This project spawned while trying to solve Stage 6 of Simon Singh's The Code Book cipher challenge. (Check it out! https://simonsingh.net/cryptography/cipher-challenge/)
This includes 3 command line programs
- playfair - For encrypting and decrypting text with the Playfair cipher
- ngramFrequency - For collecting and managing English n-gram frequencies
- playfairCracker - To help crack text encrypted with the Playfair cipher
These only work with English, sorry! I did consider allowing these to easily include or be rewritten for other languages, but due to the unique nature of this cipher, that was too difficult.
Writing tests and finish documentation right now. Tests 25% done. Documentation 50% done. 4/17/18
Use Makefile to install. Run make to build all or specify individual program. e.g. make playfair
Documentation uses Doxygen and will be generated with make if Doxygen is installed.
A simple program to encrypt/decrypt text with the Playfair cipher. Has options to specify which letter is being replaced in the message, and the replacing letter. (Default: 'J' to 'I'). Also has options to specify which letter will be inserted between doubles and/or which letter pads an odd-length message.
This is a helper program for the playfairCracker to collect and manage frequencies of n-grams for frequency analysis. The frequencies directory contains English n-gram frequencies already, but use this if you want to collect frequency analysis from any sample data. Feed it your own corpus, or selection of texts!
Use this program to help crack a message encoded with the Playfair cipher. Frequency analysis is used to determine how likely a given decrypted text is to English, which is its fitness score. The Playfair cipher's handling of double letters is likely to cause an incorrect key to produce a higher fitness score than the correct key, especially with a small message and/or many cases of double letters.
'The cat fell off the wall' becomes 'th ec at fe lx lo fx ft he wa lx lx'. The won't sentence will not produce a high fitness score!
Helpful tools, thank you!