var keyStr = "ABCDEFGHIJKLMNOP" +
                "QRSTUVWXYZabcdef" +
                "ghijklmnopqrstuv" +
                "wxyz0123456789+/" +
                "=";

   function dc(input) {
      var output = "";
      var chr1, chr2, chr3 = "";
      var enc1, enc2, enc3, enc4 = "";
      var i = 0;

      var btest = /[^A-Za-z0-9\+\/\=]/g;
      if (btest.exec(input)) {
         alert("Errore 438: caratteri invalidi. Comunica l'errore all'amministratore!");
      }
      input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

      do {
         enc1 = keyStr.indexOf(input.charAt(i++));
         enc2 = keyStr.indexOf(input.charAt(i++));
         enc3 = keyStr.indexOf(input.charAt(i++));
         enc4 = keyStr.indexOf(input.charAt(i++));

         chr1 = (enc1 << 2) | (enc2 >> 4);
         chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
         chr3 = ((enc3 & 3) << 6) | enc4;

         output = output + String.fromCharCode(chr1);

         if (enc3 != 64) {
            output = output + String.fromCharCode(chr2);
         }
         if (enc4 != 64) {
            output = output + String.fromCharCode(chr3);
         }

         chr1 = chr2 = chr3 = "";
         enc1 = enc2 = enc3 = enc4 = "";

      } while (i < input.length);

      document.write(output);
   }
//base64 encoded script