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MASAUM Journal of Computing, Volume 1 Issue 2, September 2009 258<br />

<strong>An</strong> <strong>Agent</strong> <strong>based</strong> <strong>Image</strong> <strong>Steganography</strong> <strong>using</strong><br />

<strong>Information</strong> <strong>Theoretic</strong> Parameters<br />

Sattar B. Sadkhan, Abbas M. Al-Bakry, Naween N. Muhammad<br />

Abstract- <strong>Steganography</strong> is the practice of hiding or<br />

camouflaging secret data in an innocent looking<br />

dummy container. Once the data has been embedded,<br />

it may be transferred across insure lines or posted in a<br />

public place.<br />

<strong>Agent</strong> helps in steganography task, since the cover<br />

image is important, so an agent subsystem makes<br />

decisions that help in choosing the best cover image<br />

from the image database.<br />

This paper proposed a design and simulation of an<br />

agent that helps in making decision by choosing the<br />

suitable steganography method for the chosen cover<br />

image (<strong>based</strong> on some information theoretic<br />

parameters) to embed the specified secret image.<br />

Index Term- Stego-image, Cover-image, <strong>Agent</strong>, secure<br />

communication, <strong>Information</strong> theoretic parameters.<br />

I. INTRODUCTION<br />

Chin –Chen Chang et al [1] developed an optimal<br />

least significant bit substitution in image hiding. The<br />

processing of simple least significant bit (LSB)<br />

substitution embeds the secret image in the least<br />

significant bits of the pixels in the host image. The<br />

processing may degrade the host image quality<br />

significantly so that grabbers can detect that there is<br />

something going on in the image that interest them. To<br />

over come this drawback, an exhaustive LSB method that<br />

uses a genetic algorithm to search approximate optimal<br />

solution, and computation time is no longer so huge, can<br />

be used . Experimental results show that the stego image<br />

is visually indistinguishable from the original cover –<br />

image [2].<br />

• Tao Zhang and Xijian ping [3] designed an approach to<br />

reliable detection of LSB steganography. A physical<br />

quantity is derived from the transition coefficient between<br />

different image histograms, and it’s processed version<br />

produced by setting all bits in the LSB plane to<br />

• zero. It appears that this quantity is a good measure of<br />

the week correlation between successive bit planes, and<br />

can be used to discriminate stego image from the coverimages.<br />

Further studies indicate that there exists a<br />

S. B. Sadkhan and Abbas M. Al-Bakry are with the, University of<br />

Babylon, Iraq (phone: +9647801884154; e-mail: drengsattar@<br />

ieee.org).<br />

Naween N. Muhammad is with Al-Sulaimania University<br />

functional relationship between this quantity and the<br />

embedded message length.<br />

• Najla A. Hamza [4] designed a robust technique for<br />

information hiding in which image steganography is<br />

proposed <strong>using</strong> Discrete Cosine Transform (DCT)<br />

transformation technique. The proposed system depends<br />

on substituting the similar blocks of the embedded image<br />

with in a cover image. The system composed of number<br />

of stages, transformation stage , matching stage ,<br />

substitution stage and inverse transformation stage.<br />

• A Parallel image processing system <strong>based</strong> on the<br />

concept of reactive agents was developed in [18]. The<br />

system described finely and simply the agent behaviors to<br />

detect image feature. They proposed an approach for<br />

continuity perception <strong>based</strong> on multi agent system. Each<br />

agent can move around on its environment which consists<br />

of an image made up of light and dark rings set out<br />

concentrically. <strong>Agent</strong>s are named darkening agent and<br />

lightening agent. On the other hand, the higher level<br />

communication requires that the objects (or agents) have<br />

the ability to exchange message on an asynchronous way<br />

with management of a message box in order to increase<br />

the flexibility and liability of service demands,<br />

proposition, and negotiation [19].<br />

• Sabu M. Thampi and Chandra Sekaran [5] presented<br />

an image retrieval system <strong>based</strong> on image feature,<br />

steganography, and mobile agents. By utilizing the DCT<br />

<strong>based</strong> information hiding technique, the valuable image<br />

attribute can be hidden in an image with out degrading the<br />

image quality. Mobile agents manage the query phase of<br />

the system. Based on the simulation results, the proposed<br />

system, not only show the efficiency in hiding the<br />

attributes, but also provides other advantages such as :<br />

