[GLLUG] PDF Files

[Richard Houser]

I've attached an example of the only form of PDF file that's not 
printable by a determined user.  Basically, I just created a PDF using a 
secret process then compressed it with my new lossless compression 
algorithm.  I can't disclose the details of the compression algorithm 
until I get the patent, but it compresses ALL files by a minimum of five 
percent.

Even if you are still running LPD and haven't upgrading yet (CUPS caught 
on when, around 2000?), the fundamental flaw remains that you are giving 
the user the data and trying to keep them from using that data at the 
same time.  That's why DRM schemes always fail.  If the user lacks 
access to the content, it's not usable.  If the user has access to the 
data, they have access to it, period.

In the modern printing world (CUPS/IPP), the print server just deals 
with incoming postscript data, does some manipulations to it, and sends 
it out to the printer in whatever format the printer prefers.  The PDF 
format is based on PostScript and there is actually a lot more software 
out there that deals with Postscripts files than with PDFs.

I don't doubt you found a bug in a PDF viewing program that resulted in 
printouts from that program not working properly.  Lots of software has 
bugs, that's normal (Acrobat Reader in particular is extremely buggy). 
What I doubt is that you created an unbreakable DRM system in spite of 
the mathematics that say it's not possible.  The **AA Cartels have been 
trying that for years too, but it's not going to happen.

For those still reading, yes, that was a joke earlier, but I figured it 
was pretty dang obvious :).





Sean O'Malley wrote:
> 
> On Thu, 26 Apr 2007, Richard Houser wrote:
> 
>> Umm, a postscript file is a native printing format.  lpr filename.pdf
>> and it's over.
> 
> I wish it was that simple. :) printing is a magical art. essentially you
> lpr a printjob. Then the file program looks at the printjob and determines
> how to convert it to a language the printer actually understands which is
> usually, ps/pcl/pjl/text for laser printers, inkjet printers are usually a
> whole other ballgame as far as what language they support. then lpd
> actually sends the converted (if needed) data to the actual printer.
> The point being, you don't actually even have to send it to lpr, you can
> just do the conversions by hand..
> 
> I may have run it through illustrator after the initial conversion too.
> I'm kind of picky about filesize and keeping vector image formats in
> tact.).  I really don't recall exactly =how= I did it, but it was a
> multi-step process. I may have used pdf2ps or ps2pdf (which would
> essentially be a pdf file wrapped in a pdf file.) or just converted
> the file to EPS which illustrator supported. I just remember
> it was a multi-step process and it didnt actually require hacking a
> password out of it and ended up with an editable pdf document.
> 
> 

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