The document discusses information hiding, focusing on digital watermarking, which embeds distinguishing marks into digital media without compromising quality. Watermarking is characterized by transparency, robustness, efficiency, and independence, with applications including copyright protection, tamper proofing, and quality assessment. Additionally, it outlines various watermarking schemes and potential attack types against them, emphasizing the need for security in watermarking processes.

2. CONTENTS
Background
Terminology
Characteristics
Applications
Techniques
References

3. Information Hiding
Information Hiding…..started with
Steganography (art of hidden writing):
The art and science of writing hidden messages in
such a way that no one apart from the intended
recipient knows of the existence of the message.
The existence of information is secret.

4. What is a watermark ?
What is a watermark ? A distinguishing mark
impressed on paper during manufacture;
visible when paper is held up to the light (e.g.
$ Bill)

5. What is a watermark ?
Digital Watermarking: Application of Information
hiding (Hiding Watermarks in digital Media, such
as images,audio file)
Digital Watermarking is a process of embedding
digital signals or pattern into a multimedia object
without affecting in any way the quality of the
original file.

6. CHARACTERISTICS

Transparency: watermark is not detectable

Robustness: survives digital processing (e.g., compression) and
malicious analytical attacks.

Efficiency: low cost implementation using minimal resources

Independence: of both the type and format of multimedia data (e.g.,
music, speech, video, sample rates, coding scheme, ...)

7. Applications
Copyright Protecton:To prove the ownership
of digital media
Eg. Cut paste of images
Hidden Watermarks represent
the copyright information

8. Applications
Tamper proofing: To find out if data was tampered.
Eg. Change meaning of images
Hidden Watermarks track
change in meaning

9. Applications
Quality Assessment: Degradation of Visual Quality
Loss of Visual Quality
Hidden Watermarks track change in visual quality

10. Watermarking Process
Data (D), Watermark (W), Stego Key (K),
Watermarked Data (Dw)
Embed (D, W, K) = Dw
Extract (Dw) = W’ and compare with W

11. Watermarking Process
Figure 2 shows the basic scheme of the
watermarks embedding systems.
Figure 2: Watermark embedding scheme
Inputs to the scheme are the watermark, the
cover data and an optional public or secret key.
The output are watermarked data. The key is
used to enforce security.

12. Watermarking Process
Figure 3 shows the basic scheme for
watermark recovery system.
Figure 3: Watermark recovery scheme
Inputs to the scheme are the watermarked data, the
secret or public key and, depending on the method,
the original data and/or the original watermark.
The output is the recovered watermarked W or some
kind of confidence measure indicating how likely it
is for the given watermark at the input to be present
in the data under inspection.

13. TYPES OF WATERMARKING SCHEMES
Private (non-blind) watermarking systems use the original
cover-data to extract the watermark from stego-data and
use original cover-data to determine where the watermark is.
Extract using {D, K, W}
Semi-private (semi-blind) watermarking does not use the
original cover-data for detection, but tries to answer the
same question. (Potential application of blind and semiblind watermarking is for evidence in court ownership,....)
Extract using { K, W}
Public (blind) watermarking - neither cover-data nor
embedded watermarks are required for extraction - this is
the most challenging problem.
Extract using {K}

14. ATTACKS ON DIGITAL WATERMARKING:
•Active Attacks – hacker tries to remove the watermark or
make it undetectable. An example is to crop it out.
•Passive Attacks – hacker tries to determine whether there is a
watermark and identify it. However, no damage or removal is
done.
•Forgery Attacks – hacker tries to embed a valid watermark of
their own rather than remove one.
•Decorative Attacks – hacker applies some distorted
transformation uniformly over the object in order to degrade
the watermark so that it becomes undetectable / unreadable.

15. Security
In case the key used during watermark is lost anyone
can read the watermark and remove it.
In case the watermark is public, it can be encoded
and copyright information is lost.

16. References
http://en.wikipedia.org/wiki/Steganography
http://en.wikipedia.org/wiki/Digital_watermark
http://www.cypak.com/pictures/med/Cypak