1. Digital watermarking technique for protecting digital images
Nibedita Sahoo
M.Tech (ICT)
Roll no.-10IT61B01

2. Agenda Watermark and digital watermarking Basic characteristic
Watermark attacks
Watermarking technique
Spatial Domain watermarking
Transform Domain Watermarking Techniques
Current application area
Future trends
Conclusion
Reference

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

4. What is digital watermarking?
In generally digital watermarking is a technique for inserting information into an image.
It is an evolving field that requires continuous effort to find the best possible method in protecting multimedia content.
It is a process of embedding information into digital multimedia content such that the information can later be extracted or detected for variety of purposes including identification and authentication.

5. Block diagram for watermarking digital image
Original image
Embedding procedure
Watermark digital image

6. Example : Digital watermarking
Original image
Watermark
Digital watermarking

7. Basic characteristic of digital watermarking
Capacity
The optimum amount of data that can be embedded in a given signal.
Robustness
We embed and retrieve data such that it would survive malicious or accidental attempts.
Security
We determine that the information embedded has not been tampered, forged or even removed .
Transparency
The watermark is not visible in the image under typical viewing conditions.

8. Watermark Attacks Active Attacks Passive Attacks Forgery Attacks
Hacker attempts to remove or destroy the watermark.
Passive Attacks
Hacker tries to find if a watermark is present.
Removal of watermark is not an aim.
Forgery Attacks
Hacker tries to embed a valid watermark.
Serious in authentication.
If hacker embeds a valid authentication watermark,
watermark detector can accept modified media.

9. Types of watermarking techniques

10. 1.According to working domain
Spatial domain
Direct usage of data to embed and extract Watermark.
Spatial watermarking can also be applied using color separation. In this way, the watermark appears in only one of the color bands. This renders the watermark visibly subtle such that it is difficult to detect under regular viewing. However, the mark appears immediately when the colors are separated for printing.
Frequency Domain
This technique is motivated by both perceptual transparency and watermark robustness.
This technique is very effective both in terms transparency, robustness to signal processing.

11. 2.According to the type of document
Image Watermarking
Video Watermarking
Audio Watermarking
Text Watermarking

12. 3.According to the human perception
Visible watermark
In visible digital watermarking, the information is visible in the picture or video. Typically, the information is text or a logo, which identifies the owner of the media.
Invisible-Robust watermark
Information is added as digital data to audio, picture, or video, but it cannot be perceived.
Invisible-Fragile watermark
A fragile marking system should be able to detect any changes made in a marked image after marking. Fragile watermarking is mainly used for integrity protection, which must be very sensitive to the changes of signal.

13. 4.According to application
source based
Source-based watermark are desirable for ownership identification or authentication where a unique watermark identifying the owner is introduced to all the copies of a particular image being distributed.
Destination based
In case of destination based where each distributed copy gets a unique watermark identifying the particular buyer. The destination based watermark could be used to trace the buyer in the case of illegal reselling. (EX- FINACLE SOFTWARE BY INFOSYS)

14. Digital Image Processing
An image is a 2-D Signal
– Spatial signal
– Intensity value as I(X,Y)
Digital image
– Digitized 2-D signal
Use rectangular shape areas
called pixels
Digital representation: 8-bit,
12-bit, 16-bit, …

15. Review of Digital Image Processing
Digital images are represented using matrices:

16. Types Watermarking The hidden message may be added in Spatial Domain
Discrete Fourier Transform (DFT) Domain
Discrete Cosine Transform (DCT) Domain
Discrete Wavelet Transform Domain (DWT)

17. Spatial domain Watermarking
The term spatial domain refers to the aggregate of pixel
composing an image. Spatial domain methods are procedures
that operate directly on the pixels.
Watermark message M(x,y)
– Random or pseudo random signal
– Binary { -1,+1} or { -1, 0, +1}
– other signals are used
Watermark message is added linearly as:
W(x,y)= I(x,y)+kM(x,y)

18. Contd.
The watermark message is added in the spatial Domain: IM (x, y) = I (x, y) + kM(x, y)

19. Spatial Domain Watermark Embedding Scheme
Overview:
We will first embed the watermark into X and then
redirect the watermark to the saturation component of the image .
Our original image, f is a color image of size MxN and will
be represented by :f = { f(x,y), 0 ≤ x < M, 0 ≤ y < N}
Our watermark will be a image of size M/8xN/8.
It is represented by:W={W(i,j),0≤ i<M/8, 0≤ j<N/8}.

