Naveen, the best way to avoid the double hop issue is to install the qlikview accesspoint in the same IIS as the ASP.NET website.
That would be the best choice using AD as authentication but if you want to use webtickets (in QV11) here's a document a sample files, you can also find them in the SDK online here somewhere or in the QVS install package.
A custom authentication approach as mentioned by Daniel is one way.
Another would be to use Kerberos. Please see the Microsoft article for details:
You could then carry on using standard Windows authentication.