Subject: [Ace] gerdes-ace-dcaf-authorize (DTLS PSK Generation Methods)

From: Renzo Navas <[email-masked]>
Date: Wed, 29 Apr 2015 11:47:38 +0200

Hello Steffi and DCAF authors,

I was reading the DCAF draft and I think I find nomenclature mismatch (on
section 6.1):

  6.1 <https://tools.ietf.org/html/draft-gerdes-ace-dcaf-authorize-02#section-6.1>.
DTLS PSK Transfer

     The DTLS PSK is generated by AS and transmitted to C and S using a
     secure channel.

"generated by AS" might be "generated by SAM" (or generated by The
AM). I think "AS" was the nomenclature used on version 00 of the
draft.

Also I want to say that its great that the document
draft-gerdes-ace-actors-04 the WG is arriving to a nomenclature merge
with the draft-seitz-ace-problem-description-03, as discussed on
Dallas IETF.

So in the end if the next version of DCAF aligns with Actors, the SAM
will be AS again :)

I want to mention that I have a UseCase when I need to bootstrap C
into an unknown network (but possibly federated with the trusted
home-network of C) so I cannot assume a pre-established secured
channel between C and CAM :(.
I am working on an mutually-authenticated secured bootstraping
solution. Possibly only using symmetrc criptography.

Thanks again Steffi for you work,

Have a good week Ace WG, and labour day!

Renzo NAVAS,

Telecom Bretagne (France)

---

From: Ludwig Seitz <[email-masked]>
Date: Wed, 29 Apr 2015 13:42:45 +0200

On 04/29/2015 11:47 AM, Renzo Navas wrote:
>
> I want to mention that I have a UseCase when I need to bootstrap C into an unknown network (but possibly federated with the trusted home-network of C) so I cannot assume a pre-established secured channel between C and CAM :(.
> I am working on an mutually-authenticated secured bootstraping solution. Possibly only using symmetrc criptography.
>
>

This sounds intriguing, if you do not have a security relation between C 
and CAM, who did the enrollment of C?

I would assume that as RqP enrolls C it should be able to provision a 
security relation between C and CAM. Or is it the case that RqP does not 
know which CAM to use?

Perhaps you could describe you use case in more detail so that your 
bootstrapping problem become more clear.

Regards,

Ludwig

-- 
Ludwig Seitz, PhD
SICS Swedish ICT AB
Ideon Science Park
Building Beta 2
Scheelevägen 17
SE-223 70 Lund

Phone +46(0)70-349 92 51
http://www.sics.se

---

From: Renzo Navas <[email-masked]>
Date: Wed, 29 Apr 2015 14:22:34 +0200

Hi Ludwig I will try later to describe in more detail my scenario, for the
moment I confirme that

* C and CAM DO HAVE a previous security relation (for instance a PSK or on
a Public-key setting the public key of the other)

In DCAF model C an CAM have an already a secured DTLS session.

In my UC, C bootstraps from zero. And I have intermediate nodes between C
and his CAM.

If I try to map my UC to DCAF nomenclature, this intermediate node can be
 (S+SAM)
So you cannot trust S+SAM yet, and S+SAM also needs to assure if he can
trust C.

* C is constrained
* S+SAM are not constrained

It think the architecture will be like this:

[ C ] ------unsecured channel------ [man in the middle] ----------------[
S+SAM ]  -------secured channel ------------ [CAM]

So C has NOT a previous security relation with S+SAM (shared cryptographic
material), but:

*  SAM and CAM trust each other.
 * C trust CAM (but there is not a secure channel)

So my goal :
* C and (S+SAM) securely mutually-authenticate each other (using in some
way CAM)
* Now I can try also to secure the channel between C and (S+SAM)

The draft that best maps this scenario is (EAP-over-CoAP):

https://tools.ietf.org/html/draft-marin-ace-wg-coap-eap-01

Thank you for your interest if I have not been clear I 'll work on it.

Regards,

Renzo

On Wed, Apr 29, 2015 at 1:42 PM, Ludwig Seitz <[email-masked]> wrote:

>> I want to mention that I have a UseCase when I need to bootstrap C into
>> an unknown network (but possibly federated with the trusted home-network of
>> C) so I cannot assume a pre-established secured channel between C and CAM
>> :(.
>> I am working on an mutually-authenticated secured bootstraping solution.
>> Possibly only using symmetrc criptography.
>>
>>
>>
> _______________________________________________
> Ace mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/ace
>
>

---

From: Renzo Navas <[email-masked]>
Date: Wed, 29 Apr 2015 14:44:30 +0200

Sorry I think my schema is confusing. to clarify:
* The "man-in-the-middle" is an active attacker.
* C and (S+SAM) do not need a relay to communicate (they are one-hop, on
that side of the schema I'm on a radio star-topology and S+SAM is the
central node)