15-12-2012, 02:55 PM
A New Chaos Steganography Algorithm for Hiding Multimedia Data
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Abstract
The paper is devoted to propose a new chaos
steganography algorithm for hiding the multimedia data, image,
text, or sound. The proposed algorithm based on coordinate the
data in the image dimensions using chaos distribution
arrangement. The data is embedded with the original image in
the pixels least significant bits, so can't appears within the image.
When the image received the embedded data is separated and
rearranged using the initial condition of the chaos coordination.
The algorithm is implemented using Matlab program on three
types of data, the first is image data, the second is a text data, and
the third is sound signal data. The results show a good hiding for
the tested data in the original images with high degree of security
if steganalysis is performed on the composed original image.
INTRODUCTION
Some confidential data might be stolen, copied, modified or
destroyed by an unintended observer. Therefore, security
problems become an essential issue. Encryption is a wellknown
procedure for secure data transmission. The frequently
used encryption methods include RSA and DES algorithms.
Although these two methods achieve certain security effects,
they make the secret messages unreadable and unnatural.
These unnatural messages usually attract some unintended
observer's attention. This is the reason a new security
approach called “Steganography” arises [1,2]. Steganography
literally means covered writing and is the art of hiding secret
messages within another seemingly innocuous message, or
carrier [3]. With the advent of digital technology, the list of
carriers has been made to include, images, text, e-mails, audio
and video messages. Some Steganography utilities use secret
keys. It can distinguish two kinds of keys: steganographic
keys and cryptographic keys [4]. A steganographic key
controls the embedding and extracting process. For example,
it can scatter the message to be embedded over a subset of all
suitable places in the carrier medium. Without the key, this
subset is unknown, and each sample used to detect embedding
by a statistical attack is a mixture of used and unused places
which spoils the result.
THEORETICAL DESCRIPTION
To provide a Theoretical description of steganography,
terms and concepts should first be explained an overview of
the different kinds of steganography is given at a later stage.
Some definitions common to the steganography field: cover
medium, this is the medium in which the data hide for it.
Embedded message, this is the hidden message that want to
put it in the cover medium. Stego-key, this is represented by
some secret information, which is needed in order to extract
the embedded message from the stego-medium. Stegomedium,
this is the final piece of information that the casual
observer can see. We can define this simple formula,
Steganographic Algorithm evaluation
In order to make a decision of which steganographic system
or technique is better than another an evaluation scheme for
steganographic systems is needed. Currently, no standard test
or measure is available in order to evaluate the performance or
the effectiveness of steganographic systems. However there
are some guidelines and general procedures that can be
considered when evaluating or designing steganographic
systems.
Evaluation of Imperceptibility
Two types of perceptibility can be distinguished and
evaluated in signal processing systems, namely fidelity and
quality. Fidelity means the perceptual similarity between
signals before and after processing. However, quality is an
absolute measure of the goodness of a signal to avoid any
suspension and therefore detection. Even though the peak
signal to nose ratio (PSNR) and the mean square error (MSE)
are by definition fidelity metrics, a high quality image entails
a large PSNR value and therefore both cover image and
Stego-image are very similar and quite undistinguishable.
Significantly, “fidelity" is defined as the perceptual quality of
Stego files and therefore PSNR and MSE describe how
imperceptible the secret message is. PSNR and MSE are the
most common and widely-used metrics for Steganographic
evaluation. Thus it is very important that there is no visual
difference between the cover file and the Stego file. However
PSNR values between 20 and 40 dB it is difficult for the
human visual recognize any difference between a cover and
Stego file if the PSNR value exceeds 36dB.
THE PROPOSED METHOD
To The proposed steganography algorithm started with
increasing the original image pixels from byte to word colour
capacity, and then distributes the hidden-image pixel
randomly within the lower byte of the cover image pixels
using chaos distribution. The stego-image then is ready for
transmission. The original image is separated from the
received stego-image at the first stage of the receiver. The
initial condition of the chaotic random sequence is used to
collect the stego-image from the lower byte of the pixels.
Then the hidden-image is reconstructed. Figure 1. shows
demonstrates the proposed method graphically. The same idea
is performed with any kind of data such as text or sound
signals.
CONCLUSIONS
The paper proposes a new chaos steganography algorithm
for hiding the multimedia data, image, text, or sound. The data
is embedded with the original image in the pixels least
significant bits, so can't appears within the image. The
algorithm is implemented using Matlab program on three
types of data, the first is image data, the second is a text data,
and the third is sound signal data. The results show a good
hiding for the tested data in the original images with high
degree of security if steganalysis is performed on the
composed original image.