Steganography and related works
A Novel Steganographic Technique Based on 3D-DCT Approach
Samir Kumar Bandyopadhyay
Related works
The majority of todays steganographic systems uses images as cover media because people often transmit
digital pictures over email and other Internet communication. Several methods exist to employ the concept of
Steganography as well as plenty algorithms have been proposed in this regard. To gather knowledge regarding
our approach, we have concentrated on some techniques and methods which are described below.
In the field of image security, Miroslav Dobsicek (Dobsicek, M., 2004) has developed an interesting application
of steganography where the content is encrypted with one key and can be decrypted with several other keys, the
relative entropy between encrypt and one specific decrypt key corresponds to the amount of information. Yusuk
Lim, Changsheng Xu and David Dagan Feng, 2001, described the webbased authentication system consists of
two parts: one is a watermark embedding system and the other is authentication system. In case of watermark
embedding system, it is installed in the server as application software that any authorized user, who has access to
server, can generate watermarked image. The distribution can use any kind of network transmission such as FTP,
email etc. Once image is distributed to externally, client can access to authentication web page to get verification
of image (Yusuk Lim, Changsheng Xu and David Dagan Feng, 2001).
Min Wu and Bede Liu, June, 2003, proposed (Min Wu. 2004) a new method to embed data in binary images,
including scanned text, figures, and signatures. The method manipulates flippable pixels to enforce specific
block based relationship in order to embed a significant amount of data without causing noticeable artifacts.
They have applied Shuffling before embedding to equalize the uneven embedding capacity from region to region.
The hidden data can then be extracted without using the original image, and can also be accurately extracted
after high quality printing and scanning with the help of a few registration marks.
Rehab H. Alwan, Fadhil J. Kadhim, and Ahmad T. Al- Taani, 2005, have explained a method with three main
steps. First, the edge of the image is detected using Sobel mask filters. Second, the least significant bit LSB of
each pixel is used.
Finally, a gray level connectivity is applied using a fuzzy approach and the ASCII code is used for information
hiding. The prior bit of the LSB represents the edged image after gray level connectivity, and the remaining six
bits represent the original image with very little difference in contrast. The given method embeds three images in
one image and includes, as a special case of data embedding, information hiding, identifying and authenticating
text embedded within the digital images (Rehab H. Alwan, Fadhil J. Kadhim, and Ahmad T. Al-Taani, 2005). In
2007, Nameer N. EL-Emam proposed an algorithmic approach to obtain data security using LSB insertion
steganographic method. In this approach, high security layers have been proposed through three layers to make it
difficult to break through the encryption of the input data and confuse steganalysis too(Nameer N. EL-Emam,
2007).
S. K. Bandyopadhyay, Debnath Bhattacharyya, Swarnendu Mukherjee, Debashis Ganguly, Poulami Das in 2008
has proposed a heuristic approach to hide huge amount of data using LSB steganography technique. In their
method, they have first encoded the data and afterwards the encoded data is hidden behind a cover image by
modifying the least significant bits of each pixel of the cover image. The resultant stego-image was distortion
less. Also, they have given much emphasis on space complexity of the data hiding technique
(S.K.Bandyopadhyay, Debnath Bhattacharyya, Swarnendu Mukherjee, Debashis Ganguly, Poulumi Das, 2008).
There is also a good method proposed by G. Sahoo and R. K. Tiwari in 2008. Their proposed method works on
more than one image using the concept of file hybridization. This particular method implements the
cryptographic technique to embed two information files using steganography. And due to this reason they have
used a stego key for the embedding process (G. Sahoo, R. K. Tiwari, 2008).
Unfortunately, modifying the cover image changes its statistical properties, so eavesdroppers can detect the
distortions in the resulting stego-images statistical properties. In fact, the embedding of high-entropy data (often
due to encryption) changes the histogram of colour frequencies in a predictable way. So, in order to obtain more
security in our prescribed method, we have embedded an entire image behind another image of twice the size of
target image remarkable change in the final image.
Our Work
3.1 3-D DCT:
The three-dimensional variant of the DCT is a composition of three 1D DCT along each dimension.
