engima-test.py

#!/usr/bin/env python2
#-*- coding:utf-8 -*-

from random import randint, shuffle

def invserse(wheel):
    result = [ 0 for _ in range(26) ]
    for i in range(26):
        result[wheel[i]] = i
    return result

def encrypt(data, s, wheels, u):
    result = ''
    for x in data:
        c = ord(x) - 65
        c = s[c]
        for wheel in wheels:
            c = wheel[c]
        c = u[c]
        for wheel in reversed(wheels):
            c = invserse(wheel)[c]
        c = s[c]
        result += chr(c + 65)

        for i in range(len(wheels)):
            if len(result) % 26**i == 0:
                wheels[i] = wheels[i][1:] + [wheels[i][0]]
    return result

def has_fix_point(permutation):
    for i in range(len(permutation)):
        if permutation[i] == i:
            return True
    return False

def generate_keys():
    tmp = range(26)
    wheels = []
    for i in range(4):
        shuffle(tmp)
        wheels.append(list(tmp))
    while has_fix_point(tmp):
        shuffle(tmp)
    return (wheels, tmp)

def run():
    s = range(26)
    # Proof that the Enigma-encryption is no longer it's own inverse when the "Steckbrett" contains a cycle of the length 3 
    s[0] = 2
    s[1] = 0
    s[2] = 1
    wheels, u = generate_keys()

    for pt in 'ABC':
        enc = encrypt(pt, s, wheels, u)
        dec = encrypt(enc, s, wheels, u)
        print pt + ' encrypts to ' + enc + ' which decrypts to ' + dec + '.'

if __name__ == '__main__':
    run()