i- Fast transmission of the retrieval image to the receiver<br />

ii- No need to extract the attribute separately for other<br />

application<br />

iii- Searching made easy.<br />

• Tabais S. G. G. [6] designed an agent <strong>based</strong> advising<br />

systems that relieve the user of managing large set of<br />

information, and helping to find a relevant objects in area<br />

of interest. The performance for this product should be<br />

possible to formalize. The agent is software component<br />

that acts throughout representative and authority. Acting<br />

representative means that should perform the tasks that we<br />

wish it to perform, and which it can perform better or<br />

faster than we can. This can for example be searching<br />

258


MASAUM Journal of Computing, Volume 1 Issue 2, September 2009 259<br />

one thousand online store for best price for CD you want<br />

considering.<br />

This paper proposed a steganography system for <strong>based</strong><br />

on <strong>using</strong> agent software to make decision for the best<br />

cover image existing in the available cover image<br />

database that holds for the specific selected secret<br />

message (image). The proposed agent depends on a<br />

number of specific image parameters and some<br />

measurement for the available cover images. Achieving<br />

suitable steganography method, the client will obtain or<br />

receive a better stego-image quality from the server.<br />

This paper contains in addition to the first section the<br />

following section:<br />

Section 2 provides an overview on steganography and its<br />

importance, while section 3 introduces briefly the concept<br />

of agent system. Section 4 provides the proposed system<br />

of steganography that <strong>based</strong> on the use of agent, while<br />

section 5 gives the case studies on <strong>using</strong> the DCT<br />

steganography and LSB steganography with the agent<br />

system. Section 6 provides the conclusion.<br />

II. STEGANOGRAPHY<br />

<strong>Steganography</strong> and data embedding are increasingly<br />

gaining importance in secure and robust communication<br />

of vital information. The low sensitivity of human visual<br />

system to luminance enable embedding large amount of<br />

data in a still image or video , without ca<strong>using</strong> any<br />

discernible difference between the resulting signal or data<br />

embedded signal , and original image [8].<br />

There is now substantial body of literature on<br />

steganography techniques, particularly in case when cover<br />

medium is formed of digital images. <strong>An</strong> increasing<br />

amount of steganalytic techniques for uncovering the<br />

presence of steganography [9]. In conventional<br />

cryptography, even if the information content are<br />

protected by encryption, the existence of encrypted<br />

communication is known. In view of this, steganography<br />

provides an alternative approach in which it conceals even<br />

the evidence of encrypted message. Generally,<br />

steganography is defined as the art and science of<br />

communicating in a cover fashion. It utilizes the typical<br />

digit media such as text, image, audio, video and<br />

multimedia as carrier, (which is called host or cover<br />

signal) for hiding private information in such way that the<br />

third parties (unauthorized person) cannot detect or even<br />

notice the presence of communication [10] .<br />

The goal of image steganogrohy is to embed information<br />

in a cover image <strong>using</strong> modification that are undetectable,<br />

in actual practice , however , most technique produce<br />

stego images that are perceptually identical to the cover<br />

images [11].<br />

A. <strong>Steganography</strong> Types<br />

<strong>Steganography</strong> divided into three main types, which are:<br />

• Pure steganography.<br />

• Secret key steganography.<br />

• Public key steganography.<br />

- Pure <strong>Steganography</strong><br />

A steganography system, which dose not requires a<br />

prior exchange of some secret information (like a stegokey)<br />

is called a pure steganography. Formally, the<br />

embedding process can describe as a mapping<br />

E:C×M→C. Where C is the set of possible covers, and M<br />

the set of possible message. The extraction process<br />

consists of a mapping D:C→M, to extract the secret<br />

message out of a cover. Clearly it is necessary that<br />

|C|≥|M|. Both sender and receiver must have access to the<br />

embedding and the extraction algorithm, but the algorithm<br />

should not be public [12].<br />

- Secret key <strong>Steganography</strong><br />

A secret key steganography system is similar to a<br />

symmetric cipher. The sender chooses a cover C and<br />

embeds the secret message <strong>using</strong> a secret key. If the key K<br />

