[Mipshop] Review of draft-arkko-mipshop-cga-cba-04

This is in response to the call on whether to adopt 
draft-arkko-mipshop-cga-cba-04 as a MIPSHOP WG item.  Given that the 
charter already says "MIPv6 Return Routability via both 
Cryptographically Generated Addresses and Credit-based Authorization 
for advancement as Proposed Standard

* Documents: draft-ietf-mipshop-cga-cba-XX.txt"

I am not really sure whether there is anything to say about adopting 
the I-D as a working group item.

I think the draft needs a revision and some major surgery.   Whether 
that happens before it becomes a WG item or after really doesn't matter to me.

So, I had a tough time trying to follow what's being proposed, but 
when I got to the security considerations section, things were 
clearer; that section seems to capture the problem space very 
clearly.  I think the draft needs to be revised using that as the 
guideline.  Specifically, I find that the proposed solution is too 
dependent on the 3775's solution for RO.  I think the consideration 
should be on the problem itself and a solution based on CGAs.  Any 
problems that are native to IPv6 itself need not be addressed in this 
draft.  To that end, I am proposing that the draft be split into two 
parts and considered separately.

Let me pose that as a question actually.  Are flooding attacks (from 
the last paragraph of the sec considerations section) specific to 
MIP6 or IPv6?  If there is nothing MIP6 specific there, that problem 
and the solution should be moved out of this draft.

To address redirection attacks, does a CN need to verify reachability 
of a HoA or whether the HoA is valid or not?  Perhaps the latter is sufficient?

Next, if the goal in generating a symmetric key is to amortize the 
cost of a public-key operation, it should be specified as such.  The 
concept of keygen is confusing in this draft and that seems to be due 
to the re-use of the terminology from 3775.  I think it is best to 
avoid that confusion here.

I realize those are high-level comments, but feel free to start a 
discussion on any of those if anything is unclear.

regards,
Lakshminath

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