Re: [MLS] Contribute as OTRv4 to MLS

[Ian Goldberg <[e-mail]>]

On Fri, Nov 09, 2018 at 09:41:34AM +0700, nalini elkins wrote:
>  > If deniability is something that's important to you, it would be helpful
> to think about how you could fit it in as an optional feature.
> 
> Just to comment, there is a potential human rights issue (right to life)
> with deniability.   Although extremely beneficial in a number of
> circumstances, it is my understanding that deniability can also be used by
> people such as terrorists to fight lawful subpoenas.
> 
> I wonder if that is of interest to this group.   Please correct me if my
> understanding is wrong.  I very much wish to be wrong.

I can't figure out what you mean by that.  Deniability (well, one form
of it anyway) is the property that the transcript of the protocol
messages does not imply the plaintext messages that were exchanged.
Another form is that it does not imply the participation of any
particular party.  (There are other more complex forms involving online
informants.)  Plaintext logs are deniable in these senses, since anyone
could easily forge them to say anything they like.  If we're talking
subpeonas, note that courts accept plaintext as evidence all the time;
the role of a deniable protocol is to prevent the protocol transcript
from *mathematically* implying the message contents or participation.
(While at the same time the protocol strongly authenticates the
participants and the message contents to those *in* the conversation.)
-- 
Ian Goldberg
Professor and University Research Chair
Cheriton School of Computer Science
University of Waterloo