used in the embedding process is known to the receiver,<br />

he can reverse the process and extract the secret message.<br />

<strong>An</strong>yone who does not knows the secret key should not be<br />

able to obtain evidence of the encoded information.<br />

Formally, the embedding process is a mapping<br />

E k :C×M×K→C and the extracting process is a mapping<br />

D k :C×K→M where k is the set of all possible secret<br />

keys.<br />

- Public key <strong>Steganography</strong><br />

Public key steganography system requires the use of two<br />

keys, one private and one public key. The public key is<br />

stored in a public database.<br />

One way to build a public key steganography system is<br />

the use of a public key crypto system . Public key<br />

steganography utilizes the fact that decoding function D in<br />

a steganographic system can be applied to any cover C<br />

(recall that D is a function on the entire set C). in the<br />

latter case , there are a random element of M which will<br />

be the results, which will be called the " natural<br />

randomness " of the cover . If one assumes that this<br />

natural randomness is statically indistinguishable from<br />

cipher text produced by some public key cryptosystem a<br />

secure steganography can be built by embedding cipher<br />

text rather than unencrypted secrete message [4].<br />

B. Classification Of Steganorgraphic Techniques<br />

There are several approaches to the classification of<br />

steganographic techniques. One of these approaches is to<br />

categorize them according to the cover modification<br />

applied in the embedding process. Mainly, steganographic<br />

techniques may be grouped in to six categories as shown<br />

in Fig. 1:<br />

1- Substitution Technique: it substitutes redundant parts<br />

of cover with secret message.<br />

2- Transform Domain technique: technique embeds<br />

secret information in a transform space of the signal (e.g.<br />

in the frequency domain).<br />

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MASAUM Journal of Computing, Volume 1 Issue 2, September 2009 260<br />

