1. Image Steganography and Reversible Data Embedding Techniques 影像偽裝與可逆式資訊隱藏技術
Advisor: Prof. Chin-Chen Chang (張真誠 教授)
Student: Wei-Liang Tai (戴維良)
Department of Computer Science and Information Engineering,
National Chung Cheng University

2. Outline Part I: Image Steganography Part II: Reversible Data Embedding
covert (undetectable) communication
slight modification
Part II: Reversible Data Embedding
lossless (reversibility)
original image

3. Image Steganography
Escape
Alice
Bob
Warden

4. Steganography for VQ Compressed Images Using Hamming Codes and Declustering

5. Vector Quantization (VQ)

6. LSB Embedding Codebook Y of size m : Arrange Codebook : such that
are similar
Cover compression codes : {3, 6, 5, 0} = {011, 110, 101, 000}2
Secret message bits : (0, 0, 1, 1)
Stego compression codes : {010, 110, 101, 001}2 = {2, 6, 5, 1}
Embedding efficiency =

7. Single-Error-Correcting Codes
Send 1101 1 1 1 1
Finally send

8. Single-Error-Correcting Codes (Cont.)
Receive 1
Binary (7, 4) Hamming Code

9. Single-Error-Correcting Codes (Cont.)
Receive w=
s=HwT=
Receive w=
s=HwT=
HwT ≠ 0, 1-error occurred
Corrected x = w - el(HwT)
= ( ) – ( )
= ( )

10. Proposed Method Apply binary (7, 4) Hamming Code
Codebook Y of size m :
Arrange Codebook :
such that
are similar
Two sub-codebooks:
Apply binary (7, 4) Hamming Code
7 Cover compression codes : {3, 7, 4, 1, 2, 6, 4}
7-bit Cover vector: w=( )
3-bit Message m=(011)

11. Embedding and Extraction
s=HwT=
HxT = 0
HxT = m
HxT = HwT – HwT + m
HxT = HwT – (HwT – m)
HxT = H(w - el(HwT - m))
x = w - el(HwT - m)
HwT – m = (010)-(011) = (001)
Stego vector x = w – el(001)
=( )-( )
=( )
7 Stego codes = {3, 7, 4, 1, 2, 6, 5}
Extract : m = HxT=(011)
Embedding efficiency =

12. q-ary Hamming Codes Apply 3-ary (4, 2) Hamming Code
Codebook
q -1 … Y0 Y1
Yq -1
Similar
Apply 3-ary (4, 2) Hamming Code
4 Cover vector: w=(1021)
2 Message m=(21)3
s=HwT=
HwT – m = (02)-(21) = (11)
Stego vector x = w – el(11)
=(1021)-(0010)
=(1011)
Extract : m = HxT=(21)
Embedding efficiency =

13. Analysis Use the q-ary Hamming codes to convey r q-ary symbols in
Embedding efficiency =
> 2 = LSB embedding
Use the q-ary Hamming
codes
by performing at most one embedding change.
indices
to convey r q-ary symbols in

14. VQ compressed image (PSNR = 31.26 dB)
Visual Quality
VQ compressed image (PSNR = dB)
LSB embedding
(PSNR = dB)
Proposed scheme
(PSNR = dB)

15. Reversible Data Embedding
Marked image
Authentication code
Original cover image
Cover image
= authentic
Extracted auth. code
Auth. code

16. Reversible Data Hiding Based on Histogram Modification of Pixel Differences

17. Z. Ni, Y. Q. Shi, N. Ansari, and W. Su, “Reversible data hiding,” IEEE Transactions on Circuits and Systems for Video Technology, vol. 16, no. 3, pp , Mar
Original image
peak point
zero point 2 5 3 1 4 2 6 4 1 5 3 2 6 3 1 5
Marked image
Messages:

18. Histogram Modification
Marked image 2 6 4 1 5 3
a=3
b=6 2 6 4 1 5 3
Extracted bits =
extract 2 6 4 1 5 3 2 5 3 1 4
recover
Original cover image

19. Proposed Method

20. Proposed Method Peak point P=1 Cover image 155 156 158 159 160 153 1571 2 3 4 5 6 7 8 9 10 11 12 13 14 15 xi
155
156
158
159
160
157
153 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 di
155
Peak point P=1

21. Shift xi by 1 units: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 xi
155
156
158
159
160
157
153 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 di
155 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 yi
155
159
158
157
152

22. Let m be the secret data to be embedded m={0 ,1}.
P = 1, message to be embedded: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 xi
155
156
158
159
160
157
153 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 di
155 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 yi
155
156
154
159
158
160
157
152

23. Extraction and Recovery1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 yi
155
156
154
159
158
160
157
152 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 xi
155
156
158
159
160
157
153
P=1, extracted message m=

24. Experimental Results
In the worse case, all pixel values will be increased or decreased by 1
but the first pixel. That is, the mean squared error (MSE) is (N-1)/N .
The lower bound of PSNR:
Original Lena
48.32 dB embedded
with bpp

25. Performance Comparison

26. Future Works Image Steganography Reversible Data Embedding
spatial domain, JPEG, JPEG2000, etc.
combine other codes
Reversible Data Embedding
higher hiding capacity with lower distortion.
transform domains such as wavelet