[6tsch] Feedback on draft-ohba-6tsch-security-00

[Rene Struik <[e-mail]>]

Hi Yoshi:

I had a look at your draft and reflected somewhat on the requirements 
mentioned.

Initial feedback:

General remark:
1) The draft text seems almost independent of 802.15.4e behavior. While 
the security considerations make reference to the need to authenticate 
time synch and channel hopping info in beacon frames and refer to 
potential nonce "overflow" issues, it is not that easy to see how the 
mechanisms described in the draft address these 802.15.4e-specific 
considerations.
2) The draft seems to aim at providing both (a) key establishment 
functionality (setting up a secure peer-to-peer channel); (c) key 
distribution (handing out link keys, muulticast keys, network keys). It 
would be useful to organize the draft so as to separate these 
functionalities more clearly (e.g., Phase-II KMP vs. Phase-II Key 
Distribution). What about key updates?

Security Framework (Section 3):
a) The security framework (Phase-III) seems to require incremental 
roll-out/planning of the network, witness Fig. 2. If so, it would be 
good to indicate how devices transgress through the different "phases" 
defined and to what degree this requires planning/intervention by an 
operator.
b) The bootstrapping phase (Phase-I) suggests inline interaction of a 
device with an authentication server (which is assumed to mostly be the 
coordinator of the mesh network). Since bootstrapping only results in 
issuance of credentials to be used by devices for Link Establishment 
(Phase-II), I can imagine this step to be often organized differently 
than described, e.g., by embedding a device certificate with a device at 
device manufacturing. In that case, no inline interaction with an 
authentication server seems required, at least not for *authentication* 
purposes.

KMP Requirements (Section 4):
R1-1: The requirement for mutual authentication seems to rule out 
"resurrecting duckling" policy models. Is this correct? Moreover, this 
rules out one/two pass protocols.
R1-2: The requirement for stateless relay may not work within the 
802.15.4e context: if a device A talks with an authentication server T 
via its neighbor R, where R and T operate in a secured network (i.e., 
one where all communications are cryptographically secured), R needs to 
"remember" that it should initially communicate back to A without 
security (since A and R do not have a shared key yet). Thus, R needs to 
maintain state that communications to A have to be treated differently 
(in 802.15.4e speak: A has "exempt status"). Or, is the idea that R 
somehow encodes this exempt status into its relay messages, so that it 
can pass this "hot potato" along and receive this back via T?
R2-2: I can imagine other scenarios than pre-provisioning of credentials 
or passing these along via Phase-I KMP: wouldn't piggy-backing this info 
along communication flows of Phase-II KMP also be an option?

Candidate KMPs (Section 5):
a) PANA. With bootstrapping during manufacturing, Phase-I may be 
organized differently. It would be good to show how PANA can fit 
802.15.4e needs in a stateless fashion.
b) HIP-DEX. The draft suggests this protocol (an expired draft), but at 
the same time points out that it is deficient, since does not support 
carrying certificates. This is somewhat puzzling.




On 7/5/2013 1:20 AM, Thomas Watteyne wrote:
>
> All,
>
> Below is the proposed agenda for the 6TSCH call tomorrow:
>
>   * Approval minutes last call [1min]
>   * draft-ohba-6tsch-security-00 [10min]
>   * Simulator [10min]
>   * Description of PCE [10min]
>   * Preparing for the BOF [25min]
>   * Re-organization Bitbucket [2min]
>   * AOB [1min]
>
> As usual, feel free to propose any changes to the agenda, also at the 
> beginning of the call.
>
> Remember that this call will be recorded.
>
> Pascal & Thomas
>
>
> Topic: 6TSCH Weekly
> Time: 8:00 am, Pacific Daylight Time (San Francisco, GMT-07:00)
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