3- Spread Spectrum Technique: It adopts ideas from<br />

spread spectrum communication.<br />

4- Statistical Technique: Encodes information by<br />

several statistical properties of a cover and use hypothesis<br />

testing in the extraction process.<br />

5- Distortion Technique: It covers information by signal<br />

distortion and measures the deviation from the original<br />

cover in the decoding step.<br />

6- Cover Generating Techniques: They encode<br />

information in the way that a cover for secrete<br />

communication is created.<br />

- Substitution Technique<br />

A basic and well known steganorgraphy technique for<br />

hiding Message into uncompressed digital image is the<br />

least significant bit (LSB) embedding methods. It is<br />

considered as a well known example of this<br />

steganographic technique. In this method , image pixels<br />

are traversed in a predetermine – often pseudorandom –<br />

order, and LSB for each pixels is modified to reflect the<br />

corresponding bit in the message payload . LSB<br />

embedding is preferred in many case for it's simplicity<br />

and high embedding rate.<br />

The process introduces a small amplitude noise signal,<br />

and the resulting stego-image are visually identical to the<br />

cover image [11].<br />

The popularity of the (LSB) embedding is most likely<br />

due to its simplicity as well as the [false] early belief that<br />

modification of pixels value by 1 in randomly selected<br />

pixels are undetectable because of the noise commonly<br />

present in all digital images of natural scenes [12].<br />

The LSB technique takes the advantage of random noise<br />

present in the acquired media data, such as images, video,<br />

and audio. Embedding message bits in the LSB plane will<br />

not cause any discernible difference from original visual<br />

[13].<br />

The substitution modification technique is easy ways to<br />

embed information, but they are highly vulnerable to even<br />

small cover modification. <strong>An</strong> attacker can simply apply<br />

signal processing technique in order to destroy the secret<br />

information entirely.<br />

- Transform Domain technique<br />

It has been noted early in the development of<br />

<strong>Steganography</strong> systems that embedding information in the<br />

frequency domain of a signal can be much more robust<br />

that embedding rule operating in the time domain. Most<br />

robust <strong>Steganography</strong> system known today actually<br />

operate in the same sort of transform domain [6].<br />

Transform domain methods hide messages in the<br />

significant area of the cover image which make them<br />

more robust to attacks , such as adding noise ,<br />

compression , filtering , cropping and some image<br />

processing , than the substitution approach. However<br />

while they are more robust to various kinds of signal<br />

processing , they remain imperceptible . an example of the<br />

used methods, is the discrete cosine transform (DCT) ,<br />

and the wavelet transform. Transformation could be<br />

applied over the entire image , to blocks throughout the<br />

image . One popular method of encoding secret<br />

information in the frequency domain is modulating the<br />

relative size of two (or more) DCT coefficients within one<br />

image block . During the encoding process, the sender<br />

splits the cover image in (8x8) pixel blocks, each block<br />

encodes exactly one secrete message bit . The embedding<br />

process start with selecting a pseudorandom block bit<br />

which will be used to code the ith message bit [6] .<br />

- Discrete Cosine Transform<br />

The discrete cosine transform (DCT) , like the Fast<br />

Fourier transform (FFT) , uses sinusoidal basis function.<br />

The difference is that the cosine transform basis are not<br />

complex , they use only cosine functions . Assuming ( N<br />

x N ) image , the DCT function is given by :<br />

N−1<br />

N<br />

⎡ + ⎤ ⎡ + ⎤<br />

= ∑ ∑<br />

− 1<br />

(2r<br />

1) uπ<br />

(2c<br />

1) vπ<br />

T(<br />

u,<br />

v)<br />

α ( u),<br />

α(<br />

V)<br />

I(<br />

r,<br />

c)cos⎢<br />

⎥cos<br />

(1)<br />

⎢ ⎥<br />

r= 0 c=<br />

0 ⎣ 2N<br />

⎦ ⎣ 2N<br />

⎦<br />

The inverse cosine transform is given by :<br />

N−1<br />

N<br />

⎡ + ⎤ ⎡ + ⎤<br />

= ∑ ∑<br />

− 1<br />

(2r<br />

1) uπ<br />

(2c<br />

1) vπ<br />

I(<br />

r,<br />

c)<br />

α(<br />

u),<br />

α(<br />

v)<br />

T(<br />

u,<br />

v)cos⎢<br />

⎥cos<br />

(2)<br />

⎢ ⎥<br />

r= 0 c=<br />

0<br />

⎣ 2N<br />

⎦ ⎣ 2N<br />

⎦<br />

Where α(u),α(v) = sqrt(1/N) if α(u),α(v) = 0<br />

or<br />

= sqrt(2/N) if α(u),α(v)= 1, 2, 3, .N<br />

Where, sqrt(.), means the square root.<br />

Given this interpretation of the DCT , the way to lose<br />

the unimportant image information is to reduce the size<br />

of the 64 numbers. There is a chance that this will nott<br />

degrade the image quality much. This does not always<br />

work , so in general , each of the 64 numbers is divided<br />

by the different quantization coefficient (QC) in order to<br />

reduce its size .<br />

Quantization : after each 8×8 matrix of DCT<br />

coefficient calculated it is quantized. This is the step<br />

where information loss. Each numbers in the DCT<br />

coefficient matrix is divided by the corresponding<br />

numbers from particular quantization table used and the<br />

results is rounded to the nearest integer .<br />

A simple quantization table Q is computed , <strong>based</strong> on<br />

one parameters R supplied by the user. A simple<br />

expression such as<br />

guarantees that Qs start<br />

Q = 1+<br />

( i + j)<br />

× R<br />

ij<br />

small at the upper left corner and get bigger toward the<br />

bottom right corner.<br />

The (DCT) is applied not to the entire image but to the<br />

data image units (blocks) to reduce the arithmetic<br />

operation and then speed the algorithm up [7]. One can<br />

remember that transform coefficient are the projection of<br />

the Original image on to each basis image.<br />

III. AGENT SYSTEM<br />

It is fairly young area of research, there is not yet a<br />

universal consensus definition of an agent. However, the<br />

Wooldridge and Jennings definition:<br />

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MASAUM Journal of Computing, Volume 1 Issue 2, September 2009 261<br />

" As <strong>Agent</strong> is a computer system that is situated in<br />

some environment and that is capable of autonomous<br />

action in this environment in order to meet it design<br />

objective".<br />

Let us note that we are talking about (software agent)<br />

whenever or any other researchers in the field say (agent),<br />

we really mean software agent. The typical dictionary<br />

definition of agent, as <strong>An</strong> entity having the authority to act<br />

on behalf of another [14].<br />

Some definitions were tied to specific implementation<br />

technology such as being <strong>based</strong> on theorem proves , or<br />

<strong>using</strong> internal data structure corresponding to the socalled<br />

