- >>> scytale_break('tfeulchtrtteehwahsdehneoifeayfsondmwpltmaoalhikotoere' \
- 'dcweatehiplwxsnhooacgorrcrcraotohsgullasenylrendaianeplscdriioto' \
- 'aek') # doctest: +ELLIPSIS
- (6, 0.83453041115025...)
- """
- best_key = 0
- best_fit = float("inf")
- ngram_length = len(next(iter(target_counts.keys())))
- for key in range(1, 20):
- if len(message) % key == 0:
- plaintext = scytale_decipher(message, key)
- counts = message_frequency_scaling(frequencies(
- ngrams(sanitise(plaintext), ngram_length)))
- fit = metric(target_counts, counts)
- logger.debug('Scytale break attempt using key {0} gives fit of '
- '{1} and decrypt starting: {2}'.format(key,
- fit, sanitise(plaintext)[:50]))
- if fit < best_fit:
- best_fit = fit
- best_key = key
- logger.info('Scytale break best fit with key {0} gives fit of {1} and '
- 'decrypt starting: {2}'.format(best_key, best_fit,
- sanitise(scytale_decipher(message, best_key))[:50]))
- return best_key, best_fit
-
-def column_transposition_break(message,
- wordlist=keywords,
- metric=norms.euclidean_distance,
- target_counts=normalised_english_bigram_counts,
- message_frequency_scaling=norms.normalise):
- """Breaks a column transposition cipher using a dictionary and
- n-gram frequency analysis
-
- >>> column_transposition_break(column_transposition_encipher(sanitise( \
- "Turing's homosexuality resulted in a criminal prosecution in 1952, \
- when homosexual acts were still illegal in the United Kingdom. "), \
- 'encipher'), \
- wordlist=['encipher', 'keyword', 'fourteen']) # doctest: +ELLIPSIS
- ('encipher', 0.898128626285...)
- >>> column_transposition_break(column_transposition_encipher(sanitise( \
- "Turing's homosexuality resulted in a criminal prosecution in 1952, " \
- "when homosexual acts were still illegal in the United Kingdom."), \
- 'encipher'), \
- wordlist=['encipher', 'keyword', 'fourteen'], \
- target_counts=normalised_english_trigram_counts) # doctest: +ELLIPSIS
- ('encipher', 1.1958792913127...)
- """
- best_keyword = ''
- best_fit = float("inf")
- ngram_length = len(next(iter(target_counts.keys())))
- for keyword in wordlist:
- if len(message) % len(deduplicate(keyword)) == 0:
- plaintext = column_transposition_decipher(message, keyword)
- counts = message_frequency_scaling(frequencies(
- ngrams(sanitise(plaintext), ngram_length)))
- fit = metric(target_counts, counts)
- logger.debug('Column transposition break attempt using key {0} '
- 'gives fit of {1} and decrypt starting: {2}'.format(
- keyword, fit,
- sanitise(plaintext)[:50]))
- if fit < best_fit:
- best_fit = fit
- best_keyword = keyword
- logger.info('Column transposition break best fit with key {0} gives fit '
- 'of {1} and decrypt starting: {2}'.format(best_keyword,
- best_fit, sanitise(
- column_transposition_decipher(message,
- best_keyword))[:50]))
- return best_keyword, best_fit
-
-
-def column_transposition_break_mp(message,
- wordlist=keywords,
- metric=norms.euclidean_distance,
- target_counts=normalised_english_bigram_counts,
- message_frequency_scaling=norms.normalise,
- chunksize=500):
- """Breaks a column transposition cipher using a dictionary and
- n-gram frequency analysis
-
- >>> column_transposition_break_mp(column_transposition_encipher(sanitise( \
- "Turing's homosexuality resulted in a criminal prosecution in 1952, \
- when homosexual acts were still illegal in the United Kingdom. "), \
- 'encipher'), \
- wordlist=['encipher', 'keyword', 'fourteen']) # doctest: +ELLIPSIS
- ('encipher', 0.898128626285...)
