2. Contents
What is DWM ?
Applications
Classification
Working
Attacks
Advantages and Disadvantages
Techniques
3. Digital Watermarking
We add ‘Visible’ or ‘Invisible’ structure called ‘Watermarks’
to digital media. The process of adding watermarks is called
‘Digital Watermarking’.
Adaptation of Paper Watermarks.
Describes methods and technologies that allow to hide/embed
various types of information to digital document.
In general Digital Watermarking means “Author Signature”.
5. Classification
Perceptible Watermarks and Imperceptible Watermarks
Robust Watermarks and Fragile Watermarks
Private Watermarks and Public Watermarks
6. Classification (contd.)
Perceptible Watermarks and Imperceptible Watermarks
Perceptible Watermarks are visible to human eye
Useful for primary Applications.
E.g. of watermark in a video
E.g.. Of watermark in a image
Imperceptible watermarks are Invisible to human eye.
Used in the places where the content being watermarked must
appear in unchanged form.
Remains hidden in content and can be detected only by authorized
agencies.
7. Classification (contd.)
Robust Watermarks and Fragile Watermarks
Degree to which watermarks can withstand any modification of any
type (Accidental or Intentional ).
Robust Watermarks are difficult to remove from the object in which
they are embedded.
Perceptible Watermarks are more Robust.
Fragile Watermarks can be easily destroyed by any attempt to
temper with them.
8. Classification (contd.)
Private Watermarks and Public Watermarks
Private Watermark requires at least original data to recover
watermark.
They are also known as ‘Secure Watermarks’.
Public Watermark requires neither original data nor embedded
watermark to recover watermark information.
9. Working
Typical DWM system consists of mainly 3 parts / process
Watermark Insertion
Watermark Extraction
Watermark Detection
10. A Generic Watermarking System
Cover Work
Watermarked Detected
Watermark Watermark
Watermark
Embedder Work Detector
Message
Watermark Message
11. User Key
Watermarked
Input Image Watermark Insertion
Image
Watermark
User Key
Extracted
Watermark Extraction
Watermarked Watermark
Image
User Key
Watermarked Decision
Watermark Detection
Image ( Yes or No )
Specified ID
( Watermark )
12. General Digital Watermarking Process
(a) Watermark Embedding
Digital Watermark
0101 …. . . .. . .
Original Data Watermarked Data
Embedding
Algorithm 0101 …. .
Distribution
13. General Digital Watermarking Process (contd.)
(b) Watermark Extraction
Original
Data
Watermarked Data
Extracted Watermark
Extraction
0101 …. . 0101 …. . . .. . .
Algorithm
17. Attacks (contd.)
Geometric Attack
Subtractive Attack involves ‘removing’ the mark by cropping or
digital editing.
Distortive Attack attempts to make some ‘uniform distortive
changes’ in the image such that mark becomes ‘unrecognizable’.
18. Attacks (contd.)
Forgery Attack
Also known as ‘Additive Attack’.
The attacker include his/her own watermark overlaying the original
image and marking the content as their own.
19. Advantages
Uniquely identifies the author of copyrighted work.
Implementation on PC platform is possible.
Embedding watermark is easy
Image Tampering Detection
20. Disadvantages
Watermarking doesn’t prevent image copying but we can track
down and detect ownership of copied images.
Watermarks vanishes if someone manipulates the image.
Resizing, compressing images from one file type to another
may diminish the watermark and it becomes unreadable.
21. DWM Techniques
Image Domain Encoding
Also known as Least Significant Bit (LSB).
LSB works by reducing the no of colors used by image itself and
uses the rest of the palette to encode the information.
If the colors in an image are less then more information can be
stored without quality loss.
