Classical cryptography in Haskell

Introduction

This project implements popular cryptographic ciphers in Haskell. Currently the following ciphers are implemented: Caesar Cipher, Vigenère Cipher, and One-Time Pad.

The project also demonstrates possible attacks on those ciphers: Many-Time Pad Attack, Frequency Analysis, Kasiski Examination. The Many Time Pad Attack exploits the reuse of a one-time pad key across multiple ciphertexts.

Features

• Key generation
• Message Encryption/Decryption with a key
• Decryption of multiple ciphertexts encrypted with the same one-time pad key using the Many-Time Pad attack
• Brute force attacl on Caesar Cipher ciphertexts with frequency analysis.
• Decryption of Vigenère ciphertexts using Kasiski examination and frequency analysis

Usage

For running the program:

$ stack run

The program will start and ask user for further input.

Tests

Tests are included in the test folder. To run the tests:

$ stack test

How It Works

Many Time Pad Attack

1. XOR Analysis: The program XORs different ciphertexts together to determine the locations of spaces in the corresponding plaintexts.
2. Partial Key: Using the space locations in the different ciphertexts, a partial key is constructed.

The folder ciphertexts contains text files with ciphertexts to be dectrypted. The "mtp.txt" file has the ciphertexts that are used to demonstrate the Many-Time Pad attack. They are in hex format, separated by a comma. The source of the challenge is: https://homepages.cwi.nl/~schaffne/courses/crypto/2012/.

Caesar Cipher Attack

Brute Force: Tries all possible shifts (0-25), compares them using chi-squared statistic, and displays the option that is most likely to be the original plaintext.