Transposition Cipher Text - scbaghdad.edu.iq · transposition cipher- to encrypt and decrypt...

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Republic of Iraq

Ministry of Higher Education

And Scientific Research

Baghdad University

College of Science

Transposition Cipher Text

A project Report submitted to the college of Science, Baghdad University in partial fulfillment of the

Requirements for the B.Sc. Degree of Science in computer Science

By

Rafef Jamal

Zena Hussein

Supervised By

Dr. Sarab M. Hameed

2012 - 2011

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الرحيم الرحمن هللا بسم

"ْالَحِكيمْ اْلَعلِيمُ أَنتَ كإنا َعّلْمَتَنا َما إاِلا َلَنا العلم ُسْبحاََنك َقالُوا "

العظيم هللا صدق

{ البقرة سورة: 23 يةاآل }

3

االهداء

الى القلب الحنون الرامز بالحب . . .

بالحب والحنان . . . الى السحاب الممطرة

التً تنسً قسوة الحٌاة . . . الكلمة الطٌبة الى

الى الٌد التً تعبت من اجل راحتً . . .

التً تنٌر لً دربً . . . الى اصحاب النصٌحة

الى من سهروا من أجلً . . .

والديا االحباء . . .

المهداة لً . . . الى الرحمة

ور الربانً التً تنٌر لً بصائري . . .الى مشكاة الن

ستظل بظلها . . .فروعها أل ة الطٌبة الممتدةالى الشجر

الى الشمس التً لم تغرب ٌوما فً حٌاتً . . .

زوجي العزيز. . .

. . . جوم التً تضًء لً اللٌالً الطوٌلةالى الن

اخوتي واخواتي. . .

الطوٌل . . .الى كل من ساندنً فً الدرب

اساتذتي . . .

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االمتنان الى رئاسة القسم والهٌئة التدرٌسٌةٌتقدم طلبة المشروع بالشكر الجزٌل و

..ٌصالنا إلى هذا المستوى العلمً الرفٌع.دهم إلوبجه االذٌن ساهمو

اب مجٌد التً كانت لنا سر دم بفائق الشكر والتقدٌر لالستاذة الفاضلة د.وكذلك نتق

خطٌناها فً كل خطوة لما ابدته من توصٌات مثمرة وبناءة وارشادات قٌمة خٌرعون

النجاز هذا البحث .....

.... كذلك نود ان نشكر كل من مد ٌد العون لمساعدتنا فً انجاز هذا المشروع

ومن هللا التوفٌق .....

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تأييد المشرف

كلٌة \علوم الحاسبات اؤٌد ان المشروع الموسوم قد اعد تحت اشرافً فً قسم

جامعة بغداد كجزء من متطلبات الحصول على درجة البكلورٌوس فً \العلوم

علوم الحاسبات

اسم المشرف :

التوقٌـــــــــع :

التـــــــــارٌخ :

تأييد لجنة المناقشة

لجنة المناقشة وقد تم اختبـــــــار نؤٌد اننا اطلعنا على المشروع الموسوم كأعضاء

فً محتوى التقرٌر وعلٌه --------------------------------------------الطالب

نوصً بقبول المشروع كبحث للتخرج للحصول على درجة البكلورٌوس فً علوم

الحاسبات .

االسم والتوقٌع االسم والتوقٌع االسم والتوقٌع االسم والتوقٌع

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Summary

In cryptography, a transposition cipher is methods of encryption by

which the positions held by units of plaintext (which are commonly

characters or groups of characters) are shifted according to a regular

system, so that the cipher text constitutes a permutation of the plaintext.

That is, the order of the units is changed.

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Table of Contents

Chapter One (Overview)

1.1. Introduction.………………………………………(9)

1.2. Cryptography…………………………………….(01)

1.3. Project Objective.……………………………….(12)

1.4. Project Layout.…………………………..……...(12)

Chapter Two (Transposition Cipher)

2.1. Introduction of transposition cipher...…………. (14)

2.2. Transposition technique……………………..…. (15)

2.2.1. Columnar transposition…………..……... (16)

2.2.2 Double transposition……………..………. (18)

2.3. Transposition cipher algorithms……………….. (19)

Chapter Three (Design and Implementation of

Transposition Cipher)

3.1. Introduction and form design view…………….. (24)

3.2. Experiments and Results………………………. (28)

3.3 Conclusions..…….………………………………. (41)

References

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1.1. Introduction

Information security has been threatened by the information getting

to the hand of those for which it is not intended for. But how do we know

who the information is intended for? This question is answered by

encryption of message. Encryption of a message through the use of a

password makes it possible that only the person for whom a particular

message is intended for understands it; to others without the password it

is completely unintelligible.

