation of watermarking to digital contents, but considering the images, the most important and may be the reliable technic is the steganography, which is the art of secretly hiding piece of data into an innocuous image (which will not alter the visual appearance of the image). Bits about the authors or the authenticity of images could be inserted into specific areas of the image in order to avoid total altering of this last and keeps it look the same as the original (without watermarking) (Barni & Bartolini, 2004).
Here is an example of steganography application using White Noise Storm (the first software tested and approved for its efficiency in steganography)
Figure 1: Image before and after applying steganography (Shih, 2004).
Steganography can be used either for watermarking or sending confidential messages throw images, the sender and receiver should be aware of the embedding method and encryption (if applicable) used for data insertion. The applications of steganography can be enormous, and in 2001 first rumors about terrorists using steganography to pass crucial message throw ‘apparently’ innocent images appeared. The usage of this technic can be isolated, means integrating a simple file with an image, this can be done without any software, just using the OS operations. I tried to embed test1.txt into the image called image1.jpg simply using the command line “Copy /b image1.jpg+test1.txt final1.jpg”, the final1.jpg is a normal image that I could open and preview, both image1 and final1 looks the same, but if I open final1.jpg with a notepad, I could see at the bottom lines the original text inserted from test1.txt.
Other advanced tools could provide more powerful technics and additional security layer, by encrypting the inserted text.
– Ingemar Cox, Matthew Miller, Jeffrey Bloom, Jessica Fridrich, Ton Kalker (2007). Digital Watermarking and Steganography, The Morgan Kaufmann Series in Multimedia Information and Systems. Morgan Kaufmann, 2007. ISBN: 9780080555805
– Ingemar J. Cox, Ton Kalker, Heung-Kyu Lee (2005). Digital Watermarking: Third International Workshop, IWDW 2004, Seoul, Korea, October 30 – November 1, 2004, Revised Selected Papers. Springer, 2005. ISBN: 9783540248392.
– Mauro Barni, Franco Bartolini (2004). Watermarking Systems Engineering: Enabling Digital Assets Security and Other Applications. CRC Press, 2004. ISBN: 9780824750916.
– Frank Y. Shih (2004). Digital watermarking and steganography: fundamentals and techniques. CRC Press, 2008. ISBN: 9781420047578