C#

#region Encryption
    class RijndaelEncrypt
    {
        public static void Encrypt(XmlDocument ThisDocument, string FullPath)
        {
            //Save XML to memory stream
            MemoryStream ms = new MemoryStream();
            ThisDocument.Save(ms);
            //Convert memory stream to byte array
            byte[] xmlArray = ms.ToArray();
            //Encrypt
            RijndaelManaged Rij = new RijndaelManaged();
            Rij.Key = ASCIIEncoding.ASCII.GetBytes(Constants.Misc.MyKey); //MyKey is 16 character string
            Rij.IV = ASCIIEncoding.ASCII.GetBytes(Constants.Misc.MyKey);
            ICryptoTransform rijEncrypt = Rij.CreateEncryptor();
            byte[] encryptedData = rijEncrypt.TransformFinalBlock(xmlArray, 0, xmlArray.Length);
            //Create file stream and write encrypted data
            FileStream fsout = new FileStream(FullPath, FileMode.Create);
            fsout.Write(encryptedData, 0, encryptedData.Length);
            fsout.Close();
        }

        public static XmlDocument Decrypt(string FullPath)
        {
            //Create file stream and get file length
            FileStream fsin = new FileStream(FullPath, FileMode.Open, FileAccess.Read);
            FileInfo finfo = new FileInfo(FullPath);
            //Create binary reader and read from file stream
            BinaryReader br = new BinaryReader(fsin);
            //Decrypt
            byte[] encryptedData = br.ReadBytes((int)finfo.Length);
            RijndaelManaged Rij = new RijndaelManaged();
            Rij.Key = ASCIIEncoding.ASCII.GetBytes(Constants.Misc.MyKey);
            Rij.IV = ASCIIEncoding.ASCII.GetBytes(Constants.Misc.MyKey);
            ICryptoTransform rijDecrypt = Rij.CreateDecryptor();
            byte[] decryptedData = rijDecrypt.TransformFinalBlock(encryptedData, 0, encryptedData.Length);
            //Create XML document, fill with decrypted data and return the document
            XmlDocument ThisDocument = new XmlDocument();
            ThisDocument.LoadXml(Encoding.UTF8.GetString(decryptedData));
            return ThisDocument;
        }
    }
    #endregion