This presentation features definition of watermarking, its applications, methods to implement a visible and invisible watermark and the possible attacks on watermark.

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

15.  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

16. 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

17. FREQUENCY-BASED
TECHNIQUES

18. 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

19. WAVELET WATERMARKING
TECHNIQUES

20. 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

21. WAVELET WATERMARKING
TECHNIQUES

22. Attacking Methods

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
Figure provided by Cox et al. [1].

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
Irreversible Data Loss
Quality Degradation
e.g. JPEG/MPEG

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
Specific for images/videos
rotation, translation,
scaling, and cropping operations

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
analog-to-digital,
digital-to-analog
conversion, etc.

27. 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

28. 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).

29. Example
(1) Original (2) Watermarked Differences of
(1) & (2)

30. Advantages & Disadvantages
Advantages:
• Not noticeable since the watermarks are spread out.
• Can’t be removed without severe quality degradation
since watermarks are inserted at perceptually
significant regions.
Disadvantages:
• Original watermark is required in the extraction process.

31. 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”,
Master’s Thesis, Department of Scientific Computing, University of Salzburg,
Austria, January 2001.
[4] http://www.cosy.sbg.ac.at/~pmeerw/Watermarking/source/

32. The End