mentalist concepts , such as beliefs or knowledge ,<br />

goal or desires , intention , and so on.<br />

So a good working definition of agent is that [15]:<br />

"It is a persistent computational entity that can<br />

perceive, reason, Act, and communicate".<br />

A. Software <strong>Agent</strong> Properties<br />

The basic properties of software agent are that they are:<br />

• Autonomous: being autonomous, mean that agents are<br />

independent and make their own decision, this is one<br />

property that distinguish agent from object.<br />

• Situated ness : dose not constrain the notion of an agent<br />

very much since virtually all software can be consider to<br />

be situated in an environment [14].<br />

• Flexibility : can be define to include the following<br />

property :<br />

I. Responsive: Refer to agent ability to perceive its<br />

environment and respond in a timely fashion to change<br />

that occur in it.<br />

II. Pro-active : <strong>Agent</strong> are able to exhibit opportunistic ,<br />

goal –driven behavior , take initiative where appropriate<br />

III. Social: <strong>Agent</strong> should be able to interact, where<br />

appropriate, with other agent or human in order to solve<br />

their own problem and help other with their activities.<br />

B. <strong>Agent</strong> Classification<br />

The various definitions involve a host properties of an<br />

agent. Having settled on a much less restrict definition of<br />

an agent, this property may help us further classify agents<br />

in useful ways.<br />

<strong>Agent</strong> may be usefully classified according to the subset<br />

of these properties that they enjoy. Every agent by our<br />

definition, satisfies the first four property, adding other<br />

property reduce potentially useful classes of agents. For<br />

example: mobile, learning agent. Thus a hierarchical<br />

classification <strong>based</strong> on set inclusion occurs naturally.<br />

There are of course other possible classifying scheme ,<br />

for example , we might classify software agent according<br />

to the tasks they perform. For example, information<br />

gathering agents or email filtering agent , or we might<br />

classify them according to their control architecture. Then<br />

would be fuzzy agent. Also agent could be classified by<br />

the range and sensitivity of their senses , or by the much<br />

internal state they posses [16].<br />

IV. PROPOSED IMAGE STEGANORGRAPHY BASED ON<br />

AGENT<br />

This paper uses two methods of steganorgraphy, the<br />

first one is the discrete cosine transform (DCT)<br />

<strong>Steganography</strong> , and the second one is least significant bit<br />

(LSB) steganorgraphy .<br />

A. The Proposed <strong>Agent</strong> System in steganorgraphy<br />

Our approach make general assumption about agent .<br />

Also in this section we dedicate to present images<br />

database which used by the agents. According to some<br />

features of media (image) the agent will recommend the<br />

user to select the best cover (image) and the suitable<br />

image steganorgraphy methods that are assumed to be<br />

available in this project for the selected secret image .<br />

The Model of proposed steganorgraphy <strong>based</strong> agents<br />

shown in Fig. 2, can be classified as: server agents, which<br />

provides services to other. Since the Client- Server<br />

connection is assumed to be used in this system, the<br />

server (PC ) will provide the client with the STEGO.bmp<br />

file ,which contains the secret image.<br />

The basic role of agents in the system is to select image<br />

from a database of images and make analyses of number<br />

of image features , and according to these features, the<br />

agent will choose the suitable steganography method and<br />

best cover for the specific steganography method, and<br />

give the user a recommendation for selected cover and<br />

selected steganography system .<br />

B. <strong>Agent</strong> system for <strong>Image</strong> feature calculation<br />

In this system, the agent will place at random on<br />

image (the environment). The choice of cover image is<br />

important because it is significantly influences the result<br />

obtained from the proposed system, and it will affect the<br />

resulted security of the whole system.<br />

The calculated image features by agent are:<br />

• Histogram : is a plot of gray level values versus the<br />

number of pixels. The histogram used as probability<br />

distribution of gray level:<br />

P (g) = N ( g)<br />

(3)<br />

M<br />

Where M :is number of pixels in image .<br />

N (g): is number of pixels at gray level g.<br />

• Mean: is the average value, so it tells something<br />

about general brightness of the image.<br />

−<br />

I( r,<br />

c)<br />

(4)<br />

g = ∑∑<br />

r c M<br />

Where I(r,c) is the image pixel value.<br />

• Standard deviation : which is known as square<br />

root of variance. It tells something about contrast ,<br />

and describes and expressed as follows:<br />

L 1 −<br />

=<br />

σ ( g − g ) p(<br />

g)<br />

(5)<br />

g<br />

g∑ −<br />

= 0<br />

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MASAUM Journal of Computing, Volume 1 Issue 2, September 2009 262<br />

