1 a high-capacity steganography scheme for jpeg2000 baseline system liang zhang, haili wang, and...
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1
A High-Capacity Steganography Scheme for
JPEG2000 Baseline System
Liang Zhang, Haili Wang, and Renbiao Wu,
Senior Member, IEEE
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IEEE TRANSACTIONS ON IMAGE PROCESSING, VOL. 18, NO. 8, AUGUST 2009Received September 09, 2008; revised April 01, 2009.
First published April 24, 2009; current version published July 10, 2009.
Adviser: Chih-Hung Lin
Speaker:Po-Kai Shen
Date : 98/11/24
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Outline
1. Author
2. Introduction
3. Jpeg2000 baseline coding system
4. Steganography based on twice bit-plane encoding
5. Redundancy evaluation
6. Synchronization information and scrambling measure
7. Simulation
8. Conclusion
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Author(1)
Liang Zhang was born in 1970. He received the Ph.D. degree in electronic information engineering from Tianjin University, Tianjin, China, in 2003.
He is an Associate Professor. He is currently with the Tianjin Key Lab of Advanced Signal Processing in Civil Aviation University of China.
His current research interests include image processing, information hiding, and intelligent visual surveillance.
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Author(2)
Haili Wang was born in 1983.
She is now a postgraduate specializing in signal processing.
Her current research interests include image processing and information hiding.
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Author(3)
Renbiao Wu (M’95–SM’01) received the B.Sc. And M.Sc. degrees from Northwestern Polytechnic University, Xian, China, in 1988 and 1991, respectively, and the Ph.D. degree from Xidian University, Xian,in 1994, all in electrical engineering.
From May 1994 to February 1996, he was a Postdoctoral Fellow at the College of Marine Engineering, Northwestern Polytechnic University, where he was promoted to Associate Professor in December 1995.
From March 1996 to February 1997, he was a Visiting Scholar at the Center for Transportation Research, Virginia Polytechnic Institute and State University,Blacksburg.
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From March 1997 to December 1998, he was a Visiting Scholar at the Department of Electrical and Computer Engineering, University of Florida,Gainesville.
Since January 1999, he has been with the Tianjin Key Lab for Advanced Signal Processing, Civil Aviation University of China, Tianjin, China, where he is currently a Chaired Professor and director of the lab.
Author(3)
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From August 2004 to January 2005, he was a Distinguished Research Scholar in the Department of Electrical and Electronic Engineering, Imperial College London, London, U.K. Dr. Wu was the recipient of the National Outstanding Young Investigator Award of China in 2003.
His research interests include space-time adaptive processing, adaptive arrays, feature extraction and image formation, spectral estimation and their applications to radar and wireless communication systems.
Author(3)
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Introduction
1) Modern information hiding technology is an
important branch of information security.
2) Steganography
three competing aspects :
① Capacity
② Security
③ Robustness
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Introduction
3) Section III shows procedures of JPEG2000 baseline
system and points out the problem due to bitstream
truncation.
4) Section IV describes the principle of twice bit-plane
encoding and illustrates the operation procedures.
5) Section V gives a detailed description on redundancy
evaluation, and explains how embedding points and their
intensity are adjusted.
1010
Introduction
6) Section VI, we define measures for synchronization and
security.
7) Section VII shows the simulation results.
8) Section VIII draws a conclusion.
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Jpeg2000 baseline coding system
JPEG2000 uses uniform scalar quantizers with enlarged
“deadzones.”
Truncating the embedded bitstream associated with any
given codeblock has the effect of quantizing the wavelet
coefficients in that codeblock more coarsely.
That is to say, there still exists a lossy procedure after
entropy encoding.
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Steganography based on twice bit-plane encoding
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Steganography based on twice bit-plane encoding
1) There are three sub-steps involved in the determination of
embedding points and embedding intensity for a code block.
2) Scrambled synchronization information and secret
messages are embedded into the selected embedding
points from the lowest embed-allowed bit-plane to higher
ones.
3) Secondary bit-plane encoding is operated after information
embedding.
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Steganography based on twice bit-plane encoding
Ensured at the cost of increased computational complexity
and slightly changed compression ratio.
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Redundancy evaluation
Where is the quantized wavelet coefficient with the bits
lowerthan the highest no-zero bit are replaced by zeros.
The parameter is the quantization step of the wavelet
coefficient . The parameter assumes a value between
0 and 1. According to , a typical value of is 0.7. The result
of the first step is denoted as
ix
i
ix
iy
(1)
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Redundancy evaluation
In the second step, the neighborhood masking effect is
exploited to process the wavelet coefficients as the following:
(2) The neighborhood contains wavelet coefficients within a
window of N by N, centered at the current position.
