Subject: [6lo] questions/initial feedback on draft-sarikaya-6lo-cga-nd-00

From: Rene Struik <[email-masked]>
Date: Thu, 07 Aug 2014 22:54:07 -0400

Hi Behcet:

I had a brief look at draft-sarikaya-6lo-cga-nd-00 and have the 
following initial feedback:

1) While the draft is presented as a lightweight version of SeND (RFC 
3971) using cryptographically generated addresses [CGA] (RFC 3972), 
shouldn't one consider this as an extension of CGA, where one adds 
ECC-variants to the mix. If so, would it make sense to suggest this 
draft as an update to those RFCs? {This does seem to give your draft 
wider applicability, also outside the LLN realm.}
2) In RFC 6775 (Neighbor Discovery Optimization for IPv6 over Low-Power 
Wireless Personal Area Networks), secure neighbor discovery was 
considered outside scope, although alluded to (at the end of Section 
11). I am curious as to whether you see cryptographically generated 
addresses and signatures as a viable option here. The main drawbacks I 
can see are that one cannot protect the privacy of signed messages and 
that the format of CGA itself imposes quite a low upper bound on 
security due to, e.g., impersonation attacks (~59 bits with a simple 
2nd-preimage attack).
3) It may be possible to reduce the size of some of the data formats 
(e.g., for the digital signature option in Section 4.2 of your draft) 
somewhat, both via cryptographic techniques and by using a more dense 
lossless compression mechanism. This may, e.g., result in being able to 
squeeze the LSEND message in two (rather than three) 802.15.4 frames 
{bases on back-of-the-beer-coaster estimates and your Section 5.1 packet 
sizes}. I can give some more detailed feedback, if I understand somewhat 
more how you see the #2 trade-offs.

Best regards, Rene

-- 
email: [email-masked] | Skype: rstruik
cell: +1 (647) 867-5658 | US: +1 (415) 690-7363

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From: Behcet Sarikaya <[email-masked]>
Date: Tue, 12 Aug 2014 14:55:05 -0500

Hi Rene,

Thanks for your comments.
Please see inline.

On Thu, Aug 7, 2014 at 9:54 PM, Rene Struik <[email-masked]> wrote:
> Hi Behcet:
>
> I had a brief look at draft-sarikaya-6lo-cga-nd-00 and have the following
> initial feedback:
>
> 1) While the draft is presented as a lightweight version of SeND (RFC 3971)
> using cryptographically generated addresses [CGA] (RFC 3972), shouldn't one
> consider this as an extension of CGA, where one adds ECC-variants to the
> mix. If so, would it make sense to suggest this draft as an update to those
> RFCs? {This does seem to give your draft wider applicability, also outside
> the LLN realm.}

OK.

> Wireless Personal Area Networks), secure neighbor discovery was considered
> outside scope, although alluded to (at the end of Section 11). I am curious
> as to whether you see cryptographically generated addresses and signatures
> as a viable option here. The main drawbacks I can see are that one cannot
> protect the privacy of signed messages and that the format of CGA itself
> imposes quite a low upper bound on security due to, e.g., impersonation
> attacks (~59 bits with a simple 2nd-preimage attack).

I read Section 11 of RFC 6775 again. My reading is that 6775 mentions
positively of SEND for hosts and router communication.
So I don't see a problem there.

> 3) It may be possible to reduce the size of some of the data formats (e.g.,
> for the digital signature option in Section 4.2 of your draft) somewhat,
> both via cryptographic techniques and by using a more dense lossless
> compression mechanism. This may, e.g., result in being able to squeeze the
> LSEND message in two (rather than three) 802.15.4 frames {bases on
> back-of-the-beer-coaster estimates and your Section 5.1 packet sizes}. I can
> give some more detailed feedback, if I understand somewhat more how you see
> the #2 trade-offs.

Sure, now that we are considering  improvements on the basic LSEND
that I defined such as the one Pascal proposed, I would happy to hear
from you on your proposal.

Regards,

Behcet
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