• Entropy : the entropy is a measure for how many<br />

bits we need to code the image data . As the pixels<br />

values in the image are distributed among more<br />

gray levels , the entropy increase [5]. <strong>An</strong>d it can be<br />

expressed as follows:<br />

l 1<br />

g∑ −<br />

= 0<br />

Entropy = - p(<br />

g)log<br />

[ p(<br />

)]<br />

2<br />

g<br />

Steganorgraphic agent computes the previous features,<br />

after picking up an image from images database , and<br />

make a decision or a choice. Detecting a suitable cover<br />

for the secret image for embedding and specified<br />

steganographic method. Steganographic agent tries to<br />

find or detect an image with: highest variance ,<br />

maximum contrast , and high entropy.<br />

<strong>Agent</strong> chooses the cover image suitable for<br />

steganographic method ; that is similar to secret image<br />

and nearly of the same size of cover image.<br />

(6)<br />

Corr =<br />

Where<br />

1<br />

⎡<br />

⎢<br />

⎣<br />

N<br />

N M<br />

∑∑ ( I I<br />

(9)<br />

r=<br />

1 c=<br />

1<br />

M<br />

∑∑<br />

I1(<br />

r,<br />

c)<br />

− )( I<br />

2<br />

( r,<br />

c)<br />

− )<br />

1<br />

2<br />

( I ( r,<br />

c)<br />

−<br />

1<br />

r= 1 c=<br />

1<br />

1<br />

−<br />

I<br />

−<br />

⎤ ⎡<br />

⎥ ⎢<br />

⎦ ⎣<br />

N<br />

M<br />

∑∑<br />

r= 1 c=<br />

1<br />

−<br />

−<br />

⎤<br />

( I<br />

2<br />

( r,<br />

c)<br />

− I2<br />

⎥<br />

⎦<br />

I − : is the mean value of original image<br />

I ( r,<br />

c)<br />

that is :<br />

1<br />

−<br />

1<br />

=<br />

1 M × N<br />

N<br />

M<br />

I ∑∑ I<br />

r = 1 c=<br />

1<br />

( r,<br />

c)<br />

1<br />

I − : is the mean value of modified image ( , )<br />

2<br />

I r c<br />

2<br />

−<br />

N M<br />

1<br />

I =<br />

( r,<br />

c)<br />

2<br />

2<br />

M × N<br />

∑∑I<br />

r= 1 c=<br />

1<br />

(10)<br />

that is :<br />

(11)<br />

If correlation is equal to 1, this means that the two images<br />

are perfectly similar.<br />

C. Evaluation parameters<br />

There are two types of fidelity criteria; namely, the<br />

objective and the subjective criteria. The first one<br />

provides us with equation that can be used to measure the<br />

amount of the errors in the reconstructed image. Where<br />

the second criteria requires the definition of the<br />

qualitative scale of image quality.<br />

Commonly used objective measures are the peak signal<br />

–to-noise ratio (PSNR), and correlation parameter [5].<br />

1- Peak Signal –To-Noise Ratio (PSNR )<br />

To describe the quality of the STEGO image precisely ,<br />

we use the value of the (PSNR) to judge the similarity<br />

between the host image and the STEGO image. The<br />

(PSNR) function is defined as follows [20] :<br />

PSNR = 10 2<br />

( L − 1)<br />

log db (7)<br />

10<br />

MSE<br />

Where L = 1, 2…256<br />

Here the MSE is the mean square error. Subsequently we<br />

define MSE as Follow:<br />

MSE= 1<br />

( WH )<br />

w<br />

H<br />

∑∑<br />

i= 1 j=<br />

1<br />

( α ( I,<br />

J ) − β ( I,<br />

J ))<br />

(8)<br />

The symbol α ( I,<br />

J ) and β ( I,<br />

J ) separately represent<br />

the pixels values of the cover image, and the STEGO<br />

image in position (I,J) . While the W and H represent the<br />

width and height of image respectively [18] .<br />

2- Correlation (Corr)<br />

This test measures the similarity between two images and<br />

can be defined as follows [19]:<br />

2<br />

V. CASE STUDIES<br />

The cover image (C) selected from image database by<br />

steganography agent. The visual quality of STEGO<br />

image is much better than that obtained when we select<br />

cover image arbitrary from image database .<br />

The image block size (taken into consideration in our<br />

system ) is either (2,4,8), effects on the quality of stego ,<br />

and best result ( maximum PSNR ) is obtained when<br />

(n) or block size = 2 and with R = 0.1.<br />

Although the block size chosen = 2 and the R = 0.1 , the<br />

STEGO image has distortion.<br />

We will test the effect of block size and the quantized<br />

value R that effects the STEGO quality , and we chose R<br />

value as small value, to get better STEGO image<br />

quality .<br />

Example :<br />

Let us chose the secret image that we want to embed<br />

inside the cover image . Then arbitrary selected a cover<br />

image (C1.bmp) from image database Shown in Fig. 3.<br />

