2020/2020-challenge6.md

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  11     display_name: Python 3
  12     language: python
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  14 ---
  15
  16 ```python Collapsed="false"
  17 from szyfrow.keyword_cipher import *
  18 from szyfrow.column_transposition import *
  19 from szyfrow.vigenere import *
  20 from szyfrow.support.text_prettify import *
  21 from szyfrow.polybius import *
  22 import collections
  23 ```
  24
  25 ```python Collapsed="false"
  26 challenge_number = 6
  27 plaintext_a_filename = f'plaintext.{challenge_number}a.txt'
  28 plaintext_b_filename = f'plaintext.{challenge_number}b.txt'
  29 ciphertext_a_filename = f'ciphertext.{challenge_number}a.txt'
  30 ciphertext_b_filename = f'ciphertext.{challenge_number}b.txt'
  31 ```
  32
  33 ```python Collapsed="false"
  34 ca = open(ciphertext_a_filename).read()
  35 sca = sanitise(ca)
  36 rsca = cat(reversed(sca))
  37 cb = open(ciphertext_b_filename).read()
  38 scb = sanitise(cb)
  39 ```
  40
  41 ```python Collapsed="false"
  42 fc = collections.Counter(sca)
  43 plot_frequency_histogram(fc, sort_key=fc.get)
  44 ```
  45
  46 ```python Collapsed="false"
  47 (word_a, wrap_a), score_a = keyword_break_mp(rsca, fitness=Pletters)
  48 print(word_a, wrap_a, '\n')
  49 pa = keyword_decipher(ca, word_a, wrap_a)
  50 print(pa)
  51 ```
  52
  53 ```python Collapsed="false"
  54 key_a, score_a = vigenere_frequency_break(sca, fitness=Ptrigrams)
  55 print(key_a, '\n')
  56 pa = vigenere_decipher(sca, key_a)
  57 print(pa)
  58 ```
  59
  60 ```python Collapsed="false"
  61 pa = prettify(vigenere_decipher(sca, key_a))
  62 print(pa)
  63 ```
  64
  65 ```python Collapsed="false"
  66 open(plaintext_a_filename, 'w').write(pa)
  67 ```
  68
  69 ```python Collapsed="false"
  70 tscb = column_transposition_decipher(scb, 'rdf', fillcolumnwise=False, emptycolumnwise=True)
  71 tscb
  72 ```
  73
  74 ```python Collapsed="false"
  75 ptscb = polybius_decipher(tscb, 'a', 'adfgvx', 'adfgvx', wrap_alphabet=KeywordWrapAlphabet.from_last)
  76 ptscb
  77 ```
  78
  79 ```python Collapsed="false"
  80 word_b, score_b = simulated_annealing_break(ptscb, fitness=Ptrigrams,
  81         plain_alphabet=string.ascii_lowercase, cipher_alphabet=keyword_cipher_alphabet_of('rdf', wrap_alphabet=KeywordWrapAlphabet.from_largest))
  82 print(word_b, '\n')
  83 pb = keyword_decipher(ptscb, word_b)
  84 print(pb)
  85 ```
  86
  87 ```python Collapsed="false"
  88 ppb = prettify(pb)
  89 print(ppb)
  90 ```
  91
  92 ```python Collapsed="false"
  93 open(plaintext_b_filename, 'w').write(ppb)
  94 ```
  95
  96 ```python Collapsed="false"
  97
  98 ```