利用網路聊天室傳送機密訊息 chair professor chin-chen chang feng chia university...

利用網路聊天室傳送機密訊息

Chair Professor Chin-Chen ChangFeng Chia University

National Chung Cheng University National Tsing Hua Universityhttp://msn.iecs.fcu.edu.tw/~ccc

http://msn.iecs.fcu.edu.tw/

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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

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Synonym substitution

Taichung is a 0 wonderful1 decent2 fine3 great4 nice

little0 city1 town

Secret message: (3)5(1)2

Taichung is a great little town

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

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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

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Grafting

He is detained in Japan.

He, an American citizen, is detained in Japan.

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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 the region to start flying over there.

Afghanistan has been under attack since October

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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.

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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

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Rule # Rule CodeProb

.

(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

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Inter-word spacing scheme 1

• This scheme exploits inter-word space of text to encode data.

Thisisabook.

Secret bits: {0 1 0}

Thisisabook.

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Inter-word spacing scheme 2

Weemploythecombinationoftherepeatedwords…

Secret bits: { 1 0 1 1}Space change: ＋－　　　　　＋

We employthecombinationof therepeated 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

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ExtractionExtractionSecret message

Secret message

EmbeddingEmbedding

Cover hypertext

Stego hypertext

Secret key

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<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>

Tagstext file

Secret: 010110…

<META

capital letterssmall letters

01

:the written states

01

</title>1

2

3

4

5

6

<HTML>

</HTML>

0110

<body

<p

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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

<META12

3

4

5

6

<HTML>

</HTML>

<body

<p

capital letterssmall letters

01

:the written states

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Text steganography in chat

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

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Text steganography in chatEmbedding :

“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

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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||1Phase1Phase2

Alan3c says:Just a kidding, you are the nicest guy I know in the world.Zhihui says:

0 0Phase3

Alan3c says : You are a bad student!Zhihui says:


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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

利用網路聊天室傳送機密訊息 chair professor chin-chen chang feng chia university...

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