Well,approach suggested above is pretty well.Further,you can pass values through query string after encryption.
String temp = Encrypt (Textbox1.Text);
Response.Redirect("Webform2.aspx?Value=" +temp);
To retrieve values on another end,
if(Request.QueryString["Value"] != null)
{
txtBox1.Text = Decrypt(Request.QueryString["Value"].ToString());
}
You can refer to below link for Encryption decryption
Encrypt and Decrypt Data with C#[
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Below link will explain alot about passing values.
How to: Pass Values Between ASP.NET Web Pages[
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Regards..:)