Reversible hiding in DCT-based
compressed images
Authors:Chin-Chen Chang, Chia-Chen Lin,
Chun-Sen Tseng and Wei-Liang Tai
Adviser: Jui-Che Teng
Speaker: Gung-Shian Lin
Date:2009/12/17
Outline
1. Introduction
2. Related works
3. Proposed scheme
4. Experimental results
5. Conclusions
2
Introduction

Lossless and reversible steganography
scheme for hiding secret data in each block
of quantized DCT coefficients in JPEG
images.
3
Introduction

In 2001, Fridrich et al. proposed Invertible
authentication watermark for JPEG images.

In 2004, Iwata et al. proposed Digital
steganography utilizing features of JPEG
images.
4
Related works

RGB transformation for JPEG
RGB Image
Transformation
RGB→YCbCr
Quantization
Quantization
Table
Runlength coding
Huffman coding
Huffman
Table
Composition
MCU
JPEG Image
2-D DCT
5
Proposed scheme
Embedding procedure
bi be the length of ceaseless
zeros
zi,1 represents the zero value
of the lowest frequency
R9
R7
R5
R3
R8
R6 R4
R2
R1
6
Proposed scheme
2
0
3
3
4
0
2
0
2
2
0
1
0
2
0
0
1
0
0
0
0
0
1
0
1
0
0
0
0
0
0
0
0 R3
si be the secret bit we
want to embed into set Ri
R4
R5
R2 R1
7
Proposed scheme

The embedding strategies and elimination measures for
ambiguous conditions are as follows:
Case 1:If bi ≧2, we use the value of zi,2 to indicate the hidden secret
bit in set Ri (1≦i≦9). We modify the value of zi,2 to hide
secret bit by using the Eq.
when si is 0,
0,
zi,2  
1 or  1, when si is 1,
where 1 or -1 is randomly selected.
8
Proposed scheme

Ambiguous condition A and its remedial
measure。
1
0
x
0
0
0
0
R1
9
Proposed scheme
ri , j  1  1, when ri,j-1  0,
where 3≦(j－1)≦ki
r ' i, j  1  
ri , j  1  1, when ri,j-1  0,
3
0
0
0
1
0
0
R2
10
Proposed scheme
Case 2: If bi < 2 and both zi,1 and zi,2 do not exist, none
secret bits can be hidden in a set Ri.
 Two ambiguous conditions may exist, and therefore two
remedial measures for eliminating them are described
below.

Ambiguous condition B and its remedial measure
r'i,1  1, when r'i,1  0,
r'i,1  
r'i,1  1, when r'i,1  0,

Ambiguous condition C and its remedial measure
r ' i , 2  1, when r ' i , 2  0,
r ' i,2  
r ' i , 2  1, when r ' i , 2  0,
11
Proposed scheme

Example of embedding:assume four secret bits, 0, 0, 1 and 1
12
Proposed scheme

Extracting procedure
Step 5.
1. Repeat
2.
3.
4.
Obtain
Scan
For
Extract
each
each
non-overlapping
si
Steps
set
from
block
R3iset
in
and
according
aRiblock,
4by
until
8using
*let
all
8
toblocks
rblocks
ai,jthe
predetermined
beR
following
the
of
are
quantized
highest
processed.
rules:
frequency
order.
DCT coefficients
non-zero of the Y
i
components where
component,
from a1≦i≦9
JPEG and
stego-image
1≦j≦ki. after Huffman decoding and runlength
decoding.
ri,j≠1 or -1
ri,j ＝1 or -1
ri,j+1＝0
ri,j-1＝0 and
ri,j-2＝0
si=1
mark ri,j as zi,2
ri,j-1＝0 and
ri,j-2＝0
ri,j+1≠0
j≦2
si=0
mark ri,j-2 as zi,2
si=0
mark ri,j-2 as zi,2
si does not
exist
ri,j does not exist
j≦2
si=0
mark ri,1 as zi,2
si does not
exist
13
Proposed scheme

Restoring procedure

Rule 1: If si exists and r’i,j+3＝0, where 4≦(j＋3)≦ki, then the original
value of r’i,j+2 is restored by using Eq.
r ' i , j  2  1, when r ' i , j  2  0,
ri , j  2  
r ' i , j  2  1, when r ' i , j  2  0,

where 3≦(j＋2)＜ki.
Rule 2:If si does not exist and the two highest coefficients (r’i,1，r’i,2)
of set Ri equals (x, 0), where x≠0, then the original value of r’i,1 is
restored by using Eq.
r ' i ,1  1, when r' i,1  0
ri ,1  
r ' i ,1  1, when r' i,1  0
14
Proposed scheme

Rule 3: If si does not exist and the pair having the three
highest coefficients (r’i,1, r’i,2, r’i,3) of set Ri equals (0,x,0),
where x≠0, then the original value of r’i,2 is restored by using
Eq.
r ' i , 2  1, when r ' i , 2  0,
ri , 2  
r ' i , 2  1, when r ' i , 2  0,
15
Proposed scheme
16
Proposed scheme

Modifying quantization table for better image quality and
hiding capacity
16 11 10 16 24
40
51
61
16 11 10 16 24 40 51 61
12 12 14 19 26
58
60
55
12 12 14 19 26 41 60 55
14 13 16 24 40
57
69
56
14 13 16 17 28 40 48 56
14 17 22 29 51
87
80
62
14 17 22 20 36 61 56 43
18 22 37 56 68
109 103 77
18 22 26 39 48 76 72 54
24 35 55 64 64
104 113 92
24 25 39 56 57 73 79 64
49 64 78 87 103 121 120 101
49 64 55 61 72 85 84 71
72 92 95 98 112 100 103 99
72 92 95 69 78 70 72 70
17
Experimental results
18
Experimental results
19
Experimental results
20
Conclusions

The scheme provides stego-images with acceptable
image quality and similar hiding capacity can be
achieved with the Iwata et al. scheme。

The scheme can withstand visual and statistical
attacks 。
21