2020-early/2020-a-challenge4.md

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  11     display_name: Python 3
  12     language: python
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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
  28 from support.text_prettify import *
  29 from support.utilities import *
  30 from support.plot_frequency_histogram import *
  31 %matplotlib inline
  32 ```
  33
  34 ```python
  35 challenge_number = 4
  36 plaintext_a_filename = f'{challenge_number}a.plaintext'
  37 plaintext_b_filename = f'{challenge_number}b.plaintext'
  38 ciphertext_a_filename = f'{challenge_number}a.ciphertext'
  39 ciphertext_b_filename = f'{challenge_number}b.ciphertext'
  40 ```
  41
  42 ```python
  43 ca = open(ciphertext_a_filename).read()
  44 cb = open(ciphertext_b_filename).read()
  45
  46 sca = sanitise(ca)
  47 pca = letters(ca)
  48 pta = depunctuate(ca)
  49
  50 scb = sanitise(cb)
  51 pcb = letters(cb)
  52 ptb = depunctuate(cb)
  53 ```
  54
  55 ```python
  56 kshifta, score = caesar_break(sca, fitness=Ptrigrams)
  57 kshifta
  58 ```
  59
  60 ```python
  61 pa = caesar_decipher(sca, kshifta)
  62 print(pa)
  63 ```
  64
  65 ```python
  66 fpa = lcat(tpack(segment(pa)))
  67 print(fpa)
  68 ```
  69
  70 ```python
  71 open(plaintext_a_filename, 'w').write(fpa)
  72 ```
  73
  74 ```python
  75 fc = collections.Counter(scb)
  76 plot_frequency_histogram(fc, sort_key=fc.get)
  77 ```
  78
  79 ```python
  80 (kwordb, kwrapb), score = keyword_break_mp(scb, fitness=Ptrigrams)
  81 kwordb, kwrapb
  82 ```
  83
  84 ```python
  85 kwordb, score = simulated_annealing_break(scb, fitness=Ptrigrams)
  86 kwordb
  87 ```
  88
  89 ```python
  90 print(keyword_decipher(cb, kwordb))
  91 ```
  92
  93 ```python
  94 pb = keyword_decipher(cb, 'heavywater', KeywordWrapAlphabet.from_last)
  95 print(pb)
  96 ```
  97
  98 ```python
  99 open(plaintext_b_filename, 'w').write(pb)
 100 ```
 101
 102 ```python
 103 print(keyword_cipher_alphabet_of('heavywater', KeywordWrapAlphabet.from_last))
 104 print(kwordb)
 105 ```
 106
 107 ```python
 108
 109 ```