1
CHAPTER 1
INTRODUCTION
With advancements in digital communication technology and
the growth of computer power and storage, the difficulties in ensuring
individuals’ privacy become increasingly challenging. The degrees to
which individuals appreciate privacy differ from one person to
another. Various methods have been investigated and developed to
protect personal privacy. Encryption is probably the most obvious
one, and then comes steganography.
Steganography is an old art which has been in practice since
time unknown. Steganography, from the Greek, means covered or
secret writing and is thus the art of hiding messages inside
innocuous cover carriers, e.g. images, audio, video, text, or any other
digitally represented code or transmission, in such a manner that the
existence of the embedded messages is undetectable. The hidden
message may be plaintext, ciphertext, or anything that can be
represented as a bit stream. Encryption lends itself to noise and is
generally observed while steganography is not observable.
Steganography and cryptography, though closely related, they are not
the same. The former has the intent to hide the existence of the
message whereas the later scrambles a message to absolute
illegibility.
The goal of steganography is to avoid drawing suspicion to the
transmission of a hidden message. It hide messages inside other
harmless messages in a way that does not allow any enemy to even
detect that there is a second secret message present. If suspicion is
raised, then this goal is defeated. Discovering and rendering useless
such covert messages is another art form known as steganalysis.
2
This approach of information hiding technique has recently become
important in a number of application areas. Digital audio, video, and
pictures are increasingly furnished with distinguishing but
imperceptible marks, which may contain a hiding copyright notice or
serial number or even help to prevent unauthorized copying directly.
Military communications system make increasing use of traffic
security technique which, rather than merely concealing the content of
a message using encryption, seek to conceal its sender, its receiver
or its very existence. Similar techniques are used in some mobile
phone systems and schemes proposed for digital elections.
1.1 Steganography
Steganography is the art and science of writing hidden messages in
such a way that no one, apart from the sender and intended recipient,
suspects the existence of the message, a form of security through
obscurity.
3
Figure: The different embodiment disciplines of Information Hiding.
The arrow indicates an extension and bold face indicates the focus of
this study.
Intuitively, this work makes use of some nomenclature
commonly used by steganography and watermarking communities.
The term “cover image” is used throughout this thesis to describe the
image designated to carry the embedded bits. An image with
embedded data, payload, is described as “stego-image” while
“steganalysis” or “attacks” refer to different image processing and
statistical analysis approaches that aim to break steganography
algorithms. People use to confuse steganography with cryptography,
which is wrong.
Steganography and cryptography, though closely related, they
are altogether different. The former hides the existence of the
message, while the latter scrambles a message so that it cannot be
understood (Sellars, 1999). But the two techniques must not be
perceived as mutually exclusive and if used together can prove more
powerful. As we have said of steganography, the embedded data is
not necessarily encrypted; hidden message may be plaintext,
ciphertext, or anything that can be represented as a bit stream.
Embedding encrypted message could be more secure and effective.
4
Figure 1: General scheme of steganography
1.2 Steganography vs. Cryptography
Basically, the purpose of cryptography and steganography is to
provide secret communication. However, steganography is not the
same as cryptography. Cryptography hides the contents of a secret
message from a malicious people, whereas steganography even
conceals the existence of the message. Steganography must not be
confused with cryptography, where we transform the message so as
to make it meaning obscure to a malicious people who intercept it.
Therefore, the definition of breaking the system is different [6]. In
cryptography, the system is broken when the attacker can read the
secret message. Breaking a steganographic system need the attacker
to detect that steganography has been used and he is able to read
the embedded message.
In cryptography, the structure of a message is scrambled to
make it meaningless and unintelligible unless the decryption key is
available. It makes no attempt to disguise or hide the encoded
message. Basically, cryptography offers the ability of transmitting
information between persons in a way that prevents a third party from
reading it. Cryptography can also provide authentication for verifying
the identity of someone or something.
5
In contrast, steganography does not alter the structure of the
secret message, but hides it inside a cover-image so it cannot be
seen. A message in ciphertext, for instance, might arouse suspicion
on the part of the recipient while an “invisible” message created with
steganographic methods will not. In other word, steganography
prevents an unintended recipient from suspecting that the data exists.
In addition, the security of classical steganography system relies on
secrecy of the data encoding system. Once the encoding system is
known, the steganography system is defeated.
It is possible to combine the techniques by encrypting
message using cryptography and then hiding the encrypted message
using steganography. The resulting stego-image can be transmitted
without revealing that secret information is being exchanged.
