1. Information and Computer Security CPIS 312 Lab 2
Classical Encryption
TRIGUI Mohamed Salim

2. Lab Outlines
Students should know that there are many algorithms existing for encryption and decryption; we will cover number of them during the semester.
Students should understand how Vigenere encryption and decryption works, they should implement the algorithm using a suitable programming language.
Students will learn how to adjust some parameters of Vigenere algorithm, changing encryption equation and notice the affects on the cipher text.
Students will learn how to work with Monoalphabetic encryption and decryption algorithm and they should select a suitable programming language to implement it.

3. Lab Outcomes
In the end of this lab, each student should know what the importance of encryption and decryption techniques is.
Students will also learn how to encrypt a plaintext using (Vigenere) algorithm.
At the end of this lab, students will be able to work with Vigenere algorithm by testing it practically during the lab.
Students will be able to work with Monoalphabetic encryption and decryption algorithm and they will be asked to implement it.

4. Traditional symmetric key ciphers

6. Vigenere cipher It is the simplest polyalphabetic substitution cipher:
Ci=Mi+Ki mod 26
Mi=Ci-Ki mod 26

7. Vigenere cipher
Use the vigenere cipher with key=vector to encrypt the next message: Plaintext: this is an example of the vigenere cipher
Ciphertext: OLKLWJVRGQODKPGHTKCIXBUVIITXQZKLGK

8. Vigenere cipher
Use the Vigenere cipher with key=lemon to encrypt the message “attackatdawn”
Plaintext: a= Encryption (00+11) mod Ciphertext: 11=L
Plaintext: t= Encryption (19+4) mod Ciphertext: 23=X
Plaintext: t= Encryption (19+12) mod Ciphertext: 5=F
Plaintext: a=00 Encryption (00+14) mod Ciphertext: 14=O
Plaintext: c=02 Encryption (02+13) mod Ciphertext: 15=P
…….
Ciphertext: LXFOPVEFRNHR

9. Homework
Q1. Encrypt the plaintext that you found from last homework using Vigenere Cipher and suppose the key is your first and family name.