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Authors ：Xinpeng Zhang, Shuozhong Wang,Zhenyu Zhou
Received： March 27, 2008
Revised ： May 12, 2008
Adviser ： Chih-Hung Lin
Speaker ：I-Hsing Tung
Date： 2009/12/08
Author
2. Framework
3. Multibit Assignment Method
4. Experimental Results
1.
 Shuo-zhong Wang
 Shanghai University
 Research：
 Signal Processing
 Digital Image Processing
 Xin-peng Zhang
 Shanghai University
 Zhen-yu Zhou
 Shanghai University
 In the multibit assignment steganography, the original
palette is not changed and the colors in the palette are
assigned to carry several bits ,and presents a data embedding procedure：
 Definition 1:
R,G,B=(128,256,128)
R,G,B=(0,256,0)
 Definition 2:
 If a color possesses at least one neighbor color，we say
it is a gregarious color
 Definition 3:
 if, for any gregarious color and any bit sequence with
an indefinite length, there are always at least one bitchip mapped to a member of the gregarious color’s
neighborhood set that is a prefix of the given bit
sequence
C6
101
C1
C2
C3
1
0
C2
0
C7
0
C3
11
C7
11
C7
0
0
00
10
C4
C5
C1
1
C6
101
C2
0
C5
10
C8
1
=C2C7C3C7C1C6C2C5C4C3
C4
00
C3
11
third
layer,
there areeach
three
After In
thethe
first
layer
assignment,
subsets:
gregariousnon-empty
color is mapped
to a：
bit “0” or “1”
（C4） corresponding to two bits “00”
{C1,C3,C5,C6,C8}
（C5,C6)corresponding to two bits“10”
{C2,C4,C7}
（C3） corresponding to two bits“11”
Ｃ6
For the first subset, C2 and C4
are 1-layer-gregarious,
and assign new bits “1” and “0”
101
Ｃ1
Ｃ2
Ｃ3
Ｃ7
1
0
11
0
In the fourth layer, since the
00
only subset C6 contains just one
color, it does not produce
Ｃ4
any assigned bit and the
multibit assignment procedure
terminates.
10
Ｃ5
7
Ｃ8
1
Forthe
thesecond
subset{C5,C6}
, both
For
subsetC3,C5
and
C5are
and1-layer-gregarious，
C6 are
C6
and
2-layer-gregarious,
and
new
assign new bits “1”, “0”, and “0”
bits to
“0”them,
and “1”
are assigned to
respectively
them, respectively.
 In the experiment, two 256-color palette images Lena and
Baboon, both sized 512*512, were used as covers Using a
threshold D=12 ,3.7*105 secret bits were embedded into
Lena with


PSNR=36.19 dB
MSE=15.6
 Ｄ=20，2.6*105 secret bits were embedded into Baboon
with
PSNR=32.27dB
MSE=38.5
 結束~