A Data Hiding Method for Text Documents Using Multiple-Base Encoding 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/

Outline Introduction Related works Proposed scheme - Synonym substitution - Text Steganography in Chat - Emoticon-based Text Steganography in Chat Related works - Inter-word spacing scheme - Chen et al.’s data hiding method - The multiple-based notational system Proposed scheme Experimental results Conclusions

Introduction Secrets ‧Data hiding with documents ‧Quality, capacity and security Sender Internet Secrets Receiver

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

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.

Text Steganography in Chat SMS-Texting

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

Text Steganography in Chat SMS list + abbreviated words list  Check list 0  full form, 1  abbreviated form

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”

Emoticon-based Text Steganography Emoticon-based Text Steganography in Chat

Emoticon-based Text Steganography Phase1: Classify the emoticons by their meaning

Emoticon-based Text Steganography Example: N = 16 hide log2N = 4 bits per emoticon sender uses second symbol receiver can extract 4 bits “0001”

Emoticon-based Text Steganography Phase2: emoticon || sentence : secret = 0 sentence || emoticon : secret = 1 I lost my bag secret = 0 I lost my bag secret = 1

Emoticon-based Text Steganography Phase3: emoticon , sentence : secret = 0 emoticon , sentence : secret = 1 , I lost my bag secret = 0 I lost my bag secret = 1

Emoticon-based Text Steganography Zhihui wants to send secret bits “11100000111” 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

Bender et al.’s Inter-word spacing scheme This scheme exploits inter-word space of text to encode data. Thisisabook. Secret bits: {0 1 0} Thisisabook.

Chen et al.’s data hiding method Keep spaces between groups unchanged. Weemploythecombinationoftherepeatedwords… Secret bits: { 1 0 1 1} Space change: ＋ －　　　　　 ＋ We employthecombinationof therepeated words…

The multiple-based notational system x = (48)10 = (1 3 0 0)3 5 3 2 (1 3 0 0)3 5 3 2 = (48)10 1x5x3x2 + 3x3x2 + 0x2 +0 = 48 48 mod 2 = 0 (48-0)/2 = 24 24 mod 3 = 0 (24-0)/3 = 8 8 mod 5 = 3 (8-3)/5 = 1 1 mod 3 = 1

Proposed Scheme (1/2) The embedding phase Secret: (106)10 = (???)645 Secret: (106)10 = (511)645

Proposed Scheme (1/2) The embedding phase Secret: (??)10 = (511)645 Secret: (106)10 = (511)645

Experimental results

Conclusions Provides a fast text hiding scheme that can achieve invisible security with computational efficiency.

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