Module: Introduction to Computer Security

Submodule 1: Overview of Computer Security

Encryption / Decryption using Caesar Cipher

Created: October 21, 2003
Last Updated: October 23, 2003

Version 0.1
Author: Pinkesh Valdria and T. Andrew Yang


Level of Difficulty: Moderate

Completion Time: 2 weeks

Progaramming involved: No


Objectives

The objective of this project is to learn how to use Monoalphabetic Substitution Technique to encrypt and decrypt messages


Example

A Caesar cipher is a substitution cipher in which the cipher alphabet is merely the plain alphabet rotated left by 3 number of positions.
Formula: Ci = E(pi) = pi + 3
Encrypt 

 Plain:  ABCDEFGHIJKLMNOPQRSTUVWXYZ
 Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC


The Project 

Decipher the Ciphertext message using Caesar Cipher:
Ciphertext: MAX YTNEM, WXTK UKNMNL, EBXL GHM BG HNK LMTKL UNM BG HNKLXEOXL


Resources

Book: Security in Computing - Charles P. Pfleeger


Glossary

Encryption: is a process of encoding a message so that its meaning is not obvious
Decryption: is a reverse process, transforming an encoding message back into its normal form
ciphertext: The encrypted form of the message.
plaintext: The original form of a message.