In this wise, this project used an already existing algorithm-

transposition cipher- to encrypt and decrypt message through the use of a

means not yet used when the algorithm was developed the cryptosystem

to be used in a computer.

The computer which only understands certain languages must be

used to implement this transposition cipher, hence the use of a compiler

which serves as an intermediary between the high level language to a

machine language that can be only understood by the computer. The

Visual Basic language is used to developed software which when used to

encrypt message and decrypt message.

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1.2. Cryptography

Security does not prevent unauthorized access to a system; it only makes

such access much difficult and this is what cryptology is known for. In

today's unsafe and increasingly wired world, cryptology plays a vital role

in protecting communication channels, databases, and software from

unwanted intruder [1].

Cryptology does not concern itself with the message not getting to

the intruders but making the message in the hand of the intruder

completely unintelligible to them. There exist many ways by which data

may be secured: they can be physical, early in history, all assets were

physical. Important information was all physical, as it was carved into

stone and latter written in paper. To protect these assets, physical security

was used, such as walls, moats, and guards. If the information was

transmitted, it usually went by messenger and usually a guard. The

Greeks of Classical times are said to have known of ciphers (e.g., the

scytale transposition cipher claimed to have been used by the Spartan

military). Herodotus tells us of secret messages physically concealed

beneath wax on wooden tablets or as a tattoo on a slave's head concealed

by new growth of hair, though these are not proper examples of

cryptography per se as the message, once known, is directly readable; this

is known as stenography [2]. The risk was purely physical, as there was

no way to get at the information without physically grasping it. In most

cases, if information was stolen, the original owner of the information

was deprived [3]. Besides the physical security used to protect data from

being accessed at all, means were adopted in which the physical access

were granted but the information is sent in a format that is unintelligible.

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Machines were developed to make easy the job of encryption/decryption

designed amongst which was the German Lorenz cipher machine, used in

World War II (WWII) for encryption of very high-level general staff

messages, The Enigma machine, used, in several variants, by the German

military between the late 1920s and the end of World War II,

implemented a complex electro-mechanical polyalphabetic cipher to

protect sensitive communications. Breaking the Enigma cipher at the

Biuro Szyfrów, and the subsequent large-scale decryption of Enigma

traffic at Bletchley Park, was an important factor contributing to the

Allied victory in WWII. [3].

The development of digital computers and electronics after WWII

made possible much more complex ciphers. Furthermore, computers

allowed for the encryption of any kind of data represent able within

computers in any binary format, unlike classical ciphers which only

encrypted written language texts. Thus, computers supplanted linguistic

cryptanalytic approaches. Many computer ciphers can be characterized

by their operation on binary bit sequences (sometimes in groups or

blocks), unlike classical and mechanical schemes, which generally

manipulate traditional characters (i.e., letters and digits) directly.

However, computers have also assisted cryptanalysis, which has

compensated to some extent for increased cipher complexity.

Nonetheless, good modern ciphers have stayed ahead of cryptanalysis; it

is typically the case that the use of a quality cipher is very efficient (i.e.,

fast and requiring few resources), while breaking it requires an effort

many orders of magnitude larger than before, making cryptanalysis so

inefficient and impractical as to be effectively impossible.

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1.3. Project Objective

The use of computers in cryptology is yet to be fully utilized. This work

is intended to use the computer as a tool for cryptography. This can be

achieved via the use of software programming language that employs the

use of the already existing columnar and double transposition ciphering

algorithm. The columnar and double transposition ciphering scheme

which used to be manually done will become a process achieved through

the use of software programmed in Visual Basic. The program will do the

encryption/decryption of information.

1.4. Project Layout

This project is organized as follows:

Chapter two present the basic of transposition cipher, its types, and the

algorithm for encryption and decryption of transportation cipher.

Chapter three demonstrates the design of transposition chipper and its

results.

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2.1. Introduction

In cryptography, a transposition cipher is a method of encryption

by which the positions held by units of plaintext (which are commonly

characters or groups of characters) are shifted according to a regular

system, so that the ciphertext constitutes a permutation of the plaintext.

