Crank is short for “CRyptANalysis toolKit”, and its overall purpose is to provide a powerful and extensible environment for solving classical (pen-and-paper) ciphers, providing as much automation as possible. Classical ciphers include common schemes like monoalphabetic substitutions, where each letter of the alphabet is mapped to another (usually different) letter consistently through the text. The first version of Crank is restricting itself to these special ciphers. Other algorithms forever devoid of Crank’s attentions include Enigma, RSA, DES, MurkelFish, or anything else invented after 1900. They’re hard(er).

[ http://crank.sourceforge.net/ ]