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,

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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

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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 1Map

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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

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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