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Steganalysis of Reversible Contrast Mapping Watermarking. Authors: Yeh-Shun Chen and Ran-Zan Wang Source: IEEE Signal Processing Letters, Vol. 16, No. 2, February 2009, pp. 125-128 Reporter: Chia-Chun Wu ( 吳佳駿 ) Date: 2010/08/27. Outline. 1. Reversible Watermark

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Steganalysis of reversible contrast mapping watermarking

Steganalysis of Reversible Contrast Mapping Watermarking

Authors: Yeh-Shun Chen and Ran-Zan Wang

Source: IEEE Signal Processing Letters, Vol. 16, No. 2,

February 2009, pp. 125-128Reporter: Chia-Chun Wu (吳佳駿)

Date: 2010/08/27


Outline
Outline

  • 1. Reversible Watermark

  • 2. Reversible Contrast Mapping

  • 3. Embedding

  • 4. Detection and Recovering

  • 5. Steganalysis

  • 6. Experimental results

  • 7. Conclusions


1 reversible watermark 1 4
1. Reversible Watermark (1/4)

Cover

extraction

Watermark

Stego

embedding

Watermark

Irreversible Watermarking

Cover

extraction

Watermark

Stego

embedding

Cover

Watermark

recover

Reversible Watermarking


1 reversible watermark 2 4

Internet

1. Reversible Watermark (2/4)

  • Irreversible Watermarking

Stego image

Cover image

Watermark

Watermark


1 reversible watermark 3 4
1. Reversible Watermark (3/4)

  • Irreversible Watermarking

Watermark

Cover image

xi

xi+1

mi

mi+1

mi

mi+1

yi

yi+1


1 reversible watermark 4 4

Internet

1. Reversible Watermark (4/4)

  • Reversible Watermarking

Stego image

Cover image

Cover image

Watermark

Watermark


2 reversible contrast mapping 1 2

Very Fast Watermarking by Reversible Contrast Mapping, Dinu Coltuc and Jean-Marc Chassery, IEEE Signal Processing Letters, Vol. 14,  No. 4, April 2007, pp. 255-258.

2. Reversible Contrast Mapping (1/2)

  • RCM is a simple integer transform

  • RCM applies to pairs of pixels

    • Let be a pair of pixels in original image

    • Let be a pair of pixels in stego image

    • Let [0, L] be image graylevel range (ie. L = 255)

    • is the ceil function (the smallest integer greater than or equal to )


2 reversible contrast mapping 2 2
2. Reversible Contrast Mapping Coltuc and Jean-Marc Chassery, (2/2)

  • The forward RCM :

  • The inverse RCM :

X’ and Y’ are both odd only if X and Y are both odd

  • If X and Y are not both odd

    • then inverse correct even if LSB bit set to 0


2. Reversible Contrast Mapping Coltuc and Jean-Marc Chassery, (2/2)

  • The forward RCM :

  • The inverse RCM :

(7, 4)  (10, 1)

(7, 9)  (5, 11)

(10, 1)  (7, 4)

(5, 11)  (7, 9)

(10, 0)  (7, 4)


3 embedding 1 2
3. Embedding Coltuc and Jean-Marc Chassery, (1/2)

Step1: Partition the image into pairs of pixels.

Step2: For each pair

Case 1: If and are not both odd pixel values.

- transform the pair by the forward RCM

- set the LSB of to “1”

- embed data into the LSB of

Case 2: If and are both odd pixel values.

- transform the pair by the forward RCM

- set the LSB of to “0”

- embed data into the LSB of

Case 3: If

- set the LSB of to “0” and save the true value


Case 1 Coltuc and Jean-Marc Chassery,

Case 2

10

12

11

13

embed “0”

embed “0”

embed “1”

embed “1”

Case 1

Case 3

10

13

11

21

embed “0”

embed “1”

save the LSB of X


4 detection and recovering 1 2
4. Detection and Recovering Coltuc and Jean-Marc Chassery, (1/2)

Step1: Partition the image into pairs of pixels.

Step2: For each pair

Case 1: If the LSB of is “1”

- extract the LSB of

- set the LSBs of to “0”

- transform the inverse RCM

Case 2: If the LSB of is “0” and belongs to

- extract the LSB of

- set the LSBs of to “1”

- transform the inverse RCM


4 detection and recovering 2 2
4. Detection and Recovering Coltuc and Jean-Marc Chassery, (2/2)

Case 3: If the LSB of is “0” and the pair with

the LSBs set to “1” does not belong to

- replacing the LSB of with the

corresponding true value extracted

from the watermark sequence


5 steganalysis 1 2
5. Steganalysis Coltuc and Jean-Marc Chassery, (1/2)

Case 1: If and are not both odd pixel values.

- set the LSB of to “1”

- embed data into the LSB of

Case 2: If and are both odd pixel values.

- set the LSB of to “0”

- embed data into the LSB of

Case 3: If

- set the LSB of to “0” and save the true value

LSB(X, Y) = (0, 0), (0, 1) and (1, 0)  LSB(X', Y') = (1, 1) or (1, 0)

LSB(X, Y) = (1, 1)  LSB(X', Y') = (0, 0) or (0, 1)

LSB(X, Y) = (0, 0), (0, 1) , (1, 0) and (1, 1)  LSB(X', Y') = (0, 0) or (0, 1)

14


5 steganalysis 2 2
5. Steganalysis Coltuc and Jean-Marc Chassery, (2/2)

15


6 experimental results 1 3

Mean value of the P Coltuc and Jean-Marc Chassery, LSB(1)-PLSB(0): -0.013306

Standard derivation of the PLSB(1)-PLSB(0): 0.03736

6. Experimental results (1/3)

Fig. 1. Distribution of the PLSB(1)-PLSB(0) values of RCM watermarking stego-images for various embedding ratios. (962 test images)


6 experimental results 2 3
6. Experimental results Coltuc and Jean-Marc Chassery, (2/3)

Fig. 2. Detection result of the proposed method for various threshold values. (1516 test images)


5 experimental results 3 3
5. Experimental results Coltuc and Jean-Marc Chassery, (3/3)

Table I

Mean Estimated Embedding Ratios of Hidden Messages


6 conclusions
6. Conclusions Coltuc and Jean-Marc Chassery,

  • This paper presented a simple method for cracking RCM watermarking.


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