Subject: RE: Advantages and disadvantages of using CB64 type of identifiers

From: "Christian Huitema" <[email-masked]>
Date: Mon, 5 Jul 2004 08:41:08 -0700

> Do you think that generating a new identifier every day would do the
> trick?

No, I don't think so. It would break correlation in time, but it would
still enable correlation in space, as in "these two locators lead to the
same location". That may or may not be a problem for *site* multihoming,
but it definitely is a problem for *host* multihoming, e.g. a host with
a WiFi and a GPRS connection.

Come to think of it, the only way to not disclose these relations to
third parties is to (1) make sure that the identifier is not disclosed
as part of the IPv6 address and (2) make sure that the identifier is
only exchanged over an encrypted channel between the corresponding
hosts.

-- Christian Huitema

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From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 5 Jul 2004 22:41:19 +0200

> a WiFi and a GPRS connection.

So what about a solution like NOID where this information is in the DNS?

I don't understand why you find it objectionable that someone would see 
which two IP addresses belong to the same host. I mean, what does this 
tell the third party?

As I understand it, the reason that RFC 3041 exists is because having a 
MAC-derived IP address allows a third party to follow a host's movement 
from one link to another. I can see why people wouldn't want that to 
happen. But I don't see how disclosure of a fixed relationship between 
two addresses or prefixes is similar. That is, unless multihoming is 
combined with some sort of mobility.

> only exchanged over an encrypted channel between the corresponding

But you pretty much always need to inform the correspondent, and an 
attacker who can snoop a link will often be in the position to become a 
correspondent and thus learn the information. If there is no snooping 
there is no reason for encryption.

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From: Brian E Carpenter <[email-masked]>
Date: Tue, 06 Jul 2004 09:11:21 +0200

> there is no reason for encryption.

Also, in the case of referrals, disclosure to a third party is necessary
and desirable. In any case, the current state of the Internet is that IP
addresses are public knowledge, and we are not under any obligation to
change that as part of multi6.

    Brian

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From: Brian E Carpenter <[email-masked]>
Date: Tue, 06 Jul 2004 09:15:26 +0200

> a WiFi and a GPRS connection.

Some might consider it a solution, not a problem. For example I can
imagine it helping to meet "911" requirements (an emergency VoIP call
arrives via WiFi, but back-tracking to GPRS gives better automatic
geolocation).

    Brian