examples/rosettacode/vignere_cipher.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 # This program is public domain
   3
   4 # Task: Vigenère cipher
   5 #
   6 # See: <http://rosettacode.org/wiki/Vigenère_cipher>
   7 module vignere_cipher
   8
   9 fun encrypt(src, key: String): String do
  10         var out = new Buffer
  11         var j = 0
  12
  13         for i in [0..src.length - 1] do
  14                 var c = src[i]
  15
  16                 if c >= 'a' and c <= 'z' then
  17                         c = c.to_upper
  18                 else if c < 'A' or c > 'Z' then
  19                         continue
  20                 end
  21
  22                 out.add(((c.ascii + key[j].ascii - 2u8 * 'A'.ascii) % 26u8 + 'A'.ascii).ascii)
  23                 j = (j + 1) % key.length
  24         end
  25
  26         return out.to_s
  27 end
  28
  29 fun decrypt(src, key: String): String do
  30         var out = new Buffer
  31         var j = 0
  32
  33         for i in [0..src.length - 1] do
  34                 var c = src[i]
  35
  36                 if c >= 'a' and c <= 'z' then
  37                         c = c.to_upper
  38                 else if c < 'A' or c > 'Z' then
  39                         continue
  40                 end
  41
  42                 out.add(((c.ascii - key[j].ascii + 26u8) % 26u8 + 'A'.ascii).ascii)
  43                 j = (j + 1) % key.length
  44         end
  45
  46         return out.write_to_string
  47 end
  48
  49 # Main part
  50 var str = "All your base are belong to us"
  51 var key = "CRYPTONIT"
  52 var code = encrypt(str, key)
  53 var decode = decrypt(code, key)
  54
  55 print "Text: " + str
  56 print "Key : " + key
  57 print "Code: " + code
  58 print "Back: " + decode