Furthermore, even if an attacker were to defeat the steganographic
technique and detect the message from the stego-object, he would
still require the cryptographic decoding key to decipher the encrypted
message.
Table below shows a comparision between the three
techniques.
Criterion/
Method
Steganography Watermarking Cryptography
Carrier any digital media mostly
image/audio files
usually text
based,
with some
extensions
to image files
Secret data payload watermark plain text
no changes to the structure changes the
structure
Key optional necessary
Detection blind usually blind
6
informative,
i.e.,
original cover
or watermark is
needed for
recovery
Authentication full retrieval of data usually
achieved by
cross
correlation
full retrieval of
data
Objective secrete
communication
Copyright
preserving
data protection
Result stego-file watermarked-
file
cipher-text
Concern delectability/
capacity
robustness robustness
Type of
attacks
steganalysis image
processing
cryptanalysis
Visibility never sometimes Always
Fails when it is detected It is removed/
replaced
de-ciphered
Relation to
cover
not necessarily
related to the
cover. The
message is
more important
than the cover.
usually
becomes an
attribute of the
cover image.
The cover is
more important
than the
message.
N/A
Flexibility free to choose any
suitable cover
cover choice is
restricted
N/A
History very ancient
except its digital
version
modern era modern era
7
Figure 2: Different steganography fields
Our work is Data Hiding (protection against detection). We have used
the cover object as digital image and stego object(secret data) as the
text file.
8
CHAPTER 2
DIGITAL IMAGE STEGANOGRAPHY
Steganography can also be classified a on the basis of carrier
media. The most commonly used media are text, image, audio and
video. So here Digital Images are used as the carrier media.
2.1 DIGITAL IMAGES
A digital image is defined for the purposes of this document as
a raster based, 2-dimensional, rectangular array of static data
elements called pixels, intended for display on a computer monitor or
for transformation into another format, such as a printed page. To a
computer, an image is an array of numbers that represent light
intensities at various points, or pixels. These pixels make up the
image's raster data. Digital images are typically stored in 32-, 24- or
8-bit per pixel files. In 8-bit color images, (such as GIF files), each
pixel is represented as a single byte. A typical 32 bit picture of
width=n pixels and height = m pixels can be represented by an m x n
matrix of pixels.
9
Figure 3: Matrix and bits representation of an image file.
The three 8 bit parts - red-R, blue-B and green-G - constitute
24 bits which means that a pixel should have 24 bits. 32 bit refers to
the image having an "alpha channel". An alpha channel is like an
extra color, although instead of displaying it as a color, it is rendered
translucently (see-through) with the background.
IMAGE FORMATS
There are several image formats in use nowadays. Since raw
image files are quite large, some suitable compression technique is
applied to reduce the size. Based on the kind of compression
employed a given image format can be classified as lossy or lossless.
Lossy compression is used mostly with JPEG files and may not
maintain the original image's integrity despite providing high
10
compression. Obviously it would infect any data embedded in the
image. Lossless compression does maintain the original image data
exactly but does not offer such high compression rates as lossy
compression. PNG, BMP, TIFF and GIF etc are example lossless
formats.
Some commonly used formats are JPEG, BMP, TIFF, GIF and
PNG; the last two types of images are also called palette images. We
discuss here all these formats briefly:
1. TIFF- Tagged Im age File Format (TIFF), which was
developed by the Aldus Corp. in the 1980's, stores many
different types of images ranging from monochrome to true
color. It is a lossless format using LZW (Lempel- Ziv Welch)
compression, a form of Huffman Coding. It is not lossless when
utilizing the new JPEG tag that allows for JPEG compression.
There is no major advantage over JPEG though the quality of
original image is retained. It is not as user-controllable as
claimed.
2. BMP- This is a system standard graphics file format for
Microsoft Windows and hence proprietary and platform
dependent. It is capable of storing truecolor bitmap images and
used in MS Paint and Windows wallpapers etc. Being an
uncompressed file format, it requires high storage.
3. GIF . The Graphics Interchange Format (GIF) is a lossless
format that uses the LZW algorithm which is modified slightly
for image scan line packets (line grouping of pixels). UNISYS
Corp. and CompuServe introduced this format for transmitting
graphical images over phone lines via modems. It is limited to
only 8-bit (256) color images, suitable for images with few
distinctive colors (e.g., graphics drawing). GIF format is also
used for nonphotographic type images, e.g. buttons, borders
etc. It supports simple animation.
