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Embedding Secret Messages in Texts
Chair Professor Chin-Chen Chang Feng Chia University National Chung Cheng University National Tsing Hua University
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Information hiding in general text
Synonym substitution Syntactic transformation Semantic transformation Translation Inter-word spacing schemes Information hiding in binary text Information hiding in hypertext Information hiding in chat text Text steganography in chat Emoticon-based steganography in chat
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Synonym substitution 0 wonderful 1 decent 2 fine Taichung is a 0 city
3 great 4 nice Taichung is a 0 city 1 town little Secret message: (3)5(1)2 Taichung is a great little town
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Syntactic transformations
Syntactic: the way that words and phrases are put together to form sentences in a language
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Semantic transformation
Semantic :Describe things that deal with the meanings of words and sentences Grafting: adding or repeating information Pruning: removing repeated information Substitution: replacing information
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Grafting He is detained in Japan.
He, an American citizen, is detained in Japan.
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Afghanistan has been under attack since October
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 Stego object Alice Bob Cover object
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Translation Rule # Rule Code Prob. (1) S -> AB 0.5 (2) S -> CB 1
0.5 (2) S -> CB 1 (3) A -> It is (4) A -> It’s (5) C -> That is (6) C -> That’s (7) B -> life (8) B -> the life 10 0.25 (9) B -> a life 11 Secret: 1010 Prefix Rule Output 1 (2) CB (5) That is B 10 (8) That is the life
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Inter-word spacing scheme 1
This scheme exploits inter-word space of text to encode data. Thisisabook. Secret bits: { } Thisisabook.
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Inter-word spacing scheme 2
Keep spaces between groups unchanged. Weemploythecombinationoftherepeatedwords… Secret bits: { } Space change: ＋ － ＋ We employthecombinationof therepeated words…
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Information hiding in binary text
Add-pattern Delete-pattern Binary image
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Information hiding in binary text
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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Information hiding in hypertext
Secret message Cover hypertext Embedding Stego hypertext Secret key Extraction Secret message
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Information hiding in hypertext
<HTML> </HTML> 0110 <body <p Secret: … 1 </title> capital letters small letters 0 1 :the written states Tags text file 1 2 3 4 5 6 <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"> <p align="center"><img border="0" src="msn.jpg" width="338" height="345"></p> <p align="center"><font face="標楷體" color="#f4efe8" size="7">~歡迎加入~</font></p> </body> </html> <META
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Information hiding in hypertext
capital letters small letters 0 1 :the written states text file 1 2 3 4 5 6 <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"> <p align="center"><img border="0" src="msn.jpg" width="338" height="345"></p> <p align="center"><font face="標楷體" color="#f4efe8" size="7">~歡迎加入~</font></p> </body> </html> <HTML> <META <body <p </HTML> Secret: …
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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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Text steganography in chat
SMS-Texting
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Text steganography in chat
Usual abbreviated words univ. university PC Personal Computer M.S. master of science UN United Nations Dr doctor
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Text steganography in chat
SMS list + abbreviated words list Check list 0 full form, 1 abbreviated form
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Text steganography in chat
Embedding : “Please call me when you feel upset.” secret “10” “Please CM when you feel upset.” Extracting : Check list secret bits “10”
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Emoticon-based steganography in chat
Emoticon-based Text Steganography in Chat
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Emoticon-based steganography in chat
Phase1: Classify the emoticons by their meaning
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Emoticon-based steganography in chat
Example: N = 16 hide log2N = 4 bits per emoticon sender uses second symbol receiver can extract 4 bits “0001”
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Emoticon-based steganography in chat
Phase2: emoticon || sentence : secret = 0 sentence || emoticon : secret = 1 I lost my bag secret = 0 I lost my bag secret = 1
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Emoticon-based steganography in chat
Phase3: emoticon , sentence : secret = 0 emoticon , sentence : secret = 1 , I lost my bag secret = 0 I lost my bag secret = 1
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Emoticon-based steganography in chat
Zhihui wants to send secret bits “ ” to Alan3c. Alan3c says : You are a bad student! Zhihui says: 1110 Alan3c says: Just a kidding, you are the nicest guy I know in the world. Zhihui says: Phase1 Phase3 Phase2 001||1||1
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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
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Thanks for your listening
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