Overcoming the suspicion in transmission scheme based on CDES

Oral exam Speaker : Wei-Shin Pan

Advisor : Quincy Wu

2

Outline

• Introduction • Related work

– A Confused Document Encrypting Schemes and its Implementation (Lin & Lee ,1998)

• System model– CDES module – Compression module – Encryption module – Image hiding module

• Implementation– Environment– Experiment

• Conclusion & Future work

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Introduction

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• The “Personal Privacy” becomes a popular section in information security over Internet.

• Information Hiding ( Steganography ) and Cryptography accomplish secret communication between you and me.

5The Eavesdropper (Nicolaes Maes ,1657)

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Motivation

• Provide a secret communication service for Email over Internet and demonstrate how Email services can be protected in my system

• CDES (Confused Document Encrypting Scheme) is a technique for data hiding, which sends a meaningful message to deceive the eavesdropper and increase the security

• Add the image hiding technique

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Transmitting many cheating text files

+Plaintext index file (PIF)

A Confused Document Encrypting Scheme and its Implementation (Lin & Lee ,1998)

Plaintext

From : weishin.pan@gmail.comTo : magicpanx@gmail.comSubject: Hello !Body---------------------------------------------------------------------------Confused Document Encrypting SchemeAttachments-----------------------------------------------------------------(1) ID-0005.txt(2) ID-0019.txt(3) ID-5597.txt(4) ID-2468.txt(5) ID-9870.txt(5) Encrypted plaintext index file + (Encrypted-ID 0019)

An encrypted file

Eavesdropper

Concept

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Emoticon

It is a main method in my concept. It uses the image hiding technique to hide the PIF file in an image file. For example, (Smile face), (Sad face).

Text

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Information Hiding

• Use any media to hide secret information.

• the hacker cannot sense something when he intercepts the media, because it is common behavior.

Secret information

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Related work

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CDES

• Confused Document Encrypting Scheme (CDES), Lin& Lee,1998 [1]

• Elements of CDES– Cheating text– Plaintext – Character position table (CPT)– Plaintext Index file (PIF)– Key

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Does the cheating text contains all of the

different characters in the plaintext?

Generate the character’s position table (CPT) of the cheating text

Input cheating text

Input plaintext

Encrypt the ID

Generate plaintext index file (PIF) by random

Randomly generate an ID for the cheating text

Compress the PIF

Encrypt the compressed PIF

Put the encrypted ID in the head of the encrypted and compressed PIF

Send out the compressed and encrypted PIF and the cheating text involving an ID

Receiver

Sender

2-nd key

1-st key

No

Yes

(CDES,Lin&Lee,1998 [1])

Sender

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Decrypt the encrypted ID in the given PIF

Does find out the corresponding cheating

text?

Decrypt the given PIF

Generate the character’s position table (CPT) of the cheating text

Decompress the given PIF

Use the CPT and the PIF to reverse the original plaintext

Plaintext output

Receiver

(CDES,Lin&Lee,1998 [1])

No, wait the correct cheating text to come

2-nd key

1-st keyYes

No

CPT & PIF

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Input Plaintext : Cat is my pet.{C, a , t , i, s , m , y , p , e , . , □}Cheating text : Computer security is important.{C, o , m , p, u , t , e , r , s , c , i , y , a , n , . , □}

Character Position record

C 1o 2 , 25m 3 , 23p 4 , 24u 5 , 13t 6 , 16 ,

27 , 30e 7 , 11r 8 , 14, 26s 10 , 20c 12i 15 , 19 ,

22y 17a 28n 29. 31□ 9 , 18 , 21

Table 1. Characters Position Table(CPT)

1 28 6 … … … …

Plaintext index file(PIF)

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System model

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CDES module

Plaintext Cheating text

CPT generated

PIF generated

Compression module

Encryption module

Compress the PIF

Encrypt the compressed PIF

Image-Hiding module

Hiding the PIF in image

System model

Send out via E-mail

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Text + photo

今晚我們去喝杯 City咖啡吧 .

Cheating text

PIF

這裡是秘密訊息 : 今晚8:00 在科三 409 見面

The proposal is based on Confused Document Encrypting Scheme

Sent out via Email

It looks OK !

Eavesdropper

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CDES Module

• Feature– Sender :Generate the CPT by the cheating

text, and the plaintext will generate PIF by CPT

– Receiver :Use the CPT and the PIF to reverse the original plaintext

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Compression Module

• Feature– It provides compression/decompression for

the plaintext index file(PIF), because the PIF size will be large.

– It uses the LZMA algorithm

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Data Compression

• Reduce the data size.• Decrease transmission time• Increase security of data• Lower the cost• Compression type

– Lossless data compression (Huffman coding, LZ series)– Lossy data compression (Prediction by Partial Match series)

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LZMA algorithm

• Dictionary coding – Dictionary size increased → Higher compression

rate ↑ and lower speed ↓Example:ABCDEFBCGXY1. {AB,BC,CD,DE,EF) will be added to the

dictionary and translated to a smallest unique-code .

