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  1. #1
    SitePoint Member
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    Dec 2006
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    Protecting 'paid for' pdf links being posted to forums

    A client i work for wants to sell versions of their books as pdfs on a site built with classic asp and mysql. This presents the obvious problems of how to prevent people posting live links to the pdfs on forums, blogs etc. I know that people could just send the pdf to their friends but being able to stop posting to the general public would be at least some theft limitation.

    I guess, one way would be to limit the number of downloads for a given link, or to use a unique key for each that is flagged as used when the download is made.

    Although i'm a relatively experienced developer, i have never had this kind of request before. Has anyone out there had any experience with this? Perhaps there are some known third party solutions to this avaialble? Any help would be hugely appreciated.

  2. #2
    It's all Geek to me silver trophybronze trophy
    ralph.m's Avatar
    Join Date
    Mar 2009
    Melbourne, AU
    465 Post(s)
    8 Thread(s)
    If you are selling PDFs online, normally you'd hide the location in which they are stored. Even when purchasers are sent a download link it hides the actual location. Some carts will also allow you to set a limit on the number of downloads, or to set an expiry date on the link.

  3. #3
    SitePoint Wizard siteguru's Avatar
    Join Date
    Oct 2002
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    When the PDF is purchased create a UniqueID (where UniqueID is - as you can guess - a unique ID which is is created at the time of purchase, and the download link is to an ASP page that takes the ID, updates the database and then streams the PDF file to the user).

    Your database has a record of this ID, and you could setup a clean-up task (script) that polls the database and deletes any PDF files that exceed whatever guidelines you set (be it number of downloads or elapsed time).

    Ian Anderson

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