- >>> column_transposition_break_mp(column_transposition_encipher(sanitise( \
- "Turing's homosexuality resulted in a criminal prosecution in 1952, " \
- "when homosexual acts were still illegal in the United Kingdom."), \
- 'encipher'), \
- wordlist=['encipher', 'keyword', 'fourteen'], \
- target_counts=normalised_english_trigram_counts) # doctest: +ELLIPSIS
- ('encipher', 1.1958792913127...)
- """
- ngram_length = len(next(iter(target_counts.keys())))
- with Pool() as pool:
- helper_args = [(message, word, metric, target_counts, ngram_length,
- message_frequency_scaling)
- for word in wordlist]
- # Gotcha: the helper function here needs to be defined at the top level
- # (limitation of Pool.starmap)
- breaks = pool.starmap(column_transposition_break_worker, helper_args, chunksize)
- return min(breaks, key=lambda k: k[1])
-
-def column_transposition_break_worker(message, keyword, metric, target_counts,
- ngram_length, message_frequency_scaling):
- plaintext = column_transposition_decipher(message, keyword)
- counts = message_frequency_scaling(frequencies(
- ngrams(sanitise(plaintext), ngram_length)))
- fit = metric(target_counts, counts)
- logger.debug('Column transposition break attempt using key {0} '
- 'gives fit of {1} and decrypt starting: {2}'.format(
- keyword, fit,
- sanitise(plaintext)[:50]))
- return keyword, fit
-
-def vigenere_keyword_break(message,
- wordlist=keywords,
- metric=norms.euclidean_distance,
- target_counts=normalised_english_counts,
- message_frequency_scaling=norms.normalise):
- """Breaks a vigenere cipher using a dictionary and
- frequency analysis
-
- >>> vigenere_keyword_break(keyword_encipher('this is a test message for the ' \
- 'keyword decipherment', 'elephant', 1), \
- wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
- ('elephant', 0.7166585201707...)
- """
- best_keyword = ''
- best_fit = float("inf")
- for keyword in wordlist:
- plaintext = vigenere_decipher(message, keyword)
- counts = message_frequency_scaling(letter_frequencies(plaintext))
- fit = metric(target_counts, counts)
- logger.debug('Vigenere break attempt using key {0} '
- 'gives fit of {1} and decrypt starting: {2}'.format(
- keyword, fit,
- sanitise(plaintext)[:50]))
- if fit < best_fit:
- best_fit = fit
- best_keyword = keyword
- logger.info('Vigenere break best fit with key {0} gives fit '
- 'of {1} and decrypt starting: {2}'.format(best_keyword,
- best_fit, sanitise(
- vigenere_decipher(message, best_keyword))[:50]))
- return best_keyword, best_fit
-
-def vigenere_keyword_break_mp(message,
- wordlist=keywords,
- metric=norms.euclidean_distance,
- target_counts=normalised_english_counts,
- message_frequency_scaling=norms.normalise,
- chunksize=500):
- """Breaks a vigenere cipher using a dictionary and
- frequency analysis
-
- >>> vigenere_keyword_break_mp(keyword_encipher('this is a test message for the ' \
- 'keyword decipherment', 'elephant', 1), \
- wordlist=['cat', 'elephant', 'kangaroo']) # doctest: +ELLIPSIS
- ('elephant', 0.7166585201707...)
