On 10/2/19 12:29 PM, Jon Callas wrote:
> >> When we designed DKIM, this was something we considered; it was a > concern. It wasn't so big a concern that we thought it should derail DKIM, > and it wasn't even a concern when it was taken over by the IETF. > Nonetheless, it was an issue, is an issue, and becomes a bigger issue > nearly every day. The most notorious failure here is the Podesta email > dump, where the stolen emails were verified against the DKIM signatures. > This is precisely what we didn't want to happen -- that DKIM was used for > things beyond fighting inauthentic emails. We ought to do something, the > question is what. > > On Wed, Oct 2, 2019 at 7:50 PM Jim Fenton <[email protected]> wrote: > > > Yes, we definitely considered privacy with respect to DKIM. But my > recollection is different: I don't remember discussion of the potential > forensic use of DKIM signatures to provide unintended non-repudiation of > leaked emails. I also wouldn't describe the presence of such signatures > on email messages to be surveillance -- although it does contribute to > the effectiveness of surveillance done by other means. > > > The type of surveillance we were discussing at the time was the > potential that the verification of a DKIM signature might give the > sender information on the location of the recipient (by observing the > DNS requests at the point where the key record is hosted). Use of > different selector names could also differentiate requests on behalf of > a particular target. I believe this concern was addressed by the > observation that the signature verification would typically be done by > the recipient's mail provider, and not by the recipient themselves. > > There were a lot of smart people looking at it and working on it and I am absolutely sure we didn't even consider the forensic use... or if we did (I don't remember it) I don't think a scenario was constructed by anyone that showed it. I am also certain that if we did J would have had a lot to say about it. ;-) But back then, and even now, this case is pretty fringe. -Damon
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