import norms
import logging
from itertools import zip_longest, cycle, permutations
-from segment import segment, Pwords
+from segment import segment
from multiprocessing import Pool
from math import log10
# counts[c] += 1
#return counts
return collections.Counter(c for c in text)
-letter_frequencies = frequencies
-def bigram_likelihood(bigram, bf, lf):
- return bf[bigram] / (lf[bigram[0]] * lf[bigram[1]])
+def frequency_compare(text, target_frequency, frequency_scaling, metric):
+ counts = frequency_scaling(frequencies(text))
+ return -1 * metric(target_frequency, counts)
+def euclidean_compare(text):
+ return frequency_compare(text, norms.euclidean_scale(english_counts),
+ norms.euclidean_scale, norms.euclidean_distance)
-def caesar_break(message,
- metric=norms.euclidean_distance,
- target_counts=normalised_english_counts,
- message_frequency_scaling=norms.normalise):
+
+def caesar_break(message, fitness=Pletters):
"""Breaks a Caesar cipher using frequency analysis
>>> caesar_break('ibxcsyorsaqcheyklxivoexlevmrimwxsfiqevvmihrsasrxliwyrh' \
'ecjsppsamrkwleppfmergefifvmhixscsymjcsyqeoixlm') # doctest: +ELLIPSIS
- (4, 0.080345432737...)
+ (4, -130.849890899...)
>>> caesar_break('wxwmaxdgheetgwuxztgptedbgznitgwwhpguxyhkxbmhvvtlbhgtee' \
'raxlmhiixweblmxgxwmhmaxybkbgztgwztsxwbgmxgmert') # doctest: +ELLIPSIS
- (19, 0.11189290326...)
+ (19, -128.82516920...)
>>> caesar_break('yltbbqnqnzvguvaxurorgenafsbezqvagbnornfgsbevpnaabjurer' \
'svaquvzyvxrnznazlybequrvfohgriraabjtbaruraprur') # doctest: +ELLIPSIS
- (13, 0.08293968842...)
+ (13, -126.25233502...)
"""
sanitised_message = sanitise(message)
best_shift = 0
- best_fit = float("inf")
+ best_fit = float('-inf')
for shift in range(26):
plaintext = caesar_decipher(sanitised_message, shift)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
- fit = metric(target_counts, counts)
+ fit = fitness(plaintext)
logger.debug('Caesar break attempt using key {0} gives fit of {1} '
'and decrypt starting: {2}'.format(shift, fit, plaintext[:50]))
- if fit < best_fit:
+ if fit > best_fit:
best_fit = fit
best_shift = shift
logger.info('Caesar break best fit: key {0} gives fit of {1} and '
for adder in range(26):
plaintext = affine_decipher(sanitised_message,
multiplier, adder, one_based)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
+ counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
logger.debug('Affine break attempt using key {0}x+{1} ({2}) '
'gives fit of {3} and decrypt starting: {4}'.
for wrap_alphabet in range(3):
for keyword in wordlist:
plaintext = keyword_decipher(message, keyword, wrap_alphabet)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
+ counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
logger.debug('Keyword break attempt using key {0} (wrap={1}) '
'gives fit of {2} and decrypt starting: {3}'.format(
def keyword_break_worker(message, keyword, wrap_alphabet, metric, target_counts,
message_frequency_scaling):
plaintext = keyword_decipher(message, keyword, wrap_alphabet)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
+ counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
logger.debug('Keyword break attempt using key {0} (wrap={1}) gives fit of '
'{2} and decrypt starting: {3}'.format(keyword,
best_fit = float("inf")
for keyword in wordlist:
plaintext = vigenere_decipher(message, keyword)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
+ counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
logger.debug('Vigenere break attempt using key {0} '
'gives fit of {1} and decrypt starting: {2}'.format(
def vigenere_keyword_break_worker(message, keyword, metric, target_counts,
message_frequency_scaling):
plaintext = vigenere_decipher(message, keyword)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
+ counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
logger.debug('Vigenere keyword break attempt using key {0} gives fit of '
'{1} and decrypt starting: {2}'.format(keyword,
sanitised_message = sanitise(message)
for trial_length in range(1, 20):
splits = every_nth(sanitised_message, trial_length)
- key = ''.join([chr(caesar_break(s, target_counts=target_counts)[0] + ord('a')) for s in splits])
+ key = ''.join([chr(caesar_break(s)[0] + ord('a')) for s in splits])
plaintext = vigenere_decipher(sanitised_message, key)
counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
message_frequency_scaling=norms.normalise):
"""Breaks a Beaufort cipher with frequency analysis
- >>> vigenere_frequency_break(vigenere_encipher(sanitise("It is time to " \
+ >>> beaufort_frequency_break(beaufort_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."), 'florence')) # doctest: +ELLIPSIS
sanitised_message = sanitise(message)
for trial_length in range(1, 20):
splits = every_nth(sanitised_message, trial_length)
- key = ''.join([chr(caesar_break(s, target_counts=target_counts)[0] + ord('a')) for s in splits])
+ key = ''.join([chr(caesar_break(s)[0] + ord('a')) for s in splits])
plaintext = beaufort_decipher(sanitised_message, key)
counts = message_frequency_scaling(frequencies(plaintext))
fit = metric(target_counts, counts)
projects / cipher-tools.git / blobdiff