From: Gavin McKenzie (ntlk_at_gavinmckenzie.fastmail.fm)
Date: Fri Sep 10 2004 - 04:33:37 PDT
Simon,
On Fri, 10 Sep 2004 07:54:18 +0200, "Simon Stapleton"
<simon_at_tufty.co.uk> said:
>[snip]
> PDF encryption is security by obscurity. It's trivial to decrypt, and
> there are tools out there to do it. finding those tools is left as an
> exercise to the reader.
With respect, I believe that you are confusing encryption with encoding
and compression. We need to make an accurate distinction between PDF
files that are encrypted and PDF files that are merely
encoded/compressed. I expect that you are actually referring to PDF
files that are encoded/compressed. There's no "security by obscurity"
intended by a PDF file that is LZW/Flate encoded. If you look at such a
PDF file in your text editor it may look like gibberish in the same way
that a ZIP file does, but that has nothing to do with encryption, and
chances are that if you pick-up a PDF file in the wild you'll find out
that it is merely encoded/compressed, not encrypted.
Hence, for such PDFs, there's no need to go looking for tools to defeat
encryption. Simply pick-up the published PDF specification or find some
other available PDF processing library. I'd be happy to help with Q&A
on the subject as well.
Gavin.
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