A simple vigenere solver using Index of Coincidence, Friedman and Chi-squared
Created by Giovan Battista Bellaso in 1553, a simple cipher to implement but quite hard to break it. Being even called as "The indecipherable cipher", remaining like that for 3 centuries.
It consists on a series of ceasar ciphers interlaced.
Created by William F. Friedman in 1922, a technique for counting the amount of repetition of letters. Since natural language aren't evenly distributed, the IoC of a text in natural language should be greater than a random scrambled text.
Created by William F. Friedman around 1920s, it is a method to determine the used key length used for ciphering a given text in vigenère. Basically calculating the IoC of every chunk of text separated by a given guessed key-length. The length with the greatest IoC, should be considered as the probable key length, or at least a common multiplier is shared.
It uses chi-squared distribution to evaluate a goodness fit, testing whether an observed value and an expected value share the same frequencies.
Follow the steps bellow to run it
- Make sure you have NodeJS installed on your machine
- Clone the repository
- Install dependencies by executing
npm install - Run the code by executing
npm startornode src/main.js