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My favorite pdf fact is that the security flags for things like copy protection and passwords are on the viewer to implement so you can just turn them off and a

by cgb223 6y ago

My favorite pdf fact is that the security flags for things like copy protection and passwords are on the viewer to implement so you can just turn them off and all the security is gone

Drdrdrq 6y ago
My somewhat less favorite pdf fact is that if you do that, you are still breaking protection, legally speaking.
- maxerickson 6y ago
  Seems to be a reasonable analogy with trespass, where you are violating the law when you cross an invisible line. The need for marking the line varies considerably. And even places with strong roaming rights tend place limits on well marked land.
- smegger001 6y ago
  So what if you open it in a postscript viewer instead of a PDF viewer? Because they are compatible formats except for some edge cases like security flags.
  - mkl 6y ago
    Postscript and PDF are definitely not compatible formats. The drawing model is similar, but the structure and code are completely different.
toomanybeersies 6y ago
You can also circumvent copy protection on PDFs by taking a screenshot, or taking a photo of the screen with your phone.
r00fus 6y ago
This is not entirely true, you can encrypt PDFs [1] since v1.3 of the spec but the cypher is often so weak (RC4 until v1.6) they can be bruteforced in reasonable amounts of time. [1] https://www.pdflib.com/pdf-knowledge-base/pdf-password-security/encryption/ https://www.pdflib.com/pdf-knowledge-base/pdf-password-secur...
- Thorrez 6y ago
  You can encrypt them to completely prevent them from being opened. But cgb223 wasn't talking about that, cgb223 was talking about the ability to open them but not copy text, or not print.
  - benmmurphy 6y ago
    You can make the text uncopyable by using non-standard font indexing. The reader will be able to copy the text but it will be gobbly-gook. It forces the user to OCR the PDF or reverse the font mapping.
    - hnick 6y ago
      And ain't that a treat when clients send us PDFs to sort, print, and mail, but the address extraction fails completely.
BHSPitMonkey 6y ago
Debian actually goes out of their way to patch those checks out in their PDF-related packages as part of their stance against DRM, like this example with "pdftk": https://sources.debian.org/patches/pdftk/2.02-4/drm_fix/ https://sources.debian.org/patches/pdftk/2.02-4/drm_fix/

by cgb223 6y ago

My favorite pdf fact is that the security flags for things like copy protection and passwords are on the viewer to implement so you can just turn them off and all the security is gone

Drdrdrq 6y ago

My somewhat less favorite pdf fact is that if you do that, you are still breaking protection, legally speaking.

maxerickson 6y ago
Seems to be a reasonable analogy with trespass, where you are violating the law when you cross an invisible line. The need for marking the line varies considerably. And even places with strong roaming rights tend place limits on well marked land.
smegger001 6y ago
So what if you open it in a postscript viewer instead of a PDF viewer? Because they are compatible formats except for some edge cases like security flags.
- mkl 6y ago
  Postscript and PDF are definitely not compatible formats. The drawing model is similar, but the structure and code are completely different.

toomanybeersies 6y ago

You can also circumvent copy protection on PDFs by taking a screenshot, or taking a photo of the screen with your phone.

r00fus 6y ago

This is not entirely true, you can encrypt PDFs [1] since v1.3 of the spec but the cypher is often so weak (RC4 until v1.6) they can be bruteforced in reasonable amounts of time. [1] https://www.pdflib.com/pdf-knowledge-base/pdf-password-security/encryption/ https://www.pdflib.com/pdf-knowledge-base/pdf-password-secur...

Thorrez 6y ago
You can encrypt them to completely prevent them from being opened. But cgb223 wasn't talking about that, cgb223 was talking about the ability to open them but not copy text, or not print.
- benmmurphy 6y ago
  You can make the text uncopyable by using non-standard font indexing. The reader will be able to copy the text but it will be gobbly-gook. It forces the user to OCR the PDF or reverse the font mapping.
  - hnick 6y ago
    And ain't that a treat when clients send us PDFs to sort, print, and mail, but the address extraction fails completely.

BHSPitMonkey 6y ago

Debian actually goes out of their way to patch those checks out in their PDF-related packages as part of their stance against DRM, like this example with "pdftk": https://sources.debian.org/patches/pdftk/2.02-4/drm_fix/ https://sources.debian.org/patches/pdftk/2.02-4/drm_fix/