With concealment. Steganography is the practice of masking

With the
advancement in digital communication and data set getting huge due to
computerization of data gathering worldwide, the need for data security in
transmission also increases.  Thanks to
the proliferation of multimedia data including text, images , audio and video
which are the basic elements of multimedia data including text,images,audio and
video which are the basic elements of multimedia platforms and ever growing
requests for applications based on them. 
Multimedia bid data applications include video on demand, 4k display
contents,interactive video systems,surveillance,health care etc and all of them
require secured environment during transmission and reception.  Data security ensure that information remains
confidential,no one will be able to change the information thereby increasing
integrity and also make sure data gets transferred to the intended recipients
through a secured channel.

Cryptography and
steganography are wll known methods available to provide security where the
former use techniques that control information in order to cipher or hide their
presence and the latter concentrates on data concealment.

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Steganography is
the practice of masking data especially multimedia data within another
data.  Visual contents gets more
importance from people compared to audio contents and moreover visual content
file is huge when compared to audio file thereby helping increase robustness of
the hiding algorithms.  Due to the huge
size of image and video data, they get compressed before transmission or storage
and the commonly used compression technique standards are JPEG and MPEG
respectively.  Both the encoding
standards use Discrete Cosine Transformation(DCT) internally for transforming
the signal from spatial domain into frequency domain.

            The simplest and widespread image
steganography method is the least significant bit (LSB) substitution
method.  It hides data into carrier image
by replacing the least significant bits directly.  The embedding capacity can be increased by
using up to 4 least significant bits in each pixel.  Though it is popular, it has a common weak
point as well which is that the sample vlue change asymmetrically.  To overcome these limitations,we propose to
use statistical methods in identifying the source signal based on the message
signal and then encrypt the data before embedding.

Most images
available on the internet are JPEG compressed and that is the second domain
that is considered for image steganography. 
JPEG uses discrete cosine transformation for converting the spatial domain
image into frequency domain before further processing.  The DCT transformed image contains DC and AC
coefficients.  Here the DC component
represents the average color while the AC components corresponds to color
change across the block.  Most of the steganography
algorithms use DC coefficients for hiding the message while in this work, we
tried to use both DC and AC components together which help in concealing the
data in  a more robust way there by
increasing the accuracy when compared to traditional algorithms.  XOR operations along with Chaotic encryption
is proposed.

A wavelet is a
mathematical function which is one of the recent developments and useful in
digital signal processing and image compression technologies.  The use of wavelets for these purposes is a
recent development, although the theory is not new.  Lifting scheme gives wavelet filter design to
perform discrete wavelet transform.  We
have tried to explore the same and use it in image steganography.  Data encryption standard, a symmetric-key
algorithm in which one-dimensional chaotic map is used to encrypt the image
signal before getting embedded to the carrier signal.  This helps improve the robustness of the
proposed algorithm.

The proposed
methods can be applied to the following domains including confidential
communication and secret data storing, access control system for digital
content distribution, protection of data alteration and media database systems.

            We have tested the proposed
algorithms on the USC-SIPI image database which is a collection of digitized
images and provided by the university for supporting the research people in
image processing domain.  Carrier image
size used varies from 512* 512 to 1024*1024 while the message signal falls
under 256 *256 category.

We find that the
proposed algorithms have a better PSNR value averaging close to 71 while the
traditional algorithms has values of around 56. 
XOR operations for encrypting the data along with key table usage
between the sender and receiver helps improve the efficiency in embedding the
secret data.  Moreover we have also
studied different Steganalysis methods and made sure that the proposed
algorithms are robust enough to stay safe from those methods.

Other advantages
of the proposed method include reducing the overall bit-level changes to the
cover image for the same amount of embedded data and avoiding complex
calculations.  We have achieved better
embedding capacity without compromising on the security factor as well through
these algorithms.  Finally, the new methods
proposed results in little additional distortion in the stego image, which
could be tolerated.




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