Digital Watermarking
Sapinkumar Amin
005240067
Guided By: Richard Sinn
Agenda
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What is Digital Watermarking?
Why?
How? (General Framework)
Properties
Types
Limitations
Attacks
Current Trends
Steganography
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It is a sub discipline of data hiding and part of
cryptology.
Steganography is “secret writing”. The
steganographic message is integrated
invisibly and covered inside other harmless
source, it is very difficult to detect the
message without knowing its existence and
its appropriate encoding scheme.
Digital Watermarking
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“Digital Watermarking “means embedding
information into digital material in such a way that it
is imperceptible to a human observer but easily
detected by computer algorithm.
A digital watermark is a transparent, invisible
information pattern that is inserted into a suitable
component of data source by using a specific
computer algorithm. Digital watermarks are signal
added to digital data that can be detected or
extracted later to make an assertion about the data.
Why Digital Watermarking?
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In order to protect copyrighted material from illegal duplication, two typical
technologies have been developed.
One approach uses key-based cryptographic methods which enable the
appropriate security during the transmission process, but once the
encrypted data is decoded, the control of redistribution and its spread fails.
To address limitations of encryption, the main idea is to label a digital
material with specific marks, which are called digital watermarks.
Such technology can be used as ownership proof for distribution channel
tracking and other applications in business and public domains.
Furthermore, watermarking technology enables the owner to obtain the
copyright status of certain documents and distributors can be made
accountable for the condition. Additionally, compatible media player
technology (DRM used by Microsoft in Windows media player), Divx and
DVD player, can detect distorted marks and refuse to play, display, or
execute the media asset files
General Framework (How)
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In order to combine a watermark with a digital document images, you
need an image (I), a signature (S=s1, s2, s3…..sN) that contains the
watermarking information, and an encoding algorithm (E) to create a
watermarked image (I’). The encoder takes the signature and cover
the document, and generates the watermarked image, that is
described as a function: E(I,S) = I’. Secret or public key and other
parameters can be used to extend the watermarking encoder.
General Framework (How)
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The watermark is extracted using a decoder function. In this case, the
decoder D loads the watermarked, normal or corrupted image I(w),
and extract the hidden signature S. Using non-blind watermarking
techniques, the decoder D loads an additional image I, which is often
the original image, to extract the watermarking information by
correlation. The process can be described as D(I,I(w)) = S. Give detail
about blind and non-blind technique.
General Framework (How)
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Digital watermarks are weaved into the core structure of digital
document in an invisible and unrecognizable way.
Watermark does not change the main functionality of file.
Therefore, the watermark must be inserted into the data
structure imperceptibility.
It should neither be visible, audible and , nor detected to
strangers or observers. Each watermark method consists of an
embedding algorithm and an extracting algorithm. The
embedding algorithm inserts the watermark information and
others only determine its existence. Such methods can be used
either as ownership proof or verification.
Properties and Requirements
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Robustness
Non-perceptibility
Security
Complexity
Capacity
Types of Watermarking
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LSB Watermarking
Spatial Domain Watermarking
Temporal Domain Watermarking
Spread Spectrum Watermarking
LSB Watermarking
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In general – 149 is 1001 0101
One of the most earliest techniques
Embed watermark data by alternation of certain bits
of digital image which are selected based on secret
key.
Extraction – by reading value of bits
Advantage - High Watermark channel capacity,
Algorithm has less computational complexity
Disadvantages-No robustness, Search Space is
huge, Weak against D/A and A/D
Spatial (Space) Domain Watermarking
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Ueung-Mintzer scheme
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Watermark is a binary logo smaller than image but stretched to
form as big as image (gray scale).
Scan each pixel and extract using look up table generated using
secret key.
If the extracted watermark bit is equal to the authentic watermark
bit, the pixel is left unchanged; other wise the gray scale of the
pixel is adjusted until the extracted watermark bit is equal to the
authentic one.
Wong’s public scheme
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All LSB are set to zero, than image is divided into blocks, blocks
applied to hash function and than applied to XOR operation.
Result is encrypted using private key of RAS cryptography and
embedded with original image.
Spatial (Space) Domain Watermarking
continued…
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Wong and Memon method
 Improved scheme by adding an image index and a block index to
the input of hash function. Image index is just like a unique serial
number of image. But the verifier needs to have the prior
knowledge about the image index.
Temporal Domain Watermarking
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MPEG compression
 I (Intra)-pictures
 P (Predictive)-pictures
 B (Bi-directional)-pictures
I-pictures are independently encoded in MPEG, watermark
insertion concentrates on I-pictures using spatial domain
watermarking.
It takes a watermark video that consists of a number N0 of
pictures and embeds this video in the usual way, frame by
frame. This number N0 is a parameter, clearly if N0=1, then we
have the ordinary spatial watermarking scheme. If N0 is greater
than 1, the approach is time-variant.
The information contained in N0 is entirely up to the user.
Spread Spectrum Watermarking
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Use spread spectrum to spread the
watermark all over the host image.
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b is the watermarking bit
α is a scaling factor (Coefficient)
(x ,y) is a 2-dimensional pseudo-random sequence of 1 and -1
I(n1,n2) is the original image
Used in radar, navigation and communication appliances
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Attacks on Digital Watermarking
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Simple attack
Detection Disabling attack
Ambiguity attack
Removal attack
Current Trends
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Color image watermarking, and other
multimedia signals.
Watermarking of maps, graphics and
cartoons.
Applications beyond copyright protection.
Protocols and standardization.
References
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Digital Watermarking – Juergen Seitz, 2005
http://209.85.171.104/search?q=cache:DzYR8fUUxc4J:www.ece.stevenstech.edu/~mouli/waterm_tut.ppt+digital+watermarking+ppt&hl=en&ct=clnk&cd=2&gl=us
http://105.82.185.104/search?q=cache:87TL3XW0SDYJ:www.emt.unilinz.ac.at/education/Inhalte/se_moderne_methoden/WS0405/hasslacher_digital_watermark
ing.pdf+digital+watermarking+ppt&hl=en&ct=clnk&cd=1&gl=us
http://210.11.291.104/search?q=cache:46mAyYOD8vcJ:www.cs.usu.edu/~xqi/Teaching/RE
U05/Notes/Watermarking.pdf+digital+watermarking+ppt&hl=en&ct=clnk&cd=3&gl=us
http://111.19.117.104/search?q=cache:GA6z01xD5gIJ:www.cs.virginia.edu/~evans/cs588fall2001/projects/presentations/team10.ppt+digital+watermarking+ppt&hl=en&ct=clnk&cd=4
&gl=us
Any Questions….