08-08-2012, 03:09 PM
A Novel Visual Cryptographic Steganography Technique
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INTRODUCTION
Due to increasing the technologies, security systems are
very popular in many areas. The information comes in
numerous forms and requires secure communication. Such
secure communication ranges from bank transactions,
corporate communications and credit card purchases.
Encryption and steganography are the preferred techniques
for protecting the transmitted data. Encryption hides the
contents of the message, but cannot hide the message data
itself. However, encryption clearly marks a message as
containing “interesting” information, and the encrypted
message becomes subject to attack. The commonly used
encryption schemes include DES (Data Encryption
Standard) [1], AES (Advanced Encryption Standard) [2] and
RSA [3]. DES, an encryption standard that was used by
many national governments, successfully withstood attacks
for many years. However, E. Biham and A. Shamir mention
a cryptanalytic attack that can break DES in only a few
minutes [4]. Another example of a broken encryption
algorithm is WEP. WEP was designed to provide
confidentiality to users on wireless networks.
Frequency domain steganography
In frequency domain, images are first transformed and
then the message is embedded in the image [17][18][19].
When the data is embedded in frequency domain, the hidden
data resides in more robust areas, spread across the entire
image, and provides better resistance against statistical
attacks. There are many techniques used to transform image
from spatial domain to frequency domain. The most
common frequency domain method usually used in image
processing is the 2D discrete cosine transform [20][21]. In
this technique the image is divided into 8×8 blocks and
DCT transformation on each block is performed. The data
bits are embedded in the low frequency coefficients of DCT.
SSB-4 & DCT steganography proposed by Nedal M. S.
Kafri and Hani Y Suleiman uses DCT approach with SSB-4
technique [21].
PROPOSED METHOD
The challenge in this work was to find a way to
camouflage a secret message in an image without
perceptible degrading the image quality and to provide
better resistance against the steganalysis process. The data is
first converted into cipher text using RSA encryption and
then hided into lower frequency components of image using
LSB-DCT steganography.
EXPERIMENTAL RESULTS
Since the visual detection of stego images is depending
on the nature of the image [24] so, varieties of image
categories are utilized in the experiments. The experimental
image data set consists of 100 JPEG images, which were
taken by digital camera. We focused on short messages with
length of 3000 bits because they are the most challenging to
detect [24]. Comparative analysis of LSB, Modulus
arithmetic (mod-16), and proposed method has been done
on the basis of Peak signal to noise ratio (PSNR). To
calculate PSNR, first MSE is calculated as follows:
CONCLUSION
In this paper we used mixed approach cryptography and
steganography is used for data security. By using RSA
encryption, ASCII codes corresponding to characters of
plain text are converted into 16 bits encrypted codes. Hence
it becomes difficult to get original text without knowing
decryption keys. Then cipher data is hided into cover image.
Average PSNR value of 55 is obtained for 100 images using
proposed method. The obtained experimental results
indicate that, the proposed method is a good and acceptable
scheme for data security. Furthermore, by embedding
information in the least significant bits of the DCT domain,
the hidden message resides in more robust areas, spread
across the entire stego image, and provides better resistance
against statistical attacks than other techniques. The future
work may focus on the improvement and further
development in this technique.