11
4. JPEG - A creation of Joint Photographic Expert Group was
voted as international standard in 1992. It takes advantage of
limitations in the human vision system (HVS) to achieve high
rates of compression. It is a lossy type of format which allows
user to set the desired level of quality/compression. By far one
of the most common image formats, it is primarily used for
photographs. JPEGs are extremely popular since they
compress into a small file size and retain excellent image
quality.
5. PNG - (Portable Network Graphic) is a lossless image format,
properly pronounced "ping". The PNG format was created in
December 1994 and was endorsed by The World Wide Web
Consortium (W3C) for its faster loading, and enhanced quality
platform-independent Web graphics. It was designed to
replace the older and simpler GIF format. Like GIF you can
make transparent images for buttons and icons, but it does not
support animation. The compression is asymmetric; reading is
faster than writing.
We have choosen PNG image file format as our carrier media
because of the following advantages:
1. PNG is the most flexible image format for web because it can
save images in 8-bit, 24-bit and 32-bit colours which is not
possible with GIF and JPEG file formats. For example, GIF can
only store only 8-bit or lower bit depths. Similarly, JPEGs must
be stored in 24-bit and no lower while PNG.s can be stored in
8-bit, 24-bit, or 32-bit.
2. PNG uses a lossless compression method, which means that
an image can be compressed and decompressed without any
loss of the image quality. PNG is compressed using any
number of pre-compressed filters and is then decompressed
when viewed similar to JPEG format, except the PNG format is
12
.lossless.. PNG.s compression engine typically compresses
images 5-25% better than GIF.
3. PNG can store a variable transparency value known as alpha
channel transparency. This allows an image to have up to 256
different levels of partial transparency. While, JPEG does not
support transparency, PNG can also store the gamma value of
an image on the platform it was created which can enable a
display system to present the image on its correct gamma
value, if it has been specified. Correct gamma value enables a
picture to display properly on different platform without losing
its quality during transformation.
4. Metadata for Searching and Indexing as keywords and other
text strings (compressed or otherwise) can be incorporated to
enable search engines to locate the image on web.
2.2 STEGANOGRAPHY TECHNIQUES
The following restrictions and features should be kept in mind
during the embedding process:
It is important that the embedding occur without significant
degradation or loss of perceptual quality of the cover.
For data consistency, original data of the cover rather than
header or wrapper must be used for embedding.
Intelligent attacks or anticipated manipulations such as filtering
and resampling should not mutilate the embedded data.
Four main factors that characterize the data hiding techniques in
steganography:
Hiding Capacity: the size of information that can be hidden
relative to the size of the cover.
13
Perceptual Transparency: It is important that the embedding
occur without significant degradation or loss of perceptual
quality of the cover.
Robustness: the ability of embedded data to remain intact if the
stego-image undergoes transformations.
Tamper Resistance: refers to the difficulty for an attacker to
alter or forge a message once it has been embedded.
Digital data can be embedded in many ways into the images,
e.g. sequential, random, non-random (looking for .noisy. areas of the
image, that will attract less attention), redundant etc. Each one of
these has its own merits and demerits. The most common techniques
of data hiding in images are:
1. Appending data bytes at the end of carrier:
The secret data bytes are appended at the end of the carrier
media such as image and the carrier media is then
compressed to its original size to reduce the suspects of
having secret data.
Advantage is that it is very easy to implement. Disadvantage is
it is very easy to detect and get the message.
2. Least significant bit (LSB) insertion:
LSB techniques embed the message bits directly into the least-
significant bit plane of the cover image in a deterministic
sequence. This results in a change with too low an amplitude
to be human-perceptible. LSB embedding is simple, popular
and many techniques use these methods. The problem is its
vulnerability to image manipulation.
3. Public Key Steganography
This method requires the pre-existence of a shared secret key
to designate pixels which should be tweaked. Thus both the
sender and the receiver must have this secret. The idea of
14
private/public key pair doesn.t work since the eavesdropper
can use the public key to sabotage the whole affair.
4. Transform domain based embedding:
Transform Embedding Techniques embed the data by
modulating coefficients in a transform domain, such as
Discrete Fourier Transform (DFT), Discrete Cosine Transform
(DCT) (used in JPEG compression), or Discrete Wavelet
Transform (DWT). Modifying the transform coefficients
provides more robustness to the compression (especially to
lossy), cropping, or some image processing, than LSB
techniques. The Spread-Spectrum Image Steganography
(SSIS) hides the data within noise which is then added to the
cover. The noise is of the type usually incurred during the
image acquisition process. Such a
noise is imperceptible to humans if kept to limited extent. The
decoding process involves image restoration techniques and
error control coding.
