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Re: addition of TLV to locator ID or locator ID set
On Mon, 3 Oct 2005, Erik Nordmark wrote:
There is a qualitative difference between the various leap-of-faith
security schemes (ssh being one example, I think BTNS is talking of
adding the same thing to IPsec), and HBA/CGA as it comes to
securing the locator changes in shim6.
Surely we ought to distinguish CGA from HBA here? Only HBA provides a
unique mapping. CGA is just 'anonymous' public key crypto, as IPSec
is. IPSec at least does /allow/ for key exchange schemes other than
anonymous keys, like X.509 cert chains, GSS-API, etc.
Thus in effect, the leap-of-faith provides a first-come-first-serve
approach to anybody wanting to claim an IP address as theirs.
Yep.
Compare this with using HBA.
With HBA Alice and Cesar will create the IPv6 address(es) as a hash of some
things.
Thus the only want Bob can pretend to be Alice (and have the same
IP address) is to use the identical HBA parameter data structure.
(This isn't hard, since the parameters are sent in the clear.)
Note that if Bob is not MITM, he can still get Alice's HBA, though it
requires Bob to first communicate with Alice. Eg with some innocent
unrelated pretence.
Unlike leap-of-faith schemes, which as part of their nature end up
assuming that the first host to connect is who they claim to be,
the intrinsic result of having a hash of something in the
interface-id in the address, is that we don't need to make any such
leap of faith. Which means that we can have a lot more flexibility
when it comes to handling attackers like Bob above who is on the
path for some amount of the time, but perhaps isn't permanently on
the path.
Yes, it's a very nice property of HBA, I must admit. Though, it does
completely rule out number portability, seemingly (in terms of
ULIDs).
Erik
regards,
--
Paul Jakma paul@clubi.ie paul@jakma.org Key ID: 64A2FF6A
Fortune:
When I got up this morning I took two Ex-Lax in addition to my Prozac.
I can't get off the john, but I feel good about it.