AES crypt function with C# and decrypt using javascript

For applications that require higher security I usually encode and decode using C#, and use $.ajax in JS, but there is an easy way using JS to decode a pre-encrypted string .

You can use Base64String...

C# :

string encoded = Convert.ToBase64String(Encoding.UTF8.GetBytes(str));

JS :

function decode(str) {
  var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
  var output = "";
  var chr1, chr2, chr3;
  var enc1, enc2, enc3, enc4;
  var i = 0;

  do {
     enc1 = keyStr.indexOf(str.charAt(i++));
     enc2 = keyStr.indexOf(str.charAt(i++));
     enc3 = keyStr.indexOf(str.charAt(i++));
     enc4 = keyStr.indexOf(str.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);
     }
   } while (i < str.length);

  return output;
}