5. Masking and filtering techniques:
This techniques embed information to perceptually significant
areas of the image. The use of significant parts make these
techniques very robust. Masking refers to the phenomenon
were a signal can be imperceptible to an observer in the
presence of another signal - referred to as the masker (Lin &
Delp, 1999). The phenomenon of camouflage is manifestation
of this human weakness. The image must be analyzed in
advance for the information to determine appropriate regions to
place the message data so that it is camouflaged in the
environment.
15
CHAPTER 3
DETAILED IMAGE STEGANOGRAPHY WORK BASED
ON LSB INSERTION
Flow Diagram-
Transmission
Channel
Encoding
Program Message
(Text File)
Image (Embedded within the
text message file)
Image (Cover File)
Message (Text file)
Decoding
Program
16
Probably the most popular, LSB embedding techniques embed
data bits in the least significant bits of the image under the
assumption that the resultant change would be highly imperceptible
due to obvious limitations of HVS. A significant amount of information
can be embedded without visible loss of quality of the cover image.
The overall change to the image is so minor that it can't be seen by
the human eye.
LSB insertion algorithm can be applied in two ways:
First LSB algorithm
1 0 0 1 0 0 0 1
Here only the last bit of the pixel is modified to hide the data. It is
implemented highly because of its simplicity and good picture quality.
Second LSB algorithm
1 0 0 1 0 0 0 1
Here last two bits are subjected to change to increase the amount of
data to be hidden. Eventually the picture quality is less than our first
LSB algorithm.
Steps of LSB insertion algorithm (Using java)
Step 1:
The carrier image called the cover object is converted to array
of bits.
This uses the java classes java.awt.image.BufferedImage,
javax.imageio.ImageIO, java.awt.Graphics2D,java.awt.image.
WritableRaster and java.awt.image.DataBufferByte.
BufferedImage: A bufferedImage is something to be
comfortable with when dealing with images. They are easily
used with the newly introduced ImageIO class of Java 1.5.0 as
17
well as containing methods for accessing the raster and buffer
of the image, which makes image editing much easier.
ImageIO: A useful class to handle IO operations on images.
This class has much to offer, but as far as this program is
concerned, the read() and write() methods will be sufficient.
Graphics2D: A class which has been around for a long time
as far as Java is concerned, and allows access to some of the
more in depth aspects of graphics/images. Allows for creating
editable areas in a new image or an image which already
exists. As well as allowing a way to reach the renderable area
of the image. This class also allows for an easy switch from
image space to user space, which is necessary when
modifying or reading certain bytes of an image.
WritableRaster: This by definition is the process of rendering
an image pixel by pixel, which comes in handy when you need
to access the bytes of an image, that are representing pixels.
WritableRaster is a sub-class of Raster itself, which has
methods to access the buffer of an image more directly.
DataBufferByte: The form of a byte array buffer for an image.
Figure 4: Accessing bits of an image
18
Step 2:
The secret message text file called the stego object is read
and its characters/ bytes are converted to ascii values and then
to array of bits.
For reading the file it uses StringBuffer, BufferedReader and
FileReader classes.
After reading the file, the file is stored in a String.
The String is converted array of bits by converting all
characters to ascii value and doing some bit operations.
Figure 5: Accessing the Bits of a Text File.
Step 3:
Now the text bytes are embedded in the carrier image bytes.
Here is a carrier image byte:
0 1 1 0 1 0 1 0
The decimal value of this byte is 106
When we change one LSB from 0 to 1
0 1 1 0 1 0 1 1
19
The decimal value changes to 107. This change will affect a
little bit in some of the colour of a pixel which cannot be
marked with human eye.
But if we change some bits other than LSB, there will be a
significant chane in value and can be marked with human eye.
That’s why we are replacing the LSB of the image byte with the
secret data bytes.
One bit of the secret data bit is inserted to the LSB of the
image byte. So one byte of the secret data requires 8 bytes of
the image.
The length of the text in binary form is calculated beforehand,
and hidden in the image before the text. In other words, the
steganographic information (the stego) has two parts: the size
of the binary message, followed by the message itself.
20
Figure 6: Inserting the Text Bits into the Image.
