5 from itertools
import zip_longest
, cycle
, permutations
6 from segment
import segment
7 from multiprocessing
import Pool
10 import matplotlib
.pyplot
as plt
12 logger
= logging
.getLogger(__name__
)
13 logger
.addHandler(logging
.FileHandler('cipher.log'))
14 logger
.setLevel(logging
.WARNING
)
15 #logger.setLevel(logging.INFO)
16 #logger.setLevel(logging.DEBUG)
19 from language_models
import *
24 # c5a = open('2012/5a.ciphertext', 'r').read()
25 # timeit.timeit('keyword_break(c5a)', setup='gc.enable() ; from __main__ import c5a ; from cipher import keyword_break', number=1)
26 # timeit.repeat('keyword_break_mp(c5a, chunksize=500)', setup='gc.enable() ; from __main__ import c5a ; from cipher import keyword_break_mp', repeat=5, number=1)
28 transpositions
= collections
.defaultdict(list)
30 transpositions
[transpositions_of(word
)] += [word
]
32 def frequencies(text
):
33 """Count the number of occurrences of each character in text
35 >>> sorted(frequencies('abcdefabc').items())
36 [('a', 2), ('b', 2), ('c', 2), ('d', 1), ('e', 1), ('f', 1)]
37 >>> sorted(frequencies('the quick brown fox jumped over the lazy ' \
38 'dog').items()) # doctest: +NORMALIZE_WHITESPACE
39 [(' ', 8), ('a', 1), ('b', 1), ('c', 1), ('d', 2), ('e', 4), ('f', 1),
40 ('g', 1), ('h', 2), ('i', 1), ('j', 1), ('k', 1), ('l', 1), ('m', 1),
41 ('n', 1), ('o', 4), ('p', 1), ('q', 1), ('r', 2), ('t', 2), ('u', 2),
42 ('v', 1), ('w', 1), ('x', 1), ('y', 1), ('z', 1)]
43 >>> sorted(frequencies('The Quick BROWN fox jumped! over... the ' \
44 '(9lazy) DOG').items()) # doctest: +NORMALIZE_WHITESPACE
45 [(' ', 8), ('!', 1), ('(', 1), (')', 1), ('.', 3), ('9', 1), ('B', 1),
46 ('D', 1), ('G', 1), ('N', 1), ('O', 2), ('Q', 1), ('R', 1), ('T', 1),
47 ('W', 1), ('a', 1), ('c', 1), ('d', 1), ('e', 4), ('f', 1), ('h', 2),
48 ('i', 1), ('j', 1), ('k', 1), ('l', 1), ('m', 1), ('o', 2), ('p', 1),
49 ('r', 1), ('t', 1), ('u', 2), ('v', 1), ('x', 1), ('y', 1), ('z', 1)]
50 >>> sorted(frequencies(sanitise('The Quick BROWN fox jumped! over... ' \
51 'the (9lazy) DOG')).items()) # doctest: +NORMALIZE_WHITESPACE
52 [('a', 1), ('b', 1), ('c', 1), ('d', 2), ('e', 4), ('f', 1), ('g', 1),
53 ('h', 2), ('i', 1), ('j', 1), ('k', 1), ('l', 1), ('m', 1), ('n', 1),
54 ('o', 4), ('p', 1), ('q', 1), ('r', 2), ('t', 2), ('u', 2), ('v', 1),
55 ('w', 1), ('x', 1), ('y', 1), ('z', 1)]
56 >>> frequencies('abcdefabcdef')['x']
59 return collections
.Counter(c
for c
in text
)
62 def caesar_break(message
, fitness
=Pletters
):
63 """Breaks a Caesar cipher using frequency analysis
65 >>> caesar_break('ibxcsyorsaqcheyklxivoexlevmrimwxsfiqevvmihrsasrxliwyrh' \
66 'ecjsppsamrkwleppfmergefifvmhixscsymjcsyqeoixlm') # doctest: +ELLIPSIS
67 (4, -130.849989015...)
