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Data Hiding in a Kind of PDF Texts for Secret Communication
Authors : S.P. Zhong, X.Q. Cheng, and T.R. ChenSource : International Journal of Network Security, vol. 4, no. 1, pp. 17-26, 2007Presenter : Ping-Kun Hsu(許鈵昆 )Date : 2011/01/21
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Outline Introduction TJ Operator Logistic Chaotic Map The Proposed Scheme Experiment Result Analysis Conclusion Comment
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Introduction Goal
Hiding secret data in PDF file to achieve the undetectability, perceptual transparency, and capacity.
Related Works TJ Operator Logical Chaotic Map
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TJ Operator
2D vector-graph positioning model
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Logistic Chaotic Map
Xn+1 = r × Xn × (1-Xn)0≦ Xn ≦1, 0 ≦ r ≦4
If 3.57 ≦ r ≦4, the iteration values are random
The Proposed Scheme(1/5)Secret data Key
Logistic chaotic map
Map 1 Map 2
Start point
Num1 Num2
0101|1010
5 | 10
SHA-1
01011011
91 mod 16
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FlagStr2
IND6
SHA-1
01011010
90 mod 16
10
FlagStr1
Transformed data
FlagStr2
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The Proposed Scheme(2/5)
[<01> 4 <02> -2 <03> 20 <04> 15 <05>]TJ
If the absolute value of the integer numeral is in
[1,16]
If the Num2 is bigger than φ
Replace the integer numeral by the numeral in IND
10,11,12
Replace the integer numeral by the numeral transformed
from Num1
yes no
yes
Keep the integer numeral constant
no
[<01> 10<02>11 <03> 20 <04>12 <05>]TJ
IND
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The Proposed Scheme(3/5) Key
SHA-1
01011011
91 mod 16
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FlagStr
FlagStr
Map 2
Start point
Num2
Logistic chaotic map
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The Proposed Scheme(4/5)
If the absolute value of the integer numeral is in
[1,16]
If the Num2 is bigger than φ
Extract the integer numeral and
check the next integer numeral
Check the next integer numeral
yes no
yesno
[<01> 10<02>11 <03> 20 <04>12 <05>]TJ
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The Proposed Scheme(5/5) CheckSt
rEmbedded
DataFlagStr
2
SHA-1
compare
Data have been extracted successfully
Data may have been tampered
noyes
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Experiment Result
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Analysis
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Conclusion The proposed scheme is secure, and
the embedded capacity is high.
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Comment How to calculate integer numeral by
the numeral transformed from Num1