I'm looking for a shopping cart ( or ready to run script) for selling Digital Products like eBooks, Graphic Objects etc..

I need some features in cart like

1. There should be a provision to place downloadable files at secure location like at server's root.

2. The downloadable link should be available for specific time and should be downloadable for specific number of times.

3. There should be proper user management who buys ebook

FYI: I searched internet a lot and tried various type of solutions but found some features in one cart and other in some other script because they all meant for selling physical goods not for Digital Products

Any type of help will really be appreciated.