HW10_solution - EE4414 Multimedia Communication System II,...

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EE4414 Multimedia Communication System II, Fall 2005, Yao Wang Homework 10 Solution (Data Hiding, Watermarking, Steganography) ___________________________________________________________________________________ Review questions 1. Describe the differences between data hiding, watermarking, and steganography. What are their respective applications and requirements? Is one a special case of another? Data hiding refers to a technique that embeds data in a cover media. Watermarking is a special type of data hiding, where the embedded data carries information that can be used to prove the ownership or integrity of the cover media. Steganography is also another special type of data hiding, wherein the embedded data is a secrete message that is typically unrelated to the cover media. The cover media can be chosen randomly or to facilitate the conveyance of the secrete message. Because multimedia documents (audio or image or video) have a lot of redundancy, these documents are often chosen as the cover media for embedding secret messages (which themselves could be an image or plain text or encrypted text). With watermark, the embedding algorithm should be designed so that the embedded watermark is hard to remove (except for applications using fragile watermark). On the other hand, for steganography, this is usually not a concern. 2. The following are some possible applications of watermarking. Describe what they are and their requirements. a. Ownership assertion b. Fingerprinting c. Copy prevention and control d. Detection of unauthorized alteration (authenticate integrity of the data) Ownership assertion: embedded watermark is used to proof the ownership of the cover media. The owner or its trusted delegates should be able to detect the presence of the watermark (with the help of the original and the secret key used to generate the watermark) even if the watermarked document is subjected to accidental or malicious alterations (such as compress/decompress, cropping, printing/scanning, shrink and then zoom). Fingerprinting: a different watermark is embedded to each sold copy of the original media. If this
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This note was uploaded on 01/22/2012 for the course EE 4414 taught by Professor Wang during the Fall '07 term at NYU Poly.

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HW10_solution - EE4414 Multimedia Communication System II,...

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