+ 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 column_transposition_break_mp(message, translist=transpositions,
+ fitness=Pbigrams, chunksize=500):
+ """Breaks a column transposition cipher using a dictionary and
+ n-gram frequency analysis
+
+ >>> column_transposition_break_mp(column_transposition_encipher(sanitise( \
+ "It is a truth universally acknowledged, that a single man in \
+ possession of a good fortune, must be in want of a wife. However \
+ little known the feelings or views of such a man may be on his \
+ first entering a neighbourhood, this truth is so well fixed in \
+ the minds of the surrounding families, that he is considered the \
+ rightful property of some one or other of their daughters."), \
+ 'encipher'), \
+ translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
+ (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
+ (6, 1, 0, 4, 5, 3, 2): ['keyword']}) # doctest: +ELLIPSIS
+ (((2, 0, 5, 3, 1, 4, 6), False, False), -709.4646722...)
+ >>> column_transposition_break_mp(column_transposition_encipher(sanitise( \
+ "It is a truth universally acknowledged, that a single man in \
+ possession of a good fortune, must be in want of a wife. However \
+ little known the feelings or views of such a man may be on his \
+ first entering a neighbourhood, this truth is so well fixed in \
+ the minds of the surrounding families, that he is considered the \
+ rightful property of some one or other of their daughters."), \
+ 'encipher'), \
+ translist={(2, 0, 5, 3, 1, 4, 6): ['encipher'], \
+ (5, 0, 6, 1, 3, 4, 2): ['fourteen'], \
+ (6, 1, 0, 4, 5, 3, 2): ['keyword']}, \
+ fitness=Ptrigrams) # doctest: +ELLIPSIS
+ (((2, 0, 5, 3, 1, 4, 6), False, False), -997.0129085...)
+ """
+ with Pool() as pool:
+ helper_args = [(message, trans, fillcolumnwise, emptycolumnwise,
+ fitness)
+ for trans in translist
+ for fillcolumnwise in [True, False]
+ for emptycolumnwise in [True, False]]
+ # 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 max(breaks, key=lambda k: k[1])
+column_transposition_break = column_transposition_break_mp
+
+def column_transposition_break_worker(message, transposition,
+ fillcolumnwise, emptycolumnwise, fitness):
+ plaintext = column_transposition_decipher(message, transposition,
+ fillcolumnwise=fillcolumnwise, emptycolumnwise=emptycolumnwise)
+ fit = fitness(sanitise(plaintext))
+ logger.debug('Column transposition break attempt using key {0} '
+ 'gives fit of {1} and decrypt starting: {2}'.format(
+ transposition, fit,
+ sanitise(plaintext)[:50]))
+ return (transposition, fillcolumnwise, emptycolumnwise), fit
+
+
+def scytale_break_mp(message, max_key_length=20,
+ fitness=Pbigrams, chunksize=500):
+ """Breaks a scytale cipher using a range of lengths and
+ n-gram frequency analysis
+
+ >>> scytale_break_mp(scytale_encipher(sanitise( \
+ "It is a truth universally acknowledged, that a single man in \
+ possession of a good fortune, must be in want of a wife. However \
+ little known the feelings or views of such a man may be on his \
+ first entering a neighbourhood, this truth is so well fixed in \
+ the minds of the surrounding families, that he is considered the \
+ rightful property of some one or other of their daughters."), \
+ 5)) # doctest: +ELLIPSIS
+ (5, -709.4646722...)
+ >>> scytale_break_mp(scytale_encipher(sanitise( \
+ "It is a truth universally acknowledged, that a single man in \
+ possession of a good fortune, must be in want of a wife. However \
+ little known the feelings or views of such a man may be on his \
+ first entering a neighbourhood, this truth is so well fixed in \
+ the minds of the surrounding families, that he is considered the \
+ rightful property of some one or other of their daughters."), \
+ 5), \
+ fitness=Ptrigrams) # doctest: +ELLIPSIS
+ (5, -997.0129085...)
+ """
+ with Pool() as pool:
+ helper_args = [(message, trans, False, True, fitness)
+ for trans in
+ [[col for col in range(math.ceil(len(message)/rows))]
+ for rows in range(1,max_key_length+1)]]
+ # 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)
+ best = max(breaks, key=lambda k: k[1])
+ return math.trunc(len(message) / len(best[0][0])), best[1]
+scytale_break = scytale_break_mp
+
+
+def railfence_break(message, max_key_length=20,
+ fitness=Pletters, chunksize=500):
+ """Breaks a hill cipher using a matrix of given rank and letter frequencies
+
+
+ """
+
+ sanitised_message = sanitise(message)
+ results = starmap(worker, [(sanitised_message, i, fitness)
+ for i in range(2, max_key_length+1)])
+ return max(results, key=lambda k: k[1])
+
+
+def railfence_break(message, max_key_length=20,
+ fitness=Pbigrams, chunksize=500):
+ """Breaks a railfence cipher using a range of lengths and
+ n-gram frequency analysis
+
+ >>> railfence_break(railfence_encipher(sanitise( \
+ "It is a truth universally acknowledged, that a single man in \
+ possession of a good fortune, must be in want of a wife. However \
+ little known the feelings or views of such a man may be on his \
+ first entering a neighbourhood, this truth is so well fixed in \
+ the minds of the surrounding families, that he is considered the \
+ rightful property of some one or other of their daughters."), \
+ 7)) # doctest: +ELLIPSIS
+ (7, -709.46467226...)
+ >>> railfence_break(railfence_encipher(sanitise( \
+ "It is a truth universally acknowledged, that a single man in \
+ possession of a good fortune, must be in want of a wife. However \
+ little known the feelings or views of such a man may be on his \
+ first entering a neighbourhood, this truth is so well fixed in \
+ the minds of the surrounding families, that he is considered the \
+ rightful property of some one or other of their daughters."), \
+ 7), \
+ fitness=Ptrigrams) # doctest: +ELLIPSIS
+ (7, -997.0129085...)
+ """
+ def worker(message, height, fitness):
+ plaintext = railfence_decipher(message, height)