68 >>> caesar_break('wxwmaxdgheetgwuxztgptedbgznitgwwhpguxyhkxbmhvvtlbhgtee' \
69 'raxlmhiixweblmxgxwmhmaxybkbgztgwztsxwbgmxgmert') # doctest: +ELLIPSIS
70 (19, -128.82410410...)
71 >>> caesar_break('yltbbqnqnzvguvaxurorgenafsbezqvagbnornfgsbevpnaabjurer' \
72 'svaquvzyvxrnznazlybequrvfohgriraabjtbaruraprur') # doctest: +ELLIPSIS
73 (13, -126.25403935...)
75 sanitised_message
= sanitise(message
)
77 best_fit
= float('-inf')
78 for shift
in range(26):
79 plaintext
= caesar_decipher(sanitised_message
, shift
)
80 fit
= fitness(plaintext
)
81 logger
.debug('Caesar break attempt using key {0} gives fit of {1} '
82 'and decrypt starting: {2}'.format(shift
, fit
, plaintext
[:50]))
86 logger
.info('Caesar break best fit: key {0} gives fit of {1} and '
87 'decrypt starting: {2}'.format(best_shift
, best_fit
,
88 caesar_decipher(sanitised_message
, best_shift
)[:50]))
89 return best_shift
, best_fit
91 def affine_break(message
, fitness
=Pletters
):
92 """Breaks an affine cipher using frequency analysis
94 >>> affine_break('lmyfu bkuusd dyfaxw claol psfaom jfasd snsfg jfaoe ls ' \
95 'omytd jlaxe mh jm bfmibj umis hfsul axubafkjamx. ls kffkxwsd jls ' \
96 'ofgbjmwfkiu olfmxmtmwaokttg jlsx ls kffkxwsd jlsi zg tsxwjl. jlsx ' \
97 'ls umfjsd jlsi zg hfsqysxog. ls dmmdtsd mx jls bats mh bkbsf. ls ' \
98 'bfmctsd kfmyxd jls lyj, mztanamyu xmc jm clm cku tmmeaxw kj lai ' \
99 'kxd clm ckuxj.') # doctest: +ELLIPSIS
100 ((15, 22, True), -340.601181913...)
102 sanitised_message
= sanitise(message
)
105 best_one_based
= True
106 best_fit
= float("-inf")
107 for one_based
in [True, False]:
108 for multiplier
in [x
for x
in range(1, 26, 2) if x
!= 13]:
109 for adder
in range(26):
110 plaintext
= affine_decipher(sanitised_message
,
111 multiplier
, adder
, one_based
)
112 fit
= fitness(plaintext
)
113 logger
.debug('Affine break attempt using key {0}x+{1} ({2}) '
114 'gives fit of {3} and decrypt starting: {4}'.
115 format(multiplier
, adder
, one_based
, fit
,
119 best_multiplier
= multiplier
121 best_one_based
= one_based
122 logger
.info('Affine break best fit with key {0}x+{1} ({2}) gives fit of {3} '
123 'and decrypt starting: {4}'.format(
124 best_multiplier
, best_adder
, best_one_based
, best_fit
,
125 affine_decipher(sanitised_message
, best_multiplier
,
126 best_adder
, best_one_based
)[:50]))
127 return (best_multiplier
, best_adder
, best_one_based
), best_fit
129 def keyword_break(message
, wordlist
=keywords
, fitness
=Pletters
):
130 """Breaks a keyword substitution cipher using a dictionary and
133 >>> keyword_break(keyword_encipher('this is a test message for the ' \
134 'keyword decipherment', 'elephant', Keyword_wrap_alphabet.from_last), \
135 wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
136 (('elephant', <Keyword_wrap_alphabet.from_last: 1>), -52.834575011...)