That is, the order of the units is changed. Mathematically a bijective

function is used on the characters positions to encrypt and an inverse

function to decrypt. Following are some transposition cipher techniques:

Rail Fence cipher

Route cipher

Columnar transposition

Double transposition

Myszkowski transposition

Disrupted transposition

Grilles

Detection and cryptanalysis

Combinations

Fractionation

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2.2. Transposition cipher

The transposition cipher is an already existing conventional

encryption technique. It has the algorithm as:

Step 1: Choice of a password

Step 2: The plaintext must be known

Step 3: A table is drawn with column equal to the number of alphabet in

the password with rows that are sufficient to accommodate all the

characters of the plaintext.

Step 4: The password is arranged in such a way as to its occurrence in

the alphabet i.e. the alphabet closest to letter “a” is assigned the first

position in whatever column it is.

Step 5: The positions of the alphabet is used to print out the text. The

alphabet in the column corresponding to the alphabet arrangement is read

first and the process is continued till all the password position has been

exhausted.

A reverse of this process is used in decryption.

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2.2.1. Columnar Transposition

In a columnar transposition, the message is written out in rows of a

fixed length, and then read out again column by column, and the columns

are chosen in some scrambled order. Both the width of the rows and the

permutation of the columns are usually defined by a keyword. For

example, the word ZEBRAS is of length 6 (so the rows are of length 6),

and the permutation is defined by the alphabetical order of the letters in

the keyword. In this case, the order would be "6 3 2 4 1 5".

In a regular columnar transposition cipher, any spare spaces are

filled with nulls; in an irregular columnar transposition cipher, the spaces

are left blank. Finally, the message is read off in columns, in the order

specified by the keyword. For example, suppose we use the keyword

ZEBRAS and the message WE ARE DISCOVERED FLEE AT ONCE.

In a regular columnar transposition, we write this into the grid as:

6 3 2 4 1 5

W E A R E D

I S C O V E

R E D F L E

E A T O N C

E XXXXX

Provide five nulls (XXXXX) at the end. The cipher text is then

read off as: EVLNE ACDTK ESEAQ ROFOJ DEECU WIREE

In the irregular case, the columns are not completed by nulls:

6 3 2 4 1 5

W E A R E D

I S C O V E

R E D F L E

E A T O N C

E

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This results in the following cipher text:

EVLNA CDTES EAROF ODEEC WIREE

To decipher it, the recipient has to work out the column lengths by

dividing the message length by the key length. Then he can write the

message out in columns again, and then re-order the columns by

reforming the key word.

Columnar transposition continued to be used for serious purposes

as a component of more complex ciphers at least into the 1950s.

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2.2.2 Double transposition

A double transposition was often used to make the cryptography

stronger. This is simply a columnar transposition applied twice. The same

key can be used for both transpositions, or two different keys can be used.

As an example, we can take the result of the irregular columnar

transposition in the previous section, and perform a second encryption

with a different keyword, STRIPE, which gives the permutation

"564231":

5 6 4 2 3 1

E V L N A C

D T E S E A

R O F O D E

E C W I R E

E X X X X X

As before, this is read off column wise to give the cipher text:

CAEEN SOIAE DRLEF WEDRE EVTOC

If multiple messages of exactly the same length are encrypted using the

same keys, they can be anagrammed simultaneously. This can lead to

both recovery of the messages, and to recovery of the keys (so that every

other message sent with those keys can be read).

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2.3. Transposition Cipher Algorithms

This section illustrates the encryption, decryption for columnar and

transposition cipher.

Encryption algorithm (Columnar Transposition)

Step 1: The password is small alphabet

Step 2: Each Alphabet of the password is converted into their ASCII

Code equivalent. This makes it easy to find that the alphabet which

comes first. This is found by finding the minimum of the alphabet and

replacing the minimum found with the highest possible ASCII code.

Step 3: The length of the plaintext length is found.

Step 4: The length of the password and the length of the plaintext is used

to determine the number of rows that will be created as the number of

column is already known as the number of the password letters.

Step 5: Exceptions are used to complete rows that are not completely

filled with alphabet.

Step 6: The plaintext is arranged into an array size determined in step 4.

Step 7: the columns are read with respect to the positions determined in

step 2.

Step 8: this gives the encrypted message.

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Encryption algorithm (Double Transposition)

Step 1: The password is small alphabet

Step 2: Each Alphabet of the password is converted into their ASCII

Code equivalent. This makes it easy to find that the alphabet which

comes first. This is found by finding the minimum of the alphabet and

replacing the minimum found with the highest possible ASCII code.

