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Volume-4, Issue-4, August-2014, ISSN No.: 2250-0758
International Journal of Engineering and Management Research Available at: www.ijemr.net
Page Number: 94-97
Key Based Image Steganography using Dwt and Chaotic Map
Shikha Choudhary1, Chaten Panwar
2
1,2M.Tech (IT), Assistant Professor, Shobhit University, Meerut, Uttar Pradesh, INDIA
ABSTRACT Steganography is used to increase the security
of message sent over the network. Steganography is a
Greek origin word which means “hidden writing”.
Steganography can be divided into two words Steganos
which means “secret” and graphic means “writing”. Image
Steganography has been widely studied by researchers. A
Steganography technique that uses image as a cover media
is called an image Steganography. This paper mainly
focuses on key based image Steganography using DWT
(discrete wavelet transformation) and chaotic map. In this,
the major focus on the secrecy and privacy of information.
DWT is used to perform on a grey level cover image for
secrecy and on the other hand chaotic map is applied on
the secret image for privacy.
DWT is used to transform cover image from spatial domain
into frequency domain. Transformation can be applied
over the entire image to block throughout the image. With
the help of this technique we can hide the text within an
image and hiding the image within an image and also
recover that text and image.
Keywords---DWT, Security, Information Hiding,
Steganography.
I. INTRODUCTION
Since the rise of internet is increasing day by day,
the most important factor is secret information and
communication. Message transmission over the internet
still has all kinds of security problems .Cryptography is a
way for securing the secret message. Many different
methods have been developed for encrypted and
decrypted the data in order to keep the message
consistence. Sometimes, it is not enough to keep the
consistence of message, but also it is necessary to keep
the existence of message. Steganography is the
technique to implement for this. Steganography means to
hide something i.e. information [1]. It is similar to the
Watermakingy and Crypography. Watermaking ensures
message integrity, Cryptography scrambles a message,
so it cannot be understood and Steganography hides the
message.
Steganography provides a means of communicating
a secret message. So an unauthorized user cannot
understand the existence of the message. Encryption and
Steganography have the same goal but different means.
Encryption encodes the data such that an unauthorized
person cannot get the useful meaning but
Steganography prevent the data from an unauthorized
receiver that he will not be inspects data is there. It allow
for a better private communication. The main work of
Steganography is to replace bits of useless or unused
data in regular computer files (such as graphics, sound,
text) with the bits of different invisible information. This
hidden information can be plaintext either cipher text or
even image. When encryption is not permitted,
Steganography can be used. One more common
Steganography can be used for supplement encryption,
with the help of Steganography an encrypted file may
still hide the information ..
The word Steganography is derived from the Greek
word stenos Means “cover” and graphia means writing
defined as “covered writing”. The technique has been
used in ancient time where secret message were tattoos
on the shaven heads of the messengers [2]. These
messengers were sent away after their hair grew up and
were later shaved again to recover the messages. The
main goal of Steganography is to hide the information
from an unauthorized person. The hidden information
may be plain text, cipher text or image or anything that
can be embedded into bit stream. In another aspect
Steganalysis is a way of detecting possible secret
communication using against Steganography. The
advantage of the Steganography is that it can be used to
transmit the secret message. This paper mainly focus on
DWT algorithm and Chaotic Map used for image
Steganography and also discuss the various types of
Steganography techniques.
Nowadays multimedia contents like Audio, Video,
and Images are also transferring across a network. A
digital image has also across a network to be transferred
frequently. As per this transferring needs security
because of some military, medical images, cable TV are
payable. So there is a need of technique that can provide
security to these digital images. Hence, image
Steganography is used to provide this facility to these
images. Image Steganography hides the secret image
into a cover image. So that only reliable and authorized
user can get it. Unauthorized user cannot get it [3, 4].
A. STEGANOGRAPHY Vs. CRYPTOGRAPHY
Basically the purpose of Cryptography and
Steganography is to provide secret communication.
However Steganography is different from Cryptography.
Cryptography hides the contents of secret message while
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Steganography hides the existence of the message.
Cryptography scrambles a message and Steganography
hides the message. The last result in cryptography is
ciphertext, while the result in Steganography is stego
media. If the cryptography and Steganography will
combined together to form a hybrid approach, then two
level of security achieved.
B. STEGANOGRAPHY TECHNIQUES
On the basis of different types of cover files
Steganographic techniques can be classified as shown in
the figure below
Fig.1 Steganography Techniques
(a) Text-Based Steganography
A Steganography technique that uses text as the
cover media is called text Steganography. It is the most
difficult type of Steganography technique. The Text
Based Steganography involves changing the format of an
existing text, or changing words within a text or
generates readable text. Text Steganography can be
classified in to three basic categories
Format based
Random and statistical generation.
