How to Encrypt AppSettings Keys in Web.Config File using ASP.Net

Complete sample: Encrypt appsettings Key (Tags) in Web.Config File in ASP.Net using C# and VB.Net

Namespaces

using System.IO;
using System.Xml;
using System.Text;
using System.Configuration;
using System.Security.Cryptography;

Web.Config AppSetting

<appSettings>
    <add key="Name" value="Mudassar Khan" />
  </appSettings>

Code for Encrypting

 protected void Page_Load(object sender, EventArgs e)
    {
        this.EncryptAppSetting("Name");
        string encrypted_name = ConfigurationManager.AppSettings["Name"];
        string name = Decrypt(ConfigurationManager.AppSettings["Name"]);
    }

    private void EncryptAppSetting(string key)
    {
        string path = Server.MapPath("~/Web.Config");
        XmlDocument doc = new XmlDocument();
        doc.Load(path);
        XmlNodeList list = doc.DocumentElement.SelectNodes(string.Format("appSettings/add[@key='{0}']", key));

        if (list.Count == 1)
        {
            XmlNode node = list[0];
            string value = node.Attributes["value"].Value;
            node.Attributes["value"].Value = Encrypt(value);
            doc.Save(path);
        }
    }

    private string Encrypt(string clearText)
    {
        string EncryptionKey = "MAKV2SPBNI99212";
        byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
        using (Aes encryptor = Aes.Create())
        {
            Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
            encryptor.Key = pdb.GetBytes(32);
            encryptor.IV = pdb.GetBytes(16);
            using (MemoryStream ms = new MemoryStream())
            {
                using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(clearBytes, 0, clearBytes.Length);
                    cs.Close();
                }
                clearText = Convert.ToBase64String(ms.ToArray());
            }
        }
        return clearText;
    }
    private string Decrypt(string cipherText)
    {
        string EncryptionKey = "MAKV2SPBNI99212";
        byte[] cipherBytes = Convert.FromBase64String(cipherText);
        using (Aes encryptor = Aes.Create())
        {
            Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
            encryptor.Key = pdb.GetBytes(32);
            encryptor.IV = pdb.GetBytes(16);
            using (MemoryStream ms = new MemoryStream())
            {
                using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(cipherBytes, 0, cipherBytes.Length);
                    cs.Close();
                }
                cipherText = Encoding.Unicode.GetString(ms.ToArray());
            }
        }
        return cipherText;
    }