Re: [gmime-devel] avoiding metadata leaks when handling S/MIME-signed mail in GMime and other tools that use GnuPG



Hello,

Am Freitag 02 Februar 2018 18:48:08 schrieb Daniel Kahn Gillmor:
I recently learned that default handling of signed S/MIME mail with
GnuPG causes an inherent metadata leak about the user's activity:

    https://dev.gnupg.org/T3348#110132

from briefly reading over the issue I think that "inherent metadata leak"
is too broad a term to represent the security pros and cons well enough.

Just sending an email or a webpage will also inherently leak meta data
for someone listening on the line. So you'll certainly won't disable begin 
able to send those as well.

As a MUA developer, I'd like my MUA to simply handle as much crypto as
it can on the user's behalf automatically, correctly and silently,
without needing any special configuration or asking the user to make any
tough tradeoffs that they might object to.

Users might also object to the higher exposure to revoked certificates
and a more surprising behaviour deviating from the CMS standards (which as far 
as I know mandate checking the validity of certs).

It comes down to post some trust into the implementations and the certificate 
authorities you chose to use. I think we'd do more for users if we educate 
them about some of the more basic properties.

Best Regards,
Bernhard

-- 
www.intevation.de/~bernhard   +49 541 33 508 3-3
Intevation GmbH, Osnabrück, DE; Amtsgericht Osnabrück, HRB 18998
Geschäftsführer Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner

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