EE 5359 FALL 2010 DIGITAL WATERMARKING Abrar Ahmed Syed 1000614216 abrar syed mavs uta edu Under the guidance of Dr K R Rao KEY POINTS What is digital watermarking Why do we need digital watermarking What are the different types of watermarking What are its characteristics and requirements What are the different techniques and schemes used to watermark What are the different types of attacks it is susceptible to What are the ways of counter attacking a watermarking attack PROJECT GOAL The goal of this project can be broadly classified into six steps 1 Implementing two forms of watermarking techniquesVisible Invisible 2 Implementing an attack on the visible watermark image For the sake of this project adding noise is used as a means of attack 3 The watermarked image with noise added to it is then compressed and decompressed using JPEG compression technique This acts as another form of attack 4 The next step is to remove the noise from the decompressed watermarked image 5 Next seperating both the base and the watermark images from the concatenated watermarked image 6 Finally a benchmarking of original and recovered images is done based on PSNR SSIM and SSIM map DIGITAL WATERMARKING As advances are made in field of communication it became necessary to cipher and decipher This led to discovery of stenography and watermarking Stenography Hiding information over cover Watermarking Hiding information related to cover Embedding is done by manipulating contents in the signal itself and is made imperceptible DIGITAL WATERMARKING Embedding a digital signal audio video or image with information which cannot be removed easily is called digital watermarking Figure 1 shows the block diagram of embedding digital watermark Signal Attacking function Signal Any embedding function E Detecting and retrieving function Figure 1 Block diagram of embedding digital watermark EMBEDDING For example sake figure 2 shows the block diagram for audio watermark encoding Framing Spectral analysis Original signal Watermarked signal Watermark addition DC Carrier removal Figure 2 Encoding block diagram of audio watermarking technique RETREIVING For example sake figure 3 shows the block diagram of audio watermark decoding Watermarked signal Framing Original signal Spectral analysis Watermark processing Figure 3 Decoding block diagram of audio watermarking APPLICATIONS Ownership assertion Watermarking is used to establish ownership of content Fingerprinting Watermarking is used to avoid illegal distribution of media Authentication and integrity verification Content which is protected by key verification should not be accessible without authentication Content labeling Bits embedded in data giving extra information Usage control To limit copies creation of copyrighted data by blocking using watermark Content protection Visible watermark block is used for this purpose No universal technique to satisfy all of these Source 23 N Memo and P W Wong Protecting digital media content Communications of the ACM Vol 41 pp 35 43 1998 CLASSIFICATIONS Visible Invisible Robust Fragile Public and Private Capacity Perceptibility Embedding techniques Spread spectrum Quantization Amplitude modification TECHNIQUES OR SCHEMES OF WATERMARKING Spatial domain techniques Frequency domain techniques Least significant bit coding LSB Predictive coding schemes Correlation based techniques Patchwork techniques Discrete cosine transform DCT based technique Wavelet transform based watermarking Simple watermarking ATTACKS Basic Robustness Presentation Interpretation Implementation Removal Geometrical Cryptographic Active Passive Forgery Collusion Distortive COUNTER ATTACKS Power spectrum condition Noise visiblity function PROJECT PART 1 INVISIBLE From slide 3 the part 1 of this project is Implementing two forms of watermarking techniques Visible Invisible Invisible Watermarking An image A will be selected as base image An image B will be selected as watermark image The MSB of B will be read and these will be written on the LSB of A Thus A will be watermarked with B resulting in a combined image C C therefore will now contain an image A which has its LSB s replaced with the MSBs of B The technique used will be LSB technique which is a form of spatial domain technique PART 1 INVISIBLE Image A and watermark B are read MSBs of B will be are transferred to the LSBs of A Watermarked image C contains MSBs of B and LSBs of A Figure 4 Block diagram of invisible watermarking PART 1 INVISIBLE PROGRAM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 base image input Enter base image file name with extension s watermark image input Enter watermark image file name with extension s base imread base image watermark imread watermark image figure 1 imshow base title Original Image Cover Image Base Image figure 2 imshow watermark title Watermark Image Image which will hide in cover image base double base watermark double watermark bits 1 watermark shifted bitshift watermark 8 bits for i 1 bits base bitset base i 0 End watermarked image uint8 base watermark shifted figure 3 imshow watermarked image title Watermarked Image Final watermarked image imwrite watermarked image invsible watermarked image bmp Save modified image PART 1 INVISIBLE EXPLANATION s PART 1 INVISIBLE EXPLANATION PART 1 INVISIBLE EXPLANATION PART 1 INVISIBLE EXPLANATION PART 1 INVISIBLE RESULT Figure 5 Base Image Figure 6 Watermark Image Figure 7 Watermarked Image PROJECT PART 1 VISIBLE From slide 3 the part 1 of this project is Implementing two forms of watermarking techniques Visible Invisible Visible Watermarking A raw bitmap base image A will be selected from the set of standard test images A raw bitmap watermark image B will be selected from the set of standard test images Now both images A and B will be concatenated to get a watermarked image D D therefore will now contain the base image A and the watermark image B This technique is used to add visible watermark in the image PART 1 VISIBLE Image A and watermark B are read and displayed Watermarked image thus obtained is displayed Zero matrix initialized with dimensions 512x512 Process repeated for all 256 column of base and watermark images respectively The first column of pixels of the zero matrix is filled with the first column of pixels of base image The second column of pixels of the zero matrix is filled with the second column of pixels of watermark image Figure 8 Block diagram of visible watermarking technique PART 1 VISIBLE PROGRAM 1
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