139 best_wrap_alphabet
= True
140 best_fit
= float("-inf")
141 for wrap_alphabet
in Keyword_wrap_alphabet
:
142 for keyword
in wordlist
:
143 plaintext
= keyword_decipher(message
, keyword
, wrap_alphabet
)
144 fit
= fitness(plaintext
)
145 logger
.debug('Keyword break attempt using key {0} (wrap={1}) '
146 'gives fit of {2} and decrypt starting: {3}'.format(
147 keyword
, wrap_alphabet
, fit
,
148 sanitise(plaintext
)[:50]))
151 best_keyword
= keyword
152 best_wrap_alphabet
= wrap_alphabet
153 logger
.info('Keyword break best fit with key {0} (wrap={1}) gives fit of '
154 '{2} and decrypt starting: {3}'.format(best_keyword
,
155 best_wrap_alphabet
, best_fit
, sanitise(
156 keyword_decipher(message
, best_keyword
,
157 best_wrap_alphabet
))[:50]))
158 return (best_keyword
, best_wrap_alphabet
), best_fit
160 def keyword_break_mp(message
, wordlist
=keywords
, fitness
=Pletters
, chunksize
=500):
161 """Breaks a keyword substitution cipher using a dictionary and
164 >>> keyword_break_mp(keyword_encipher('this is a test message for the ' \
165 'keyword decipherment', 'elephant', Keyword_wrap_alphabet.from_last), \
166 wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
167 (('elephant', <Keyword_wrap_alphabet.from_last: 1>), -52.834575011...)
170 helper_args
= [(message
, word
, wrap
, fitness
)
172 for wrap
in Keyword_wrap_alphabet
]
173 # Gotcha: the helper function here needs to be defined at the top level
174 # (limitation of Pool.starmap)
175 breaks
= pool
.starmap(keyword_break_worker
, helper_args
, chunksize
)
176 return max(breaks
, key
=lambda k
: k
[1])
178 def keyword_break_worker(message
, keyword
, wrap_alphabet
, fitness
):
179 plaintext
= keyword_decipher(message
, keyword
, wrap_alphabet
)
180 fit
= fitness(plaintext
)
181 logger
.debug('Keyword break attempt using key {0} (wrap={1}) gives fit of '
182 '{2} and decrypt starting: {3}'.format(keyword
,
183 wrap_alphabet
, fit
, sanitise(plaintext
)[:50]))
184 return (keyword
, wrap_alphabet
), fit
186 def scytale_break(message
, fitness
=Pbigrams
):
187 """Breaks a Scytale cipher
189 >>> scytale_break('tfeulchtrtteehwahsdehneoifeayfsondmwpltmaoalhikotoere' \
190 'dcweatehiplwxsnhooacgorrcrcraotohsgullasenylrendaianeplscdriioto' \
191 'aek') # doctest: +ELLIPSIS
192 (6, -281.276219108...)
195 best_fit
= float("-inf")
196 for key
in range(1, 20):
197 if len(message
) % key
== 0:
198 plaintext
= scytale_decipher(message
, key
)
199 fit
= fitness(sanitise(plaintext
))
200 logger
.debug('Scytale break attempt using key {0} gives fit of '
201 '{1} and decrypt starting: {2}'.format(key
,
202 fit
, sanitise(plaintext
)[:50]))
206 logger
.info('Scytale break best fit with key {0} gives fit of {1} and '
207 'decrypt starting: {2}'.format(best_key
, best_fit
,
208 sanitise(scytale_decipher(message
, best_key
))[:50]))
209 return best_key
, best_fit
212 def column_transposition_break_mp(message
, translist
=transpositions
,
213 fitness
=Pbigrams
, chunksize
=500):
214 """Breaks a column transposition cipher using a dictionary and
215 n-gram frequency analysis
217 # >>> column_transposition_break_mp(column_transposition_encipher(sanitise( \
218 # "It is a truth universally acknowledged, that a single man in \
219 # possession of a good fortune, must be in want of a wife. However \
220 # little known the feelings or views of such a man may be on his \
221 # first entering a neighbourhood, this truth is so well fixed in the \
222 # minds of the surrounding families, that he is considered the \
223 # rightful property of some one or other of their daughters."), \
225 # translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
226 # (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
227 # (6, 1, 0, 4, 5, 3, 2): ['keyword']}) # doctest: +ELLIPSIS
228 # (((2, 0, 5, 3, 1, 4, 6), False), 0.0628106372...)
