cipher/cadenus.py

   1 from utilities import *
   2 from language_models import *
   3 from itertools import chain
   4
   5 from logger import logger
   6
   7 def make_cadenus_keycolumn(doubled_letters = 'vw', start='a', reverse=False):
   8     """Makes the key column for a Cadenus cipher (the column down between the
   9         rows of letters)
  10
  11     >>> make_cadenus_keycolumn()['a']
  12     0
  13     >>> make_cadenus_keycolumn()['b']
  14     1
  15     >>> make_cadenus_keycolumn()['c']
  16     2
  17     >>> make_cadenus_keycolumn()['v']
  18     21
  19     >>> make_cadenus_keycolumn()['w']
  20     21
  21     >>> make_cadenus_keycolumn()['z']
  22     24
  23     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['a']
  24     1
  25     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['b']
  26     0
  27     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['c']
  28     24
  29     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['i']
  30     18
  31     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['j']
  32     18
  33     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['v']
  34     6
  35     >>> make_cadenus_keycolumn(doubled_letters='ij', start='b', reverse=True)['z']
  36     2
  37     """
  38     index_to_remove = string.ascii_lowercase.find(doubled_letters[0])
  39     short_alphabet = string.ascii_lowercase[:index_to_remove] + string.ascii_lowercase[index_to_remove+1:]
  40     if reverse:
  41         short_alphabet = cat(reversed(short_alphabet))
  42     start_pos = short_alphabet.find(start)
  43     rotated_alphabet = short_alphabet[start_pos:] + short_alphabet[:start_pos]
  44     keycolumn = {l: i for i, l in enumerate(rotated_alphabet)}
  45     keycolumn[doubled_letters[0]] = keycolumn[doubled_letters[1]]
  46     return keycolumn
  47
  48 def cadenus_encipher(message, keyword, keycolumn, fillvalue='a'):
  49     """Encipher with the Cadenus cipher
  50
  51     >>> cadenus_encipher(sanitise('Whoever has made a voyage up the Hudson ' \
  52                                   'must remember the Kaatskill mountains. ' \
  53                                   'They are a dismembered branch of the great'), \
  54                 'wink', \
  55                 make_cadenus_keycolumn(doubled_letters='vw', start='a', reverse=True))
  56     'antodeleeeuhrsidrbhmhdrrhnimefmthgeaetakseomehetyaasuvoyegrastmmuuaeenabbtpchehtarorikswosmvaleatned'
  57     >>> cadenus_encipher(sanitise('a severe limitation on the usefulness of ' \
  58                                   'the cadenus is that every message must be ' \
  59                                   'a multiple of twenty-five letters long'), \
  60                 'easy', \
  61                 make_cadenus_keycolumn(doubled_letters='vw', start='a', reverse=True))
  62     'systretomtattlusoatleeesfiyheasdfnmschbhneuvsnpmtofarenuseieeieltarlmentieetogevesitfaisltngeeuvowul'
  63     """
  64     rows = chunks(message, len(message) // 25, fillvalue=fillvalue)
  65     columns = zip(*rows)
  66     rotated_columns = [col[start:] + col[:start] for start, col in zip([keycolumn[l] for l in keyword], columns)]
  67     rotated_rows = zip(*rotated_columns)
  68     transpositions = transpositions_of(keyword)
  69     transposed = [transpose(r, transpositions) for r in rotated_rows]
  70     return cat(chain(*transposed))
  71
  72 def cadenus_decipher(message, keyword, keycolumn, fillvalue='a'):
  73     """
  74     >>> cadenus_decipher('antodeleeeuhrsidrbhmhdrrhnimefmthgeaetakseomehetyaa' \
  75                          'suvoyegrastmmuuaeenabbtpchehtarorikswosmvaleatned', \
  76                  'wink', \
  77                  make_cadenus_keycolumn(reverse=True))
  78     'whoeverhasmadeavoyageupthehudsonmustrememberthekaatskillmountainstheyareadismemberedbranchofthegreat'
  79     >>> cadenus_decipher('systretomtattlusoatleeesfiyheasdfnmschbhneuvsnpmtof' \
  80                         'arenuseieeieltarlmentieetogevesitfaisltngeeuvowul', \
  81                  'easy', \
  82                  make_cadenus_keycolumn(reverse=True))
  83     'aseverelimitationontheusefulnessofthecadenusisthateverymessagemustbeamultipleoftwentyfiveletterslong'
  84     """
  85     rows = chunks(message, len(message) // 25, fillvalue=fillvalue)
  86     transpositions = transpositions_of(keyword)
  87     untransposed_rows = [untranspose(r, transpositions) for r in rows]
  88     columns = zip(*untransposed_rows)
  89     rotated_columns = [col[-start:] + col[:-start] for start, col in zip([keycolumn[l] for l in keyword], columns)]
  90     rotated_rows = zip(*rotated_columns)
  91     # return rotated_columns
  92     return cat(chain(*rotated_rows))
  93
  94 if __name__ == "__main__":
  95     import doctest