1. Digital Watermarking By: Li Yang
Nov. 14 , 2003

2. Outline Overview of Digital Watermark Information Hiding
Watermarking Techniques
Applications of Watermarking
Attacks against Watermarking
Conclusion

3. Overview of Digital Watermark

4. What is Digital Watermark?
A set of secondary digital data embedded in the primary digital media (e.g. digital image, video, and audio).

5. Why Use Digital Watermark?
Ownership protection
Copy control
Authentication
Convey other information

6. Types of Watermarks working Domain Type of Document Human Perception
Spatial domain
Frequency Domain
Type of Document
Text
Image
Audio
Video
Invisible
Visible
Human Perception
Fragile
Robust
Private
Public
Application
Source Based
Destination Based

7. Desired Characteristics of Visible Watermarks
Be visible but not obscure the cover image
Spreads in a large or important area of the image in order to prevent its deletion by clipping
Difficult to remove the watermark

8. Desired Characteristics of Invisible Robust Watermarks
Neither be noticeable to the viewer nor should degrade the quality of the content
Must be robust to common signal distortions and must be resistant to various intentional tampering solely intended to remove the watermark
Retrieval of watermark should unambiguously identify the owner
Minimize the amount of pixel modification on high quality images and art works
Insertion of watermark should require little human intervention or labor

9. Desired Characteristics of Invisible Fragile Watermarks
Neither be noticeable to the viewer nor should degrade the quality of the content
Should be readily modified when image pixels values have been altered
Be secure: not be able to be recover or regenerate the watermark after the image is altered
For high quality images, the amount of individual pixel modification should be as small as possible

10. Desired Characteristics of Video Watermark
The presence of watermark should not cause any visible or audible effects on the playback of video
Should not affect the compressibility of the digital content
Should be detected with high degree of reliability. The probability of false detection should be extremely small
Be Robust to various intentional and unintentional attacks
The detection algorithm should be implemented in circuitry with small extra cost

11. Visible Digital Watermark

12. Invisible watermark

13. Information Hiding

14. History of Information Hiding
Steganography
The art and science of information hiding so that its presence can not be detected
Derived from Greek, means “Cover Writing”
Example:
Wax-covered tablets in ancient Greek
Messenger’s Tattoo
Invisible Ink in WWII
Null Cyphers (unencrypted message)
Digital watermarking & copyright

15. vs Digital Watermarking Steganography
Commercial Application of Steganography
Visible Digital Watermarking is not Steganography in definition
Add copyright information to message (can be visible)
The object of communication is the cover
Steganography
Theory behind the Digital Watermarking
Hide very existence of messages
The object of communication is the hidden messages vs

16. Note: Can Combine the two methods to obtain double protection.
Steganography
Cover Writing
steganography hides its message so it cannot be seen (conceals their very existence)
Steganography’s niche in security is to supplement cryptography, not replace it.
Cryptography
Secret Writing
cryptography scrambles a messages so it cannot be understood
vs.
Note: Can Combine the two methods to obtain double protection.

17. Watermarking Techniques

18. Basic Watermarking Model
Encoding,
Error correction,
modulation
Payload (P)(n bits)
E(w,I)=I’
Watermark
Embedding
Watermark(W)
Watermarked Image (I’)
Distortions
Key (K)
Cover Image (I)
Attacks
D(I,I’’)=W’
Watermark
Detection or
Extraction
Possible Corrupted marked Image (I’’) C W W’ c 1
C(W,W’)=1 or 0 x x

19. Techniques in Digital Watermarking
Spatial Domain Techniques
LSBs
Frequency Domain Techniques
DCT,FFT
Wavelet Domain Techniques
DWT
DCT(Discrete cosine transform): An algorithm in JPEG and MPEG compressions that connects data from the time domain into the frequency domain;
used to transform discrete data from the domain of time or space to the frequency domain, without analyzing the phase of the signal
Used principally in digital video compression systems such as MPEG-2, which are designed to remove unimportant or irrelevant ("redundant") information from television pictures, thus reducing the amount of data to be conveyed to the receiver. Redundant information could be, for example, the static background of a scene in which only a single person or object is moving, which only needs to be sent to the receiver once. The DCT is one mathematical technique for identifying and removing this redundant data without unduly degrading the picture quality.
Thi
Wavelet- A mathematical function useful in digital signal processing and image compression. In the internet communications, wavelet has been used to compress images to a greater extent than is generally possible with other methods such as JPEG or MPEG.
FFT(Fast Fourier Transform): a computationally efficient algorithm for implementing the Discrete Fourier Transform which is used to transform discrete data from the domain of time or space to the frequency domain
The fast Fourier transform is a technique for the rapid calculation of discrete Fourier transform of a function specified discretely at regular intervals. The technique makes use of a butterfly data structure.