Linguistic method
(b) Audio /Video based Steganography
A Steganography technique that uses audio as a
cover media is called an audio Steganography. It is the
most challenging task in Steganography because the
human auditory system has a large dynamic range so it
can listen over. Thus if we slightly change in audio
quality it can also be detected by human ears. Like Text
files, sound files may be modified in such a way that
they contains hidden information .To hide information in
audio files is the similar technique which is used for
image files. The commonly used method of audio
Steganography as follows:
LSB coding.
Parity coding.
Phase coding
Spread spectrum.
Echo hiding.
Video files generally a collection of images and
sound .So the technique used in image and audio
can be applied to video files too.
(c) Image Steganography
A Steganography technique that uses image as a
cover media is called Image Steganography. Compare to
other types of Steganography, Image Steganography has
been widely used in research area. Images are the most
popular cover objects used for Steganography. An image
is a collection of numbers that consist different light
intensity in different areas of the image.
The numeric representation of an image is grid and
individual points are referring as pixel. These pixels are
display horizontally row by row. Grayscale images and
Monochrome images uses 8 bit pixel and are able to
display256 different colors. Compression techniques
play a vital role in choosing a Steganography algorithm
to use. Two types of Compression can be used in
Images, one is lossy compression and another is lossless
compression. An Image Steganography consist a secret
image, cover image and a hidden method where the
secret message is hidden in digital image with some
hiding method and then uses a proper embedding
procedure to recover the hidden message from image.
The original image is called cover image, and the
message embedding image is called a stego-image in
Steganography.
II. METHODOLOGY
With the help of chaotic map we are trying
to improve the security and space for the data to be
hidden. We have used chaotic map as they work best on
multimedia data and they have been found better than
the traditional scheme. To control the redundancy in the
data which is to be hidden a scheme works well for light
weight application. The proposed work is key based image
Steganography using Haar-DWT and chaotic method.
The circle map is a type of chaotic map which we used.
The circle map is used to generate the sequence of value
between the space of the data to be hidden. The steps of
algorithm have been summarized as follows:
Step 1: Select the cover image.
Step 2: Check the dimension of the cover image,
whether it is power of 2 or not, If it is not make it power
of 2.
Step 3: Apply Haar transform on the cover image.
Step 4: Extract 4 Subband from resultant Haar transform
Image.
Step 5: Select the hidden image.
Step 6: Key generated with the help of chaotic map is
XOR with the selected hidden image.
Step 7: Embedded the message bit in 2 LSB of LH, HL,
and HH Subband.
Step 8: Use LSB technique to hide the secret image.
Step 9: Apply IDWT to get the stego-image
Step 10: Find out the PSNR using cover image and
stegoimage
III. PRIOR APPROACH
Till now many image Steganography schemes
have been proposed as using LSB. LSB is the least
significant bit technique. This technique is very simple
for both embedding and de-embedding [5]. In this
technique secret bit is embedded into the least significant
bit of the cover image.
Another technique DCT is the Discrete Cosine
Transform technique. It is similar to Discrete Fourier
Steganography
Text Audio / Video Image
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Transform. The DCT transform a signal from an image
representation into a frequency representation by
grouping the pixel into 8*8 pixel blocks into 64 DCT
Another technique is Spread spectrum Technique.
In this technique the message is spread over a wide
frequency bandwidth than the minimum required
bandwidth to send the information.
IV. OUR APPROACH
Fig. 1 Original Image
Fig 2.Secret Image
Fig.3 Stego Image
Fig.4 Recover Hidden Image
Fig.5 Cover Image
Fig.6 Text is to be Hidden
Fig 9Stego Image
Fig.10RecoverText
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V. CONCLUSION
A new image Steganography scheme is proposed
in this paper. In this paper, the major importance is given
on the secrecy as well as the privacy of information. The
proposed approach provides higher security and can
protect the message from stego image. The embedding
process is hidden under the DWT transformation of the
cover image. This operation provides sufficient secrecy.
On the other hand to obtain privacy chaotic map is used.
We have performed experiment in Matlab 8.0 and
comparison of proposed algorithm is done through the
imperceptibility measure PSNR. Furthermore respectable
privacy is maintained with the help of key which is
generated through chaotic map. Since no message can be
extracted without the key and decoding rules.
Experimental result shows that PSNR value and
embedding capacity of our proposed method is better than
the other. We have achieved a PSNR value up to 80 db
which is our major advantage.
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