Digital Watermarking-Interim Report (EE5359: Multimedia processing)

Under the Guidance of Dr. K. R. Rao

Submitted by: Ehsan Syed

1000671971seaquadri@gmail.com

The University of Texas at Arlington – Spring 2011

Introduction

• Digital watermarking is based on the science of steganography [1] or data hiding. Steganography comes from the Greek meaning ‘covered writing’.

• Steganography is defined as the practice of undetectably altering a work to embed a secret message. It is an area of research of communicating in a hidden manner.

Introduction..

• Steganography and watermarking rely on imperfections of human senses.

• The human eye has a limited dynamic range so low quality images can be hidden within high quality images [2].

Basic Principle

There are three main stages in the watermarking process [3]:

• generation and embedding • attacks • retrieval/detection

Generation and Embedding

• Generation of watermarks is an important stage of the process. Watermarks contain information that must be unique otherwise the owner cannot be uniquely identified.

• In embedding, an algorithm accepts the host and the data to be embedded and produces a watermarked signal. Various algorithms have been developed so far [4-13].

Attacks

• The watermarked signal is then transmitted or stored, usually transmitted to another person

• If this person makes a modification, this is called an attack. There are many possible attacks.

Retrieval/Detection

• Detection is an algorithm which is applied to the attacked signal to attempt to extract the watermark from it.

• If the signal was not modified during transmission, then the watermark is still present and it can be extracted.

Block diagram

Fig.1: Basic block diagram of digital watermarking

Types of watermarking

There are mainly three types of watermarking [14]:

• Visible watermarking• Invisible watermarking• Dual watermarking

Techniques of watermarking

There are two major techniques of watermarking [15]:

• Spatial domain: slightly modifies the pixels of one or two randomly selected subsets of an image

• Frequency domain: this technique is also called transform domain. Values of certain frequencies are altered from their original.

Project Goals

The goals of this project are:• to embed a watermark into an image using

LSB technique• compressing the watermarked image• decompressing it • extract the watermark from the image

Program for making watermarked images• host_image = input('Enter the host image file name with extension : ', 's') ;• wmrk_image = input('Enter watermark image file name with extension: ', 's'); • host = imread(host_image);• wmrk = imread(wmrk_image);• figure(1)• imshow(host,[])• title('Host Image')• figure(2)• imshow(wmrk,[])• title('Watermark Image')• host=double(host);• wmrk=double(wmrk);• bits=3; • wmrk_shifted=bitshift(wmrk,-(8-bits)); • for i=1:bits• host=bitset(host,i,0);• end • watermarked_image = uint8(host+wmrk_shifted); • figure(3)• imshow(watermarked_image,[])• title('Watermarked Image')

Host Image

Results so far

• Watermarked images are created • JPEG compression and decompression will be

done in the final report• Extraction of the watermark from the

watermarked image will be done in the final report

Watermark Image

Visible Watermarked image

Invisible Watermarked image

References1. L.M. Marnel et al, “Spread spectrum image steganography”, IEEE Transactions on Image Processing, pp 1075-

1083, Aug 19992. J.J.K O-Ruanaidh et al, “Watermarking digital images for copyright protection, IEE Proceedings in Vision”, Image

and Signal Processing, pp250-256, Aug 19963. I. J. Cox and M. L. Miller, “A review of watermarking and the importance of perceptual modeling”, Proceedings

of Electronic Imaging, February 19974. H.J. Wang et al, “Wavelet based digital image watermarking “, Optics Express, PP 491-496, Dec 19985. P.-T.Yu et al, “ Digital watermarking based on neural networks for color images”, Signal Processing, PP 663-671,

Mar 20016. J. O-Ruanaidh et al, “Cryptographic copyright protection for digital images based on watermarking techniques”,

Theoretical Computer Science, pp 117-142, Sep 19997. C. Fornaro and A.Sanna, “Public key watermarking for authentication of CSG models”, Computer-Aided design,

pp 727-735, Oct 20008. M. Barni et al, “Copyright protection of digital images by embedded unperceivable marks”, Image and Vision

Computing, pp897-906, Aug 19989. J.R. Hernandez et al, “Improving the performance of spatial watermarking of images using channel coding”,

Signal Processing, pp 1261-1279, July 200010. S. Pereira et al, “Optimal transform domain watermark embedding via linear programming”, Signal Processing,

pp 1251-1260, July 200111. F. Perez-Gonzalez et al, “Approaching the capacity limit in image watermarking: a perspective on coding

techniques for data hiding applications”, Signal Processing, pp 1215-1238, July 200112. R. Baitello et al, “From watermark detection to watermark decoding: a PPM approach”, Signal Processing, pp

1261-1271 , July 200113. M. Barni et al, “A DCT-domain system for robust image watermarking”, Signal Processing, pp 357-372, May

199814. S. P. Mohanty, et al, “A Dual Watermarking Technique for images”, Proceedings of the seventh ACM

international conference on Multimedia, pp 49-51, 1999 15. F. Hartung and M. Kutter, “Multimedia watermarking techniques”, Proceedings of the IEEE, Vol. 87, No. 7, pp

1079 – 1107, July 1999