Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
Survey of Digital Watermarking Technology
Watermarking is best known for official company letterheads or a hundred dollar
bill. However, in today’s world of advanced technology, protecting copyrighted works
gained a new urgency. Since the exponential rise of the Internet in the early 1990’s,
illegal distribution of copyrighted material has followed the exponential rise. It is
estimated that by 2005, book publishers and record label companies will lose 4.6 billion
dollars a year (Forrester Research).
This paper will focus on three main issues. First, the paper will disclose the
reason why digital watermarking has become so important. Second, the paper will focus
on different technical approaches to watermarking technology and describe different
techniques. Finally, commercial applications and new research will be discussed in order
to gain understanding of what the future holds.
In order to proceed, some basic terms need to be defined. A watermark in its
basic form is extra data that is inserted into a medium such as an image or audio file. A
robust watermark is one that could withstand malicious or accidental attacks, such as
cropping, scaling, file conversion/compression, printing, and rotation. A fragile
watermark, on the other hand, is one that is destroyed once any changes to the document
occur. Under ideal circumstances, a robust watermark would also pinpoint exact pixels
that have been tampered with.
When working with images, watermarking can be implemented using the spatial
or frequency domain. Several techniques for the procedure exist, to use in both domains,
such as color separation in the spatial domain, and Fast Fourier Transform in the
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
frequency domain. Watermarking using these methods, as well as other schemes, will be
discussed in detail.
A simple watermarking algorithm uses metatags to embed secret code in the
header of the file. However, this technique is very fragile, as any type of file conversion
is likely to remove the watermark. Another simple technique takes advantage of the
Contrast Sensitivity Function (CSF). CSF is an index characterizing how well the human
could see at different frequencies. Particularly it shows that at high frequencies the eye is
very insensitive to change. Therefore, encompassing a watermark in high frequency will
make it transparent to the human eye. Unfortunately, a simple low pass filter will remove
the watermark.
Watermarking research has yielded algorithms, not only for use with ordinary
images, but with text as well. Though fragile, three proposed methods are text line
coding, word space coding, and character encoding. These methods depend on the
spacing between the lines of a text, spacing between words, and spacing between
characters. While some techniques are more fragile (watermark is easily removed) than
others, the purposes, potential use and security issues regarding each technique made its
way into our research, and will be discussed in full detail.
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
A superior watermarking method has been developed by Kodak. Either a logo or
a bitstream could be embedded in any image or movie. The bitstream is embedded using
positive or negative Dirac Delta function. (x,y)= C(x,y)C(x,y), where  is defined as
cyclic correlation. In other words, the formula above is equivalent to multiplying the
magnitudes of two signals, while subtracting their phases in the Fourier domain.
The process is designed to split the image into M x N blocks. A secret key is used to
generate a ‘random’ phase that resembles noise. The ‘noise’ and watermark are
convolved and scaled to a small amplitude. This result is then added to each block of the
original image. Because it resembles noise, the key cannot be easily intercepted in the
image. Mathematically, the process is
I’(x,y)= (M(x,y)*C(x,y))+I(x,y), where
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
* is cyclic convolution, I(x,y) is original image, I’(x,y) is the image embedded with a
watermark, M(x,y) is the message image, C(x,y) is the carrier image, and  is arbitrary
constant to make image invisible and robust
The reverse is performed when extracting the watermark. The image is broken up
into M x N pieces and all the pieces are added together to cancel the effects of possible
noise. As a separate process, the same ‘random’ noise is generated using the same key.
The noise is then correlated with the sum of all blocks. If the correct key has been used,
the original watermark will appear. The image below, courtesy of Kodak, demonstrates
the process.
Courtesy of Kodak
This same technology could be applied to the digital movie industry. An invisible
watermark could be embedded into the frames of a movie, containing theatre and
distributor information. If a pirated copy should fall into the hands of law enforcement
officials, the watermark could be extracted and used to prosecute the responsible parties.
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
Kodak has demonstrated an accuracy of over 99.9%, given 23 or more frames which are
watermarked (half a second).
Another method has been proposed by Wong and Memon, both of whom are
professors at Polytechnic University. In fact, Wong and Memon have two variants to
their method. The first includes a secret key, and the second a public key. In the secret
key scheme, only two people have the key, the owner and the verifier. The key must be
passed along with the image, but on a different, yet secure channel. While this greatly
increases security, it is not always desirable. For instance, if an organization wants to
broadcast copyrighted material, having a secret decryption key would negate the purpose.
The public key resolves the problem by allowing anyone to verify the authenticity
of the document, while only one person is able to embed the watermark into the content.
Regardless of whichever method is used, the image must be grayscale. Otherwise, the
watermarking process has to be applied to each color plane separately (i.e., R, G, B).
The image is divided into N x M blocks where Xr denotes the rth block. First, all
LSBs are set to 0. The user key along with the LSBs and other parameters are used to
create a hash function output. In a good hash function, given x and y, where x is not
equal to y, h(x) will never equal h(y). Once the hash output has been calculated it is
XORed with the watermark to receive signals Cr. Cr is the inserted into the LSBs to
make the final image. Since only LSBs have been modified, no significant degradation is
visible. The figures below, courtesy of Wong and Memon, show embedding and
extracting algorithms.
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
The remaining work for this paper consists of obtaining various commercial uses
of watermarking technology, and how such technology would be implemented in a
commercial environment. Suffice it to say, questions regarding the usefulness of such
technology will be addressed.
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
New research has yet to be considered to see where digital watermarking is going.
However, it is evident that the field contains much promise, and is undergoing active
research. Possible uses of such technology include proof of occurrence, when a picture
has been modified using software such as Adobe Photoshop, the watermark will reveal
which part of the photograph has been tampered with. Another application currently
under development is duplication control. In such an application, additional hardware is
added to devices such as DVD players, where a watermark is read and modified each
time the media is copied. After a pre-programmed number of copies, the hardware will
not allow the creation of duplicates.
Just as importantly, a watermark could be inserted into a photo ID or a passport,
where the watermark would contain an index to the national database. Each time the
passport is scanned, the national database will be contacted to validate the passport. Such
system would make fake photo IDs almost impossible.
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
Sources

