By ryanthered on

Does anyone know a way to do the following with Drupal?

1. Sell a digital asset, specifically PDF (I guess ecommerce module)?
2. Encrypt the PDF automatically with a key such as the recipient's email address as the password?
3. Provide a limited-time download link to get the unique encrypted file above?

I know that savvy users can break the encryption scheme of most PDFs, but for most users this would stop wide redistribution of the published work.

Ryan

⋅ Categories: Drupal 4.7.x, Drupal 5.x, Drupal 6.x

Comments

patrickharris’s picture

patrickharris commented

for Drupal 5.0 or 6.0 that will let you sell products (I use it to sell files). I then also have a custom module that uses the api to provide time limited download links to the files. I'm not sure how to encrypt a pdf file to the recipients e-mail address - is that really necessary though? Once unencrypted, the file could still be distributed, so I don't see how that gives you much more protection.

ryanthered’s picture

ryanthered commented

I guess what I'm looking for is a way to password-protect the download for the specific user who bought the file, through some automated process.

Preferably the password would be something the user did not want to give away to everyone in the world, like a credit card number. And, of course, the pdf would have a different password per user.

I could do this individually for each purchase manually, but that would really kind of suck.

Maybe I'm being too paranoid - I just want to be able to sell ebooks, which otherwise are the perfect product, without having them shared to the world for free in violation of copyright.

patrickharris’s picture

patrickharris commented

to create a unique download url that will timeout and tie it to the users IP etc. As I said, I'm not sure about password protecting pdfs - what would be the point? A user could unpack it with a password, and then shove it on rapidshare.

If anyone is interested, the paypal_api module for Drupal 5 is at www.troikastrings.com/drupal/paypal_api.rar ... if you need a Drupal 6 version, let me know.

ryanthered’s picture

ryanthered commented

So I guess I'm not making myself clear.

I've bought ebooks before that were password-protected for open using the email address I provided when I bought the thing. This happened so quickly that I'm sure it was a script providing the URL and the modified, password protected PDF.

This password wasn't the same as the password to do things like print the book or edit the book of course.

I'm wondering how this is done and more to the point how it could be done on Drupal... in an automated fashion.

If it can't be done, understand. That's kind of what I'm getting from this. I guess I would have to use an adobe server in that case.

ricknorth’s picture

ricknorth commented

A commercial product which would help you to achieve #3 on your list (secure time-limited links) is Linklokurl, from http://www.vibralogix.com/linklokurl/. The license is not expensive and I use it on a Drupal site which I maintain. There may be other products out there or you could roll your own but I found this one to be effective and it doesn't interfere with Drupal. It has features like secure email links which I don't use.

Implementation: CCK document type with a document title for display, the document name (PDF), and a computed field for the secure link. The resulting computed links look like this http://example.com/pdflinks?linklokauth=ZmFxcy9DT0xPQlVTIExJTUlURUQgd2Vi... PDF.pdf, which hides the file effectively.

PHP for the computed field:

$computed_field_title = $node->field_doctitle[0]['value'];
$computed_field_url = linklokurl_api($node->field_docname[0]['value'],0,1,'',0);
$node_field[0]['value'] = '<a href="' . $computed_field_url . '">' . $computed_field_title . '</a>';

The "linklokurl_api" function is part of the product, so I
renamed linklokurl.php from the distribution to linklokurl.module so that Drupal could see the function, added a .info file and installed it using admin/modules.

Re: encryption of the PDF, sorry can't help.

doperz’s picture

doperz commented

Hi,
i have this script linklokurl but i can't get it worked in any content, can you please more explain how to do this.
thanks

balagurumoorthy’s picture

balagurumoorthy commented

I will brief about the available solution for pdf encryption. so far found to be effective.

You can search through the adobe site for the pdf client to implement drm. Adobe server is costly. There are other options. Three parts in this solution. The pdf generator, pdf plugin for client and pdf authenticator in the server side.
The pdf generator - encrypts the pdf, sets permission for printing/opening/number of times to open, reference to your site... etc..
Pdf authenticator - authenticates whenever the user tries any operation on the pdf.
The pdf client plugin - gets the key from the server, authenticates the user, verifies the permission against your website.

Integration is very easy
pdf authenticator can be written in php , ony few lines..
pdf generator - use your own. send it for encriypting(purchase) - can be any language (java,cpp,c).
pdf plugin (purchase)- of course should be in the pdf viewer platform.

joshua1979ks’s picture

joshua1979ks commented

I understand what u mean.....but can u elaborate how it can be implemented with drupal?
http://www.fileopen.com/fileopen_pdf_control.php
I looked at the above link......especially print once option.....but fileopen option is quite expensive, is there anyway that the same can be achieved if its custom built for drupal?

Let me know.