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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

    http://www.ijemr.net/

  • 95

    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