Key Based Image Steganography using Dwt and Chaotic · PDF filefocuses on key based image Steganography using ... Fig.1 Steganography Techniques (a) Text-Based Steganography ... The

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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: C