1. A separable reversible data hiding scheme for encrypted JPEG bitstreams
Source : Signal Processing, Volume 133, April 2017, Pages
Authors : Jen-Chun Chang, Yi-Zhi Lu, Hsin-Lung Wu
Speaker : Si-Liang He
Date : 2017/12/21

2. Outline
Introduction Proposed scheme Experimental results Conclusions

3. JPEG compression 1/4
Procedure of JPEG compression

4. JPEG compression 2/4 DCT Original Image 52 55 61 66 70 64 73 63 59 90
109 85 69 72 62 68
113
144
104 58 71
122
154
106 67
126 88 79 65 60 77 75 83 87 76 78 94
-415
-30
-61 27 56
-20 -2 4
-22 10 13 -7 -9 5
-47 7 77
-25
-29 -6
-49 12 34
-15
-10 6 2
-13 -4 -3 3 -8 1 -1
DCT
Original Image

5. JPEG compression 3/4 DC(direct current )
The others are AC(alternating current ) 26 2 3 -1 1
DC: differential pulse code modulation (DPCM)
Quantification
JPEG
file
Entropy encoding
AC: Run Length Coding (RLC)
Quantization table

6. QF = QF = 50

7. JPEG compression 4/4 AC coefficients :
{0, 2, -1,0, 0, 0, 3, 0, 1, }
ZRV(zero-run-value)(R,V):
{(1, 2), (0, -1), (3, 3), (1,1), …}
RSV (Run/Size and Value)
Denote as [(RL, BL), A]:
{[(1, 2), 10], [(0, 1), 0], [(11, 2), 11], [(1, 1), 1], …}
RL : Binary representation of number of zero
BL : Bit length of the binary representation of non-zero value
A : Binary representation of non-zero value

8. Proposed scheme - flow chart

9. Proposed scheme - 1/6 Generate a pseudo-random permutation block
(1, 1) → (1, 2) → (2, 1) → (2, 2) → (1, 1)

10. Proposed scheme - 2/6 Zig-zag order {-3, -2, 2, 3}

11. Proposed scheme - 3/6
G 2 = (-3, 2, -2, 3, 2, -2, -3, 3, -2, -2, 2, 3, 2, 2, 3, 2, -2, 2, 2, 2, 2, -2, 2, 2, 2)
𝐺 2 = (11, 00, 10, 01, 00, 10, 11, 01, 10, 10, 00, 01, 00, 00, 01, 00, 10, 00, 00, 00, 00, 10, 00, 00, 00)
LSB( 𝐺 2 ) = (1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
k = 6, n = 25
𝑓 𝐶 (LSB( 𝐺 2 ) ) = (0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0)

12. Proposed scheme - 4/6
𝑓 𝐶 (LSB( 𝐺 2 ) ) = (0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0)

13. Proposed scheme - 5/6
LSB( 𝐺 2 ) = (1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
𝑓 𝐶 (LSB( 𝐺 2 ) ) = (0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0)
LSB( 𝐺 2 ′ ) = (0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0)
𝐺 2 ′ = (10, 01, 11, 00, 00, 10, 10, 01, 10, 10, 00, 01, 01, 01, 00, 01, 11, 00, 00, 00, 00, 10, 00, 00, 00)
(-2, 3, -3, 2, 2, -2, -2, 3, -2, -2, 2, 3, 3, 3, 2, 3, -3, 2, 2, 2, 2, -2, 2, 2, 2)

14. Proposed scheme - 6/6 embedding & extraction
LSB( 𝐺 2 ′ ) = (0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0)
= 5 → k = = 18
recovery
(0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0)
( )2 = t
LSB( 𝐺 2 ) = (1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)

15. Experimental results

16. Conclusions Proposed a lossless compression algorithm.
Decryption and extraction can be separable.