20. Spatial Domain: Least-Significant-Bits
Manipulating Least-Significant-Bits(LSBs)
To hide information in the least-significant bits of a source image
Goal: hide image B in image A

21. LSB cont’d 24-bit Image example:
24-bit images use 3 bytes to represent a color value (8 bits = 1 byte)
1 pixel = ( )
red green blue
Embed secret data 101
1 pixels = ( )
Insert 101: ( )
red green blue
Embed image B in Image A by replacing the LSBs in A by Most Significant-Bits in ImageB

22. LSB Results - Original Pictures
To be embedded
Cover Page
Embedded Watermark

23. The first LSB replaced by first MSB
The 7 LSB replaced by the 7 MSB

24. LSB cont’d Simple and quick
Vulnerable to compression, cropping, and some image processing.
Can be used for Invisible Fragile Watermark(spatial domain watermarks is that picture cropping (a common operation of image editors) can be used to eliminate the watermark.)

25. Simple Comparisons Spatial Domain Watermarking
Simple and fast
Vulnerable to compression, cropping, and some image processing
Frequency Domain Watermarking
More robust than Spatial Domain Watermarking

26. Applications of Digital Watermarking

27. Application: Owner Identification
Enhance copyright protection
Indicate ownership originals
a visible watermark is in the video domain where CNN and other television networks place their translucent logo at the bottom right of the screen image

28. Application: Authentication
Detect alternation (Authentication)
Example
Epson’s digital camera with authentication watermark

29. Fragile digital watermark
Watermark extraction
PUEE
Tampered
PUEE

30. Application: Traitor Tracing
Digital Cinema
Cinema #1
Copy #1
With digital watermark #1
Film Server
Copy #2
With digital watermark #2
Cinema #2
Distribute Protected Films
Copy #n
With digital watermark #n
Cinema #n

31. Application:Broadcast Monitoring
Enables content owner and distributors to track the dissemination of their content
Embedded with a unique identifier , distributor, date, time information
Detectors are placed in major markets, where broadcasts are received and processed
The digital watermark is decoded and used to reference a database,resulting in reports to the owner or distributor that the content has been played in the given market, at a given time, and wether in a full-length.
A related db links the content identification to the content owner, and the distributor identification to the content aggregator, or service provider for broadcast video, as well as distributor or retailer for recorded media. Currently in radio, TV, future: multicast streams.

32. Watermarks Attacks

33. What is watermark attack ?
Intensionally obliterate watermarks
Passive Attack (Detection Attack)
Prove the existence of hidden data
Active Attack (Distortion Attack)
Forge / remove watermarks
Make watermarks useless

34. Why Study Attacks? Identify watermarking technique weakness
Propose improvement and enhancement

35. Types of Attacks Lossy Compression (JPEG, MPEG) Geometric Distortions
Save space but can not maintain the original images’ integrity
Geometric Distortions
Rotation, Scaling, and Cropping
Common Signal Processing
Addition noise
Other Intentional Attacks
Mosaic Attack
StirMark Attack

36. SDMI and its Public Challenge
Secure Digital Music Initiative
A consortium or forum aiming at protecting the playing, storing and distributing digital music
200+ companies/organizations worldwide
Recording industry, consumer electronics
Information/secures technology & Internet service providers
Pursue “robust & secure” audio watermarking or access and copy control

37. Conclusion
Digital watermarking is being used in many Industries such as the Digital Multimedia.
More enhancements are being under research around the World to provide us with higher information security in the near future.

38. Any Questions?