Subject: DT's review of draft-ietf-send-cga-00.txt

From: "Dave Thaler" <[email-masked]>
Date: Thu, 19 Jun 2003 15:52:08 -0700

I found lots of typos and grammatical errors (although far fewer than in

the SEND draft), but here I'll just list the comments on actual
substance...

1) The title of the document is "Cryptographically Generated Addresses
(CGA)".
   However, the content is currently limited to their use in SEND.
Hence,
   a more appropriate title would be "Securing IPv6 Neighbor Discovery 
   Using Cryptographically Generated Addresses (CGAs)", since it is not
   a generic spec.

2) On the other hand, I'd prefer the existing title, but the document as

   specified appears to preclude the use of CGAs in general.
Specifically, 
   since the u and g bits MUST be 0 (as opposed to 1, as they were
before 
   in both Aura's spec and in Arkko's), there is now no way to
distinguish 
   a CGA from another address, and hence it becomes impossible to
prevent 
   spoofing of a CGA.  This seems like a major design flaw.  I don't see

   this mentioned in Appendix B, why is the more general use of CGA in 
   the future now being prevented?  (Since a SEND node now would drop
any 
   packet with g,u = 1, one cannot interoperate with a node that does
that.)

   The simple fix is to just remove the statement about dropping if 
   u and g are not 0.

3) Section 7.1 states:
   > The purpose of CGA addresses is to prevent stealing and spoofing of

   > IPv6 addresses in the secure neighbor discovery protocol.

   I strongly disagree with this statement.  The purpose of CGA
   addresses is to prevent stealing and spoofing of IPv6 addresses 
   _in general_.  The purpose is not limited to SEND.
   
4) Section 6 seems to imply that only that section is specific to SEND,
   and the rest are generally applicable.  As mentioned above, I don't
   believe that is true, as the other sections appear to preclude any
   use outside of SEND.

5) Section 7.2 states:
   >  The effectiveness of the hash extension depends of the assumption
   >  that the computational capacity of the attacker and the address
   >  generator will grow and the same (potentially exponential) rate.
   >  This is clearly not true if the addresses are generated on low-end
   >  mobile devices.

   Why is it "clearly" not true?  I don't think it's obvious that
Moore's
   law does not apply to low-end mobile devices.  Do you have a
well-known
   reference that indicates it does not?
  
6) Re appendix A: "TBW"?

-Dave

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