[1] AN ANALYSIS OF DIGITAL WATERMARKING IN FREQUENCY DOMAIN

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. [2]

REQUIREMENTS Perceptual transparency Robustness Security Payload of watermark Oblivious and non-oblivious [3]

FREQUENCY DOMAIN WATERMARKING First transformed to frequency domain. Low frequency components are modified to contain text or signal. DCT DFT DWT STFT [4]

BLOCK DIAGRAM REPRESENTATION [5]

Two techniques for embedding Additive multiplicative I=original image, W=watermark, I=watermarked image, a=scaling factor. [6]

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 detection embedding casting [7]

DISCRETE FOURIER TRANSFORM Translation invariant Modulated DFT amplitude coefficients Makes watermark image content dependent [8]

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 [9]

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. [10]

APPLICATIONS Copyright protection Fingerprinting Copy protection Broadcast monitoring Indexing Medical safety [11]

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. [12]