X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=cipherbreak.py;h=7c6cea7ef9758f638dc396049cb833c874d02820;hb=687c0a0c78242810cc617fa2135b6eb6f730d020;hp=f1ab58e50a4f293368ef9d5382aef9dabf590420;hpb=60a697926e04e109769b205534c08eeac712a28f;p=cipher-tools.git diff --git a/cipherbreak.py b/cipherbreak.py index f1ab58e..7c6cea7 100644 --- a/cipherbreak.py +++ b/cipherbreak.py @@ -266,7 +266,7 @@ def vigenere_keyword_break_mp(message, wordlist=keywords, fitness=Pletters, >>> vigenere_keyword_break_mp(vigenere_encipher(sanitise('this is a test ' \ 'message for the vigenere decipherment'), 'cat'), \ wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS - ('cat', -52.947271216...) + ('cat', -52.9472712...) """ with Pool() as pool: helper_args = [(message, word, fitness) @@ -297,11 +297,11 @@ def vigenere_frequency_break(message, max_key_length=20, fitness=Pletters): "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...) + ('florence', -307.5473096...) """ def worker(message, key_length, fitness): splits = every_nth(sanitised_message, key_length) - key = cat([chr(caesar_break(s)[0] + ord('a')) for s in splits]) + key = cat([unpos(caesar_break(s)[0]) for s in splits]) plaintext = vigenere_decipher(message, key) fit = fitness(plaintext) return key, fit @@ -311,6 +311,33 @@ def vigenere_frequency_break(message, max_key_length=20, fitness=Pletters): 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 @@ -324,17 +351,111 @@ def beaufort_frequency_break(message, max_key_length=20, fitness=Pletters): ('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]) + 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([unpos(-caesar_break(s)[0]) for s in splits]) + plaintext = beaufort_variant_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 polybius_break_mp(message, column_labels, row_labels, + letters_to_merge=None, + wordlist=keywords, fitness=Pletters, + number_of_solutions=1, chunksize=500): + """Breaks a Polybius substitution cipher using a dictionary and + frequency analysis + + >>> polybius_break_mp(polybius_encipher('this is a test message for the ' \ + 'polybius decipherment', 'elephant', 'abcde', 'abcde'), \ + 'abcde', 'abcde', \ + wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE + (('elephant', , 'abcde', 'abcde', False), \ + -54.53880...) + >>> polybius_break_mp(polybius_encipher('this is a test message for the ' \ + 'polybius decipherment', 'elephant', 'abcde', 'abcde', column_first=True), \ + 'abcde', 'abcde', \ + wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE + (('elephant', , 'abcde', 'abcde', True), \ + -54.53880...) + >>> polybius_break_mp(polybius_encipher('this is a test message for the ' \ + 'polybius decipherment', 'elephant', 'abcde', 'abcde', column_first=False), \ + 'abcde', 'abcde', \ + wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE + (('elephant', , 'abcde', 'abcde', False), \ + -54.53880...) + >>> polybius_break_mp(polybius_encipher('this is a test message for the ' \ + 'polybius decipherment', 'elephant', 'abcde', 'pqrst', column_first=True), \ + 'abcde', 'pqrst', \ + wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE + (('elephant', , 'abcde', 'pqrst', True), \ + -54.53880...) + """ + if letters_to_merge is None: + letters_to_merge = {'j': 'i'} + with Pool() as pool: + helper_args = [(message, word, wrap, + column_labels, row_labels, column_first, + letters_to_merge, + fitness) + for word in wordlist + for wrap in KeywordWrapAlphabet + for column_first in [False, True]] + # Gotcha: the helper function here needs to be defined at the top level + # (limitation of Pool.starmap) + breaks = pool.starmap(polybius_break_worker, helper_args, chunksize) + if number_of_solutions == 1: + return max(breaks, key=lambda k: k[1]) + else: + return sorted(breaks, key=lambda k: k[1], reverse=True)[:number_of_solutions] + +def polybius_break_worker(message, keyword, wrap_alphabet, + column_order, row_order, column_first, + letters_to_merge, + fitness): + plaintext = polybius_decipher(message, keyword, + column_order, row_order, + column_first=column_first, + letters_to_merge=letters_to_merge, + wrap_alphabet=wrap_alphabet) + if plaintext: + fit = fitness(plaintext) + else: + fit = float('-inf') + logger.debug('Polybius break attempt using key {0} (wrap={1}, merging {2}), ' + 'columns as {3}, rows as {4} (column_first={5}) ' + 'gives fit of {6} and decrypt starting: ' + '{7}'.format(keyword, wrap_alphabet, letters_to_merge, + column_order, row_order, column_first, + fit, sanitise(plaintext)[:50])) + return (keyword, wrap_alphabet, column_order, row_order, column_first), fit + def column_transposition_break_mp(message, translist=transpositions, fitness=Pbigrams, chunksize=500):