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Digital Watermark

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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
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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.


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