Step 3: The length of the plaintext length is found.

Step 4: The length of the password and the length of the plaintext is used

to determine the number of rows that will be created as the number of

column is already known as the number of the password letters.

Step 5: Exceptions are used to complete rows that are not completely

filled with alphabet.

Step 6: The plaintext is arranged into an array size determined in step 4.

Step 7: the columns are read with respect to the positions determined in

step 2.

Step 8: this gives the encrypted message and then back to step 1 and

repeat step 2, 3, 4,5,6,7

Step 9: this gives the encrypted message with second password.

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Decryption algorithm (Columnar Transposition)

This is just the reverse of the encryption algorithm. Step1 - 2 is the same

as that in encryption algorithm.

Step 3: the length of the cipher text and password are used to determine

the number of alphabet that would be placed in the columns determined

by the password arrangement

Step 4: there are exception cases introduced.

Step 5: the plaintext is achieved by reading the alphabets row by row.

Decryption algorithm (Double Transposition)

This is just the reverse of the encryption algorithm. Step1 - 2 is the same

as that in encryption algorithm.

Step 3: the length of the cipher text and password are used to determine

the number of alphabet that would be placed in the columns determined

by the password arrangement

Step 4: there are exception cases introduced.

Step 5: the plaintext with first password is achieved by reading the

alphabets row by row then back to step 1 and repeat step 2, 3, 4.

Step 6: the plaintext is achieved by reading the alphabets row by row.

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Figure (2.1) is a simplified flow chart representation of the transposition

cipher for encryption and decryption process

START

ENCRYPT? PROCESS ENCRYPTION

PROCESS DECRYPTION

DO YOU WISH TO CONTINUE?

END

YES

N

O

NO

YES

Figure 2.1 Encryption and decryption process

The first thing to be determined is whether the user wants to perform

an encryption or decryption process. Based on the option selected, the

process will be performed an output whether plaintext or cipher text will

be produced which corresponds to the option chosen in this case

decryption and encryption respectively.

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3.1 Introduction

The software Designed in VB is divided into two parts:

The Form Design: these are forms used to create the windows application

package

FORM DESIGN VIEW

Form 1: interface form contains start command to begin the program

as shown in figure 3.1.

Figure 3.1: Start Form

In Form 2 contains two menus including file and transposition as depicts

in figure 3.2

Figure 3.2: Transposition cipher form

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First: select to open or save the file or end the program a in figure 3.3

Figure 3.3: select open or save file or exit the program

Second: select the type of the encryption and decryption in figure 3.4

Figure 3.4: select the type of the encryption and decryption

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In form 3 the key and the plain text must be entered then the command

encryption is pressed to display the cipher text. The other command for

decryption is used to return the cipher text to plain text. Also, the form 3

contains command save to the result to file and command exit to return to

form2. Figure 3.5

Figure 3.5: encryption and decryption with one key

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The form 4: contains text for the 1st and 2

nd keys , text for the plain text ,

two command one for encryption to display the cipher text and the other

command for decryption to display the plaintext. Form4 contains

command save to save the result and command to exit to return to form 2.

Figure 3.6

Figure 3.6: encryption and decryption of tow key

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3.2Experiments and Results

Example 1: figure 3.7

Key: key

Plain text: computer

Cipher text: ourcpemtX

Decipher text: computerX

Figure 3.7: example encryption and decryption with one key

Save the result: figure 3.8

Figure 3.8: save the rustle of decryption of one key

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Figure 3.9: save to file

Open a plain text from file: figure 3.10

Figure 3.10: open plaintext

Figure 3.11: open plaintext from file

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Key: good

Plain text: computer

Cipher: prcuotme

Decipher: computer

Figure 3.12: example of encryption and decryption of one key


Key: aaaa

Plain: computer

Cipher: cuotmepr

Decipher: computer


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Key: akea

Plain: computer

Cipher: cuprmeot

Decipher: computer


32

Experiments and result two key:


Key 1: bad

Key 2: key

Plain: computer

Cipher 1: ourcpemt

Cipher 2: uptocmre

Decipher 1: ourcpemt

Decipher 2: computer

Figure 3.15: example of encryption and decryption of two key

Save the result: figure 3.16

Figure 3.16: save the rustle of decryption of two key

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Figure 3.17: save the rustle of decryption of two key to file

