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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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