ISP customer assignments

Valdis.Kletnieks at Valdis.Kletnieks at
Mon Oct 5 22:35:09 UTC 2009

On Mon, 05 Oct 2009 16:13:37 CDT, Dan White said:

> a publicly routeable stateless auto configured address is no less
> secure than a publicly routeable address assigned by DHCP. Security is, and
> should be, handled by other means.

The problem is user tracking and privacy.

RFC4941's problem statement:

   Addresses generated using stateless address autoconfiguration
   [ADDRCONF] contain an embedded interface identifier, which remains
   constant over time.  Anytime a fixed identifier is used in multiple
   contexts, it becomes possible to correlate seemingly unrelated
   activity using this identifier.

   The correlation can be performed by

   o  An attacker who is in the path between the node in question and
      the peer(s) to which it is communicating, and who can view the
      IPv6 addresses present in the datagrams.

   o  An attacker who can access the communication logs of the peers
      with which the node has communicated.

   Since the identifier is embedded within the IPv6 address, which is a
   fundamental requirement of communication, it cannot be easily hidden.
   This document proposes a solution to this issue by generating
   interface identifiers that vary over time.

   Note that an attacker, who is on path, may be able to perform
   significant correlation based on

   o  The payload contents of the packets on the wire

   o  The characteristics of the packets such as packet size and timing

   Use of temporary addresses will not prevent such payload-based
(end quote)

Or phrased differently - if I DCHP my laptop in a Starbuck's, on Comcast, at
work, at a hotel, and a few other places, you'll get a whole raft of answers
which will be very hard to cross-corrolate.  But if all those places did
IPv6 autoconfig, the correlation would be easy, because my address would
always end in 215:c5ff:fec8:334e - and no other users should have those
last 64 bits.

Amazingly enough, some people think making it too easy to Big-Brother you
is a security issue...

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 227 bytes
Desc: not available
URL: <>

More information about the NANOG mailing list