Finding the problem, of controlling access to specific resources for a certain amount of time and for a certain amount of downloads, to be quite interesting. So I decided to design a solution that would take advantage of the services made available by the Windows Azure platform.
Create single use URIs that invalidate after 15 minutes.
Companies that sell digital products often try to limit the number of downloads per purchase. Consequently, discouraging customers from sharing their download links becomes a priority. By creating public URIs constrained by a time to live and by a limited number downloads, can help accomplish this goal.
Building on the Valet Key Pattern explored in “Keep Your Privates Private!” I used Shared Access Signatures to create a time to live for all public URIs. Then to control access to the actual resources I created a REST service using Web API, which tracks individual access to each URI using the Windows Azure Table Storage Service.