RevsUp Lab: Encryption

resources:
Encryption
Caesar Cipher

This lab will have some encrypting and decrypting, as well as some simple password cracking. We will begin with the digital forensics lab07 to familiarize ourselves with Caesar and substitution ciphers.

lab07
Follow the steps and look at the references to complete each portion of this lab. Because you have no yet been given student accounts on sleipnir, you will instead download a zip from my CSUB page and unzip all the files you will need.
lab files
Download the file encryption.zip and unzip. Along with the lab files you will also see a script I made, decipher. This script can take a cipher and apply it to a text file, which you can use to test if you found the correct cipher to decipher ciphertext3. Remember, if your permissions are not set up correctly the file will not be executable. You will need to use the chmod command in order to run the script. 
    $ chmod 755 decipher
    $ ./decipher
    OR give your cipher as an argument to speed up testing 
    $ ./decipher (your cipher)
After you have finished the lab, attempt to complete the following activities.
(1) Encrypt the phrase "HELLO WORLD" using Caesar Cipher with a 12-character shift.
(2) A ciphertext under encryption by Caesar Cipher becomes "KITKCTCA". Decode.
(3) Consider the following sentence: 
            Pierre de Fermat is a French mathematician who is often called the founder of the modern theory of numbers.
Encrypt the passage using the Substitution Cipher with key word "SAN FRANCISCO" and key letter "X".
(4) Decode a Substitution Cipher sheet (a handout will be given).
(5) What can you say about the practicality of the simple substitution cipher? (easy to encode/decode?)
(6) What can you say about the security of simple substitution cipher (is it easy to break?)
What techniques have you learned for breaking the cipher?
(7) Is there any way you can make this encryption scheme more secure?