2020-early/2020-a-challenge9.md

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  11     display_name: Python 3
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  15
  16 ```python
  17 import os,sys,inspect
  18 currentdir = os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))
  19 parentdir = os.path.dirname(currentdir)
  20 sys.path.insert(0,parentdir)
  21 ```
  22
  23 ```python
  24 from cipher.caesar import *
  25 from cipher.affine import *
  26 from cipher.keyword_cipher import *
  27 from cipher.column_transposition import *
  28 from cipher.vigenere import *
  29 from cipher.autokey import *
  30
  31 from support.text_prettify import *
  32 from support.utilities import *
  33 from support.plot_frequency_histogram import *
  34 %matplotlib inline
  35 ```
  36
  37 ```python
  38 challenge_number = 9
  39 plaintext_a_filename = f'{challenge_number}a.plaintext'
  40 plaintext_b_filename = f'{challenge_number}b.plaintext'
  41 ciphertext_a_filename = f'{challenge_number}a.ciphertext'
  42 ciphertext_b_filename = f'{challenge_number}b.ciphertext'
  43 ```
  44
  45 ```python
  46 ca = open(ciphertext_a_filename).read()
  47 cb = open(ciphertext_b_filename).read()
  48
  49 sca = sanitise(ca)
  50 pca = letters(ca)
  51 pta = depunctuate(ca)
  52
  53 scb = sanitise(cb)
  54 pcb = letters(cb)
  55 ptb = depunctuate(cb)
  56 ```
  57
  58 ```python
  59 fc = collections.Counter(sca)
  60 plot_frequency_histogram(fc, sort_key=fc.get)
  61 ```
  62
  63 ```python
  64 kworda, score = vigenere_frequency_break(sca, fitness=Ptrigrams)
  65 kworda
  66 ```
  67
  68 ```python
  69 pa = vigenere_decipher(sca, kworda)
  70 pa
  71 ```
  72
  73 ```python
  74 fpa = lcat(tpack(segment(pa)))
  75 print(fpa)
  76 ```
  77
  78 ```python
  79 open(plaintext_a_filename, 'w').write(fpa)
  80 ```
  81
  82 ```python
  83 morse_letters = {}
  84 morse_codes = {}
  85 with open('morse.txt') as f:
  86     for line in f.readlines():
  87         l, c = line.split()
  88         morse_letters[c] = l
  89         morse_codes[l] = c
  90 morse_letters
  91 ```
  92
  93 ```python
  94 mcb = wcat(cat(morse_letters[l] for l in w.split()) for w in cb.split(' / '))
  95 smcb = sanitise(mcb)
  96 mcb
  97 ```
  98
  99 ```python
 100 fc = collections.Counter(sanitise(mcb))
 101 plot_frequency_histogram(fc, sort_key=fc.get)
 102 ```
 103
 104 ```python
 105 index_of_coincidence_scan(smcb, max_key_length=30)
 106 ```
 107
 108 ```python
 109 kwordb, score = vigenere_frequency_break(smcb, fitness=Ptrigrams, max_key_length=30)
 110 kwordb
 111 ```
 112
 113 ```python
 114 kwordb, score = autokey_sa_break(smcb, fitness=Ptrigrams, max_keylength=10, max_iterations=5000)
 115 kwordb
 116 ```
 117
 118 ```python
 119 autokey_decipher(smcb, kwordb)
 120 ```
 121
 122 ```python
 123 tgs = [smcb[i:i+3] for i in range(len(smcb)-2)]
 124 collections.Counter(tgs).most_common(10)
 125 ```
 126
 127 ```python
 128 wcat(w for w in mcb.split() if len(w) == 3)
 129 ```
 130
 131 ```python
 132 wcat(w if len(w) >= 3 and w.lower() in keywords else w.lower()
 133      for w in mcb.split())
 134 ```
 135
 136 ```python
 137 [(i, w) for i, w in enumerate(mcb.split())
 138  if len(w) >= 3
 139  if w.lower() in keywords ]
 140 ```
 141
 142 ```python
 143 [(i, w) for i, w in enumerate(mcb.split())
 144  if i % 26 == 25 ]
 145 ```
 146
 147 ```python
 148 pb = wcat(caesar_decipher(w, i + 1) for i, w in enumerate(mcb.split()))
 149 pb
 150 ```
 151
 152 ```python
 153 open(plaintext_b_filename, 'w').write(pb)
 154 ```
 155
 156 ```python
 157
 158 ```