secure spread spectrum
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TRANSCRIPT
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