First 32 bytes of the image consists of the size of the secret
data. Because size of data is an integer and integer takes 4
bytes or 32 bits in java. So to accommodate 32 bits of the size
of data(integer), it require 32 bytes as each bit will be inserted
to LSB first 32 bytes of data.
Size of message Message
32 bytes
Step 4:
The message de-embedded/ extracted from the image.
Extracting the text from the modified image involves copying
the LSB of the modified image’s bytes and recombining them
into bytes in a text file as shown in the figure.
After that hidden bytes are constructed by shift left operation
and inserting hidden bytes.
All those hidden bytes are collected and finally written to a new
text file and saved.
21
Figure 7: Extracting text from modified image
Figure 8: Constructing hidden Bytes array by shift left operation
Here we can see two images. The first image is original image
dolphin.png and the second one is outputImage.png which contains
the text information. The change in picture cannot be detected with
human eye.
22
Original image- Dolphin.png
Embedded stego image- outputImage.png
3.1 ADVANTAGES OF LSB ALGORITHM
The advantages of LSB are its simplicity to embed the bits of
the message directly into the LSB plane of cover-image and many
techniques use these methods. Modulating the LSB does not result in
a human-perceptible difference because the amplitude of the change
is small. Therefore, to the human eye, the resulting stego-image will
look identical to the cover-image. This allows high perceptual
transparency of LSB.
The advantages of LSB techniques are:
Popularity
Easy to understand and comprehend
High perceptual transparency.
Low degradation in the image quality
23
More and more commercial software available which follow this
approach. Examples are WebStego, Stego, S-Tools etc.
3.2 DISADVANTAGES
However, there are few weaknesses of using LSB. It is very
sensitive to any kind of filtering or manipulation of the stego-image.
Scaling, rotation, cropping, addition of noise, or lossy compression to
the stego-image will destroy the message.
On the other hand, for the hiding capacity, the size of
information to be hidden relatively depends to the size of the cover-
image. The message size must be smaller than the image. A large
capacity allows the use of the smaller cover-image for the message of
fixed size, and thus decreases the bandwidth required to transmit the
stego-image.
Another weakness is an attacker can easily destruct the
message by removing or zeroing the entire LSB plane with very little
change in the perceptual quality of the modified stego-image.
Therefore, if this method causes someone to suspect something
hidden in the stego-image, then the method is not success.
So the disadvantages are:
Low robustness to malicious attacks
Vulnerable to accidental or environmental noise
Low temper resistance
24
CHAPTER 4
SCREENSHOTS
1. Start Page
It contains a password field to authenticate user. By giving
correct password and pressing ENTER BUTTON, a user
will be directed to the main page of the application.
If password is not known then simply clicking on EXIT
BUTTON the application will terminate.
25
2. Main Interface
This interface contains the functionalities:
ENCODE- The secret message file is encoded/
embedded with the image file.
DECODE- The message is de-embedded from the
modified image file.
HELP- To know about the applications.
ABOUT US- Contains information about mentor and
developer.
EXIT- To terminate application.
26
3. ENCODE INTERFACE
This interface contains-
A text field with browse button to browse an image
cover. This will open filechooser to select a file.
Second text Field with browse button to browse the
secret message file.
Third textbox is for the name of output image which
contains the secret message.
ENCODE BUTTON to start encoding.
CANCEL BUTTON to cancel the encoding operation.
27
4. Successful encoding information
After successful encoding the dialog box will displayed
showing name of the output image and the resultant image
will be opened with the windows default image viewer.
28
5. DECODE INTERFACE
This interface contains-
First textbox with a browse button to browse the image
file containing the secret message. Only the supported
file formats will be displayed in the file chooser.
29
6. Successful decode message
After successful decoding process the information will be
displayed in a dialog box showing the output file secret text
file name and the size of the file.
After the successful decoding of the image the secret text
file is saved and the file will be displayed using notepad.
30
7. About Us screen shot
8. A screenshot of file chooser
31
CHAPTER 5
STEGANOGRAPHY APPLICATIONS
Steganography is applicable to, but not limited to, the following
areas. The area differs in what feature of the steganography is utilized
in each system.
5.1 Confidential communication and secret data
storing
The "secrecy" of the embedded data is essential in this area.
Historically, steganography have been approached in this area.
Steganography provides us with:
(A) Potential capability to hide the existence of confidential data
(B) Hardness of detecting the hidden (i.e., embedded) data
(C) Strengthening of the secrecy of the encrypted data
In practice, when you use some steganography, you must first
select a vessel data according to the size of the embedding data. The
vessel should be innocuous. Then, you embed the confidential data
by using an embedding program (which is one component of the
steganography software) together with some key. When extracting,
you (or your party) use an extracting program (another component) to
recover the embedded data by the same key ( "common key" in terms
of cryptography). In this case you need a "key negotiation" before you
start communication.
