"I'm sorry Wesley, I can't let you do that…"

These are not words that I often let my own computers tell me (for long).

When it comes to controlling resources, it’s relatively easy to keep people from reading things (access controls, authentication, cryptography, etc).  We’re pretty good at that.  If we own the medium, it’s even fairly easy to keep people from writing things to it.  We can’t, however prevent people from writing to their own media.

So what does this mean?  We have security mechanisms that work (more or less) for reading and writing, but controlling someone’s ability to copy is a Problem.

I ran into this the other day, in OS X’s Preview app, when I tried to copy and paste a quote out of a PDF :

Right.  So, given:

• An environment that I could conceivably control, instrument, or log every aspect of
• A file format that’s typically friendly towards copying text (Highlighted the quote with a text tool, so it’s being represented as glyphs, not images I’d have to OCR or curves I’d have to put back together).
• Permission to read

…there’s no way this kind of protection can work.  If someone has the ability to write to some media, including their own (out of your control!) then giving them read access to some data is tantamount to granting them the ability to copy as well.  Error messages like this are nothing more than polite requests.

I’d have put a tutorial on how to get around this on here, but there’s really just one step:

1. Use Skim.  It’s nicer anyways.