- """
- with Pool() as pool:
- helper_args = [(message, word, metric, target_counts,
- message_frequency_scaling)
- for word in wordlist]
- # Gotcha: the helper function here needs to be defined at the top level
- # (limitation of Pool.starmap)
- breaks = pool.starmap(vigenere_keyword_break_worker, helper_args, chunksize)
- return min(breaks, key=lambda k: k[1])
-
-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))
- fit = metric(target_counts, counts)
- logger.debug('Vigenere keyword break attempt using key {0} gives fit of '
- '{1} and decrypt starting: {2}'.format(keyword,
- fit, sanitise(plaintext)[:50]))
- return keyword, fit
-
+ t_message = message.translate(translation)
+ pairs0 = [f_grid[l] for l in sanitise(t_message)]
+ if period:
+ chunked_pairs = [pairs0[i:i+period] for i in range(0, len(pairs0), period)]
+ if len(chunked_pairs[-1]) < period and fillvalue:
+ chunked_pairs[-1] += [f_grid[fillvalue]] * (period - len(chunked_pairs[-1]))
+ else:
+ chunked_pairs = [pairs0]
+
+ pairs1 = []
+ for c in chunked_pairs:
+ items = [j for i in c for j in i]
+ gap = len(c)
+ p = [(items[i], items[i+gap]) for i in range(gap)]
+ pairs1 += p
+
+ return cat(r_grid[p] for p in pairs1)
+
+
+def autokey_encipher(message, keyword):
+ """Encipher with the autokey cipher
+
+ >>> autokey_encipher('meetatthefountain', 'kilt')
+ 'wmpmmxxaeyhbryoca'
+ """
+ shifts = [pos(l) for l in keyword + message]
+ pairs = zip(message, shifts)
+ return cat([caesar_encipher_letter(l, k) for l, k in pairs])
+
+def autokey_decipher(ciphertext, keyword):
+ """Decipher with the autokey cipher
+
+ >>> autokey_decipher('wmpmmxxaeyhbryoca', 'kilt')
+ 'meetatthefountain'
+ """
+ plaintext = []
+ keys = list(keyword)
+ for c in ciphertext:
+ plaintext_letter = caesar_decipher_letter(c, pos(keys[0]))
+ plaintext += [plaintext_letter]
+ keys = keys[1:] + [plaintext_letter]
+ return cat(plaintext)
+
+
+class PocketEnigma(object):
+ """A pocket enigma machine
+ The wheel is internally represented as a 26-element list self.wheel_map,
+ where wheel_map[i] == j shows that the position i places on from the arrow
+ maps to the position j places on.
+ """
+ def __init__(self, wheel=1, position='a'):
+ """initialise the pocket enigma, including which wheel to use and the
+ starting position of the wheel.
+
+ The wheel is either 1 or 2 (the predefined wheels) or a list of letter
+ pairs.
+
+ The position is the letter pointed to by the arrow on the wheel.
+
+ >>> pe.wheel_map
+ [25, 4, 23, 10, 1, 7, 9, 5, 12, 6, 3, 17, 8, 14, 13, 21, 19, 11, 20, 16, 18, 15, 24, 2, 22, 0]
+ >>> pe.position
+ 0
+ """
+ self.wheel1 = [('a', 'z'), ('b', 'e'), ('c', 'x'), ('d', 'k'),
+ ('f', 'h'), ('g', 'j'), ('i', 'm'), ('l', 'r'), ('n', 'o'),
+ ('p', 'v'), ('q', 't'), ('s', 'u'), ('w', 'y')]
+ self.wheel2 = [('a', 'c'), ('b', 'd'), ('e', 'w'), ('f', 'i'),
+ ('g', 'p'), ('h', 'm'), ('j', 'k'), ('l', 'n'), ('o', 'q'),
+ ('r', 'z'), ('s', 'u'), ('t', 'v'), ('x', 'y')]
+ if wheel == 1:
+ self.make_wheel_map(self.wheel1)
+ elif wheel == 2:
+ self.make_wheel_map(self.wheel2)
+ else:
+ self.validate_wheel_spec(wheel)
+ self.make_wheel_map(wheel)
+ if position in string.ascii_lowercase:
+ self.position = pos(position)
+ else:
+ self.position = position
+
+ def make_wheel_map(self, wheel_spec):
+ """Expands a wheel specification from a list of letter-letter pairs
+ into a full wheel_map.