Attaching a stego file to an e-mail message is the simplest
example in this application area. But you and your party must do a
32
"sending-and-receiving" action that could be noticed by a third party.
So, e-mailing is not a completely secret communication method.
There is an easy method that has no key-negotiation. We have
a model of "Anonymous Covert Mailing System."
There is some other communication method that uses the
Internet Webpage. In this method you don't need to send anything to
your party, and no one can detect your communication. Each secrecy
based application needs an embedding process which leaves the
smallest embedding evidence. You may follow the following.
(A) Choose a large vessel, larger the better, compared with the
embedding data.
(B) Discard the original vessel after embedding.
For example, in the case of Qtech Hide & View, it leaves some latent
embedding evidence even if the vessel has a very large embedding
capacity. You are recommended to embed only 25% or less (for PNG
/ BMP output) of the maximum capacity, or only 3% of the vessel size
(for JPEG output).
5.2 Protection of data alteration
We take advantage of the fragility of the embedded data in this
application area.
The embedded data can rather be fragile than be very robust."
Actually, embedded data are fragile in most steganography programs.
Especially, Qtech Hide & View program embeds data in an extremely
fragile manner. However, this fragility opens a new direction toward
an information-alteration protective system such as a "Digital
Certificate Document System." The most novel point among others is
33
that "no authentication bureau is needed." If it is implemented, people
can send their "digital certificate data" to any place in the world
through Internet. No one can forge, alter, nor tamper such certificate
data. If forged, altered, or tampered, it is easily detected by the
extraction program.
5.3 Access control system for digital content
distribution
In this area embedded data is "hidden", but is "explained" to
publicize the content.
Today, digital contents are getting more and more commonly
distributed by Internet than ever before. For example, music
companies release new albums on their Webpage in a free or
charged manner. However, in this case, all the contents are equally
distributed to the people who accessed the page. So, an ordinary
Web distribution scheme is not suited for a "case-by-case" and
"selective" distribution. Of course it is always possible to attach digital
content to e-mail messages and send to the customers. But it will
takes a lot of cost in time and labor.
If you have some valuable content, which you think it is okay to
provide others if they really need it, and if it is possible to upload such
content on the Web in some covert manner. And if you can issue a
special "access key" to extract the content selectively, you will be very
happy about it. A steganographic scheme can help realize a this type
of system.
We have developed a prototype of an "Access Control System"
for digital content distribution through Internet. The following steps
explain the scheme.
34
(1) A content owner classify his/her digital contents in a folder-
by-folder manner, and embed the whole folders in some large
vessel according to a steganographic method using folder
access keys, and upload the embedded vessel (stego data) on
his/her own Webpage.
(2) On that Webpage the owner explains the contents in depth
and publicize worldwide. The contact information to the owner
(post mail address, e-mail address, phone number, etc.) will be
posted there.
(3) The owner may receive an access-request from a customer
who watched that Webpage. In that case, the owner may (or
may not) creates an access key and provide it to the customer
(free or charged)..
In this mechanism the most important point is, a "selective
extraction" is possible or not.
We have already developed such a selective extraction
program to implement the system. We have a downloadable demo
program on the other page.
5.4 Media Database systems
In this application area of steganography secrecy is not
important, but unifying two types of data into one is the most
important.
Media data (photo picture, movie, music, etc.) have some
association with other information. A photo picture, for instance, may
have the following.
35
(1) The title of the picture and some physical object information
(2) The date and the time when the picture was taken
(3) The camera and the photographer's information
Formerly, these are annotated beside the each picture in the
album.
Recently, almost all cameras are digitalized. They are cheap in
price, easy to use, quick to shoot. They eventually made people feel
reluctant to work on annotating each picture. Now, most home PC's
are stuck with the huge amount of photo files. In this situation it is
very hard to find a specific shot in the piles of pictures. “Photo album
software" may help a little. You can sort the pictures and put a couple
of annotation words to each photo. When you want to find a specific
picture, you can make a search by keywords for the target picture.
However, the annotation data in such software are not unified with the
target pictures. Each annotation only has a link to the picture.
Therefore, when you transfer the pictures to a different album
software, all the annotation data are lost.
