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Re: [ietf-smtp] DKIM encryption, was Request for discussion

2013-10-16 16:14:35
--On Wednesday, October 16, 2013 19:45 +0000 John Levine
<johnl(_at_)taugh(_dot_)com> wrote:

Presumably you are referring to using the destination domain
DKIM keys to encrypt ...

Sort of.  Here's a straw man I sent to one of the MAAWG lists
last month:

Sender fetches TXT  If it
exists, it uses the p= public key to encrypt the whole
message, embeds it as a MIME application/dkim-encrypted body
in a new message to the original address, and sends it off.


Interesting idea as long as both sender and recipient trust the
delivery server.  For reasons identified in one of my earlier
notes today, that might not be wise... but that depends entirely
on one's threat model, what threats are considered important,
and who one chooses to trust.

Specifically, mail sent to you or me and received one our
personally-operated mail servers falls into a rather different
category than mail sent to
SuperGiantEmailProviderInLowerSlobbovia with whom one might have
issues about either the business model of that provider or what
deals they might have with the Slobbovian secret police.

But _please_ don't use Postmaster.  Not only is the appropriate
use of that mailbox pretty well spelled out (and does not
include acting as a decryption and redelivery service) but it is
handled specially in many installations in ways that would
interfere with your model.  Since rather special recipient
processing would be needed anyway, it seems to me that there
would be little harm in inventing a new specialized address,
like "encrypted@...".  If a site already uses that address,
they'd have to adapt before advertising the keys, etc., but that
shouldn't be a really big deal.


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