Open file to get the plain text : figure 3.18

Figure3.18: Open file to get the plain text

Figure3.19: Open file to get the plain text from file

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Example 2:figure 3.20

Key 1: good

Key 2: baye

Plain: computer

Cipher 1: prcuotme

Cipher 2: rtpouecm

Decipher 1: prcuotme


Figure3.20: example of encryption and decryption of two key

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Key 1: baye

Key 2: good

Plain: computer

Cipher 1: otcuprme

Cipher 2: ueoptrcm

Decipher 1: otcuprme



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Key 1: good

Key 2: seed

Plain: computer

Cipher 1: prcuotme

Cipher 2: uretcmpo

Decipher 1: prcuotme



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Key 1: aaaa

Key 2: asdf

Plain: computer

Cipher 1: cuotmepr

Cipher 2: cmoptrue

Decipher 1: cuotmepr



38


Key 1: asdf

Key 2: aaaa

Plain: computer

Cipher 1: cumeprot

Cipher 2: cpurmoet

Decipher 1: cumeprot



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Example 7: figure 25

Key 1: aaaa

Key 2: aaaa

Plain: computer

Cipher 1: cuotmepr

Cipher 2: cmueoptr




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Key 1: aaaa

Key 2: bbbb

Plain: computer

Cipher 1: cuotmepr

Cipher 2: cmueoptr




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3.3 CONCLUSIONs

It will be seen that the result obtained from the decryption is slightly

different from the original text this is because the space that was in the

original message was removed as it might weaken the encryption

algorithm .it is recommended to further improve this algorithm that the

space be replaced by any special characters during encryption and this

should be done in a consciousness of the decryption algorithm..

Transposition cipher may be viewed as an obsolete encryption

cipher but no matter how obsolete it appears it still has its merit. No

matter how strong an encryption tool may prove when it is discovered

that is the scheme used it defeats its purpose. To this end the users of this

software will not in the slightest be told that the software operates using

transposition cipher. If not told it can be any cipher algorithm. The

password must be held in high esteem as it is the key to this encryption

and decryption process. VB has been used to transform the transposition

cipher which was done manually to a software program that can use

anywhere information security is of paramount importance.

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REFERENCES

[1] Stamper, David, “Essential of Data Communication”, Saratoga

Group

[2] Eric Maiwald, “Network Security a Beginner’s Guide”, Second

Edition, McGraw Hill, Osborne, 2003.

[3] Wikipedia Encyclopedia, available at

http://en.wikipedia.org/wiki/historyofcrytography

[4]Ed Tittel, “Theory and Problems of Computer Networking”, McGraw

Hill, Osborne, 2002

[5] R.I Salawu & S.O Adetona, “The Art and Science of Secured

Communication”, Institute of Security of Nigeria, Nigeria 2007

[6]James Irvine & David Harie, “Data Communications & Network: An

Engineering Approach”, John Wiley & Sons ltd., 2002

[7] Gilman, Larry "Cipher Machines." Encyclopedia.com. 2 Sep. 2009

available at:

<http://www.encyclopedia.com>.

[8] Brian J. Winkel, Cipher A. Deavours, David Kahn, and Louis Kruh

“The German Enigma Cipher Machine: Beginnings, Success, and

Ultimate Failure”, Artech House, August 2005.

[9] Tyma Paul, “Software Development Secure”, Start Newsletter, Feb

2003.

[10] Sigmon Richard, www.articlearchives.com , 2007

[11] Madsen Wayne, “An International Survey of Encryption Policy”,

1998

[12] Tabor Bob, Learn Visual Studio, www.learnVisualstudio.Net ,

2005.

[13] S.O Adetona, “Messages Secrecy in Electioneering environment”,

proceedings of Institute of Security, Nigeria,2009

http://www.encyclopedia.com/doc/1G2-3403300147.html

http://www.encyclopedia.com/

43

العراق جمهورٌة العالً التعلٌم وزارة

العلمً والبحث بغداد جامعة

العلوم كلٌة

والشفرات النص تبديل

الحصول على درجة من متطلبات كجزء بغداد العلوم جامعة لكلٌة المشروع المقدمتقرٌرعن

حاسباتال البكلورٌوس فً علوم

خالل من المقدم

جمال رفٌف

حسٌن زٌنة

اشراف تحت

حمٌد مجٌد سراب. د

2012 - 2011

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