[messaging] Value of deniability

Natanael natanael.l at gmail.com
Fri Dec 12 07:05:05 PST 2014

Den 12 dec 2014 13:41 skrev "Petter Ericson" <pettter at acc.umu.se>:
> > > For deniability to have any real world effect, there'd need to be a
> > of people forging chat logs pretty routinely. As it's only relevant when
> > there's some breakdown in privacy, and that should hopefully be rare in
> > good cryptographic system, getting people to routinely forge or edit
> > seems .... hard.
> >
> > It doesn't need to be routine, just frequent enough that nobody assumes
> > authencity.
> The point is: it isn't, and frankly I'm highly sceptical it will ever be.
> Further, an unauthenticated chat log _is_ potentially more convincing
than you
> are (see the anakata case for example), and no one stores authenticated
> logs that I know of. Do you?  Relatedly: have you altered chat logs at
> point? Specifically, have you _added_ stuff to a chat log? Do you know of
> instance where this has happened?
> Would a judge, police office, prosecutor or jury have any knowledge about
> a thing having happened? Would they decide that this is likely to have
> in any specific instance?

I see this as a problem of education, not inherently of the technology.
There's no reason for anybody to find a text file convincing without
knowledge about where it comes from.

If they do anyway, facts and explanations should fix that by showing that
the blind trust in authencity is unfounded and unjustifiable. Making
comparisons to something fairly well known like Photoshop should help them
understand. And then you explain how much easier it is to modify text to
look plausible.

For myself, I've never yet been part of a discussion interesting enough for
deniability to matter. As in I'm still young and haven't yet been making
any negotiations with a potential employer in a field where it matters, or
anything else with high stakes. I'm also not very extrovert, so there's not
much at all of my private thoughts and matters that's even written down
anywhere at all. But that's just me, and that's just today, and when the
stakes go up it becomes more important with higher security.

I'm always trying to apply creativity and imagine plausible edge cases.
Sometimes when you look into them closer you'll even get surprised by how
much more common they are than you thought. Try to think like an attacker -
if I'm trying to achieve A and the current attack X is foiled, what else
can be done to get closer to A? Don't dismiss Y and Z on seeming
implausible. If they can work at all, they must be considered.

And don't forget about simple failures. Like previously mentioned, sending
to the wrong person.

> Deniability is a solution looking for a problem, and so far it's not
doing a
> great job of finding it.

The problem exists, it is a valid solution, it just doesn't show its
strength because it is the other layers of security around it which is
failing. Don't blame the pillars of the bridge when it is all the other
parts that's falling down. Make them stronger and then you'll see the value
of it. Taking it away and strengthening the others will only result in a
different failure.
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