2. Later, if BC has been stored in the dictionary, so it will be translated to a smallest unique-code ,and add the strings {BCG,XY} to the dictionary.

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從窗戶外看到的景色會先存在眼睛的緩衝區從窗戶外看到的景色會先存在眼睛的緩衝區

台中我看過的地方我看過的地方

台南台中台南1

2台中 雲林

雲林 3

大腦儲存區 ( 字典 )

這地方我看過了，所以直接轉換成代碼 這地方我看過了，所以直接轉換成代碼 11 ，不再存入字典，不再存入字典

第一次看過這裡，將它存入字典第一次看過這裡，將它存入字典

LZMA Diagram

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Encryption Module

• Feature– Encrypt the plaintext index file (PIF)– It uses the Blowfish algorithm

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Cryptography

• It will modify the file or message to a unreadable content and receiver must use a key to decrypt the content.

M

(Encryptor) E

KEY1

(Decryptor) D

KEY2

M = Dk2(C)

Hacker

C = Ek1(M)

M ( Plaintext) = original messageC ( Cipher text) = encrypted message

Ek (M) = Encryption function

Dk (C) = Decryption function

Public area

Private area

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Blowfish algorithm

• Symmetric block cipher

• Key sizes : 32-448 bits

• Block sizes : 64 bits

• Structure : Feistel network

• Easy to implement

• Fast encryption

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Image-hiding Module

• Feature – It provides image hiding for the plaintext index

file (PIF)– It uses the” JPHS“ (open source software)– It uses the Blowfish algorithm to encrypt the

PIF in an image

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Implementation

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Environment

• Windows XP SP3

• Visual Studio 2005

• Mozilla Thunderbird 3 (3.0.4)

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Do you want to have a coffee with me ?

Do you want to have a coffee with me ?

這裡是秘密訊息 : Even if I knew that tomorrow the world would go to pieces,

I would still plant my apple tree.

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Receive a mail

Cheating text

Plaintext index file embedded

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Flow chart (Sender)

Read the plaintext

Read the cheating text

Generate the CPT of the cheating text

Generate the plaintext index file

Compress the PIF

Encrypt the compressed PIF

1-st Key

Hiding the PIF in image

Compose a mail to receiver

From : weishin.pan@gmail.com

To: magicpanx@gmail.com

Subject: Hello ,magicpanx !

Do you want to have a coffee with me?

Attached file :

ncnu.jpg

PIF embedded

Cheating text

2-nd Key

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Flow chart (Receiver)

From : weishin.pan@gmail.com

To: magicpanx@gmail.com

Subject: Hello ,magicpanx !

Do you want to have a coffee with me?

Attached file :

ncnu.jpg

PIF embedded

Cheating text

Read the cheating text

Seek PIF from the attach image

Decrypt the PIF

2-nd Key

1-st Key

Generate the CPT of the cheating text

Decompress the PIF

Using the CPT and the PIF to reverse the original plaintext

Plaintext outputEven if I knew that tomorrow the world would go to

pieces, I would still plant my apple tree.

Plaintext

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Image hiding(JPHS)

+

PIF

JPHSwin

33,767 bytes

200 bytes

13,449 bytes

ncnu_original.jpg

ncnu.jpg

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Decrypt the plaintext

Plaintext

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Conclusion

• Increase the security in email services

• In original CDES, the PIF was sent in encrypted form, which looks meaningless and suspicious

• Through the behavior observed in chatting, the image hiding technique is applied to hide the PIF in an emoticon or a photo, which looks meaningful

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Future work

• The framework can use for instant message (IM), like Windows Live Messenger, Yahoo Messenger in the future work.

• Because human use the emoticon and photo in the chat, it has been a common behavior.

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Reference

• [ 1 ] Chu-Hsing Lin and Tien-Chi Lee, “A Confused Document Encrypting Scheme and its Implementation”,Computers & Security,Vol. 17, No. 6, pp.543-551, 1998.

• [ 2 ]Wen-Hung Yeh and Jing-Jang Hwang, “Hiding Digital Information Using a Novel System Scheme”, Elsevier Science Ltd, 2001.

• [ 3 ]Yeh, W. H. and Hwang J. J., "A scheme of hiding secret Chinese information in confused documents" , Journal of Information Management, Vol.7 (2),2001b, pp. 183-191

• [ 4 ]Bi-feng Liang, etc, “On the study and implementation for confused document encrypting scheme of data hiding”, Technical Report, Department of Information Management, Ta Hwa Institute of Technology, R.O.C.,2002.

• [ 5 ]Tzu-jung Yao and Quincy Wu, "On the Study of Overhead Reduction for Confused Document Encrypting Schemes", International Conference on Multimedia Computing and Information Technology (MCIT 2010) University of Sharjah(UoS), Sharjah, United Arab Emirates (UAE), March 2-4, 2010.