20. Contd. Step 1: Find the achromatic component of the host image
Compute the achromatic component of a color image .
Step 2: Break the achromatic image into blocks.
Step 3:Perform a permutation of the watermark to reduce its vulnerability.
Step 4:Embed the watermark into the Achromatic Component.
Step 5: Redirect the Watermark into the Saturation Component of the Color Image.

21. Spatial Domain Watermark Extraction Scheme
This type of extraction is called a nonblind extraction because original image, along with the watermarked image, are needed to extract the watermark.
Step 1: Find Achromatic Component of Original Image
Step 2: Reverse the Saturation Adjustment and Find the
Achromatic Component of the Watermarked Image.
Step 3: Break the achromatic components into blocks.
Step 4: Extract the permuted Watermark.
Step 5: Reverse Pseudorandom Permutation.

22. THE PROPOSED MODEL

23. Transform Domain Watermarking
Transform domain watermarking techniques are more robust in comparison to spatial domain methods.
Among the transform domain watermarking techniques discrete wavelet transform (DWT) based watermarking techniques are gaining more popularity because DWT has a number of advantages over other transform such as progressive and low bit-rate transmission, quality scalability .
The watermark message is inserted in the transform domain.
Different transforms behaves differently to different attacks.

24. Transform Domain Watermarking
Discrete Fourier Transform (DFT) is superior for shifting attacks-
Shifting in the space domain leads to a phase shift in the frequency domain.

25. Transform Domain Watermarking
Discrete Cosine Transform (DCT)
Supports block-based transform (8x8),(16x16), (32x32), …
Compacts the energy of each block according to its frequency content.
Used in JPEG compression
The watermark message is embedded in the intermediate frequency coefficients.
Example of adding watermark image to the intermediate frequency of each block.

26. Transform Domain Watermarking
Discrete Cosine Transform
– Example of adding watermark image to the intermediate frequency of each block

27. Transform Domain Watermarking
Discrete Wavelet Transform (DWT)
DWT locally separates the content
of the image into low frequency and
high frequency subbands.
Most of the energy is concentrated
in the low frequency subband.
In watermarking: The message is
inserted in the high frequency
subbands (HL,LH and HH)

28. Transform Domain Watermarking
Non-Regular Transform
– Spreads the energy content into different subbands
– The subbands are similar to the original image
Similar images
Similar histogram

29. Application Ownership assertion
Watermarks can be used for ownership assertion.
Copy prevention or control
Recording device may inhibit recording a signal if detected watermark indicates that it is prohibited.
DVD video and digital music distribution.
Secret Communications
Hide information such that general public do not know its presence.

30. Application Authentication Broadcast Monitoring Fingerprinting
Detect If image/video has been altered
Broadcast Monitoring
Keep track of when and where an advertisement is played.
Fingerprinting
Identify the source of an illegal copy.
Unique watermark embedded in each copy

31. Future trends
A number of companies, such as Sony and IBM have introduced digital watermarking software applications that allow individuals to imbed watermarks within image, audio and video files to protect them from copyright.
Companies are also offering on-line tracking services so that the copyright owner can see how the owner's materials are used via the Web.

32. Conclusion
As described recent developments in the digital watermarking of images in which the watermarking technique is invisible.
Digital watermarking is a rapidly evolving area of research and development.
Digital watermarking technology can provide a new way to protect the copyright of multimedia information and to ensure the safe use of multimedia information.

33. Reference http://en.wikipedia.org/wiki/Steganography
W. Bender D. Gruhl N. Morimoto and A. Lu. Techniques for data hiding. IBM Systems
Journal, 35(3-4):313–336, 1996.
[2] S. Bhattacharjee, “Compression Tolerant Image Authentication”, Proceedings, Int. Conf. Image
Proc., Chicago, Oct

34. Reference
S.P. Mohanty, et aI., "A Dual Watennarking Technique for Images",
Proc. 7th ACM International Multimedia Conference, ACM-MM'99,
Part 2, pp , Orlando, USA, Oct
[2] I. Cox, J. Kilian, F. T. Leighton, and T. Shamoon, "Secure spread
spectrum watennarking for multimedia," IEEE Transactions on
Image Processing, vol. 6, no. 12, December, 1997, pp
[3] F. M. Boland, J. J. K. 6 Ruanaidh and C. Dautzenberg,
"Watennarking digital images for copyright protection," Proceedings
of the International Conference on Image Processing and its
Applications, Edinburgh, Scotland, July 1995, pp

35. THANK YOU