+
+ >>> pe.make_wheel_map(pe.wheel2)
+ [2, 3, 0, 1, 22, 8, 15, 12, 5, 10, 9, 13, 7, 11, 16, 6, 14, 25, 20, 21, 18, 19, 4, 24, 23, 17]
+ """
+ self.validate_wheel_spec(wheel_spec)
+ self.wheel_map = [0] * 26
+ for p in wheel_spec:
+ self.wheel_map[pos(p[0])] = pos(p[1])
+ self.wheel_map[pos(p[1])] = pos(p[0])
+ return self.wheel_map
+
+ def validate_wheel_spec(self, wheel_spec):
+ """Validates that a wheel specificaiton will turn into a valid wheel
+ map.
+
+ >>> pe.validate_wheel_spec([])
+ Traceback (most recent call last):
+ ...
+ ValueError: Wheel specification has 0 pairs, requires 13
+ >>> pe.validate_wheel_spec([('a', 'b', 'c')]*13)
+ Traceback (most recent call last):
+ ...
+ ValueError: Not all mappings in wheel specificationhave two elements
+ >>> pe.validate_wheel_spec([('a', 'b')]*13)
+ Traceback (most recent call last):
+ ...
+ ValueError: Wheel specification does not contain 26 letters
+ """
+ if len(wheel_spec) != 13:
+ raise ValueError("Wheel specification has {} pairs, requires 13".
+ format(len(wheel_spec)))
+ for p in wheel_spec:
+ if len(p) != 2:
+ raise ValueError("Not all mappings in wheel specification"
+ "have two elements")
+ if len(set([p[0] for p in wheel_spec] +
+ [p[1] for p in wheel_spec])) != 26:
+ raise ValueError("Wheel specification does not contain 26 letters")
+
+ def encipher_letter(self, letter):
+ """Enciphers a single letter, by advancing the wheel before looking up
+ the letter on the wheel.
+
+ >>> pe.set_position('f')
+ 5
+ >>> pe.encipher_letter('k')
+ 'h'
+ """
+ self.advance()
+ return self.lookup(letter)
+ decipher_letter = encipher_letter
+
+ def lookup(self, letter):
+ """Look up what a letter enciphers to, without turning the wheel.
+
+ >>> pe.set_position('f')
+ 5
+ >>> cat([pe.lookup(l) for l in string.ascii_lowercase])
+ 'udhbfejcpgmokrliwntsayqzvx'
+ >>> pe.lookup('A')
+ ''
+ """
+ if letter in string.ascii_lowercase:
+ return unpos(
+ (self.wheel_map[(pos(letter) - self.position) % 26] +
+ self.position))
+ else:
+ return ''
+
+ def advance(self):
+ """Advances the wheel one position.
+
+ >>> pe.set_position('f')
+ 5
+ >>> pe.advance()
+ 6
+ """
+ self.position = (self.position + 1) % 26
+ return self.position
+
+ def encipher(self, message, starting_position=None):
+ """Enciphers a whole message.
+
+ >>> pe.set_position('f')
+ 5
+ >>> pe.encipher('helloworld')
+ 'kjsglcjoqc'
+ >>> pe.set_position('f')
+ 5
+ >>> pe.encipher('kjsglcjoqc')
+ 'helloworld'
+ >>> pe.encipher('helloworld', starting_position = 'x')
+ 'egrekthnnf'
+ """
+ if starting_position:
+ self.set_position(starting_position)
+ transformed = ''
+ for l in message:
+ transformed += self.encipher_letter(l)
+ return transformed
+ decipher = encipher
+
+ def set_position(self, position):
+ """Sets the position of the wheel, by specifying the letter the arrow
+ points to.
+
+ >>> pe.set_position('a')
+ 0
+ >>> pe.set_position('m')
+ 12
+ >>> pe.set_position('z')
+ 25
+ """
+ self.position = pos(position)
+ return self.position