Transcript of invisible watermarking
- 1. Priyanka Sharma
- 2. Introduction The process of embedding information into a
digital signal in a way that is difficult to remove. The signal may
be text, images, audio, video. The information is also carried in
the copy if the signal is copied.
- 3. Example:
- 4. GENERAL APPLICATIONS Copyright Protection To prove the
ownership of digital media.
- 5. Tamper proofing To find out if data was tampered. GENERAL
APPLICATIONS
- 6. Quality Assessment Degradation of Visual Quality Loss of
Visual Quality GENERAL APPLICATIONS
- 7. LIFE-CYCLE PHASES Attemp to extract watermark from signal
The marked signal is modified Produce watermarke d signal
- 8. CLASSIFICATION Digital watermarking techniques can be
classified in many ways : Visibility Robustness Perceptibility
Capacity Embedding method
- 9. VISIBILITY Visible Text or a logo which identifies the owner
of the media. Invisible Information is added as digital data to
audio, picture or video, but it cannot be perceived. May be a form
of Steganography.
- 10. ROBUSTNESS Robust Resisted a designated a class of
transformations. Against adversary based attack. (e.g. noise
addition to images) Used in copy protection application. Example:
Robust Private Spatial Watermarks
- 11. SPECIFIC WATERMARKING TECHNIQUES ON IMAGES
- 12. A very simple yet widely used technique for watermarking
images is to add a pattern on top of an existing image. Usually
this pattern is an image itself - a logo or something similar.
SIMPLE WATERMARKING
- 13. Bit Plane Slicing Examine the contribution of each bit For
PGM images each pixel is an eight bit value A bit plane is a binary
image representing each bit
- 14. Watermarking in the frequency domain involves selecting the
pixels to be modified based on the frequency of occurrence of that
particular pixel. Transform an image into the frequency domain. A
block-based DCT watermarking approach is implemented. An image is
first divided into blocks and DCT is performed on each block. The
watermark is then embedded by selectively modifying the middle-
frequency DCT coefficients. FREQUENCY-BASED TECHNIQUES
- 15. What is DCT ? Formally, the discrete cosine transform (DCT)
is a linear, invertible function F : RN -> RN (where R denotes
the set of real numbers), or equivalently an invertible N N square
matrix FREQUENCY-BASED TECHNIQUES
- 16. FREQUENCY-BASED TECHNIQUES
- 17. Discrete wavelet transform (DWT) The image is separated
into different resolution The original image is high-pass filtered,
yielding the three large images, each describing local changes
details in the original image It is then low-pass filtered and
downscaled, yielding an approximation image. This image is
high-pass filtered to produce the three smaller detail images. And
low-pass filtered to produce the final approximation image in the
upper-left. WAVELET WATERMARKING TECHNIQUES
- 18. WAVELET WATERMARKING TECHNIQUES
- 19. Embedding the watermark The host image and watermark are
transformed into wavelet domain. The transformed watermark
coefficients were embedded into those of host image at each
resolution level with a secret key. WAVELET WATERMARKING
TECHNIQUES
- 20. WAVELET WATERMARKING TECHNIQUES
- 21. Attacking Methods
- 22. Attacks on Watermark Transmission Lossy Other Compression
International TamperingsProcessing I I' Watermarked Object
Corrupted Object Transmission Typical Distortions and International
Tampering Geometrical Distortion Common Signal Figure provided by
Cox et al. [1].
- 23. Attacks on Watermark Transmission Lossy Other Compression
International TamperingsProcessing I I' Watermarked Object
Corrupted Object Transmission Typical Distortions and International
Tampering Geometrical Distortion Common Signal Irreversible Data
Loss Quality Degradation e.g. JPEG/MPEG
- 24. Attacks on Watermark Transmission Lossy Other Compression
International TamperingsProcessing I I' Watermarked Object
Corrupted Object Transmission Typical Distortions and International
Tampering Geometrical Distortion Common Signal Specific for
images/videos rotation, translation, scaling, and cropping
operations
- 25. Attacks on Watermark Transmission Lossy Other Compression
International TamperingsProcessing I I' Watermarked Object
Corrupted Object Transmission Typical Distortions and International
Tampering Geometrical Distortion Common Signal analog-to-digital,
digital-to-analog conversion, etc.
- 26. Attacks on Watermark Transmission Lossy Other Compression
International TamperingsProcessing I I' Watermarked Object
Corrupted Object Transmission Typical Distortions and International
Tampering Geometrical Distortion Common Signal Rewatermarking
- 27. Desired Characteristics of Invisible Watermarks 1.
Perceptually unnoticeable 2. Robust to common watermark attacks 3.
Quality degradation upon removal of watermarks 4. Unambiguously
identifies the owner of the digitized medium (audio, video, or
image).
- 28. Example (1) Original (2) Watermarked Differences of (1)
& (2)
- 29. Advantages & Disadvantages Advantages: Not noticeable
since the watermarks are spread out. Cant be removed without severe
quality degradation since watermarks are inserted at perceptually
significant regions. Disadvantages: Original watermark is required
in the extraction process.
- 30. References: [1]Ingemar J. Cox, et al., Secure Spread
Spectrum Watermarking for Multimedia, IEEE Trans. on Image
Processing, Vol. 6, No.12, Dec 1997, pp.1673-1687. [2] Saraju P.
Mohanty, Digital Watermarking: A Tutorial Review, Department of
Computer Science and Engineering, University of South Florida. [3]
Peter Meerwald, Digital Image Watermarking in the Wavelet Transform
Domain, Masters Thesis, Department of Scientific Computing,
University of Salzburg, Austria, January 2001. [4]
http://www.cosy.sbg.ac.at/~pmeerw/Watermarking/source/
- 31. The End