The results of the objective test are as follows:<br />

The Maximal value among all values of PSNR , it's<br />

corresponding Stego image is most similar to the host<br />

image (Cover image ). The block size = 2. <strong>An</strong>d quantize<br />

R value =0.1. <strong>An</strong>d the feature of Cover image (C1.bmp)<br />

or statistical feature is shown in table 1and 2.<br />

VI. CONCLUSIONS<br />

- The agent helps to identify component which offers<br />

benefits.<br />

- The agent makes decision. In this paper we have<br />

analyzed different parameters by the agent. The<br />

agent we have deal with have information about<br />

cover image and can adapted to BMP type of cover<br />

image.<br />

262


MASAUM Journal of Computing, Volume 1 Issue 2, September 2009 263<br />

- The goal of steganography is to avoid attacker from<br />

discovering the secret images embedded in the<br />

cover image. To improve security level we must<br />

obtain acceptable STEGO image quality. Overall,<br />

the proposed system matches the requirements to<br />

obtain acceptable STEGO image.<br />

REFERENCES<br />

[1] Chin- Chen C., Ju-Yuan H., and Chi-Shiang C., "finding optimal<br />

least significant –bit substitution in image hiding by dynamic<br />

programming strategy" department of computer science and<br />

information engineering Taiwan pattern Recognition,36, pp. 1583 -<br />

1595, 2003.<br />

[2] Chin –Chang Tung –Shung –Shon C and Lou- Zo C , "A<br />

steganography method <strong>based</strong> upon JPEG and quantization table",<br />

information engineering and computer science department , national<br />

Chung Cheng university , 141 pp 123-138, 2002.<br />

[3] Tao Z. and Xijian P., "A new approach to reliable detection of LSB<br />

steganography in natural images", Signal Processing, (83), pp. 2085-<br />

2093, 2003.<br />

[4] Najla'a H.M, "New robust information hading technique",<br />

<strong>Information</strong> institute university of technology, Baghdad, Iraq M.Sc.<br />

thesis, 2005.<br />

[5] Sabu . M. Th. and K. Chandra S. ,"<strong>Steganography</strong> <strong>based</strong> WWW<br />

distribution image retrieval with mobile agents ", department of<br />

computer engineering national institute of technology, Karnataka,<br />

department of computer science and engineering L.B.S collage of<br />

engineering , Kasaragod, 2004.<br />

[6] Tabais S.G.G, " <strong>Agent</strong>-Based recommendation systems",<br />

Department of computer and system science, university of Stockolm,<br />

royal institute of technology, M.Sc. Thesis,1999.<br />

[7] Qi D. and Robert K. A., "Fostering multimedia learning of science:<br />

Exploring the role of an animated agent's image". Computer and<br />

education, 2005.<br />

[8] Katzenbeisser and F. A. P. Petitcolas, " <strong>Information</strong> hiding<br />

techniques for steganography and digital watermarking", ARTECH<br />

HOUSE, 2000.<br />

[9] David Salmon, "Data compression", SPRINGER-VERLAG New<br />

York, 1998.<br />

[10] Scott E. Umborgh, "Computer vision and image processing a<br />

practical approach <strong>using</strong> CVIP tools", PRENTIC HALL, 1998.<br />

[11] Stan Franklin and Art. G., "It is <strong>An</strong> AGENT OR JUST A Program?<br />

A taxonomy for <strong>Agent</strong> institute for intelligent system university of<br />

Memphis Springer –Verlage 1996.<br />

[12] Willam Stalling, "Cryptography and network security principle<br />

and practice", PRINTIC-HALL, 1999.<br />

[13] Sorina D , Xiaolin W, and Zhe W, "Detection of GSB<br />

<strong>Steganography</strong> via sample pair analysis" , Electronic and computer<br />

engineering department , Mc Mcmaster university Hamilton Ontario ,<br />

Canada L8s 4 Ki 2003.<br />

[14] <strong>An</strong>derw D. Ker, "Quantitative evaluation of pairs and RS<br />

steganalysis", computing laboratory, Oxford University England 2004.<br />

[15] K.Goplan, "Cepstral Domain modification of audio signals for<br />

data embedding preliminary result" department of engineering purdue<br />

university Calument Hammond in 46323, 2004.<br />

[16] Chi-Kwong C. and L. M. Cheng, "Hiding data in images by simple<br />

least significant bit", department of computer Engineering and<br />

information technology , university of Hong Kong ,pattern recognition ,<br />

37, pp 469-474, 2004.<br />

[17] Jessica F. and Miroslav G., "On Estimation of secret message<br />

Length in LSB-<strong>Steganography</strong> in Spatial Domain ", Department of<br />

