IETF Mobile IP Working Group Charles E. Perkins
INTERNET-DRAFT Nokia Research Center
5 Apr 2003
Preconfigured Binding Management Keys for Mobile IPv6
<draft-perkins-mobileip-precfg-kbm-00.txt>
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.
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Abstract
A mobile node and a correspondent node may preconfigure a Binding
Management Key for authorizing Binding Updates.
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1. Preconfiguring a Binding Management Key (Kbm)
A mobile node and a correspondent node may preconfigure a Binding
Management Key (Kbm) for authorizing binding management messages,
especially Binding Update and Binding Acknowledgement messages. The
key MUST be the same length as that configured using inputs from
Mobile IPv6 [1] return routability.
When a Binding Update is to be authenticated using such a
preconfigured binding key (Kbm), the Binding Authorization Data
suboption MUST be present. The Nonce Indices option SHOULD NOT
be present. If it is present, the nonce indices supplied MAY be
ignored and are not included as part of the calculation for the
authentication data, which is to be carried exactly as specified
in [1].
2. Security Considerations
A correspondent node and a mobile node MAY use a preconfigured
binding management key (Kbm) to manage the authentication
requirements for binding cache management messages. Such keys must
be handled carefully to avoid inadvertent exposure to the threats
outlined in [2].
A mobile node MUST use a different binding management key (Kbm)
for each node in its Binding Update List. This ensures that the
sender of a Binding Update can always be uniquely determined. This
is necessary, as this authorization method does not provide any
guarantee that the given care-of address is legitimate. For the same
reason, this method SHOULD only be applied between nodes that are
under the same administration. The return routability procedure is
RECOMMENDED for all general use and MUST be the default, unless the
user explicitly overrides this by entering a key for a particular
peer.
Replay protection for the Binding Authorization Data option
authentication mechanism is provided by the Sequence Number field
of the Binding Update. This method of providing replay protection
fails when the Binding Update sequence numbers cycle through the
16 bit counter (i.e., not more than 65,536 distinct uses of Kbm),
or if the sequence numbers are not protected against reboots. If
the mobile node were to move every hour, 24 hours a day, every day
of the year, this would require changing keys every 7 years. Even
if the mobile node were to move every minute, this would provide
protection for over a month. Given typical mobility patterns, there
is little danger of replay problems; nodes for which problems might
arise are expected to use methods other than manual configuration for
Kbm anyway. When the sequence number field rolls over, the parties
SHOULD configure another value for Kbm.
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3. IANA Considerations
No new protocol numbers are required.
4. Acknowledgement
Thanks are due to everyone who reviewed the discussion of issue #146.
References
[1] D. Johnson and C. Perkins. Mobility support in IPv6 (work in
progress). Internet Draft, Internet Engineering Task Force,
November 2002.
[2] Tuomas Aura and Jari Arkko. MIPv6 BU Attacks and Defenses (work
in progress). Internet Draft, Internet Engineering Task Force,
February 2002.
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Author's Address
Questions about this document can also be directed to the author:
Charles E. Perkins
Nokia Research Center
313 Fairchild Drive
Mountain View, CA 94043
USA
Phone: +1 650 625-2986
Fax: +1 650 625-2502
E-mail: charliep@iprg.nokia.com
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