Recent developments in_text_steganography

Recent Developments in Text
Steganography
Chair Professor Chin-Chen Chang
National Tsing Hua University
National Chung Cheng University
Feng Chia University
http://msn.iecs.fcu.edu.tw/~ccc
http://msn.iecs.fcu.edu.tw/

2
Information hiding in general text

Synonym substitution

Syntactic transformation

Translation

Semantic transformation
Information hiding in hypertext
Information hiding in binary text

Inter-word spacing schemes
Information hiding in chat text

Text steganography in chat

Emoticon-based steganography in chat

3
Synonym substitution
Taichung is a
0 wonderful
1 decent
2 fine
3 great
4 nice
little
0 city
1 town
Secret message: (3)5(1)2
Taichung is a great little town

4
Syntactic transformations
Syntactic: the way that words and phrases are put together to form sentences in a language

5
Semantic transformation
• Grafting: adding or repeating information
• Pruning: removing repeated information
• Substitution: replacing information
Semantic :Describe things that deal with the meanings of words and sentences

6
Grafting
He is detained in Japan.
He, an American citizen, is detained in Japan.

7
Pruning
The Pentagon ordered two new spy planes
to the region to start flying over
Afghanistan.
Afghanistan has been under attack since October,
and the Pentagon ordered two new spy planes to
Afghanistan has been under attack since October

8
Substitution
The Pentagon ordered two new spy planes to
the region to start flying over Afghanistan.
Afghanistan Taliban ruled country
The Pentagon ordered two new spy planes to the
region to start flying over the Taliban ruled country.

9
Translation
法文 : C’est la vie
英文 :
That’s life.
That is the life.
It is the life.
It’s life.
Message
Alice Bob
Stego object
Cover object

10
Rule # Rule Code
Prob
.
(1) S -> AB 0 0.5
(2) S -> CB 1 0.5
(3) A -> It is 0 0.5
(4) A -> It’s 1 0.5
(5) C -> That is 0 0.5
(6) C -> That’s 1 0.5
(7) B -> life 0 0.5
(8) B -> the life 10 0.25
(9) B -> a life 11 0.25
Prefix Rule Output
1 (2) CB
0 (5) That is B
10 (8) That is the life
Secret: 1010
Translation

11
Inter-word spacing scheme 1
• This scheme exploits inter-word space of
text to encode data.
Thisisabook.
Secret bits: {0 1 0}
Thisisabook.

12
Inter-word spacing scheme 2
Weemploythecombinationoftherepeatedwords…
cret bits: { 1 0 1 1}
ce change: ＋－　　　　　＋
We employthecombinationof therepeated words…
• Keep spaces between groups unchanged.

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Add-pattern Delete-pattern
Binary image

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• Embedding
Secret bit 0 : A-pattern  D-pattern
D-pattern  D-pattern
Secret bit 1 : D-pattern  A-pattern
A-pattern  A-pattern
• Extracting
D-pattern  Secret bit 0
A-pattern  Secret bit 1

15
ExtractionExtractionSecret message
Secret message
EmbeddingEmbedding
Cover hypertext
Stego hypertext
Secret key

16
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=big5">
<title> 多媒體暨網路安全實驗室 </title>
</head>
<body bgcolor="#D27D1O">
<img border="0" src="msn.jpg" width="338" height="345">
~ 歡迎加入
~
</body>
Tags
text file
Secret: 010110…
<META
capital letters
small letters
0
1
:the written states
01
</title>
1
2
3
4
5
6
<HTML>
</HTML>
0110
<body
<p

17
Secret: 010110…
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=big5">
<title> 多媒體暨網路安全實驗室 </title>
</head>
<body bgcolor="#D27D1O">
<img border="0" src="msn.jpg" width="338" height="345">
~ 歡迎加入
~
</body>
</html>
text file
<META1
2
3
4
5
6
<HTML>
</HTML>
<body
<p
capital letters
small letters
0
1
:the written states

18
Shirali-Shahreza, M.H., Shirali-Shahreza,
M., “Text Steganography in Chat,”
Proceedings of the Third IEEE/IFIP
International Conference in Central Asia
on Internet the Next Generation of
Mobile, Wireless and Optical
Communications Networks, Tashkent,
Uzbekistan, Sep. 2007, pp. 1-5.

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SMS-Texting

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Usual abbreviated words
• univ.  university
• PC  Personal Computer
• M.S.  master of science
• UN  United Nations
• Dr  doctor

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• SMS list + abbreviated words list
 Check list
• 0  full formfull form, 1  abbreviated formabbreviated form

22
Embedding :
“Please call me when you feel upset.”
secret “10”
“Please CM when you feel upset.”
Extracting :
“Please CM when you feel upset.”
secret bits “10”
Check list

23
Emoticon-based Text Steganography in Chat

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Phase1: Classify the emoticons by their meaning

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Example: N = 16
hide log2N = 4 bits per emoticon
sender uses second symbol
receiver can extract 4 bits “0001”

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Phase2: emoticon || sentence : secret = 0
sentence || emoticon : secret = 1
I lost my bag
I lost my bag
secret = 0
secret = 1

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Phase3: emoticon , sentence : secret = 0
emoticon , sentence : secret = 1
,I lost my bag secret = 0
secret = 1I lost my bag

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Zhihui wants to send
secret bits
“11100000111”
to Alan3c.
1110
001||1||1
Phase1Phase2
Alan3c says:
Just a kidding, you are the nicest guy I know in the world.
Zhihui says:
0 0
Phase3
Alan3c says :
You are a bad student!
Zhihui says:

29
Future Research Direction
• Chinese text steganography
壞的毛病壞毛病
山東的蘋果山東蘋果
我的媽媽我媽媽
主要的問題主要問題
另外的一件事另外一件事
其他的問題其他問題
北京的大學北京大學

Recent developments in_text_steganography

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