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AN ANALYSIS OF DIGITAL WATERMARKING IN FREQUENCY DOMAIN
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DIGITAL WATERMARKING Form of data hiding or steganography. Hides the message, so cannot be seen. Maintains privacy and protects data from other
viewers like hackers. It may include hiding of numbers, logo or
signature in the form of signal, image or video.
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REQUIREMENTS
Perceptual transparency
Robustness
Security
Payload of watermark
Oblivious and non-oblivious
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FREQUENCY DOMAIN WATERMARKING
First transformed to frequency domain.Low frequency components are modified to
contain text or signal.DCTDFTDWTSTFT
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BLOCK DIAGRAM REPRESENTATION
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Two techniques for embeddingAdditivemultiplicative
I=original image, W=watermark, I’=watermarked image, a=scaling factor.
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)**(' WIaII
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DISCRETE COSINE TRANSFORM
Real domain transform Represents image as coefficient of different
frequencies of cosines. Forms the basis of the JPEG image compression
algorithm. Watermark
detectionembedding casting
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DISCRETE FOURIER TRANSFORM
Translation invariant
Modulated DFT amplitude coefficients
Makes watermark image content dependent
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)),(1(|),(||),(| vuWkvuDFTvuWDFT
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DISCRETE WAVELET TRANSFORM
Used when a signal is being sampled like digital signal or image processing.
Provides sufficient information for both analysis and synthesis of signal.
Reduction in computation time.
Separates image into sub images
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SHORT TIME FOURIER TRANSFORM
The signal is divided into small stationary segments.
Used to acquire frequency representation of the actual frames.
Precision determined by size of window.
Not a flexible approach.
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APPLICATIONSCopyright protection
Fingerprinting
Copy protection
Broadcast monitoring
Indexing
Medical safety
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CONCLUSION We can work for digital protection by the
help of certain laws.Time complexity of watermark signal can be
enhanced by extending the length of watermark.
Can be used in any frequency domain that involves quantization and transformation.
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