Caesar Cipher

A Python package and command line script for encoding, decoding and cracking messages with the Caesar Shift Cipher.

Table of Contents

Features

• Encoding
• Decoding
• Cracking (decoding ciphertext without known offset)
• Arbitrary cipher offsets
• Command Line Interface
• Test suite
• Support for both Python 2 and 3
• PEP8. Praise the Dark Lord

Installation

The latest version can be installed via pip.

$ pip install caesarcipher

If that doesn't work, give easy_install a try:

$ easy_install caesarcipher

Usage

Command Line

Encoding a message:

$ caesarcipher --encode "This is a message I want to encode."

Encoding a message with a specific offset:

$ caesarcipher --offset 14 --encode "This is a message I want to encode."

Decoding a ciphertext with a specific offset:

$ caesarcipher --offset 14 --decode "W kobh hc sbqcrs hvwg ghfwbu."

Cracking a ciphertext without knowing the offset:

$ caesarcipher --crack "W kobh hc sbqcrs hvwg ghfwbu."

Library

Encoding a message:

>>> from caesarcipher import CaesarCipher
>>> cipher = CaesarCipher('I want to encode this string')
>>> cipher.encoded
'W kobh hc sbqcrs hvwg ghfwbu.'

Encoding a message with a specific offset:

>>> from caesarcipher import CaesarCipher
>>> cipher = CaesarCipher('I want to encode this string.',
...     offset=14)
>>> cipher.encoded
'W kobh hc sbqcrs hvwg ghfwbu.'

Decoding a ciphertext with a specific offset:

>>> from caesarcipher import CaesarCipher
>>> cipher = CaesarCipher('W kobh hc sbqcrs hvwg ghfwbu.',
...    offset=14)
>>> cipher.decoded
'I want to encode this string.'

Cracking a ciphertext without knowing the offset:

>>> from caesarcipher import CaesarCipher
>>> cipher = CaesarCipher('W kobh hc sbqcrs hvwg ghfwbu.')
>>> cipher.cracked
'I want to encode this string.'

Development

Hacking

To hack on the project, clone the GitHub repo:

$ git clone https://github.com/RobSpectre/Caesar-Cipher.git

Then install in a virtualenv.

$ pip install -e ./

Tests

The project uses Nose for tests. Simply run from the project root.

$ nosetests -v

Go ahead and check on coverage and PEP8 while you're at it!

$ nosetests -v --with-coverage --with-tissue

Meta

• Written by Rob Spectre
• Used for Hacker Olympics London 2014
• Released under MIT License
• Software is as is - no warranty expressed or implied.
• The Caesar Shift Cipher is known to be ridiculously easy to crack, as evidenced by this very package. Do not confuse with actual cryptography or use in anything that is important - it's just a fun math problem for a sunny vacation afternoon.