IPsec Working Group Stephen Kent
Internet Draft BBN Technologies
Expires August 2004 February 2004
Extended Sequence Number Addendum to IPsec DOI for ISAKMP
draft-ietf-ipsec-esn-addendum-03.txt
Status of This Memo
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
The IP Security Authentication Header (AH) and Encapsulating Security
Payload (ESP) protocols use a sequence number to detect replay. This
document describes extensions to the Internet IP Security Domain of
Interpretation (DOI) for the Internet Security Association and Key
Management Protocol(ISAKMP). These extensions support negotiation of
the use of traditional 32-bit sequence numbers or extended 64-bit
sequence numbers for a particular AH or ESP security association.
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1. Introduction
The specifications for the IP Authentication Header (AH) [AH] and the
IP Encapsulating Security Payload (ESP) [ESP] describe an option for
use of Extended (64-bit) Sequence Numbers. This option permits
transmission of very large volumes of data at high-speeds over an
IPsec Security Association, without rekeying to avoid sequence number
space exhaustion. This document describes the additions to the IPsec
DOI for ISAKMP [DOI] that are needed to support negotiation of the
Extended Sequence Number option.
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in RFC 2119 [Bra97].
2. IPsec Security Association Attribute
The following SA attribute definition is used in Phase II of an IKE
negotiation. The attribute type is Basic (B). Encoding of this
attribute is defined in the base ISAKMP specification [ISAKMP].
Attributes described as basic MUST NOT be encoded as variable. See
[IKE] for further information on attribute encoding in the IPsec DOI.
All restrictions listed in [IKE] also apply to the IPsec DOI and to
this addendum.
Attribute Type
class value type
---------------------------------------------------------
Extended (64-bit) Sequence Number TBD B
Class Values
This class specifies that the Security Association will be using
64-bit Sequence Numbers. (See [AH] and [ESP] for a description
of Extended (64-bit) Sequence Numbers.)
RESERVED 0
64-bit Sequence Number 1
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3. Attribute Negotiation
If an implementation receives a defined IPsec DOI attribute (or
attribute value) which it does not support, an ATTRIBUTES-NOT-SUPPORT
SHOULD be sent and the security association setup MUST be aborted.
If an implementation receives any attribute value but the value for
64-bit Sequence Numbers, the security association setup MUST be
aborted.
4. Security Considerations
This memo pertains to the Internet Key Exchange protocol ([IKE]),
which combines ISAKMP ([ISAKMP]) and Oakley ([OAKLEY]) to provide for
the derivation of cryptographic keying material in a secure and
authenticated manner. Specific discussion of the various security
protocols and transforms identified in this document can be found in
the associated base documents and in the cipher references.
The addition of the ESN attribute does not change the underlying
security characteristics of IKE. In using extended sequence numbers
with ESP, it is important to employ an encryption mode that is secure
when very large volumes of data are encrypted under a single key.
Thus, for example, DES in CBC mode would NOT be suitable for use with
the ESN, because no more than 2^32 blocks should be encrypted under a
single DES key in that mode. Similarly, the integrity algorithm used
with ESP or AH should be secure relative to the number of packets
being protected. To avoid potential security problems imposed by
algorithm limitations, the SA lifetime may be set to limit the volume
of data protected with a single key, prior to reaching the 2^64
packet limit imposed by the ESN.
5. IANA Considerations
This document contains a "magic" number to be maintained by the IANA.
No additional class values will be assigned for this attribute. Upon
approval of this draft for publication as an RFC, IANA is to allocate
an IPsec Security Attribute value for "Attribute Type". This value
is to replace the TBD under the heading "value" in the table in
Section 2.
Acknowledgments
The author would like to thank the members of the IPsec working
group. The author would also like to acknowledge the contributions of
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Karen Seo for her help in the editing of this specification.
References
[AH] Kent, S., "IP Authentication Header", RFC ???, ??? 2003.
[DOI] Piper, D., "The Internet IP Security Domain of
Interpretation for ISAKMP", RFC 2407, November 1998.
[ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
???, ??? 2003.
[IKE] Harkins, D., and D. Carrel, D., "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[ISAKMP] Maughan, D., Schertler, M., Schneider, M., and J. Turner,
"Internet Security Association and Key Management Protocol
(ISAKMP)", RFC 2408, November 1998.
[OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol", RFC
2412, November 1998.
Author Information
Stephen Kent
BBN Technologies
10 Moulton Street
Cambridge, MA 02138
USA
Phone: +1 (617) 873-3988
EMail: kent@bbn.com
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Expires August 2004
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