隱匿學之應用
TBPC與MPC
隱匿學
使用載體來隱匿傳送的訊息，讓第三者無法得知有藏
匿秘密訊息。
接收者
藏匿演算法
傳送者
? ? ? ? ? ?
解匿演算法
今天下午兩點
在星巴克見面
今天下午兩點
在星巴克見面
2
隱匿學
常用術語
Host
載體
Stego
隱匿檔案
接收者
傳送者
藏匿演算法
Logo
秘密資訊
今天下午兩點
在星巴克見面
? ? ? ? ? ?
解匿演算法
今天下午兩點
在星巴克見面
3
隱匿學的應用
資料的任何形式(文字、圖像、聲音或影片)都可能被
數位化，祕密的二位元資訊可能在數位化過程中被嵌
入。
它可能被用來保護版權、防止篡改，或者增加額外的
資訊。
隱匿學-掩飾文：可能是文字，有很多方法可用來嵌
入二位元資料到無害的文章中。例如
Host
載體
Logo
秘密資訊
Thisbookismostlyaboutcryptography,notsteganography.
0100001
Stego
This book is mostly about cryptography, not steganography.
隱匿檔案
4
0
1 0
0
0
0
1
Contents
TBPC
Data Hiding With Tree Based Parity Check
MPC
An Optimal Data Hiding Scheme With Tree-Based Parity Check
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
In this paper, we propose a novel algorithm
namely tree based parity check (TBPC).
I. Tree Formation
In TBPC, an N-ary complete tree namely Master
Tree is filled up by the value of these embeddable
locations.
Every node of an N-ary complete tree except leaf
nodes has N child nodes.
In the proposed algorithm, one leaf node is needed
to hold one information bit.
To embed an L bits logo, L leaves are required in
the Master Tree.
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
Master Tree
𝑡1
𝒉=𝟑
𝑡2
𝒉=𝟐
𝒉=𝟏
𝒉=𝟎
𝑡3
𝑡5
𝑡4
𝑡8
𝑡9
𝑡10
𝑡7
𝑡6
𝑡11
𝑡12
𝑵=𝟐
𝑳 = 𝑵𝒉 = 𝟐𝟑 = 𝟖
𝑡13
𝑡14
𝑡15
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
II. Parity Calculation
To find out the information held by a leaf node, we
travel from the leaf node to the root of the Master
Tree.
If the occurrence of '1' is an odd number, the
information bit of the leaf node is said to be '1'.
Otherwise, the information bit is said to be '0'.
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
 Master Tree
𝑁115
𝑁113
𝑁114
𝑁010
𝑁19
𝑁01
𝑁12
𝑁112
𝑁011
𝑁13
𝑁14
𝑁05
𝑁16
𝑁07
𝑁08
1
1
0
1
1
1
Master string
1
0
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
III. Fountain Investigation
By performing bitwise logical exclusive-OR (XOR)
operation between the logo and the information
carried by the Master Tree.
 Master string obtained is {10110111}.
 Assume the logo is {10000100}.
 Toggle string becomes {00110011}.
The array is called "toggle array" is simply
because that any '1' in the array represents a toggle
is needed in one of the embeddable locations of the
original image.
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
Master string
1
0
1
1
0
1
1
1
0
0
0
0
1
0
0
1
1
0
0
1
1
Logo
1
Toggle string
0
0
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
 Toggle Tree
0
0
0
0
0
1
0
0
0
1
0
0
0
0
0
0
0
1
1
0
0
1
1
Toggle string
0
0
msalab.ncut.edu.tw
Data Hiding With Tree Based Parity Check
 Master Tree'
𝑁115
𝑁113
𝑁114
𝑁1
010
𝑁19
𝑁01
𝑁0
112
𝑁011
𝑁12
𝑁13
𝑁14
𝑁05
𝑁16
𝑁07
𝑁08
0
0
0
0
1
0
0
Logo
1
msalab.ncut.edu.tw
An Optimal Data Hiding Scheme
With TreeBased Parity Check
Reducing distortion between the cover object and
the stego object is an important issue for
steganography.
The tree-based parity check method is very
efficient for hiding a message on image data due to
its simplicity.
Based on this approach, we propose a majority
vote strategy that results in least distortion for
finding a stego object.
msalab.ncut.edu.tw
An Optimal Data Hiding Scheme
With TreeBased Parity Check
I. Preliminary And TBPC Method
The TBPC method is a least significant bit (LSB)
steganographic method .
The TBPC method constructs a complete N-ary
tree, called the master tree, to represent the LSBs
of the cover object.
Then it fills the nodes of the master tree with the
LSBs of the cover object level by level, from top
to
bottom
and
left
to
right.
msalab.ncut.edu.tw
An Optimal Data Hiding Scheme
With TreeBased Parity Check
Master and toggle strings of a master tree with 𝐿 =
4 for LSBs {0110101} of the cover object.
0
Master tree
1
1
0
1
0
1
Master string 1
0
1
0
Message
1
1
0
1
Toggle string
0
1
1
1
msalab.ncut.edu.tw
An Optimal Data Hiding Scheme
With TreeBased Parity Check
Toggle tree in the bottom-up order and fills the
leaves with the bit values of the toggle string and
the other nodes with 0.
Then, level by level, from the bottom to the root,
each nonleaf node together with its child nodes are
flipped if all its child nodes have bits 1 .
We can extract the message by performing parity
check on each root-leaf path of the stego tree from
left
to
right.
msalab.ncut.edu.tw
An Optimal Data Hiding Scheme
With TreeBased Parity Check
Step1
0
0
0
0
1
1
1
Step2 (Toggle tree)
0
0
0
1
1
0
0
msalab.ncut.edu.tw
An Optimal Data Hiding Scheme
With TreeBased Parity Check
 Modify the master tree into the stego tree by the toggle tree
constructed from the toggle string {0111}.
Master tree
Toggle tree
0
0
1
1
0
1
=
0
0
1
1
0
1
0
Toggle tree
1
0
0
0
0
1
0
0