229 # >>> column_transposition_break_mp(column_transposition_encipher(sanitise( \
230 # "It is a truth universally acknowledged, that a single man in \
231 # possession of a good fortune, must be in want of a wife. However \
232 # little known the feelings or views of such a man may be on his \
233 # first entering a neighbourhood, this truth is so well fixed in the \
234 # minds of the surrounding families, that he is considered the \
235 # rightful property of some one or other of their daughters."), \
237 # translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
238 # (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
239 # (6, 1, 0, 4, 5, 3, 2): ['keyword']}, \
240 # target_counts=normalised_english_trigram_counts) # doctest: +ELLIPSIS
241 # (((2, 0, 5, 3, 1, 4, 6), False), 0.0592259560...)
244 helper_args
= [(message
, trans
, columnwise
, fitness
)
245 for trans
in translist
.keys()
246 for columnwise
in [True, False]]
247 # Gotcha: the helper function here needs to be defined at the top level
248 # (limitation of Pool.starmap)
249 breaks
= pool
.starmap(column_transposition_break_worker
,
250 helper_args
, chunksize
)
251 return max(breaks
, key
=lambda k
: k
[1])
252 column_transposition_break
= column_transposition_break_mp
254 def column_transposition_break_worker(message
, transposition
, columnwise
,
256 plaintext
= column_transposition_decipher(message
, transposition
, columnwise
=columnwise
)
257 fit
= fitness(sanitise(plaintext
))
258 logger
.debug('Column transposition break attempt using key {0} '
259 'gives fit of {1} and decrypt starting: {2}'.format(
261 sanitise(plaintext
)[:50]))
262 return (transposition
, columnwise
), fit
265 def transposition_break_exhaustive(message
, fitness
=Pbigrams
):
266 best_transposition
= ''
267 best_pw
= float('-inf')
268 for keylength
in range(1, 21):
269 if len(message
) % keylength
== 0:
270 for transposition
in permutations(range(keylength
)):
271 for columnwise
in [True, False]:
272 plaintext
= column_transposition_decipher(message
,
273 transposition
, columnwise
=columnwise
)
274 fit
=fitness(plaintext
)
275 logger
.debug('Column transposition break attempt using key {0} {1} '
276 'gives fit of {2} and decrypt starting: {3}'.format(
277 transposition
, columnwise
, pw
,
278 sanitise(plaintext
)[:50]))
280 best_transposition
= transposition
281 best_columnwise
= columnwise
283 return (best_transposition
, best_columnwise
), best_pw
286 def vigenere_keyword_break(message
, wordlist
=keywords
, fitness
=Pletters
):
287 """Breaks a vigenere cipher using a dictionary and
290 >>> vigenere_keyword_break(vigenere_encipher(sanitise('this is a test ' \
291 'message for the vigenere decipherment'), 'cat'), \
292 wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
293 ('cat', -52.947271216...)
296 best_fit
= float("-inf")
297 for keyword
in wordlist
:
298 plaintext
= vigenere_decipher(message
, keyword
)
299 fit
= fitness(plaintext
)
300 logger
.debug('Vigenere break attempt using key {0} '
301 'gives fit of {1} and decrypt starting: {2}'.format(
303 sanitise(plaintext
)[:50]))
306 best_keyword
= keyword
307 logger
.info('Vigenere break best fit with key {0} gives fit '
308 'of {1} and decrypt starting: {2}'.format(best_keyword
,
310 vigenere_decipher(message
, best_keyword
))[:50]))
311 return best_keyword
, best_fit
313 def vigenere_keyword_break_mp(message
, wordlist
=keywords
, fitness
=Pletters
,
315 """Breaks a vigenere cipher using a dictionary and
318 >>> vigenere_keyword_break_mp(vigenere_encipher(sanitise('this is a test ' \
319 'message for the vigenere decipherment'), 'cat'), \
320 wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
321 ('cat', -52.947271216...)
