17-06-2013, 01:54 PM
A Novel Data Embedding Method Using Adaptive Pixel Pair Matching
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Abstract
This paper proposes a new data-hiding method based
on pixel pair matching (PPM). The basic idea of PPM is to use
the values of pixel pair as a reference coordinate, and search a
coordinate in the neighborhood set of this pixel pair according to a
givenmessage digit. The pixel pair is then replaced by the searched
coordinate to conceal the digit. Exploiting modification direction
(EMD) and diamond encoding (DE) are two data-hiding methods
proposed recently based on PPM. The maximum capacity of EMD
is 1.161 bpp and DE extends the payload of EMD by embedding
digits in a larger notational system. The proposed method offers
lower distortion than DE by providing more compact neighborhood
sets and allowing embedded digits in any notational system.
Compared with the optimal pixel adjustment process (OPAP)
method, the proposed method always has lower distortion for
various payloads. Experimental results reveal that the proposed
method not only provides better performance than those of OPAP
and DE, but also is secure under the detection of some well-known
steganalysis techniques.
INTRODUCTION
DATA hiding is a technique that conceals data into a carrier
for conveying secret messages confidentially [1], [2].
Digital images are widely transmitted over the Internet; therefore,
they often serve as a carrier for covert communication. Images
used for carrying data are termed as cover images and images
with data embedded are termed as stego images. After embedding,
pixels of cover images will be modified and distortion
occurs. The distortion caused by data embedding is called the
embedding distortion [3]. A good data-hiding method should
be capable of evading visual and statistical detection [4] while
providing an adjustable payload [5].
RELATED WORKS
OPAP effectively reduces the image distortion compared with
the traditional LSB method. DE enhances the payload of EMD
by embedding digits in a -ary notational system. These two
methods offer a high payload while preserving an acceptable
stego image quality. In this section, OPAP and DE will be briefly
reviewed.
Comparison of Experimental Results
Six images Lena, Jet, Boat, Elaine, Couple, and Peppers,
each sized 512 512, are taken as test images to compare the
MSE obtained by APPM, OPAP, and DE. The payloads were
set to 400 000, 650 000, and 1 000 000, respectively. Message
bits were generated by using a pseudorandom number generator
(PRNG). The results are shown in Tables IV–VI.
Tables IV–VI reveal that the performance of the proposed
APPM method is the best under various payloads. For example,
with the payload 400 000 bits, the averaged MSE of 2-bit OPAP
is 1.244, whereas the averaged MSE of DE is 0.887.
SECURITY ANALYSIS
The goal of steganography is to evade statistical detection. It
is apparent that MSE is not a good measure of security against
the detection of steganalysis. For example, low-MSE embedding
such as LSB replacement is known to be highly detectable
[1], [6]. In this section, we analyze the security of APPM under
two statistical steganalysis schemes, including Subtractive
Pixel Adjacency Matrix (SPAM) steganalyzer proposed by
Pevný et al. [19] and the HVDH scheme proposed by Zhao et
al. [20]. SPAM steganalyzer is a novel Steganographic method
for detecting stego images with low-amplitude independent
stego signal, while the HVDH scheme is used to detect the
presence of hiding message according to the distance between
vertical and horizontal histograms. All the test images used in
this section are obtained from the UCID [21] and RSP [22]
image database, where some literature [13], [23] also adopt this
database for their experiments.
CONCLUSION
This paper proposed a simple and efficient data embedding
method based on PPM. Two pixels are scanned as an embedding
unit and a specially designed neighborhood set is employed to
embed message digits with a smallest notational system. APPM
allows users to select digits in any notational system for data embedding,
and thus achieves a better image quality.