Subject: [Dtls-iot] Issue#19: AES CCM vs. AES GCM

From: Hannes Tschofenig <[email-masked]>
Date: Wed, 10 Dec 2014 09:10:01 +0100

I created issue#19 in response to the discussions about AES CCM vs. AES
GCM and the misalignment with the UTA working group. Here is the ticket:
http://trac.tools.ietf.org/wg/dice/trac/ticket/19

The recently submitted version -08 of UTA document (see​
http://tools.ietf.org/html/draft-ietf-uta-tls-bcp-08) talks about the
relationship between the UTA document and the DTLS profile document
indirectly by saying:

"
Some devices have hardware support for AES-CCM but not AES-GCM.
There are even devices that do not support public key cryptography at
all. This BCP does not cover such devices.
"

The UTA BCP document also points out that there are more specific
document providing further information than the generic guideline document.

"
This document does not change the mandatory-to-implement TLS cipher
suite(s) prescribed by TLS or application protocols using TLS. To
maximize interoperability, RFC 5246 mandates implementation of the
TLS_RSA_WITH_AES_128_CBC_SHA cipher suite, which is significantly
weaker than the cipher suites recommended here. Implementers should
consider the interoperability gain against the loss in security when
deploying that cipher suite. Other application protocols specify
other cipher suites as mandatory to implement (MTI).
"

While further refinements of the text are in discussion the issues is
being dealt with in the UTA working group.

For this reason I have closed the ticket.

Ciao
Hannes

---

From: Zach Shelby <[email-masked]>
Date: Wed, 10 Dec 2014 00:19:55 -0800

Hannes,

Sounds reasonable to close this one then. Thanks for following up on this!

Zach

On Dec 10, 2014, at 10:10 AM, Hannes Tschofenig <[email-masked]> wrote:

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---

From: Russ Housley <[email-masked]>
Date: Wed, 10 Dec 2014 06:32:18 -0500

Seems fine.  I would like to see larger devices support AES-CCM, but that is not an issue for this working group.

Russ

On Dec 10, 2014, at 3:10 AM, Hannes Tschofenig wrote:

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