Digimarc is a commercial provider of watermarking technologies. The site offers
many solutions for modern business.
http://www.digimarc.com/watermarking/default.asp

“Digital Watermarking” by R. Chandramouli, Dept. of ECE, Stevens Institute of
Tecnology, Nasir Memon, Dept. of CS, Polytechnic University, and Majid
Rabbani, Imaging Research & Advanced Development, Eastman Kodak Co.
http://isis.poly.edu/memon/pdf/3.pdf

“Data Embedding Using Phase Dispersion” by Chris Honsinger and Majid
Rabbani, Copyright 2000, Eastman Kodak Co.

“Secret and Public Key Imgae Watermarking Schemes for Image Authentication
and Ownership Verificaiton” by Ping Wah Wong, and Nasir Memon, IEEE June
29, 1999.

Cannon has developed an error correcting approach, and is planning to improve it
further.
http://www.canon.com/technology/system/digital_watermark/content.html

ACM article describing different approaches and watermarking techniques.
http://www1.acm.org:82/~hlb/publications/dw_n/dw_n.html

Paper published by two German researchers regarding a new watermarking
technique. http://syscop.igd.fhg.de/Publications/Roth02a.pdf
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Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
----------http://www.digimarc.com/watermarking/default.asp
WHAT IS DIGITAL WATERMARKING?
Digimarc's digital watermarking technologies allow users to embed in audio, images,
video and printed documents a digital code that is imperceptible during normal use
but readable by computers and software. The science of creating these imperceptible
codes is known as digital watermarking. Digimarc is a leading owner of intellectual
property relating to digital watermarks and a pioneer in the commercial application
of this technology.
copyright communication and
tracking of digital images
Digimarc ImageBridge
watermarking
Digimarc Excalibur Copy Detection counterfeit detection of ID cards
and packaging
Digimarc Excalibur Secure
Authentication
authentication and linking of
packaging and documents
Digimarc MediaBridge technology
linking of packaging, tags and
labels
----------http://www.businessweek.com/1997/35/b3542095.htm
----------Performance
In general, the performance of a data embedding algorithm is a tradeoff between
three factors:
1. Data capacity (number of embedded bits)
2. Visibility of the embedded message
3. Robustness (ability to withstand image-processing tasks)
Commonly, performance of a digital watermarking technology is evaluated by
keeping (1) and (2) constant, and then measuring the message survival rate when
the picture is subjected to varying degrees of image manipulation and degradation.
http://www.kodak.com/US/en/corp/researchDevelopment/technologyFeatures/aboutDW.s
html
--------http://syscop.igd.fhg.de/Publications/Roth02a.pdf
--------Data for still pictures is frequency-converted using Fourier conversion, where the converted data is manipulated
according to the key information- embedding location and strength-and pulse signals are inserted for the inverse
Fourier conversion that restores the picture data. The inserted pulse signals for different pieces of information are
Page 9 of 8
Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
dispersed throughout the picture during the inverse conversion process and retained in an invisible state in the picture
data, forming a digital watermark.
Canon's New Technologies Using Error-Correction Encoding
Digital watermarking is one form of security technology to ensure copyright protection. This technology
provides a high level of safety, because the location of embedded information is secret, and neither the
watermark algorithm nor the location of embedding is made public.
Although effective when used within one organization, the secrecy required for this method is a hindrance
when several users are involved, or when standardization is desired.
Working under the premise that making both algorithms for protecting image copyrights and embedding
locations public would enable many people to use the technology for copyright protection, Canon
