On Mon, Mar 28, 2016 at 9:49 AM, Jim Schaad <ietf(_at_)augustcellars(_dot_)com>
wrote:
I am open to suggestions, but until somebody gives be a better answer I do
not know how to do the following:
* A better mechanism than sign-encrypt-sign to get both authentication
and
confidentiality (or at least a non-strippable way of doing it)
Using and AEAD algorithm only solves part of the problem as one can do an
encrypt-sign but the outer integrity cannot be validated by a third party.
This is also set to be able for third parties to add the outer signature
layer and that has been used in several specifications so it is not clear
to me that this is one issue that needs to be fixed.
I do to totally agree that we need to start moving to AEAD algorithms
however.
(Caveat: I'm not familiar with these techniques, and am posting in part to
learn if this is a good idea.)
Have folks here considered authenticated key exchange to generate per
message symmetric key for AEAD? Making the exchange asynchronous appears
to be possible as was done in TextSecure. There more description in the
SoK paper (link <http://cacr.uwaterloo.ca/techreports/2015/cacr2015-02.pdf>)
around 13-16. Criticism of TextSecure suggest though, the pre-keying could
cause problems for email applications.
-Wei
jim
-----Original Message-----
From: smime [mailto:smime-bounces(_at_)ietf(_dot_)org] On Behalf Of Sean
Turner
Sent: Monday, March 28, 2016 6:11 AM
To: Wei Chuang <weihaw(_at_)google(_dot_)com>
Cc: IETF SMIME <smime(_at_)ietf(_dot_)org>
Subject: Re: [smime] Message takeover attacks against S/MIME
If the patient is on the table, then all of these look like items we’d
need to
address.
spt
On Mar 26, 2016, at 09:57, Wei Chuang <weihaw(_at_)google(_dot_)com>
wrote:
Some more work item suggestions (I'm posting on behalf of someone who
wishes to avoid the rough and tumble of discussion on the mailing list
though
reads it):
* Making ECC an official part of S/MIME, RFC5753 is only informational.
* Authenticated encryption.
* A better mechanism than sign-encrypt-sign to get both authentication
and
confidentiality (or at least a non-strippable way of doing it)
* Dropping obsolete ciphers and hashes from the spec: drop SHA-1, MD5,
etc.
* A modernized RFC 4134 (practical examples of S/MIME messages, it
could
avoid the fiasco of 3rd party forgetting ASN-1 tags in their messages).
-Wei
On Sun, Mar 13, 2016 at 9:38 AM, Wei Chuang
<weihaw(_at_)google(_dot_)com> wrote:
Some interesting usability consideration were raised on the PKIX list
by Martin
Rex in the thread "another attempt to canonicalize local parts" that
could be
addressed by a rechartered WG. He points out problems with
- Incompletely specified cert chains preventing signature verification
i.e.
missing CA certs and no ability to fetch them. Fully specifying the
chains would
resolve this.
- Reverifying old "archived" emails on his MUA not possible as the
certs have
expired. Fixing a verification time on delivery or other scheme is
desirable.
-Wei
On Thu, Mar 10, 2016 at 11:12 AM, Wei Chuang
<weihaw(_at_)google(_dot_)com>
wrote:
On Mon, Mar 7, 2016 at 10:58 PM, Russ Housley
<housley(_at_)vigilsec(_dot_)com>
wrote:
I am hearing interest in these topics (a combination of things on this
list and
side conversations).
(1) Specify the way to use authenticated encryption in S/MIME. Note
that it is
already done for CMS.
(2) Specify conventions for AES-CCM, AES-GCM, and ChaCha20 with
Poly1305
authenticated encryption algorithms.
(3) Specify conventions for using Curve25519 and Curve448 for key
agreement.
(4) Specify conventions for using the CFRG chosen curves for elliptic
curve
digital signature.
(5) Specify a way to use PGP public keys in addition to PKIX
certificates.
Anything else?
While I'm afraid of scope creep as resolving the above would be very
useful,
could also mail header integrity and privacy be considered? Perhaps the
WG
scope be split into near and long term work to help prioritize. The
above five
items be categorize as near term and the mail header work considered
longer
term?
-Wei
(PS yes there is RFC7508 which is experimental, and does not keep
private the
sender and recipient. Still it is an improvement...)
Is this enough to re-charter the S/MIME WG?
Russ
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