return max(results, key=lambda k: k[1])
+def beaufort_sub_break(message, fitness=Pletters):
+ """Breaks one chunk of a Beaufort cipher with frequency analysis
+
+ >>> beaufort_sub_break('samwpplggnnmmyaazgympjapopnwiywwomwspgpjmefwmawx' \
+ 'jafjhxwwwdigxshnlywiamhyshtasxptwueahhytjwsn') # doctest: +ELLIPSIS
+ (0, -117.4492...)
+ >>> beaufort_sub_break('eyprzjjzznxymrygryjqmqhznjrjjapenejznawngnnezgza' \
+ 'dgndknaogpdjneadadazlhkhxkryevrronrmdjnndjlo') # doctest: +ELLIPSIS
+ (17, -114.9598...)
+ """
+ best_shift = 0
+ best_fit = float('-inf')
+ for key in range(26):
+ plaintext = [unpos(key - pos(l)) for l in message]
+ fit = fitness(plaintext)
+ logger.debug('Beaufort sub break attempt using key {0} gives fit of {1} '
+ 'and decrypt starting: {2}'.format(key, fit,
+ plaintext[:50]))
+ if fit > best_fit:
+ best_fit = fit
+ best_key = key
+ logger.info('Beaufort sub break best fit: key {0} gives fit of {1} and '
+ 'decrypt starting: {2}'.format(best_key, best_fit,
+ cat([unpos(best_key - pos(l)) for l in message[:50]])))
+ return best_key, best_fit
+
+
def beaufort_frequency_break(message, max_key_length=20, fitness=Pletters):
"""Breaks a Beaufort cipher with frequency analysis
"that he is sure"), 'florence')) # doctest: +ELLIPSIS
('florence', -307.5473096791...)
"""
+ def worker(message, key_length, fitness):
+ splits = every_nth(message, key_length)
+ key = cat([unpos(beaufort_sub_break(s)[0]) for s in splits])
+ plaintext = beaufort_decipher(message, key)
+ fit = fitness(plaintext)
+ return key, fit
+ sanitised_message = sanitise(message)
+ results = starmap(worker, [(sanitised_message, i, fitness)
+ for i in range(1, max_key_length+1)])
+ return max(results, key=lambda k: k[1])
+
+
+def beaufort_variant_frequency_break(message, max_key_length=20, fitness=Pletters):
+ """Breaks a Beaufort cipher with frequency analysis
+
+ >>> beaufort_variant_frequency_break(beaufort_variant_encipher(sanitise("It is time to " \
+ "run. She is ready and so am I. I stole Daniel's pocketbook this " \
+ "afternoon when he left his jacket hanging on the easel in the " \
+ "attic. I jump every time I hear a footstep on the stairs, " \
+ "certain that the theft has been discovered and that I will " \
+ "be caught. The SS officer visits less often now " \
+ "that he is sure"), 'florence')) # doctest: +ELLIPSIS
+ ('florence', -307.5473096791...)
+ """
def worker(message, key_length, fitness):
splits = every_nth(sanitised_message, key_length)
key = cat([chr(-caesar_break(s)[0] % 26 + ord('a'))
for s in splits])
- plaintext = beaufort_decipher(message, key)
+ plaintext = beaufort_variant_decipher(message, key)
fit = fitness(plaintext)
return key, fit
sanitised_message = sanitise(message)
for i in range(1, max_key_length+1)])
return max(results, key=lambda k: k[1])
-
def polybius_break_mp(message, column_labels, row_labels,
letters_to_merge=None,
wordlist=keywords, fitness=Pletters,