vendor/plugins/rubyzip-0.9.1/lib/quiz1/t/solutions/James Edward Gray II/solitaire.rb

   1 #!/usr/bin/ruby -w
   2
   3 $deck = (1..52).to_a + ["A", "B"]               # Unkeyed deck - Keystream Step 1
   4
   5 def encrypt(message)
   6         # Step 1
   7         message = message.upcase.tr("^A-Z", "")
   8         i = 5
   9         while i < message.size
  10                 message[i, 0] = " "
  11                 i += 6
  12         end
  13         message += "X" while message.rindex(" ") != message.size - 6
  14
  15         # Step 2
  16         key_stream = generate(message.count("^ "))
  17
  18         # Step 3
  19         values = message.split("").map { |letter| letter[0] - ?A + 1 }
  20
  21         # Step 4
  22         key_values = key_stream.split("").map { |letter| letter[0] - ?A + 1 }
  23
  24         # Step 5
  25         values.each_with_index do |value, index|
  26                 next if value < 0
  27                 values[index] = value + key_values[index]
  28                 values[index] -= 26 if values[index] > 26
  29         end
  30
  31         # Step 6
  32         message = (values.map { |number| (number - 1 + ?A).chr }).join("")
  33
  34         return message
  35 end
  36
  37 def decrypt(message)
  38         # Step 1
  39         key_stream = generate(message.size)
  40
  41         # Step 2
  42         values = message.split("").map { |letter| letter[0] - ?A + 1 }
  43
  44         # Step 3
  45         key_values = key_stream.split("").map { |letter| letter[0] - ?A + 1 }
  46
  47         # Step 4
  48         values.each_with_index do |value, index|
  49                 next if value < 0
  50                 if value <= key_values[index]
  51                         values[index] = value + 26 - key_values[index]
  52                 else
  53                         values[index] = value - key_values[index]
  54                 end
  55         end
  56
  57         # Step 5
  58         message = (values.map { |number| (number - 1 + ?A).chr }).join("")
  59
  60         return message
  61 end
  62
  63 def generate(count)             # Keystream Steps
  64         key_stream = [ ]
  65
  66         until key_stream.size == count
  67                 # Step 2
  68                 a = $deck.index("A")
  69                 if a == 53
  70                         $deck.insert(1, $deck.pop)
  71                 else
  72                         $deck.insert(a + 1, $deck.delete_at(a))
  73                 end
  74
  75                 # Step 3
  76                 b = $deck.index("B")
  77                 if b == 53
  78                         $deck.insert(2, $deck.pop)
  79                 elsif b == 52
  80                         $deck.insert(1, $deck.delete_at(b))
  81                 else
  82                         $deck.insert(b + 2, $deck.delete_at(b))
  83                 end
  84
  85                 # Step 4
  86                 a = $deck.index("A")
  87                 b = $deck.index("B")
  88                 top = [a, b].min
  89                 bottom = [a, b].max
  90                 $deck = $deck.values_at((bottom + 1)..53, top..bottom, 0...top)
  91
  92                 # Step 5
  93                 if $deck[53].kind_of? Integer
  94                         $deck = $deck.values_at($deck[53]..52, 0...$deck[53], 53)
  95                 end
  96
  97                 # Step 5
  98                 if $deck[0].kind_of? Integer
  99                         if $deck[$deck[0]].kind_of? Integer
 100                                 key_stream.push($deck[$deck[0]])
 101                         end
 102                 else
 103                         if $deck[53].kind_of? Integer
 104                                 key_stream.push($deck[53])
 105                         end
 106                 end
 107         end             # Step 7
 108
 109         key_stream.map! do |number|
 110                 if number > 26
 111                         (number - 26 - 1 + ?A).chr
 112                 else
 113                         (number - 1 + ?A).chr
 114                 end
 115         end
 116         key_stream = key_stream.join("")
 117         i = 5
 118         while i < key_stream.size
 119                 key_stream[i, 0] = " "
 120                 i += 6
 121         end
 122         return key_stream
 123 end
 124
 125 # Mind reading interface
 126 if ARGV.size == 1 and ARGV[0] =~ /^(?:[A-Z]{5} )*[A-Z]{5}$/
 127         puts decrypt(ARGV[0])
 128 elsif ARGV.size == 1
 129         puts encrypt(ARGV[0])
 130 else
 131         puts "Usage:  solitaire.rb MESSAGE"
 132 end