ASP.NET security works behind the scenes to protect your data.

Encryping Query string’s avoid the leakage of sensitive page
Information.For encrypting Query string’s we need hexa decimal
Encryption’s.

Plaese see the below Method,

public EncryptedQueryString(string encryptedData)
{
    // Decrypt data passed in using DPAPI
    byte[] RawData = HexEncoding.GetBytes(encryptedData);
    byte[] ClearRawData = ProtectedData.Unprotect(
                RawData, null, DataProtectionScope.LocalMachine);
    string StringData = Encoding.UTF8.GetString(ClearRawData);

    // Split the data and add the contents
    int Index;
    string[] SplittedData = StringData.Split(new char[] { ‘&’ });
    foreach (string SingleData in SplittedData)
    {
        Index = SingleData.IndexOf(‘=’);
        base.Add(
            HttpUtility.UrlDecode(SingleData.Substring(0, Index)),
            HttpUtility.UrlDecode(SingleData.Substring(Index + 1))
        );
    }
}

In aspx page,

<form id=”form1″ runat=”server”>
<div>
Enter some data here: <asp:TextBox runat=”server” ID=”MyData” />
<br />
<br />
<asp:Button ID=”SendCommand” runat=”server” Text=”Send Info”
            OnClick=”SendCommand_Click” />
</div>
</form>

for ex, in SendCommand event,

protected void SendCommand_Click(object sender, EventArgs e)
{
    EncryptedQueryString QueryString = new EncryptedQueryString();

    QueryString.Add(“MyData”, MyData.Text);
    QueryString.Add(“MyTime”, DateTime.Now.ToLongTimeString());
    QueryString.Add(“MyDate”, DateTime.Now.ToLongDateString());

    Response.Redirect(“Recipient.aspx?data=” +
                      QueryString.ToString());
}

In destination Page load,

protected void Page_Load(object sender, EventArgs e)
{
    // Deserialize the encrypted query string
    EncryptedQueryString QueryString =
        new EncryptedQueryString(Request.QueryString["data"]);//Method we used

    // Write information to the screen
    StringBuilder Info = new StringBuilder();
    foreach (String key in QueryString.Keys)
    {
        Info.AppendFormat(“{0} = {1}<br>”, key, QueryString[key]);
    }
    QueryStringLabel.Text = Info.ToString();
}

Hope,this helps

Happy Coding.