+"""Monoalphabetic substitution ciphers, mainly done by keyword. Enciphering
+and deciphering, and a couple of ways to break these ciphers.
+"""
from enum import Enum
-# from itertools import starmap
import multiprocessing
import math
from szyfrow.support.utilities import *
class KeywordWrapAlphabet(Enum):
+ """Ways to list the rest of the alphabet after use of a keyword.
+
+ * `from_a` : continue the alphabet from 'a': `bayescdfg...`
+ * `from_last`: continue from the last letter of the keyword:
+ `bayestuvwxyzcdf...`
+ * `from_largest`: continue from the "largest" letter of the keyword:
+ `bayeszcdfg...`
+ """
from_a = 1
from_last = 2
from_largest = 3
def keyword_cipher_alphabet_of(keyword, wrap_alphabet=KeywordWrapAlphabet.from_a):
"""Find the cipher alphabet given a keyword.
- wrap_alphabet controls how the rest of the alphabet is added
- after the keyword.
+
+ [`wrap_alphabet`](#szyfrow.keyword_cipher.KeywordWrapAlphabet) controls
+ how the rest of the alphabet is added after the keyword.
>>> keyword_cipher_alphabet_of('bayes')
'bayescdfghijklmnopqrtuvwxz'
return message.lower().translate(cipher_translation)
-def keyword_break(message, wordlist=keywords, fitness=Pletters):
+def keyword_break_single_thread(message, wordlist=None, fitness=Pletters):
"""Breaks a keyword substitution cipher using a dictionary and
frequency analysis.
+ If `wordlist` is not specified, use
+ [`szyfrow.support.langauge_models.keywords`](support/language_models.html#szyfrow.support.language_models.keywords).
+
>>> keyword_break(keyword_encipher('this is a test message for the ' \
'keyword decipherment', 'elephant', KeywordWrapAlphabet.from_last), \
wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
(('elephant', <KeywordWrapAlphabet.from_last: 2>), -52.834575011...)
"""
+ if wordlist is None:
+ wordlist = keywords
+
best_keyword = ''
best_wrap_alphabet = True
best_fit = float("-inf")
best_wrap_alphabet = wrap_alphabet
return (best_keyword, best_wrap_alphabet), best_fit
-def keyword_break_mp(message, wordlist=keywords, fitness=Pletters,
+def keyword_break(message, wordlist=None, fitness=Pletters,
number_of_solutions=1, chunksize=500):
"""Breaks a keyword substitution cipher using a dictionary and
- frequency analysis
+ frequency analysis.
+
+ If `wordlist` is not specified, use
+ [`szyfrow.support.langauge_models.keywords`](support/language_models.html#szyfrow.support.language_models.keywords).
+
>>> keyword_break_mp(keyword_encipher('this is a test message for the ' \
'keyword decipherment', 'elephant', KeywordWrapAlphabet.from_last), \
[(('elephant', <KeywordWrapAlphabet.from_last: 2>), -52.834575011...),
(('elephant', <KeywordWrapAlphabet.from_largest: 3>), -52.834575011...)]
"""
+ if wordlist is None:
+ wordlist = keywords
+
with multiprocessing.Pool() as pool:
helper_args = [(message, word, wrap, fitness)
for word in wordlist
return (keyword, wrap_alphabet), fit
-def monoalphabetic_break_hillclimbing(message,
+def monoalphabetic_break_hillclimbing_single(message,
max_iterations=20000,
plain_alphabet=None,
cipher_alphabet=None,
swap_index_finder=None,
fitness=Pletters, chunksize=1):
+ """Break a monalphabetic substitution cipher using hillclimbing to
+ guess the keyword. Hillclimbing is done by using the simulated annealing
+ approach with a temperature of zero.
+
+ This version uses a single worker.
+ """
return monoalphabetic_sa_break(message,
workers=1,
initial_temperature=0,
fitness=fitness, chunksize=chunksize)
-def monoalphabetic_break_hillclimbing_mp(message,
+def monoalphabetic_break_hillclimbing(message,
workers=10,
max_iterations=20000,
plain_alphabet=None,
cipher_alphabet=None,
swap_index_finder=None,
fitness=Pletters, chunksize=1):
+ """Break a monalphabetic substitution cipher using hillclimbing to
+ guess the keyword. Hillclimbing is done by using the simulated annealing
+ approach with a temperature of zero.
+
+ This version uses a several workers.
+ """
return monoalphabetic_sa_break(message,
workers=workers,
initial_temperature=0,
def gaussian_swap_index(a):
+ """Return an index to use as the partner of `a` in a swap. The partners
+ are drawn from a Gaussian distribution.
+ """
return (a + int(random.gauss(0, 4))) % 26
def uniform_swap_index(a):
+ """Return an index to use as the partner of `a` in a swap. The partners
+ are drawn from a uniform distribution.
+ """
return random.randrange(26)
def monoalphabetic_sa_break(message, workers=10,
cipher_alphabet=None,
swap_index_finder=None,
fitness=Ptrigrams, chunksize=1):
+ """Break a monalphabetic substitution cipher using simulated annealing to
+ guess the keyword. This function just sets up a stable of workers who
+ do the actual work, implemented as
+ `szyfrow.keyword_cipher.monoalphabetic_sa_break_worker`.
+
+ See a [post on simulated annealing](https://work.njae.me.uk/2019/07/08/simulated-annealing-and-breaking-substitution-ciphers/)
+ for detail on how this works.
+ """
worker_args = []
ciphertext = sanitise(message)
if swap_index_finder is None:
swap_index_finder,
t0, max_iterations, fitness,
logID):
+ """One thread of a simulated annealing run.
+ See a [post on simulated annealing](https://work.njae.me.uk/2019/07/08/simulated-annealing-and-breaking-substitution-ciphers/)
+ for detail on how this works.
+ """
def swap(letters, i, j):
if i > j:
i, j = j, i
projects / szyfrow.git / blobdiff