The parameter is the total number of wavelet coefficients
in the neighborhood.
(2)
i
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Redundancy evaluation
The parameter assumes a value between 0 and 1,
together with , is used to control the strength of
embedding intensity adjustment due to neighborhood
masking.
The symbol denotes the neighboring wavelet coefficients
greater than or equal to 16, and all its bits lower than the
highest no-zero bit are set to be zeros.
(2)
i
kx̂
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Redundancy evaluation
(3)
(4) In the third step, a weighting factor about brightness
sensitivity is used in the processing.
The symbol denotes the subband at resolution level
.and with orientation .
The symbol denotes the wavelet coefficient
located at in subband .
The levels of discrete wavelet decomposition is k.
lI
kl ...1,0 HHHLLHLL ,,,
jiI l ,
ji, lI
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Redundancy evaluation
The pixel value has a dynamic range of [ -128, 127]. The local
average brightness is normalized by dividing 128. Then the
result of the third step, , is given byiz
(5)
Quantization redundancy is calculated by the following equation:
(6)
The redundancy of the wavelet coefficient can be
measured by .irix
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Redundancy evaluation
Use the wavelet coefficients with not less than 2 to carry
message bits.
The rule of adjustment on embedding points and intensity is
as follows:
ir
1) If , then this candidate embedding point should
be removed.
2) If , then the embedding capacity of this
point is determined to be n bits.
2ir
122 ni
n r
2121
Synchronization information and scrambling measure
The first part of the synchronization information is a 2-bit flag
that indicates whether a certain code block contains secret
message.
The second part of the synchronization information is a 12-bit
fragment that indicates the length of the secret message
embedded in this code block.
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Synchronization information and scrambling measure
The third part of the synchronization information is a 12-bit
fragment that indicates the length of the secret message
embedded in this code block.
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Synchronization information and scrambling measure
A 64-bit secret key is used as a seed to generate a
sequence of pseudo random binary numbers, which is used
to scramble the message bits.
N is the total number of message bits.
The symbol denotes the message bit, and the
binary number of the pseudo random sequence. The
operator ⊕ denotes binary addition. The scrambled
message bits, denoted as , are to be embedded into
selected wavelet coefficients.
is
im in
is
thithi
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Simulation
Fig. 6.
(a)Original image used as cover media.
(b)the binary logo image used as secret message.
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Simulation
In the first step, the lowest embed-allowed bit-plane of each
code block is determined.
In the second step, the wavelet coefficients with magnitudes
not less than a given threshold are chosen as candidate
embedding points.
In the third step, the candidate embedding points are
adjusted image adaptively based on redundancy evaluation
to increase hiding capacity
In the fourth step, we embed message bits into the selected
wavelet coefficients and finish encoding the stego-image
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Simulation
The threshold is set to 16
The parameters in those equations are set to be: N=5 ,
α=0.7 , β=0.2
Evaluation results for wavelet coefficients A, B, and D are as
follows: 72.1Ar 59.2Br 4.13Cr
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Simulation
21 259.22 43 24.132
1) If , then this candidate embedding point should
be removed.
2) If , then the embedding capacity of this
point is determined to be n bits.
2ir
122 ni
n r
B:
D:
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Simulation
Experiment shows that information hiding has caused slight
change on PSNR (Peak Signal to Noise Ratio) and the
actual compression ratio.
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Simulation
In order to test and measure the effectiveness on hiding
capacity enlargement, we simply bypass the redundancy
evaluation for comparison. Two methods are tested in the
experiments.
Method 1: With redundancy evaluation.
Method 2: Without redundancy evaluation.
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Simulation
Fig. 10.
(a) Crown
(b) Baboon
TABLE IHIDING CAPACITY OF THE THREE TEST IMAGES
( A compression ratio of 0.8 bits per pixel)
3131
Simulation
Fig. 11. Hiding capacity of different compression ratios.
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Simulation
Fig. 12. Four images in the database
3333
Simulation
Fig. 13. ROC curves tested on different payloads.
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Simulation
The detector does work only if the message length greatly
exceeds the hiding capacity.
The proposed steganography scheme can be considered
undetectable in the situation of lower payloads than hiding
capacity.
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Conclusion
The contributions of this work are mainly focused on
dealing with two problems: bitstream truncation and
redundancy measurement.
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備註( 1)