secure data export

[Oleg Goldshmidt]

On Sun, Jun 26, 2011 at 9:44 AM, Nadav Har'El <nyh at math.technion.ac.il> wrote:
> A trivial (though
> perhaps suboptimal) way to do this is for that machine to export the document
> to PDF; Presumably this conversion will lose all invisible information,

I suppose a sophisticated attacker may, in principle, devise a way to
create a, say, Word file that will preserve hidden data even when
converted into PDF or another format. I don't know how, but things
like font metadata, white-on-white text, whatever, come to mind as
possibilities.

> and
> if you assume your human verifier can verify the visible information somehow
> (it isn't clear how...), you're safe.

Not really as extra information may be hidden in the (plain) text itself.

It's a tough problem. It is a lot more difficult than AV since you
want to prevent essentially arbitrary data from leaking, not just data
that may damage another machine. In fact, I would not be surprised
that resisting a theoretical attacker may be a hopeless proposition in
practice. If you know what I mean.

-- 
Oleg Goldshmidt | oleg at goldshmidt.org