developed its own error-correction encoding technology. This method uses mathematical processing to
restore signals that are difficult to distinguish from noise to their original state. With this technology, the
data in picture and voice contents that contain embedded watermark information is processed as a whole to
correct errors. It is possible to restore embedded information in the contents by dispersing and embedding
the watermark information and subjecting the entire contents to the error-correction encoding process. This
works even if the information has been erased or illegally rewritten.
This new technology, developed by attacking the problem from a different angle, protects copyright holders
and purchases by preventing embedded data from being illegally rewritten. The software that reads the
watermark is commercially available to facilitate the detection of illegal activity.
In addition to the aforementioned method of protecting image copyrights, Canon is developing digital watermark using
wavelet conversion adopted for JPEG 2000, as well as other digital watermark including those for high-quality printing.
http://www.canon.com/technology/system/digital_watermark/content.html
------------Techniques, applications, links, etc
http://www1.acm.org:82/~hlb/publications/dw_n/dw_n.html
-----Despite claims that digital watermarks can survive image alteration and cannot be
stripped without seriously affecting image quality, a recent CyberTimes report revealed
that the digital watermarks on some images "may have been weakened or [may have]
disappeared by the time the images were processed for the Internet." Resizing,
compressing and converting images from one file type to another may add noise to an
image or diminish its watermark in such a manner that the watermark becomes
unreadable. Further, even when a digital watermark remains intact, tracking services are
of limited use to copyright owners in searching for illegal copies of their works on the
Internet when such copies are within sites protected by passwords.
http://www.webreference.com/content/watermarks/tracking.html
------An international meeting point for scientists, researchers and companies active in digital
watermarking.

Why not add the copyright information into the file format?
One could define a new audio file format, in which the watermark is a part of the
header block but is not removable without destroying the original signal, because
part of the definition of the file format requires the watermark to be therein. In
this case the signal would not really be literally 'destroyed' but any application
using this file format would not touch it without a valid watermark. Some
electronic copyright management system propose mechanisms like this. Such
Page 10 of 8
Mikhail Pomeranets
Kathy Zaslavskaya
Final Project Report
EE3414
Prof. Yao Wang
schemes are weak as anyone with a computer or a digital editing workstation
would be able to convert the information to another format and remove the
watermark at the same time. Finally this new audio format would be incompatible
with the existing one. Thus the watermark should really be embedded in the audio
signal.
This is very similar to S.C.M.S. When Philips and Sony introduced the 'S/PDIF'
(Sony/Phillips Digital Interchange Format), they included the S.C.M.S. (Serial
Code Management System) which provides a way copies of digital music are
regulated in the consumer market. This information is added to the stream of data
that contains the music when one makes a digital copy (a 'clone'). This is in fact
just a bit saying: digital copy prohibited or permitted. Some professional
equipment are exempt for needing S.C.M.S.
With watermarking however, the copy control information is part of the audiovisual signal and aim at surviving file format conversion and other
transformations.
http://www.watermarkingworld.org/
-------estimates of losses
http://www.fasoo.com/eng/sub_news01read.html
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