Digital Watermark Essay

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We are living in the era of information where billions of bits of data is created in every fraction of a second and with the advent of internet, creation and delivery of digital data (images, video and audio files, digital repositories, web publishing) has spread like fire. With this copying a digital data is easy and fast too so, issues like, copyright protection and proving ownership, arises this causes digital documents to be duplicated, modified and distributed easily. For this reason, researchers have started looking at techniques that allow for copy control of digital multimedia data and enable copyright enforcement. It was realized that common cryptographic methods are not sufficient: cryptography only protects the work during transmission and distribution; no protection is provided after the work has been decrypted and all work must eventually be decrypted if consumers are to enjoy the photograph, music, or movie. Steganography is not applicable either. In steganography, the message itself is usually of value and must be protected through clever hiding techniques; here the media for hiding a message is not of value. Digital watermark is proposed as an approach to solve this problem [1]. A watermark, a secret imperceptible signal, is embedded into the original data in such a way that it remains present as long as the perceptible quality of the content is at an acceptable level.The digital watermark has the specialty that even if it is copied it remains intact to the cover work. So copyrights of data can be proving when watermark is extracted and tested. This makes it very difficult for hackers to remove or change watermark.

Any watermarking technique [3] has to be evaluated to judge its performance .Three factors, as give...

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...erent methods of JND estimation, and study of DCT, SVD and DWT domain is given. Chapter 3 describes problem identification in existence watermarking techniques. Chapter 4 describe a embedding and extracting process of color image digital watermarking based on hybrid DWT-DCT-SVD technique using Human Visual System Model . Chapter 5 analyses the proposed results, demonstrate that the extracted watermark is imperceptible and robust by calculating PSNR, MSE and correlation between extracted watermarks with original. Furthermore, result demonstrates that our scheme is also resistant to the following attacks: counterfeit, collusion or by adding different noise, and image rotation, while almost all robust watermarking schemes are vulnerable to these attacks. Finally Chapter 6 gives a concluding remark that is specified. Possible extensions and improvements are discussed.

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