Internet DRAFT - draft-narayanan-psk-addr-gen
draft-narayanan-psk-addr-gen
Network Working Group N. Venkitaraman
Internet-Draft Motorola
Expires: August 14, 2006 V. Narayanan
Qualcomm
February 10, 2006
Pre-Shared Key (PSK) Based Addresses (PBA)
draft-narayanan-psk-addr-gen-00.txt
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Copyright (C) The Internet Society (2006).
Abstract
Cryptographically generated addresses (CGAs) provide a means of
generating an IP address that is tied to a public key of a node.
Using this means, the address ownership of the node can be verified
by using the public key of the node to decrypt data signed by the
node using its private key. In AAA-based systems, there is currently
no means of performing such absolute address ownership checks, since
address authorization is traditionally outside the scope of AAA.
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However, in some key generation protocols, it may be critical to
perform address ownership verification or authorization before the
generated key can be used. When such key generation protocols are
AAA-based, there is no known method of address authorization to allow
this operation.
This draft provides a means of IPv6 address generation using a shared
secret so that the IP address of a node can be verified by the entity
with which the node shares the secret.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. PBA Generation . . . . . . . . . . . . . . . . . . . . . . . . 4
4. PBA Verification . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 7
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1. Introduction
Cryptographically generated addresses (CGAs) provide a means of
generating an IP address that is tied to a public key of a node.
Using this means, the address ownership of the node can be verified
by using the public key of the node to decrypt data signed by the
node using its private key. In AAA-based systems, there is currently
no means of performing such absolute address ownership checks, since
address authorization is traditionally outside the scope of AAA.
However, in some key generation protocols, it may be critical to
perform address ownership verification or authorization before the
generated key can be used. When such key generation protocols are
AAA-based, there is no known method of address authorization to allow
this operation.
For instance, AAA-based authentication and authorization are often
used in cellular and WiMax systems. Nodes running Mobile IP may use
a secret shared with the AAA server as a means for authentication and
derivation of shared keys with the home agent. In the case of Fast
Mobile IP (FMIP), handover keys may be derived using AAA between the
MN and AR.
This draft provides a means of IPv6 address generation using a shared
secret so that the IP address of a node can be verified by the entity
with which the node shares the secret. For instance, an MN may use
an MN-AAA key to derive an IPv6 address suffix that can be verified
by the AAA server for address authorization. Any AAA-assisted key
derivation protocols may use the method specified in this draft to
verify the address and bind the derived keys to the IP address of the
MN.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC- 2119 [1].
In addition, this document uses the following terms:
Pre-Shared Key (PSK) Based Address (PBA)
An IPv6 address generated cryptographically using a pre-shared
key.
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Address Generation Key (AGK)
A key generated from the PSK specifically to use in the creation
of PBAs.
3. PBA Generation
This section describes a method of using a Pre-Shared Key (PSK) to
derive the IPv6 address of a node. The input parameters for PBA
Generation include an Address Generation Key (AGK) generated using
the PSK, a link ID of the node (e.g., MAC address), a nonce, the ID
of the router advertising the prefix and the advertised network
prefix itself. The AGK is derived from the PSK as follows.
AGK = PRF (PSK, Node ID | Key Generation Nonce | "Address Generation
Key"), where | denotes concatenation.
In AAA-based scenarios, the PSK is the key that the node shares with
the AAA server (e.g., MN-AAA secret). The Node ID in this case is
the NAI of the node. The Key Generation Nonce is a random value
generated by the node. It is recommended that the nonce be a
cryptographically generated value for added privacy.
The IPv6 suffix of the address of the node is derived as follows.
Address Suffix = PRF (AGK, Router ID | Collision Count), where |
denotes concatenation.
The Router ID is the IP address of the router advertising the IPv6
prefix. The collision count by default is 0 and is incremented by 1
every time there is a collision on the generated address. The Pseudo
Random Function (PRF) used is HMAC-SHA1.
The generated suffix is then concatenated with the advertised prefix
to form a complete IPv6 address for the node.
4. PBA Verification
The PBA may be sent to an entity that shares the PSK with the node
for address ownership verification. Such a message must contain a
hash of the address generated using the PSK. For instance, a node
may use the AAA key to sign the message to the AAA server. The other
parameters such as the nonce, router ID and collision count must also
be sent to the AAA server. The collision count should be considered
to be 0 if it is not specifically sent to the AAA server or other
verifying entity.
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After successful verification of the signature, the AAA server must
generate the AGK corresponding to the node based on the PSK as in the
previous section. The AGK can then be used along with the other
parameters in generating the address suffix in exactly the same
manner as done by the node. It is generally sufficient to verify
that the node is claiming the right suffix.
5. Security Considerations
This document describes a means of address authorization using pre-
shared keys. It is not known to introduce any security
vulnerabilities. In general, the PSK and nonce used must be strong
to avoid any observer being able to generate the same address or
being able to tie multiple PBAs of a node together to derive the key.
6. IANA Considerations
No IANA services are required in this document.
7. Acknowledgments
8. References
8.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[2] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
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Authors' Addresses
Narayanan Venkitaraman
Motorola
1301 E. Algonquin Road
Schaumburg, IL 60196
US
Email: narayanan.venkitaraman@motorola.com
Vidya Narayanan
Qualcomm
5775 Morehouse Dr
San Diego, CA 92121
US
Email: vidyan@qualcomm.com
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Acknowledgment
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Internet Society.
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