01-09-2012, 05:08 PM
A DWT based Approach for Steganography Using Biometrics
steganography by skintone detection.pdf (Size: 345.35 KB / Downloads: 31)
Abstract-
Steganography is the art of hiding the existence of data
in another transmission medium to achieve secret
communication. It does not replace cryptography but rather
boosts the security using its obscurity features. Steganography
method used in this paper is based on biometrics. And the
biometric feature used to implement steganography is skin tone
region of images [1]. Here secret data is embedded within skin
region of image that will provide an excellent secure location
for data hiding. For this skin tone detection is performed using
HSV (Hue, Saturation and Value) color space. Additionally
secret data embedding is performed using frequency domain
approach - DWT (Discrete Wavelet Transform), DWT
outperforms than DCT (Discrete Cosine Transform). Secret
data is hidden in one of the high frequency sub-band of DWT
by tracing skin pixels in that sub-band. Different steps of data
hiding are applied by cropping an image interactively.
Cropping results into an enhanced security than hiding data
without cropping i.e. in whole image, so cropped region works
as a key at decoding side. This study shows that by adopting
an object oriented steganography mechanism, in the
sense that, we track skin tone objects in image, we get a
higher security. And also satisfactory PSNR (Peak-
Signal-to-Noise Ratio) is obtained.
INTRODUCTION
In this highly digitalized world, the Internet serves as an
important role for data transmission and sharing. However,
since it is a worldwide and publicized medium, some
confidential data might be stolen, copied, modified, or
destroyed by an unintended observer. Therefore, security
problems become an essential issue. Encryption is a wellknow
procedure for secured data transmission [2].
Frequently used encryption methods include RSA, DES
(Data encryption standard). Although encryption achieves
certain security effects, they make the secret messages
unreadable and unnatural or meaningless. These unnatural
messages usually attract some unintended observers’
attention. This is the reason a new security approach called
“steganography” arises.
Steganography in Frequency Domain
Robustness of steganography can be improved if
properties of the cover image could be exploited. For
example it is generally preferable to hide message in noisy
regions rather than smoother regions as degradation in
smoother regions is more noticeable to human HVS (Human
Visual System). Taking these aspects into consideration
working in frequency domain becomes more attractive.
Here, sender transforms the cover image into frequency
domain coefficients before embedding secret messages in it
[7]. Different sub-bands of frequency domain coefficients
give significant information about where vital and non vital
pixels of image resides. These methods are more complex
and slower than spatial domain methods; however they are
more secure and tolerant to noises. Frequency domain
transformation can be applied either in DCT or DWT.
Performance of the proposed method
After embedding secret data in cropped image, resulted
cropped stego image is shown in Fig. 6. (Result of step 5 of
embedding process). As this doesn’t look like cover image
merging is performed to obtain final stego image that is
shown in Fig. 7. (Result of step 6 of embedding process).
For merging co-ordinates of first and last pixels of cropped
image in original image are calculated. After performing
extraction process retrieved image is shown in figure 8.
Above method uses cropping. Same proposed method is
implemented for without cropping case. In without cropping
case secret data is hidden in one of the sub-band which is
obtained by performing the DWT on whole image and not
only to cropped region. PSNR is calculated for four different
final stego images resulted from a considered image and
three more sample images. This PSNR for different cases is
shown in table 1. Average PSNR of proposed method is
calculated based on the obtained PSNR.
CONCLUSION
Digital Steganography is a fascinating scientific area
which falls under the umbrella of security systems. In this
paper biometric steganography is presented that uses skin
region of images in DWT domain for embedding secret data.
By embedding data in only certain region (here skin region)
and not in whole image security is enhanced. Also image
cropping concept introduced, maintains security at
respectable level since no one can extract message without
having value of cropped region. Features obtained from
DWT coefficients are utilized for secret data embedding.
This also increases the quality of stego because secret
messages are embedded in high frequency sub-bands which
human eyes are less sensitive to. According to simulation
results, proposed approach provides fine image quality.