Plain Text : ABCDEFGHIJKLMNOPQRSTUVWXYZ

Cipher Text : HETJWOPSQYAZIVMBDUKNRGLCXF

Turns the plain text "BOY" into the cipher text "EMX". Note the substitution is a permutation of the 26 letters of the alphabet, so we can uniquely decipher a cipher text by reading the substitution backwards; that is, cipher text "A" is plain text "k".

You are required to:

1. Write an algorithm in pseudo code to solve the above problem.

2. Determine the time complexity class of the above algorithm.

3. Using any programming language of you choice convert the above algorithm into a program that takes as input a plain text word file of not less than 2 mb, generate a random substitution, and then encrypts the plain text using that substitution.

4. Write a decrypt program that will decrypt the cipher text into a plain text.

5. By using the system clock analyze the performance of the program in (3) above with that of the algorithm in (2) above.

Specific requirements:

Menu driven and loops until i chose to exit and number 3 & 4 are option.

Example:

1 Encrypts

2 Decrypts

3 Exit