Digitalwatermarking
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Transcript of Digitalwatermarking
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DIGITAL WATERMARKING
Sejal Visawadia
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Watermark
“ Watermarking can be considered as a special technique
of steganography where one message is embedded in another and the two messages are related to each other in some way. “
Example :-
The presence of specific patterns in currency notes which are visible only when the note is held to light is a well known example for watermark.
What is Watermarking?
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Example of a conventional watermark
Courtesy of Blue Spike, Inc.
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Digital Watermark
“ Digital watermarking is similar to watermarking physical objects, except that the watermarking technique is used for digital content instead of physical objects.”
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Digital Watermark (Cont..)In digital watermarking a low-energy
signal is imperceptibly embedded in another signal. The low-energy signal is called watermark.
The main signal in which the watermark is embedded is referred to as cover signal since it covers the watermark.
An entity called watermark key used for embedding and detecting watermark signal
Watermark key is private
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Behind The Technology
Sending Side …
Watermark Embedding process Water mark Original message Key Water marked image
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Behind The Technology
Watermark retrieval process Water marked image KeyConfidential message
Receiving Side …
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The Overall SystemThe Technology
Roars…
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Importance Of Digital Watermarking
©Copyright Information©On-line music industry©News gathering using digital
cameras
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Types of Digital Watermarking
Robust & Fragile Watermarking
Visible & Invisible Watermarking
Public & Private Watermarking Asymmetric & Symmetric
Watermarking Steganograhic & Non-
Steganographic watermarking
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Robust & Fragile Watermarking
Robust Watermarking:-Modification of watermarked content will not affect watermark
Fragile Watermarking:-Watermark get destroyed when watermarked content is modified or tampered with
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Visible & Invisible Watermarking
On Visible watermarking, contents are visible
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Visible & Invisible Watermarking (Cont..) Invisible watermarking are not
viewed on just looking
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Public & Private Watermarking• Public Watermarking Users of content are authorized to
detect watermark
• Private Watermarking Users not authorized to detect
watermark
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Asymmetric & Symmetric watermarking
In Asymmetric watermarking different keys used for embedding and detecting watermark
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Asymmetric & Symmetric watermarking (Cont..)
In symmetric watermarking same keys are used for embedding and detecting watermarks
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Steganographic & Non-Steganographic Watermarking
Steganographic Watermarking User unaware of the presence of a
watermark eg:-Used in finger printing
applicationsNon-Steganographic WM:- User aware of the presence of a
watermark.
e.g.:-User to detect piracy
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Digital Watermarking Techniques
LSB WatermarkingColor Separation TechniqueBit Stream WatermarkingWord Space Coding, Line Space
Coding &Character Coding
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LSB Watermarking
Lower order bits of selected pixels in the image are used to store watermarks
Replacing lower order bits of each pixel with higher order bit of different image
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Color Separation Technique
Watermark appears only in one of the color bands
Used to watermark in still imagesCan be extended to moving
images
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Bit Stream Watermarking
Used in audio watermarking
Data is directly inserted into compressed audio files
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Word Space Coding, Line Space Coding & Character Coding
Used for watermarking in text documents
In word space coding, the spaces between words are altered to embed watermark code. In line space coding the space between the lines are altered and in character coding some of the characters are imperceptibly modified (i.e., made larger, serifs enhanced, etc).
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Applications of Digital Watermarking
Copy ProtectionContent AuthenticationCopyright ProtectionMetadata Tagging
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Copy Protection
It limits the access to copyrighted material and inhibit the copy process
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Content Authentication
Robust watermarks are used in this area
Example:-A photographic information that may be presented as evidence in court. Since digital images can be easily manipulated, there is a need to provide proof that an image has not been altered.
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Content Authentication
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Copyright Protection
One of the main application
Embedding watermarks in digital photographs
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Metadata Tagging
Watermarks convey object specific information to users of the object.
Used to attach patient identification data to medical images, or to highlight regions of diagnostic significance.
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Attacks to Digital Watermarking
Stirmark Mosaic Attack
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Stirmark
It is tool developed to test the robustness of image marking system
Stirmark is commonly produced by printers and scanners
IBM researchers have recently announced a technique that defeats the stir mark attack.
Detects and measures the geometric distortions in images, and removes the distortion to restore image geometry
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Stirmark Example
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Mosaic Attack
Use of a web crawlerDividing into sub images with
rendition instructionsBrowser will be rearranging the sub
images to appear as the originalSub images will be sufficiently small
that no single image on its own will contain a recognizable mark.
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Mosaic Attack Example
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ConclusionDRM systems and content management are
important for protection of rights of digital multimedia creations that are distributed on the Internet. Digital watermarking is an effective technique for embedding rights information in digital multimedia data.
Digital watermark technology can be used in consumer electronic devices like digital still camera, digital video camera, DVD players, MP3 players, etc., for various applications like providing controlled access, preventing illegal replication and watermark embedding
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Conclusion (Contd..)
Digital information can easily be disseminated and copied via global networks.
The future of digital watermarking relies on setting standards and creating applications so that creators of digital content can easily implement it.
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THANK YOU