SECURE SPREAD SPECTRUMWATERMARKING FOR MULTIMEDIA

PRESENTERS : Mahhek Tahir ,Khizra Samad , Asma Shaheen

Ingemar J.Cox – Senior Member IEEEJoe Kilian – Member IEEEF.Thomson Leighton – Member IEEETalal Shamoon – Member IEEE

IEEE TRANSATIONS ON IMAGE PROCESSING , VOL 6 - DECEMBER 1997

Authors :

INTRODUCTION

This paper presents a secure algorithm for watermarking images, and a methodology for digital watermarking that may be generalized to audio, video and multimedia data. A watermark should be constructed as an independent and identically distributed Gussain random vector that is imperceptibly inserted in a spread spectrum like fashion into the perceptually most significant spectral components of data. It argue that insertion of a watermark under this rule makes the watermark robust to signal processing operations and common geometric transformation provided that the original image is available and it can be successfully registered against the transform image.

SPREAD SPECTRUM WATERMARK

The problem: how to insert watermark into most perceptually significant region of spectrum in a reliability protective manner.

To solve: this problem, frequency domain of the image or sound at hand is viewed as communication channel, and the mark is viewed as a signal that is transmitted through it

SECURE SPREAD SPECTRUM WATERMARKS FOR MULTIMEDIA Spread spectrum watermark based on DCT In order for a watermark to be robust, it

needs to be placed in the most significant part of the image.

The watermark will be composed of random numbers drawn from a Gaussian N(0,1) distribution

Inserting the watermark to the image. Inverse DCT

Image and Watermarked Image

METHODOLOGY

Embedding Detection and Comparison

EMBEDDINGYCrCb Y DC

T

Convert to vector

Descending order of DCT values

Reshape back

EXTRACTION

YCrCb Y DCT

Convert to vector

Descending order of DCT values

X =

COMPARISON

Watermark detected

Watermark not detected

EXPERIMENTS

Uniqueness of Watermark

Scaling

Print Xerox and Scan

Crop

Collision Attack

IMPLEMENTED EXPERIMENT - SCALING

Half size Double size

IMPLEMENTED EXPERIMENT - COPPING