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Re: flow label demultiplexing
On Mon, 18 Apr 2005, marcelo bagnulo braun wrote:
Note that HBA+CGA in one doesn't help (AFAICS) because otherwise you'd be
trusting anyone you have a public key with to not hijack any of your
sessions?
Well, i guess not.
In the CGA case, the address being used as the ULID for the communication is
a CGA that contains a hash of the publich key in the iid. In this case, you
will only trust a public key whose hash matches the iid of the ulid.
Sure.
So, when you use CGA capabilities of the address, the CGA parameter data
structure is exchanged upfront and it contains the public key.
Next, the node can use a new address (that was not included in the CGA
parameter data structure) because it can authorize it by signing it with the
private key corresponding to the CGA. Moreover, such signature could even be
included in a packet that contains the new address as source address (i
think)
I mean, with CGA there is no need to know the addresses before hand.
OK, I guess you'll assume that:
1) the CGA implementations would check the prefix, i.e., that anyone
who claims to be of prefix A::/64 has a certificate to use that
prefix, and can present that? Otherwise you trusting me would allow
me to say I'm in control of a third party's prefix, right?
2) delegation path discovery works across the internet so you can
actually find a common trust anchor, and
3) you sign the whole [shim6 exchange, and in this case everything,
if it's piggybacked] packet. But CGA is only defined for neighbor
discovery options...
As such, embedding the public key in the CGA/HBA address protects
against the third parties trying to spoof another person's identity,
but does not protect against the responder lying. (This is really bad
if one would use something like opportunistic encryption rather than
real "he's my very good friend, he won't try tricks" trust.) We need
to deal with that as well. The above three mitigate this to a great
extent, I think, but to a significant cost..
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings