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RESISTING RST WATERMARKING ALGORITHM FOR IMAGE CONTENT AUTHENTICATION
ABSTRACT: Our Paper aims to propose a
semi-fragile watermarking algorithm resisting to
RST (Rotation, Scaling, Translation). The
algorithm can be used to verify the authenticity
and integrity of image content. Firstly, the
algorithm generates watermarking information
by using the edge of the scaled image and
embeds watermarking information based on
human visual system. Before detecting
watermarking, the parameters of geometric
distortions are estimated and restored by using
the original moment information. Finally, users
compare the extracted watermarking information
with the reconstructed watermarking
information of the watermarked image to
achieve authentication. The experiment results
show the watermarking algorithm has the
immunity to common operation (Compression,
Noise, Filtering, RST, etc). The watermarking
algorithm can also achieve accurate
authentication and tampering localization to
malicious processing (Cropping, Replacing).
INTRODUCTION : With the development of digital watermarking technology authentication watermarking technology which is used to determine the image authenticity problem has become a hotspot of current research. In recent years, people have proposed unceasingly many new algorithms for the image authentication watermarking technology. The research paper
“Semi-fragile watermarking for Image Content Authentication” shows that based on HVS (Human Visual System) adaptively embedded watermark into host image in the wavelet domain by using group quantization, and compared the extracted watermarking information with the original one to achieve tampering authentication. Nevertheless, the algorithm requires the original watermark, which was logo image, for image authentication. The paper, “A new semi-fragile colour image watermarking algorithm”, which has made the improvement to the earlier proposed algorithm, has realized content-based adaptive digital watermarking, and extracted watermark without resorting to the original host image. However, because it has not involved the asymmetrical watermark, practicality and safety of the algorithm was not strong. Generally speaking, because robustness of image content authentication take does not affect user to distinguish image content as the principle, and RST (Rotation, Scaling, Translation) does not change people to distinguish image content, so image content authentication watermark should have the RST invariability, but the existing algorithm did not take into account such a situation.
Problem definition:
Relevance of the project: In a world today
when images are exchanged between people on
a regular basis, it becomes imperative to have an
image authentication system in order to validate
the image data. Our project furthers this cause
by detecting changes made by an unauthorized
person in an image.
Scope: The image in question is watermarked
such that any alteration in the image would
result in an altered watermark thereby helping in
detection of change in the image content.
REVIEW OF LITERATUREA watermark is an image which appears on fine
papers or on some documents to prevent
counterfeiting. There are two types of
watermarks: true watermarks and artificial
watermarks.
A true watermark is applied during the paper
manufacturing process using a special tool
called a dandy roll. The dandy roll is pressed
against the paper pulp while it is drying, and
marks on the dandy roll will transfer to the paper
pulp, creating an image. This image is called a
watermark because it is made while the paper
pulp is still wet with water.
An artificial watermark is applied during the
printing process. Artificial watermarks are made
using specially formulated inks or varnishes
which will only show up at certain angles or
under certain conditions, such as black light.
These watermarks are cheaper than true
watermarks, and can be easily customized for
individual uses. They are also easier to fake by
skilled counterfeiters. Personal checks and
official documents such as passports often use
artificial watermarks.
Watermarking is addition of an image or
pattern to paper by causing variations in paper
thickness by using various specialized machines.
The main use of watermarking is to provide a
level of certainty about the authenticity and/or
ownership of a document.
Watermarking life-cycle phases:
The information to be embedded is called a
digital watermark, although in some contexts the
phrase digital watermark means the difference
between the watermarked signal and the cover
signal. The signal where the watermark is to be
embedded is called the host signal. A
watermarking system is usually divided into
three distinct steps, embedding, attack and
detection. In embedding, an algorithm accepts
the host and the data to be embedded and
produces a watermarked signal.
The watermarked signal is then transmitted or
stored, usually transmitted to another person. If
this person makes a modification, this is called
an attack. While the modification may not be
malicious, the term attack arises from copyright
protection application, where pirates attempt to
remove the digital watermark through
modification. There are many possible
modifications, for example, lossy compression
of the data, cropping an image or video or
intentionally adding noise.
Detection (often called extraction) is an
algorithm which is applied to the attacked signal
to attempt to extract the watermark from it. If
the signal was unmodified during transmission,
then the watermark is still present and it can be
extracted. In robust watermarking applications,
the extraction algorithm should be able to
correctly produce the watermark, even if the
modifications were strong. In fragile
watermarking, the extraction algorithm should
fail if any change is made to the signal.
The first applications that came to mind were
related to copyright protection of digital media.
In the past duplicating art work was quite
complicated and required a high level of
expertise for the counterfeit to look like the
original. However, in the digital world this is not
true. Now it is possible for almost anyone to
duplicate or manipulate digital data and not lose
data quality. Similar to the process when artists
creatively signed their paintings with a brush to
claim copyrights, artists of today can watermark
their work by hiding their name within the
image. Hence, the embedded watermark permits
identification of the owner of the work. It is
clear that this concept is also applicable to other
media such as digital video and audio. Currently
the unauthorized distribution of digital audio
over the Internet in the MP3 format is a big
problem. In this scenario digital watermarking
may be useful to set up controlled audio
distribution and to provide efficient means for
copyright protection, usually in collaboration
with international registration bodies.
Digital Watermarking gets its name from
watermarking. Digital watermarking is the
process of embedding information into a digital
signal, i.e. audio, pictures, video, etc. If the
signal is copied, then the embedded information
is also in the copy. The embedding takes place
by manipulating the content of the digital data,
which means the information is not embedded in
the frame around the data. The hiding process
has to be such that the modifications of the
media are imperceptible.
The most important properties of digital
watermarking techniques are transparency,
robustness, security, capacity, invertibility
(reversibility) and complexity and possibility of
verification. Based on these parameters the
algorithms can be evaluated if a specific
algorithm has adequate properties and can be
used for a certain application area.
CLASSIFICATION:
Watermarking vs Steganography
Steganography is about concealing their very
existence. It comes from Greek roots, literally
means 'covered writing', and is usually
interpreted to mean hiding information in other
information. Examples include sending a
message to a spy by marking certain letters in a
newspaper using invisible ink, and adding sub-
perceptible echo at certain places in an audio
recording. As the purpose of steganography is
having a covert communication between two
parties whose existence is unknown to a possible
attacker, a successful attack consists in detecting
the existence of this communication.
Watermarking, as opposed to steganography,
has the (additional) requirement of robustness
against possible attacks. In most cases the
information hidden using steganographic
techniques is not related at all to the cover.
These differences in goal lead to very different
hiding techniques.
Classification of watermarking:
Imperceptible (Invisible) watermarking: In
watermarking, we traditionally seek high
fidelity, i.e. the watermarked work must look or
sounds like the original. Invisible watermarking
is the digital data that is added to audio, images
or video. But it cannot be perceived as such.
Because of its different applications, there are
two very different types of invisible
watermarking. Invisible watermarking, which is
destroyed when the image is manipulated
digitally in any way may be useful in proving
authenticity of an image. If the watermark is still
intact, then the image has not been "doctored." If
the watermark has been destroyed, then the
image has been tampered with. Such a
technology might be important, for example, in
admitting digital images as evidence in court.
Invisible watermarking, which is very resistant
to destruction under any image manipulation
might be useful in verifying ownership of an
image suspected of misappropriation. Digital
detection of the watermark would indicate the
source of the image.
Visible watermarking: Visible watermarking is
a visible translucent image, which is overlaid on
the image. It could be your name, copyright,
comment, website address, your logo, text or
graphical objects. Image filters, dates, photo
details and other EXIF information, which holds
the rights to the primary image can also be used
for image watermarking. Watermarking
processing allows the primary image to be
viewed, but still marks it clearly as the property
of the owning organization.
(Semi-) fragile vs Robust watermarks : The
aims of such watermarks are completely
different: A (semi-) fragile watermark is a mark
which is (highly) sensitive to a modification of
the stego-medium. A fragile watermarking
scheme should be able to detect any change in
the signal and identify where it has taken place
and possibly what the signal was before
modification. It serves at proving the
authenticity of a document. On the opposite, a
robust watermark should be stuck to the
document it has been embedded in, in such a
way that any signal transform of reasonable
strength cannot remove the watermark. Hence a
pirate willing to remove the watermark will not
succeed unless they debase the document too
much to be of commercial interest.
Invisible vs Visible Watermarking
INVISIBLE VISIBLE
WATERMARK
PERCEPTIBILI
TY
IMPERCEP
TIBLE
DISTORTI
ON
VISIBLY
MEANINGF
UL
PATTERN
ROBUSTNESS INTENTIO
NAL
ATTACKS
AND
COMMON
SIGNAL
PROCESSI
NG
USER
INTERVENT
ION BASED
WATERMA
RK
REMOVAL
PROTECTION PASSIVE ACTIVE
EXTRACTION EXPLICIT
EXTRACTI
ON
MODULE
DIRECT
VIEWING
CURRENT
RESEARCH
STATUS
HOT ONLY FEW
PAPERS
Applications of Invisible Watermarking:
1. Rights Management: One of the traditional
applications of the watermark is copyright
protection. The primary reason for using
watermarks is to identify the owner of the
content by an invisible, hidden “mark” that is
imprinted into the image. In many cases, the
watermark is used in addition to the content
encryption, where the encryption provides the
secure distribution method from the content
owners to the receivers and the watermark offers
the content owners the opportunity to trace the
contents and detect the unauthorized use or
duplications. Without watermarking, there is no
way to extend the control of the content owner
once the content leaves the protected digital
domain and is released to the user.
The technical requirements for this application
are as follows:
The watermark does not incur visible (or
audible) artifacts to the ordinary users.
The watermark is independent of the data
format.
The information carried by the watermark is
robust to content manipulations, compressions,
etc.
The watermark can be detected without the
unwatermarked original content.
The watermark can be identified by some kind
of “keys” that are used to identify large number
of individual contents uniquely.
2. Authentication and Tamper Proofing: The
objective in this case is not to protect the content
from being copied or stolen, but to provide a
method to authenticate the image and assure the
integrity of the image. The technical
requirements are as follows:
Invisible to the ordinary users
Applicable to compressed image format (most
digital cameras use JPEG compatible format)
Sensitive to content manipulations, compression,
etc.
3. DVD Playback and Record Control:
Watermarking technology can be viewed as a
way to provide a secure data channel along with
the contents without modifying the installed-
base Consumer Electronics (CE) devices. The
embedded watermark is transparently passing
through the conventional data path, and will
only be detected at the digital recorders. When
the watermark detection is mandated in the
recorders, it can be used to trigger the copy
protection mechanism implemented in it. The
watermarking data embedded into the video is
difficult to remove without damaging the quality
of the content because it is carefully woven into
the visible part of the video data. A list of
thirteen essential technical requirements is
shown below:
Transparency
Low cost digital detection
Digital detection domain
Generational copy control for one copy
Low false positive detection
Reliable detection
Watermark will survive normal video processing
in consumer use
Licensable under reasonable terms
Export/Import
Technical maturity
Data payload
Minimum impact on content preparation
Data rate
Application of Visible Watermarking:
Electronic Distribution: Unlike the other
digital watermarking technologies described
earlier, the visible reversible watermark is
visible. It is available as a commercial product.
This unique form of watermarking technology
by IBM allows the content owners to embed a
visible shape or logo mark such as a company’s
logo on top of the image. The mark is removed
(the watermark is reversed) only with the
application of an appropriate decryption key and
watermark remover software. With this visible
watermark on the image, the content becomes
self-protective, and content owners can
distribute the entire image as a sample to various
open media or to the Internet. When a user
wants to use a clean copy of the image, all
he/she needs to do is to request a decryption key
and pay some fee for it. This will reduce the
security risk and the amount of data
transmission per each buy/sell transaction.
VISIBLE WATERMARKING TECHNIQUES
LSB MODIFICATION : One of the first
techniques for watermarking is the Least-
Significant-Bit modification. It is based on the
substitution of LSB plane of the cover image
with the given watermark. The idea behind this
watermarking technique is the following: if you
see you image as a matrix NxM (where N and M
are the dimension of the image) you can
represent the value of the pixel in the position
(i,j) as a binary number; this binary can be then
divided in all of its bit, so that you will have a
most significant bit (the one that contains quite a
lot of information, and a least significant bit that
contains few information).
If your image is for example in gray scale, you
can make changes to the value of the LSB
without any perceptible distortion for the human
user therefore you can think of taking the LSB
of an image (the cover image) and change its
value in every pixel with the MSB of another
image, that we would like to embed in a
secret/non perceptible way in the cover image).
SPREAD SPECTRUM WATERMARKING:
The watermark should not be placed in
perceptually insignificant regions of the image
(or its spectrum), since many common signal
and geometric processes affect these
components. The problem then becomes how to
insert a watermark into the most perceptually
significant regions of the spectrum in a fidelity
preserving fashion. Clearly, any spectral
coefficient may be altered, provided such
modification is small. However, very small
changes are very susceptible to noise. To solve
this problem, the frequency domain of the image
is viewed as a communication channel and
correspondingly, the watermark is viewed as a
signal that is transmitted through it. Attacks and
unintentional signal distortions are thus treated
as noise that the immersed signal must be
immune to. The watermark is spread over many
frequency bins so that the energy in any one bin
is very small and certainly undetectable. To
insert a watermark in the frequency domain of
an image we first apply Discrete Cosine
Transform (DCT), perform the corresponding
transformation and in the end find the inverse
DCT. Such a watermark is very robust to most
of the common signal processing and geometric
distortions.
USING AUTHENTICATION IN
WATERMARKING
Three-way handshaking technique:
This is the most suitable technique that can be
used for image content authentication since the
recipient can send an acknowledgement to the
sender once the authentic image is received. If
acknowledgement is not received the sender will
realize that the image content has been altered
and thus both, the sender and receiver, will be
aware of a change in the image.
TECHNIQUES OF ENCRYPTION /
AUTHENTICATION IN
WATERMARKING
RANDOM NUMBER GENERATOR
A random number generator (often abbreviated
as RNG) is a computational or physical device
designed to generate a sequence of numbers or
symbols that lack any pattern, i.e. appear
random.
Physical methods: The earliest methods for
generating random numbers — dice, coin
flipping, roulette wheels — are still used today,
mainly in games and gambling as they tend to be
too slow for most applications in statistics and
cryptography. A physical random number
generator can be based on an essentially random
atomic or subatomic physical phenomenon
whose unpredictability can be traced to the laws
of quantum mechanics. Sources of entropy
include radioactive decay, thermal noise, shot
noise, avalanche noise in Zener diodes, clock
drift, the timing of actual movements of a hard
disk read/write head, and radio noise. However,
physical phenomena and tools used to measure
them generally feature asymmetries and
systematic biases that make their outcomes not
uniformly random. A randomness extractor,
such as a cryptographic hash function, can be
used to obtain uniformly distributed bits from a
non-uniformly random source, though at a lower
bit rate.
Computational methods: Pseudo-random
number generators (PRNGs) are algorithms that
can automatically create long runs of numbers
with good random properties but eventually the
sequence repeats (or the memory usage grows
without bound). The string of values generated
by such algorithms is generally determined by a
fixed number called a seed. One of the most
common PRNG is the linear congruential
generator.
RANDOM PASSWORD GENERATOR:
A random password generator is software
program or hardware device that takes input
from a random or pseudo-random number
generator and automatically generates a
password. Random passwords can be generated
manually, using simple sources of randomness
such as dice or coins, or they can be generated
using a computer.
While there are many examples of "random"
password generator programs available on the
Internet, generating randomness can be tricky
and many programs do not generate random
characters in a way that ensures strong security.
A common recommendation is to use open
source security tools where possible, since they
allow independent checks on the quality of the
methods used. Note that simply generating a
password at random does not ensure the
password is a strong password, because it is
possible, although highly unlikely, to generate
an easily guessed or cracked password.
A password generator can be part of a password
manager. When a password policy enforces
complex rules, it can be easier to use a password
generator based on that set of rules than to
manually create passwords.
HADAMARD TRANSFORM:
The Hadamard transform is an example of a
generalized class of Fourier transform. It
performs an orthogonal, symmetric,
involutional, linear operation on 2m real numbers
(or complex numbers, although the Hadamard
matrices themselves are purely real).The
Hadamard transform is based on the Hadamard
matrix which is a square array having entries
of+1 and -1 only.
The Hadamard transform can be regarded as
being built out of size-2 discrete Fourier
transforms (DFTs), and is in fact equivalent to a
multidimensional DFT of size
. It decomposes an
arbitrary input vector into a superposition of
Walsh functions.
WALSH TRANSFORM:
It is a kind of non-sinusoidal orthogonal
transform. Walsh introduced a complete set of
orthogonal square wave functions, which can be
used to represent any arbitrary function. It is
defined for N=2^n.It requires that no. of samples
should be integer power of 2. The rows of
discrete Walsh transform matrix Wm of size M
x M is generated by sampling the Functions
having the sequence length less than or equal to
M-1, at equi-spaced M points, where M should
be an integer power of 2.
For M=8, the matrix Wm becomes
1 1 1 1 1 1 1 1
1 1 1 1 -1 -1 -1 -1
1 1 -1 -1 -1 -1 1 1
1 1 -1 -1 1 1 -1 -1
1 -1 -1 1 1 -1 -1 1
1 -1 -1 1 -1 1 1 -1
1 -1 1 -1 -1 1 -1 1
1 -1 1 -1 1 -1 1 -1
The Walsh transform matrix is obtained from
the Hadamard matrix by re-arranging the rows in
increasing order. Re-arranging the rows of the
Hadamard matrix to get an increasing order of
sign changes gives us the Walsh matrix.
WALSH-HADAMARD TRANSFORM:
Image processing method uses a modified
Walsh-Hadamard transform to remove noise and
preserve image structure in a sampled image.
Image signals representative of the light value of
elements of the image are grouped into signal
arrays corresponding to blocks of image
elements. These signals are mapped into larger
signal arrays such that one or more image
signals appear two or more times in each larger
array. The larger arrays are transformed by
Walsh-Hadamard combinations characteristic of
the larger array into sets of coefficient signals.
Noise is reduced by modifying--i.e., coring or
clipping--and inverting selected coefficient
signals so as to recover processed signals--less
noise--representative of each smaller signal
array.
MESSAGE DIGEST 5 (MD5) ALGORITHM
MD5 is a message digest algorithm developed
by Ron Rivest at MIT. It is basically a secure
version of his previous algorithm, MD4 which is
a little faster than MD5. This has been the most
widely used secure hash algorithm particularly
in Internet-standard message authentication. The
algorithm takes as input a message of arbitrary
length and produces as output a 128-bit message
digest of the input. This is mainly intended for
digital signature applications where a large file
must be compressed in a secure manner before
being encrypted with a private (secret) key under
a public key cryptosystem. Assume we have an
arbitrarily large message as input and that we
wish to find its message digest. The processing
involves the following steps.
(1) Padding: The message is padded to ensure that
its length in bits plus 64 is divisible by 512. That
is, its length is congruent to 448 modulo 512.
Padding is always performed even if the length
of the message is already congruent to 448
modulo 512. Padding consists of a single 1-bit
followed by the necessary number of 0-bits.
(2) Appending length: A 64-bit binary
representation of the original length of the
message is concatenated to the result of step.
The expanded message at this level will exactly
be a multiple of 512-bits. Let the expanded
message be represented as a sequence of L 512-
bit blocks Y0, Y1,..,Yq,..,YL-1 . IV and CV
represent initial value and chaining variable
respectively.
(3) Initialize the MD buffer: The variables IV and
CV are represented by a four–word buffer
(ABCD) used to compute the message digest.
Here each A, B, C, D is a 32-bit register and
they are initialized as IV to the following values
in hexadecimal. Low-order bytes are put first.
Word A: 01 23 45 67; Word B: 89 AB CD EF;
Word C: FE DC BA 98; Word D: 76 54 32 10
(4) Process message in 16-word blocks: This is the
heart of the algorithm, which includes four
“rounds” of processing. It is represented by
HMD5 in and its logic is given in Figure 2. The
four rounds have similar structure but each uses
different auxiliary functions F, G, H and I.
SHA-1:
In cryptography, SHA-1 is a cryptographic hash
function designed by the National Security
Agency (NSA) and published by the NIST as a
U.S. Federal Information Processing Standard.
SHA stands for Secure Hash Algorithm. The
three SHA algorithms are structured differently
and are distinguished as SHA-0, SHA-1, and
SHA-2. SHA-1 is very similar to SHA-0, but
corrects an error in the original SHA hash
specification that led to significant weaknesses.
The SHA-0 algorithm was not adopted by many
applications. SHA-2 on the other hand
significantly differs from the SHA-1 hash
function. SHA-1 is the most widely used of the
existing SHA hash functions, and is employed in
several widely-used security applications and
protocols.
3 IMPLEMENTATION
a. Software Requirement:
Matlab7.0
WindowsXP Professional
b. Hardware Requirement: Intel Core2 Duo
processor
c. Database Requirement: Image database.
4. FURTHER WORK
We aim to do the following:
Implement the mentioned algorithm for image
content authentication.
Design a suitable GUI.
Perform adequate testing
REFERENCES[1] Lintao Lv, Liang Hao, Hui Lv, “Resisting
RST algorithm for image content
authentication”, 2010 Second International
Conference on Networks Security, Wireless
Communications and Trusted Computing.
[2] Dhananjay Theckdath, “Digital Signal and
Image Processing”.
[3] Todor Todorov, “Spread Spectrum
Watermarking Technique for Information
System Securing”, International Journal
“Information Theories & Applications” Vol.11.
[4] “Digital Watermarking of Image”, SGN-
1650/1656 Signal Processing Laboratory.
[5] Norishige Morimoto IBM Japan, Ltd., Tokyo
Research Laboratory, “Digital Watermarking
Technology with Practical Applications”,
Informing Science Special Issue on Multimedia
Informing Technologies-Part 1 Vol. 2 No 4,
1999.
[6] “Introduction to Visible Watermarking”, IPR
Course: TA Lecture, 2002/12/18 NTU CSIE
R105.