I want my application to be unsearchable from the App Store. I would like that only those users who sign in to my web site and then click the link of my iPhone application on ap
I think, without meaningful keywords your app should vanish amongst the 99.999 other apps.
As an alternative you could let everyone (search and) download the app and disable it until the user signed in.
You can also use in-house-distribution with the enterprise program (see here).