Collection of tools to solve Nihilist ciphers
Home Tools List Guides Puzzles BlogsThe Nihilist cipher can be thought of as a vigenere cipher working in numeric space meaning the same cryptanalysis techniques can be used to solve it. Additionally, the restriction that only certain grid cordinates are valid (e.g. 11 to 55 for a 5x5 but not 56 77 etc) allow limits to be placed on possible keylengths. A a-z/a-z0-9 charset is supported and both the monoalph and hill-climbing read the Polybius grid for their input. The monoalph can be used when the grid is known and will likely get the correct key straight away while the hill-climbing searches for both the grid and key by default (Can be changed to only search for key with option).
Credit to James Lyons at http://practicalcryptography.com/cryptanalysis/text-characterisation/quadgrams/ for quadgram frequencies and fitness method.