You are required to implement the following modes of operation:

Cipher Block Chaining (CBC)

Cipher Feedback (CFB-8)

Output Feedback (OFB)

After implementation of the modes, you are required to encrypt text (as mentioned in the dataset below) and compute Index of Coincidence (IC) for each mode of operation, including Electronic Codebook (ECB).

Dataset: You will use a text file with the following characteristics

i) Text length must be at least 2000 characters (main file).

ii) From the above original file, create two more sets of this file, in which the text is duplicated with approximately 25% and 50% ratio.

Report your observations and analysis for values of IC for each of the above four modes using each of the three text files.

A table in the following format must be provided with Mode (ECB, CBC,CFB-8,OFB), File with % duplication (9,25,50) and IC (0 25 50)

You may use any publicly available AES code or the AES code provided at

www.cs.albany.edu/~patrey/ICSI526-426/assignments/ass2/AES.java.

Provide the details of the source of the AES code that you use.