22-09-2012, 01:48 PM
StegCure: A Comprehensive Steganographic Tool using Enhanced LSB
Scheme
1StegCure.pdf (Size: 1.13 MB / Downloads: 30)
Abstract:
Protected and encrypted data sent electronically is vulnerable to various attacks such as spyware and
attempts in breaking and revealing the data. Thus, steganography was introduced to conceal a secret message
into an unsuspicious cover medium so that it can be sent safely through a public communication channel.
Suspicion becomes the significant key determinant in the field of steganography. In other words, an efficient
stegnographic algorithm will not cause any suspicion after the hidden data is embedded. This paper presents an
overview of steganography on GIF image format in order to explore the potential of GIF in information hiding
research. A platform, namely StegCure is proposed by using an amalgamation of three different Least
Significant Bit (LSB) insertion algorithms that is able to perform steganographic methods. This paper explains
about the enhancement of the Least Significant Bits (LSB) insertion techniques from the most basic and
conventional 1 bit to the LSB colour cycle method. Various kinds of existing steganographic methods are
discussed and some inherent problems are highlighted along with some issues on existing solutions. In
comparison with the other data hiding applications, StegCure is a more comprehensive security utility where it
offers user-friendly functionality with interactive graphic user interface and integrated navigation capabilities.
Furthermore, in order to sustain a higher level of security, StegCure has implemented a Public Key
Infrastructure (PKI) mechanism at both sender and receiver sites.
Introduction
Steganography is derived from the Greek word
steganos which literally means “covered” and
graphia which means “writing”, i.e. covered writing
[1], [18]. Currently, research in steganography has
grown explosively in terms of further exploring
message hiding within an object, a text or even a
picture.
Steganography often draws confusion with
cryptography [2] in terms of appearance and usage.
The most significant difference between
steganography and cryptography is the suspicion
factor. In fact, when both cryptography and
steganography are being implemented together, an
acceptable amount of security could be achieved.
Hence, a security utility which is called StegCure is
built to essentially protect the privacy of
confidential data with non-encryption method that is
without using direct password authentication during
the transmission of information. This kind of
method is used to make the presence of a secret data
appear invisible to eavesdroppers such as
keyloggers or harmful tracking cookies which can
monitor a user’s keystroke when entering password
and personal information.
Least Significant Bit insertion method
Least significant bit insertion is a common, simple
approach to embed information in a cover file [6],
[17]. The LSB is the lowest order bit in a binary
value. This is an important concept in computer data
storage and programming that applies to the order in
which data are organized, stored or transmitted [21].
Usually, three bits from each pixel can be stored to
hide an image in the LSBs of each byte of a 24-bit
image. Consequently, LSB requires that only half of
the bits in an image be changed [27] when data can
be hidden in least and second least significant bits
and yet the resulting stego-image which will be
displayed is indistinguishable to the cover image to
the human visual system [17].
Least Significant Bit in GIF
Graphics Interchange Format, also known as GIF, is
one of the machine independent compressed formats
for storing images [14]. The significance of using
GIF is because GIF is one of the most widely used
image compression formats in web applications.
LSB insertion in GIF is a very efficient algorithm to
use when embedding a reasonable amount of data in
a grayscale image [4],[13].
The compression scheme used in GIF is lossless
which is called Lempel-Ziv-Welch (LZW). LZW
reduces the file size without affecting the quality of
the image [8]. LZW works by noting redundant
areas of images, removing them and then reinserting
them when the graphic is displayed [9].
GIF was developed by CompuServe to show
images online (in the year 1987 for 8 bits video
boards, before JPEG and 24 bits colour were used).
Table 2 shows the bit depth and the number of
colours in an image. The advantage of using GIF is
it allows for a smaller storage file size and
minimizes the transfer time over the network.
StegCure Design
StegCure is proposed in image steganography which
marries three different steganography algorithms in
one single steganography application. The graphic
user interface of StegCure is shown in Figure 5 and
Figure 6. Eventually, the original image and the
stego-image are shown in Figure 7 after performing
steganography in data embedding.
Preliminary Experimental Results
Relatively, the result of the stego-image (refer to
Figure 13) does not generate any suspicion at all.
The difference of the stego-image can hardly be
distinguished after using the LSB method insertion.
It is proven that human visual system is not able to
differentiate the original image and the stego-image,
but computer system can detect the modification of
the bits through hexadecimal representation by
using a hex editor tool. Figure 14 and Figure 15
illustrates the error messages when a user has
selected some inappropriate options in StegCure.
Conclusions and Future Work
A combination of three steganography algorithms
on GIF image is proposed through StegCure system.
The unique feature about the StegCure is being able
to integrate three algorithms in one steganography
system. By implementing Public Key Infrastructure,
unauthorized user is forbidden from intercepting the
transmission of the covert data during a
communication because the stego-key is only
known by the sender and the receiver.