1. Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh
CRYPTOGRAPHY
Block 6, Unit 1, Section 2
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

2. Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh
Contents
Overview
Method of Encryption
Caesar Technique (Shift cipher)
Improved Caesar Method (code word)
Transposition Cipher (n-gram)
One-time pad scheme (ploy-alphabetic)
Q & A + Implementation of Java code
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

3. Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh
Overview
In this section, we will discuss how each of the following encryption technique works a Caesar cipher or often called shift cipher. Then, an enhanced version of Caesar's code using ‘code word’. After that, we will discuss the Transposition encryption techniques. And before we end this presentation will know how One-time pad scheme is calculated. Finally, Questions & Answers and a short demo.
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

4. Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh
Method of Encryption
There are two method of encryption:
Substitution
Transposition
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

5. Caesar Technique (Shift cipher)
One of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

6. Caesar Technique (Shift cipher)
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

7. Caesar Technique (Shift cipher)
Example (TMA06-Q2(i)(a)):
The message: WILLIAMSHAKESPEARE
Key: 12
Encipher to: IUXXUMYETMWQEBQMDQ
HOW?
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

8. Caesar Technique (Shift cipher)
The Vigneree table used to map each letter in the message to its equivalent : WILL = IUXX
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

9. Improved Caesar Method (code word)
An improved technique of shift-cipher were introduced which relays on two elements:
Code Word
Shift number (the Key)
Since the previous method is weak and easy to break, an improved version must be found to increase the level of security.
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

10. Improved Caesar Method (code word)
Example (TMA06,Q2(i)(b)):
Message: WILLIAMSHAKESPEARE
Code word: TEMPLAR
Key: 4
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

11. Improved Caesar Method (code word)
Step1: Generating the alphabet-table A B C D E F G H I J K L T M P R M N O P Q R S T U V W X Y Z H I J K
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

12. Improved Caesar Method (code word)
Step2: Transforming the letters (Simple letter mapping):
Message: WILLIAMSHAKESPEARE
Transformed to: WCGGCTHQBTFLQKLTOL A B C D E F G H I J K L T M P R M N O P Q R S T U V W X Y Z H I J K
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

13. Improved Caesar Method (code word)
Step3: Shifting the letters
Take the transformed text and shift each letter by 4 (refer to Vigenere table)
Transformed to: WCGGCTHQBTFLQKLTOL
Shift by 4: AGKKGXLUFXJPUOPXSP
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

14. Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh
So far…
Overview
Method of Encryption
Caesar Technique (Shift cipher)
Improved Caesar Method (code word)
Transposition Cipher (n-gram)
One-time pad scheme (ploy-alphabetic)
Q & A + Implementation of Java code
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

15. Transposition Cipher (n-gram)
Also, known as mono-alphabetic. Simply, it’s a process that divide the message into number of columns called grams. See next example for explanations.
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

16. Transposition Cipher (n-gram)
Example:
Message: SEND ME SEVEN HUNDRED POUNDS TOMORROW
Using 8-gram (8 columns) , we distribute the message letters like this:
Key 1 2 3 4 5 6 7 8 S E N D M V H U R P O T W
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

17. Transposition Cipher (n-gram)
Now we choose an 8-digist key. E.g. the key is :
After that, we combined all letters of each column, to get the cipher. The order of combination has to be the same as the key.
The result will be: svetnnpmmuursddoeedodhooennrersw
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

18. One-time pad scheme (ploy-alphabetic)
Also known as a poly-alphabetic code. This code is theoretically unbreakable.
Let’s take an example.. >>
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

19. One-time pad scheme (ploy-alphabetic)
Example:
Plaintext: TESTMESSAGE
one-time pad: 3,19,21,4,7,22,17,25,3,11,3,
Plaintext T E S M A G
# in Alpha. 19 4 18 12 6
1-time pad 3 21 7 22 17 25 11
Addition 23 39 26 35 43
Mod 26 13 9
Cipher W X N J R D H
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh

20. Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh
Q & A + Demo
Prepared by: Sameer Ali Aljaroodi, Tutor: Mr. Ahmad Kananh