Vigenere Cipher

[Eric]

Well, I got a stupid letter from a university, anyways they explained a cipher on it. So... I decided to make a script. Here it is:
String.prototype.Vigenere = function(key, side)
{
   str = this.toLowerCase();
   key = key.toLowerCase();
   var alph = 'abcdefghijklmnopqrstuvwxyz';
   var enc = '';
   var k = 0;
   var temp = 0;
   for(var s = 0; s < str.length; s++)
   {
      if(alph.indexOf(str.charAt(s)) != -1)
      {
         if(side)
         {
            temp = alph.indexOf(str.charAt(s)) - alph.indexOf(key.charAt(k));
            if(temp < 0)
               temp += 26;
         } else {
            temp = alph.indexOf(str.charAt(s)) + alph.indexOf(key.charAt(k));
            if(temp > 25)
               temp -= 26;
         }
         enc += alph.charAt(temp);
         if(k < key.length - 1)
            k++;
         else
            k = 0;
      } else {
         enc += str.charAt(s);
      }
   }
   return enc;
}

Ex:
var testStr = 'test message';
document.write(testStr.viginere("foo", 0)); // Encrypt

key: What you use to encrypt, must be the same to encrypt and decrypt

side: As in which side of the encryption process (enc or dec). Anyways, use a true or false/1 or 0 value. 0 is encrypt, 1 is decrypt.

Have fun!

[acoolie530]

Its kinda like the php str_rot13 function except its more like str_rot-1 :-P