How do I protect a download file on My Server

I wish to sell a product from my server that the buyer must download, like a zip file. How do I set up the system to allow the buyer to download the file only once, or to place a time limit that they can download the file, say 12 hours. Then after the download has been completed or the time has expired, they can not get to the file again without buying the product again, if necessary. Is there a program that does this?

Thanks

 

The only way I see is to keep the file hidden and use code to initiate a download so they never see where the file is on the server. But to help you out with finding code that does this I need to know what language youll be programming in, ASP or PHP? Youll also need to keep a database with the username and passwords that also shows the last time they downloaded each file, youll need to compare that to the current time to make sure it hasnt been less than 12 hours. Youll need some work to get this going.

 

Also what type of database, SQL or Access?