electrical and computer engineering , SUNY,BINGHAMTON, NY<br />

13902-6000.<br />

[18] Federico B., Marie –pierre .G. and Franco. Z. "Methodology and<br />

software engineering for agent system" KLUWER ACADEMIC<br />

PUBLISHERS, 2004.<br />

[19] Padghame & Michael Winkoff, "developing intelligent agent<br />

system" JHON WEILY & SONS 2000.<br />

[20] Nine L and K .P.S., "Vector quantization <strong>based</strong> scheme for data<br />

embedding for image ." network and communication laboratory ,<br />

department of computer and electronic engineering , Steven institute of<br />

technology , HOBOKEN,NJ030,2004.<br />

TABLE 1. THE OBJECTIVE MEASURES FOR S1.BMP &<br />

C1.BMP CHOSEN BY STEGANORGRAPHY AGENT<br />

ACCORDING TO IMAGE FEATURE.<br />

Block size Quantize value R PSNR(db) Correlation<br />

2 0.1 30.5913 0.998366<br />

4 0.1 25.1837 0.994315<br />

8 0.1 22.2076 0.988698<br />

TABLE 2. C1.BMP FEATURES<br />

Mean 111.5858<br />

Entropy 7.763618<br />

Energy 5.252129e-<br />

003<br />

Variance 4918.591<br />

Contrast 70.13267<br />

Secret image ( S1.bmp) Cover image (C1.bmp )<br />

STEGO <strong>Image</strong><br />

Fig. (3) The Secret image (s1), the cover image C1,<br />

and the resulted stego image used in example.<br />

263


MJC010234 264<br />

STEGANOGRAOHY<br />

Substitution<br />

system<br />

Transform<br />

Domain<br />

technique<br />

Spread<br />

spectrum<br />

technique<br />

Statistical<br />

method<br />

Distortion<br />

technique<br />

Cover<br />

generation<br />

method<br />

Fig. (1) Steganorgraphy Classification<br />

<strong>Agent</strong> read cover<br />

image &Extract<br />

feature<br />

Cover<br />

<strong>Image</strong><br />

DB<br />

DCT<br />

Steganograph<br />

STEGO<br />

<strong>Image</strong><br />

Server Computer<br />

<strong>Agent</strong> make a decision<br />

for best cover image and<br />

choose suitable<br />

steganography method<br />

LSB<br />

<strong>Steganography</strong><br />

DCT<br />

Steganograph<br />

Dr. Eng Sattar Bader Sadkhan , Chief<br />

Scientific Researcher Science 1997,<br />

Technology Expert Since 2003, Chairman of<br />

IEEE IRAQ SECTION and (currently)<br />

Postgraduate Lecturer in Babylon University.<br />

Expert in : Wireless Digital Communication<br />

and <strong>Information</strong> Security.<br />

Diploma in Radar Equipments Repairing (1970-<br />

1974)- from Wireless and Radar training Center – B.Sc. (1974-1978)<br />

Baghdad – IRAQ – Electrical and Electronic Engineering. M.Sc. (1979-1981)<br />

in VAAZ Academy- BRNO – CZECH Republic –Wireless Communication<br />

Engineering. Ph.D. (1981-1984) in VAAZ Academy- BRNO- CZECH<br />

Republic- Detection of Digital Modulated Signals. Diploma in Cryptography<br />

in 1988 – From Switzerland.<br />

Since 1991 up to 2003, in Communication Research and Development Center<br />

–Institute of Research and Development. I am engaged as Researcher in this<br />

Center and I obtained the director position of this center in 2000 till 8 April<br />

2003.<br />

Postgraduate Lecturer, Director of Cultural Relation and Scientific Affairs,<br />

Director of Research Centers of Babylon Studies,<br />

Editor-in-Chief, for the International Scientific Journal of Advancement<br />

in Computing Technology, (IJACT), in South Korea, since beginning of<br />

2009.<br />

http://www.aicit.org/ijact/<br />

Member of (80) Scientific and Editing Committees of International<br />

Scientific Journals, and International Conferences (Arabic and International).<br />

Advisor of more than (100) Postgraduate theses (M.Sc. <strong>An</strong>d Ph.D.).<br />

Publishing more than (160) papers in (Arabic, and International)<br />

Academicals journals and conferences.<br />

Reconstructed<br />

Reconstructed<br />

image<br />

image<br />

Extraction<br />

process<br />

Extraction<br />

process<br />

Client Computer<br />

STEG<br />

O file STEG<br />

O file<br />

Fig. (2): The Agency of Stenography system Diagram<br />

264

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