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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. Chen Source : International Journal of Network Security, vol. 4, no. 1, pp. 17-26, 2007 Presenter : Ping-Kun Hsu( 許鈵昆 ) Date : 2011/01/21. Outline. Introduction
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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. Chen Source : International Journal of Network Security, vol. 4, no. 1, pp. 17-26, 2007 Presenter : Ping-Kun Hsu(許鈵昆) Date : 2011/01/21
Outline Introduction TJ Operator Logistic Chaotic Map The Proposed Scheme Experiment Result Analysis Conclusion Comment
Introduction • Goal • Hiding secret data in PDF file to achieve the undetectability, perceptual transparency, and capacity. • Related Works • TJ Operator • Logical Chaotic Map
TJOperator 2D vector-graph positioning model
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 FlagStr2 Start point SHA-1 SHA-1 0101|1010 Map 1 Map 2 01011011 01011010 5 | 10 Num1 Num2 91 mod 16 90 mod 16 Logistic chaotic map 11 10 FlagStr1 Transformed data FlagStr2 IND
The Proposed Scheme(2/5) 10,11,12 IND [<01> 4 <02> -2 <03> 20 <04> 15 <05>]TJ [<01> 10<02>11 <03> 20 <04>12 <05>]TJ no If the absolute value of the integer numeral is in [1,16] Keep the integer numeral constant yes If the Num2 is bigger than φ yes no Replace the integer numeral by the numeral in IND Replace the integer numeral by the numeral transformed from Num1
The Proposed Scheme(3/5) Key FlagStr Start point SHA-1 Map 2 Num2 01011011 Logistic chaotic map 91 mod 16 11 FlagStr
The Proposed Scheme(4/5) [<01> 10<02>11 <03> 20 <04>12 <05>]TJ If the absolute value of the integer numeral is in [1,16] yes no If the Num2 is bigger than φ yes no Extract the integer numeral and check the next integer numeral Check the next integer numeral
The Proposed Scheme(5/5) CheckStr Embedded Data FlagStr2 SHA-1 compare yes no Data have been extracted successfully Data may have been tampered
Conclusion The proposed scheme is secure, and the embedded capacity is high.
Comment How to calculate integer numeral by the numeral transformed from Num1