324 helper_args
= [(message
, word
, fitness
)
325 for word
in wordlist
]
326 # Gotcha: the helper function here needs to be defined at the top level
327 # (limitation of Pool.starmap)
328 breaks
= pool
.starmap(vigenere_keyword_break_worker
, helper_args
, chunksize
)
329 return max(breaks
, key
=lambda k
: k
[1])
331 def vigenere_keyword_break_worker(message
, keyword
, fitness
):
332 plaintext
= vigenere_decipher(message
, keyword
)
333 fit
= fitness(plaintext
)
334 logger
.debug('Vigenere keyword break attempt using key {0} gives fit of '
335 '{1} and decrypt starting: {2}'.format(keyword
,
336 fit
, sanitise(plaintext
)[:50]))
341 def vigenere_frequency_break(message
, fitness
=Pletters
):
342 """Breaks a Vigenere cipher with frequency analysis
344 >>> vigenere_frequency_break(vigenere_encipher(sanitise("It is time to " \
345 "run. She is ready and so am I. I stole Daniel's pocketbook this " \
346 "afternoon when he left his jacket hanging on the easel in the " \
347 "attic. I jump every time I hear a footstep on the stairs, " \
348 "certain that the theft has been discovered and that I will " \
349 "be caught. The SS officer visits less often now that he is " \
350 "sure"), 'florence')) # doctest: +ELLIPSIS
351 ('florence', -307.5473096791...)
353 best_fit
= float("-inf")
355 sanitised_message
= sanitise(message
)
356 for trial_length
in range(1, 20):
357 splits
= every_nth(sanitised_message
, trial_length
)
358 key
= ''.join([chr(caesar_break(s
)[0] + ord('a')) for s
in splits
])
359 plaintext
= vigenere_decipher(sanitised_message
, key
)
360 fit
= fitness(plaintext
)
361 logger
.debug('Vigenere key length of {0} ({1}) gives fit of {2}'.
362 format(trial_length
, key
, fit
))
366 logger
.info('Vigenere break best fit with key {0} gives fit '
367 'of {1} and decrypt starting: {2}'.format(best_key
,
369 vigenere_decipher(message
, best_key
))[:50]))
370 return best_key
, best_fit
372 def beaufort_frequency_break(message
, fitness
=Pletters
):
373 """Breaks a Beaufort cipher with frequency analysis
375 >>> beaufort_frequency_break(beaufort_encipher(sanitise("It is time to " \
376 "run. She is ready and so am I. I stole Daniel's pocketbook this " \
377 "afternoon when he left his jacket hanging on the easel in the " \
378 "attic. I jump every time I hear a footstep on the stairs, " \
379 "certain that the theft has been discovered and that I will " \
380 "be caught. The SS officer visits less often now " \
381 "that he is sure"), 'florence')) # doctest: +ELLIPSIS
382 ('florence', -307.5473096791...)
384 best_fit
= float("-inf")
386 sanitised_message
= sanitise(message
)
387 for trial_length
in range(1, 20):
388 splits
= every_nth(sanitised_message
, trial_length
)
389 key
= ''.join([chr(-caesar_break(s
)[0] % 26 + ord('a')) for s
in splits
])
390 plaintext
= beaufort_decipher(sanitised_message
, key
)
391 fit
= fitness(plaintext
)
392 logger
.debug('Beaufort key length of {0} ({1}) gives fit of {2}'.
393 format(trial_length
, key
, fit
))
397 logger
.info('Beaufort break best fit with key {0} gives fit '
398 'of {1} and decrypt starting: {2}'.format(best_key
,
400 beaufort_decipher(message
, best_key
))[:50]))
401 return best_key
, best_fit
405 def plot_frequency_histogram(freqs
, sort_key
=None):
406 x
= range(len(freqs
.keys()))
407 y
= [freqs
[l
] for l
in sorted(freqs
.keys(), key
=sort_key
)]
409 ax
= f
.add_axes([0.1, 0.1, 0.9, 0.9])
410 ax
.bar(x
, y
, align
='center')
412 ax
.set_xticklabels(sorted(freqs
.keys(), key
=sort_key
))
416 if __name__
== "__main__":