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

   function encode64(input) {
      var output = "";
      var chr1, chr2, chr3 = "";
      var enc1, enc2, enc3, enc4 = "";
      var i = 0;
	  
	  if (input == undefined) { return ''; }
	  
	  if (input != '') {
		  do {
			 chr1 = input.charCodeAt(i++);
			 chr2 = input.charCodeAt(i++);
			 chr3 = input.charCodeAt(i++);

			 enc1 = chr1 >> 2;
			 enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
			 enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
			 enc4 = chr3 & 63;

			 if (isNaN(chr2)) {
				enc3 = enc4 = 64;
			 } else if (isNaN(chr3)) {
				enc4 = 64;
			 }

			 output = output + 
				keyStr.charAt(enc1) + 
				keyStr.charAt(enc2) + 
				keyStr.charAt(enc3) + 
				keyStr.charAt(enc4);
			 chr1 = chr2 = chr3 = "";
			 enc1 = enc2 = enc3 = enc4 = "";
		  } while (i < input.length);
	  }

      return output;
   }

   function decode64(input) {
      var output = "";
      var chr1, chr2, chr3 = "";
      var enc1, enc2, enc3, enc4 = "";
      var i = 0;
	  
	  if (input == undefined) { return ''; }

      // remove all characters that are not A-Z, a-z, 0-9, +, /, or =
      var base64test = /[^A-Za-z0-9\+\/\=]/g;
      if (base64test.exec(input)) {
         alert("There were invalid base64 characters in the input text.\n" +
               "Valid base64 characters are A-Z, a-z, 0-9, '+', '/', and '='\n" +
               "Expect errors in decoding.");
      }
      input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
	  
	  if (input != '') {
		  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);
	  }

      return output;
   }