2020-early/2020-a-challenge5.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
  29 from support.text_prettify import *
  30 from support.utilities import *
  31 from support.plot_frequency_histogram import *
  32 %matplotlib inline
  33 ```
  34
  35 ```python
  36 challenge_number = 5
  37 plaintext_a_filename = f'{challenge_number}a.plaintext'
  38 plaintext_b_filename = f'{challenge_number}b.plaintext'
  39 ciphertext_a_filename = f'{challenge_number}a.ciphertext'
  40 ciphertext_b_filename = f'{challenge_number}b.ciphertext'
  41 ```
  42
  43 ```python
  44 ca = open(ciphertext_a_filename).read()
  45 cb = open(ciphertext_b_filename).read()
  46
  47 sca = sanitise(ca)
  48 pca = letters(ca)
  49 pta = depunctuate(ca)
  50
  51 scb = sanitise(cb)
  52 pcb = letters(cb)
  53 ptb = depunctuate(cb)
  54 ```
  55
  56 ```python
  57 fc = collections.Counter(sca)
  58 plot_frequency_histogram(fc, sort_key=fc.get)
  59 ```
  60
  61 ```python
  62 kshifta, score = caesar_break(sca, fitness=Ptrigrams)
  63 kshifta
  64 ```
  65
  66 ```python
  67 pa = caesar_decipher(sca, kshifta)
  68 print(pa)
  69 ```
  70
  71 ```python
  72 (kworda, kwrapa), score = keyword_break_mp(sca, fitness=Ptrigrams)
  73 kworda, kwrapa
  74 ```
  75
  76 ```python
  77 pa = keyword_decipher(sca, kworda, kwrapa)
  78 print(pa)
  79 ```
  80
  81 ```python
  82 fpa = lcat(tpack(segment(pa)))
  83 print(fpa)
  84 ```
  85
  86 ```python
  87 open(plaintext_a_filename, 'w').write(fpa)
  88 ```
  89
  90 ```python
  91 fc = collections.Counter(scb)
  92 plot_frequency_histogram(fc, sort_key=fc.get)
  93 ```
  94
  95 ```python
  96 rscb = cat(reversed(cb))
  97 rscb
  98 ```
  99
 100 ```python
 101 (kwordb, fillb, emptyb), score = column_transposition_break_mp(scb, fitness=Ptrigrams)
 102 (kwordb, fillb, emptyb), score
 103 ```
 104
 105 ```python
 106 pb = column_transposition_decipher(scb, kwordb, fillcolumnwise=fillb, emptycolumnwise=emptyb)
 107 pb
 108 ```
 109
 110 ```python
 111 fpb = lcat(tpack(segment(pb)))
 112 print(fpb)
 113 ```
 114
 115 ```python
 116 open(plaintext_b_filename, 'w').write(fpb)
 117 ```
 118
 119 ```python
 120 transpositions[kwordb]
 121 ```
 122
 123 ```python
 124
 125 ```