I think theres a way to do that.
Declare a function in your codebehind file that encrypts the values, and use it in your aspx file, like this
NavigateUrl='<%# "NewsDetails.aspx?NewsId="+enc(DataBinder.Eval(Container, "DataItem.NewsId")) %>' Text='<%# DataBinder.Eval(Container, "DataItem.subject") %>'>
enc(), is your function.......get what I mean