2020-early/2020-a-challenge8.md

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  11     display_name: Python 3
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  14 ---
  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
  30 from support.text_prettify import *
  31 from support.utilities import *
  32 from support.plot_frequency_histogram import *
  33 %matplotlib inline
  34 ```
  35
  36 ```python
  37 challenge_number = 8
  38 plaintext_a_filename = f'{challenge_number}a.plaintext'
  39 plaintext_b_filename = f'{challenge_number}b.plaintext'
  40 ciphertext_a_filename = f'{challenge_number}a.ciphertext'
  41 ciphertext_b_filename = f'{challenge_number}b.ciphertext'
  42 ```
  43
  44 ```python
  45 ca = open(ciphertext_a_filename).read()
  46 cb = open(ciphertext_b_filename).read()
  47
  48 sca = sanitise(ca)
  49 pca = letters(ca)
  50 pta = depunctuate(ca)
  51
  52 scb = sanitise(cb)
  53 pcb = letters(cb)
  54 ptb = depunctuate(cb)
  55 ```
  56
  57 ```python
  58 fc = collections.Counter(sca)
  59 plot_frequency_histogram(fc, sort_key=fc.get)
  60 ```
  61
  62 ```python
  63 kworda, score = vigenere_frequency_break(sca, fitness=Ptrigrams)
  64 kworda
  65 ```
  66
  67 ```python
  68 pa = vigenere_decipher(sca, kworda)
  69 pa
  70 ```
  71
  72 ```python
  73 fpa = lcat(tpack(segment(pa)))
  74 print(fpa)
  75 ```
  76
  77 ```python
  78 open(plaintext_a_filename, 'w').write(fpa)
  79 ```
  80
  81 ```python
  82 fc = collections.Counter(scb)
  83 plot_frequency_histogram(fc, sort_key=fc.get)
  84 ```
  85
  86 ```python
  87 (kmb, kab, kob), score = affine_break(scb, fitness=Pletters)
  88 kmb, kab, kob
  89 ```
  90
  91 ```python
  92 acb = affine_decipher(scb, kmb, kab, kob)
  93 acb
  94 ```
  95
  96 ```python
  97 (kwordb, fillb, emptyb), score = column_transposition_break_mp(acb, fitness=Ptrigrams)
  98 (kwordb, fillb, emptyb), score
  99 ```
 100
 101 ```python
 102 pb = column_transposition_decipher(acb, kwordb, fillcolumnwise=fillb, emptycolumnwise=emptyb)
 103 pb
 104 ```
 105
 106 ```python
 107 fpb = lcat(tpack(segment(pb)))
 108 print(fpb)
 109 ```
 110
 111 ```python
 112 open(plaintext_b_filename, 'w').write(fpb)
 113 ```
 114
 115 ```python
 116 transpositions[kwordb]
 117 ```
 118
 119 ```python
 120
 121 ```