+++ /dev/null
-from utilities import *
-from language_models import *
-
-from logger import logger
-
-
-class PocketEnigma(object):
- """A pocket enigma machine
- The wheel is internally represented as a 26-element list self.wheel_map,
- where wheel_map[i] == j shows that the position i places on from the arrow
- maps to the position j places on.
- """
- def __init__(self, wheel=1, position='a'):
- """initialise the pocket enigma, including which wheel to use and the
- starting position of the wheel.
-
- The wheel is either 1 or 2 (the predefined wheels) or a list of letter
- pairs.
-
- The position is the letter pointed to by the arrow on the wheel.
-
- >>> pe.wheel_map
- [25, 4, 23, 10, 1, 7, 9, 5, 12, 6, 3, 17, 8, 14, 13, 21, 19, 11, 20, 16, 18, 15, 24, 2, 22, 0]
- >>> pe.position
- 0
- """
- self.wheel1 = [('a', 'z'), ('b', 'e'), ('c', 'x'), ('d', 'k'),
- ('f', 'h'), ('g', 'j'), ('i', 'm'), ('l', 'r'), ('n', 'o'),
- ('p', 'v'), ('q', 't'), ('s', 'u'), ('w', 'y')]
- self.wheel2 = [('a', 'c'), ('b', 'd'), ('e', 'w'), ('f', 'i'),
- ('g', 'p'), ('h', 'm'), ('j', 'k'), ('l', 'n'), ('o', 'q'),
- ('r', 'z'), ('s', 'u'), ('t', 'v'), ('x', 'y')]
- if wheel == 1:
- self.make_wheel_map(self.wheel1)
- elif wheel == 2:
- self.make_wheel_map(self.wheel2)
- else:
- self.validate_wheel_spec(wheel)
- self.make_wheel_map(wheel)
- if position in string.ascii_lowercase:
- self.position = pos(position)
- else:
- self.position = position
-
- def make_wheel_map(self, wheel_spec):
- """Expands a wheel specification from a list of letter-letter pairs
- into a full wheel_map.
-
- >>> pe.make_wheel_map(pe.wheel2)
- [2, 3, 0, 1, 22, 8, 15, 12, 5, 10, 9, 13, 7, 11, 16, 6, 14, 25, 20, 21, 18, 19, 4, 24, 23, 17]
- """
- self.validate_wheel_spec(wheel_spec)
- self.wheel_map = [0] * 26
- for p in wheel_spec:
- self.wheel_map[pos(p[0])] = pos(p[1])
- self.wheel_map[pos(p[1])] = pos(p[0])
- return self.wheel_map
-
- def validate_wheel_spec(self, wheel_spec):
- """Validates that a wheel specificaiton will turn into a valid wheel
- map.
-
- >>> pe.validate_wheel_spec([])
- Traceback (most recent call last):
- ...
- ValueError: Wheel specification has 0 pairs, requires 13
- >>> pe.validate_wheel_spec([('a', 'b', 'c')]*13)
- Traceback (most recent call last):
- ...
- ValueError: Not all mappings in wheel specificationhave two elements
- >>> pe.validate_wheel_spec([('a', 'b')]*13)
- Traceback (most recent call last):
- ...
- ValueError: Wheel specification does not contain 26 letters
- """
- if len(wheel_spec) != 13:
- raise ValueError("Wheel specification has {} pairs, requires 13".
- format(len(wheel_spec)))
- for p in wheel_spec:
- if len(p) != 2:
- raise ValueError("Not all mappings in wheel specification"
- "have two elements")
- if len(set([p[0] for p in wheel_spec] +
- [p[1] for p in wheel_spec])) != 26:
- raise ValueError("Wheel specification does not contain 26 letters")
-
- def encipher_letter(self, letter):
- """Enciphers a single letter, by advancing the wheel before looking up
- the letter on the wheel.
-
- >>> pe.set_position('f')
- 5
- >>> pe.encipher_letter('k')
- 'h'
- """
- self.advance()
- return self.lookup(letter)
- decipher_letter = encipher_letter
-
- def lookup(self, letter):
- """Look up what a letter enciphers to, without turning the wheel.
-
- >>> pe.set_position('f')
- 5
- >>> cat([pe.lookup(l) for l in string.ascii_lowercase])
- 'udhbfejcpgmokrliwntsayqzvx'
- >>> pe.lookup('A')
- ''
- """
- if letter in string.ascii_lowercase:
- return unpos(
- (self.wheel_map[(pos(letter) - self.position) % 26] +
- self.position))
- else:
- return ''
-
- def advance(self):
- """Advances the wheel one position.
-
- >>> pe.set_position('f')
- 5
- >>> pe.advance()
- 6
- """
- self.position = (self.position + 1) % 26
- return self.position
-
- def encipher(self, message, starting_position=None):
- """Enciphers a whole message.
-
- >>> pe.set_position('f')
- 5
- >>> pe.encipher('helloworld')
- 'kjsglcjoqc'
- >>> pe.set_position('f')
- 5
- >>> pe.encipher('kjsglcjoqc')
- 'helloworld'
- >>> pe.encipher('helloworld', starting_position = 'x')
- 'egrekthnnf'
- """
- if starting_position:
- self.set_position(starting_position)
- transformed = ''
- for l in message:
- transformed += self.encipher_letter(l)
- return transformed
- decipher = encipher
-
- def set_position(self, position):
- """Sets the position of the wheel, by specifying the letter the arrow
- points to.
-
- >>> pe.set_position('a')
- 0
- >>> pe.set_position('m')
- 12
- >>> pe.set_position('z')
- 25
- """
- self.position = pos(position)
- return self.position
-
-
-def pocket_enigma_break_by_crib(message, wheel_spec, crib, crib_position):
- """Break a pocket enigma using a crib (some plaintext that's expected to
- be in a certain position). Returns a list of possible starting wheel
- positions that could produce the crib.
-
- >>> pocket_enigma_break_by_crib('kzpjlzmoga', 1, 'h', 0)
- ['a', 'f', 'q']
- >>> pocket_enigma_break_by_crib('kzpjlzmoga', 1, 'he', 0)
- ['a']
- >>> pocket_enigma_break_by_crib('kzpjlzmoga', 1, 'll', 2)
- ['a']
- >>> pocket_enigma_break_by_crib('kzpjlzmoga', 1, 'l', 2)
- ['a']
- >>> pocket_enigma_break_by_crib('kzpjlzmoga', 1, 'l', 3)
- ['a', 'j', 'n']
- >>> pocket_enigma_break_by_crib('aaaaa', 1, 'l', 3)
- []
- """
- pe = PocketEnigma(wheel=wheel_spec)
- possible_positions = []
- for p in string.ascii_lowercase:
- pe.set_position(p)
- plaintext = pe.decipher(message)
- if plaintext[crib_position:crib_position+len(crib)] == crib:
- possible_positions += [p]
- return possible_positions
-
-if __name__ == "__main__":
- import doctest
- doctest.testmod(extraglobs={'pe': PocketEnigma(1, 'a')})
\ No newline at end of file
projects / cipher-tools.git / blobdiff