This problem is technically referred to as "Metadata (e.g.,
annotation data) in a media database system (a photo album
software) are separated from the media data (photo data) in the
database managing system (DBMS)." This is a big problem.
Steganography can solve this problem because a
steganography program unifies two types of data into one by way of
embedding operation. So, metadata can easily be transferred from
one system to another without hitch. Specifically, you can embed all
your good/bad memory (of your sight-seeing trip) in each snap shot of
the digital photo. You can either send the embedded picture to your
36
friend to extract your memory on his/her PC, or you may keep it silent
in your own PC to enjoy extracting the memory ten years after.
If a "motion picture steganography system" has been
developed in the near future, a keyword based movie-scene retrieving
system will be implemented. It will be a step to a "semantic movie
retrieval system."
Steganography is also employed in various useful applications,
e.g., for human rights organizations, as encryption is prohibited in
some countries (Frontline Defenders, 2003), copyright control of
materials, enhancing robustness of image search engines and smart
IDs, identity cards, where individuals’ details are embedded in their
photographs (Jain & Uludag, 2002). Other applications are video-
audio synchronization, companies’ safe circulation of secret data, TV
broadcasting, TCP/IP packets, for instance a unique ID can be
embedded into an image to analyze the network traffic of particular
users (Johnson &Jajodia, 1998), and also checksum embedding
(Chang et al., 2006a) and (Bender et al.,2000).
In (Petitcolas, 2000), the author demonstrated some
contemporary applications, one of which was in Medical Imaging
Systems where a separation was considered necessary for
confidentiality between patients’ image data or DNA sequences and
their captions, e.g., physician, patient’s name, address and other
particulars. A link must be maintained between the image data and
the personal information. Thus, embedding the patient’s information in
the image could be a useful safety measure and helps in solving such
problems. Steganography would provide an ultimate guarantee of
authentication that no other security tool may ensure. Miaou (Miaou et
al., 2000) present an LSB embedding technique for electronic patient
37
records based on bi-polar multiple-base data hiding. A pixel value
difference between an original image and its JPEG version is taken to
be a number conversion base.
Mobile phone and Internet technologies have progressed along
each other. The importance of both these technologies has resulted in
the creation of a new technology for establishing wireless Internet
connection through mobile phone, known as Wireless Application
Protocol (WAP). However, considering the importance of the issue of
data security and especially establishing hidden communications,
many methods have been presented. In the meanwhile,
steganography is a relatively new method.In this paper, a method for
hidden exchange of data has been presented by using steganography
on WML pages (WML stands for Wireless Markup Language, which is
a language for creating web pages for the WAP). The main idea in
this method is hiding encoded data in the ID attribute of WML
document tags. The coder program in this method has been
implemented using the Java language. The decoder program to be
implemented on the mobile phone has been written with a version of
Java language specifically used for small devices, which is called
J2ME (Java 2 Micro Edition).
Inspired by the notion that steganography can be embedded
as part of the normal printing process, the Japanese firm Fujitsu is
developing technology to encode data into a printed picture that is
invisible to the human eye, but can be decoded by a mobile phone
with a camera as exemplified in Figure (BBC News, 2007).
38
Figure 9: Fujitsu exploitation of steganography (BBC News, 2007)
shows a sketch representing the concept
Figure 10: Displays the application of deployment into a mobile phone
The process takes less than one second as the embedded
data is merely 12 bytes. Hence, users will be able to use their cellular
phones to capture encoded data. Fujitsu charges a small fee for the
use of their decoding software which sits on the firm's own servers.
The basic idea is to transform the image colour scheme prior to
printing to its Hue, Saturation and Value components, HSV, then
embed into the Hue domain to which human eyes are not sensitive.
Mobile cameras can see the coded data and retrieve it.
39
This application can be used for “doctor’s prescriptions, food
wrappers, billboards, business cards and printed media such as
magazines and pamphlets” (Frith, 2007), or to replace barcodes.
40
CHAPTER 6
CONCLUSION
Steganography is the art and science of hiding information
such that its presence cannot be detected and a communication is
happening. Secret information is encoding in a manner such that the
very existence of the information is concealed.
The past few years have seen an increasing interest in using
images as cover media for steganographic communication. There
have been a multitude of public domain tools, albeit many being ad-
hoc and naive, available for image based steganography. Given this
fact, detection of covert communications that utilize images has
become an important issue. In this tutorial we have reviewed some
fundamental notions related to steganography and steganalysis.
Very fewer techniques have been developed in this field. It is
like a modulation technique. We have acquired some basic idea
about the steganographic techniques. We mainly used this algorithm
for its simplicity and also there is very negligible change in image after
embedding text. . So there is a very little chance of suspecting of the
presence of hidden message. Also size of hidden data is significant.
We can use these techniques along with some modification to
enhance this algorithm for more security and versatility. We have
used mainly the png file format for the carrier cover image.
This LSB algorithm can be changed in many ways very easily
to increase security. LSB algorithm can be changed to random LSB
algorithm for better security.
41
CHAPTER 7
SCOPE FOR THE FUTURE WORK
Steganography is an old art which has been in practice since
time unknown. This research has opened new avenues for us and
scores of new ideas have now sprouted. of these some are blurred
but many pose a clear picture of our future directions. Some of these
are outlined below:
Four main factors, viz. hiding capacity, perceptual transparency,
robustness and tamper resistance, were identified elsewhere to
characterize the data hiding techniques in steganography. We
mainly concentrated on the hiding capacity. In our technique, it is
very difficult to detect or suspect the presence of the secret
message because a very little change occurs which cannot be
detected by human eye. So no one can suspect the presence of
message.
But if suspected then the message can be decoded. So we have
to apply some more algorithms for the security purpose. The LSB
algorithm can also be modified in various ways to increase the
security of the data.
By tempering the coded image, our secret data may be lost.
Tempering can be cropping, blurring of the image or resizing the
image. So this operation may lead to the loss of data. So some
more work to be done on these so that the stego image will be
temper resistant.
As far as perceptual transparency is concerned it was beyond the
scope of this thesis. Future work should take this into account.
This aspect promises greater room for research. In this context
we are currently working on a new method that will use random
embedding in a novel way. Blue print of the method is almost
ready.
42
We mainly dealt with PNG picture as these were not specifically
investigated in any of the works at least known to us. The
technique we employed was a sort of worst case, i.e. LSB
technique with sequential embedding. Hence the worst-case limit
has been set. The future research on the robustness of PNG
images should be extended to the more robust embedding
techniques like, masking, SSIS, patchwork techniques etc so that
the best case is identified.
One interesting java API, the JAI, has made image manipulation
a lot easier. The dyadic and monadic image operations are now a
lot easier and binary operations of addition subtraction,
multiplication and division etc can now be applied to images.
Similarly magnifier can now be employed on images
conveniently. All these give rise to scores of new ideas to develop
novel steganographic and steganalytic methods. These need to
be explored.
We have to compress the image so as to decrease the suspect
and also for easy send and receive operation. The operations will
be faster if we will compress the image without the loss of data
and also the quality.
We have used only LSB insertion technique in our algorithm. In
future the other techniques will be using to enhance security.
43
CHAPTER 8
REFERENCES
[1]. Java Prog. Techniques for Games. Java Art Chapter 6. Stego
Draft #1 (7th June 09)
[2]. Steganoflage: A New Image Steganography Algorithm by Abbas
Cheddad.
[3]. SLSB: Improving the Steganographic Algorithm LSB by Juan Jose
Roque, Jesus Maria Minguet, Universidad Nacional de Educación
a Distancia (Spain).
[4]. Information hiding Using steganography by Muhalim Mohamed
Amin, Subariah Ibrahim , Mazleena Salleh , Mohd Rozi Katmin.
[5]. Image Steganography: Concepts and Practice by Mehdi Kharrazi,
Husrev T. Sencar, and Nasir Memon.
[6]. New approach in steganography by integrating different LSB
algorithms and applying randomization concept to enhance Data
security A.Karthic , III CSE Kalasalingam university Krishnankoil.
[7]. Investigation of inherent robustness of png images for lsb
steganography by Khizar Hayat Khan.
44
CHAPTER 9
APPENDIX
List of Figures
Figure 1 General scheme of steganography 4
Figure 2 Different steganography fields 7
Figure 3 Matrix and bits representation of an image file 9
Figure 4 Flow Diagram of PDS Steganography 15
Figure 5 Accessing bits of an image 17
Figure 6 Accessing the Bits of a Text File 17
Figure 7 Inserting the Text Bits into the Image 19
Figure 8 Extracting text from modified image 21
Figure 9 Constructing hidden Bytes array by shift left operation
21
Figure 10 Fujitsu exploitation of steganography (BBC News,
2007) shows a sketch representing the concept
39
Figure 11 Displays the application of deployment into a
mobile phone
39
