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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 5106

   EAP WG
   Internet-Draft                                       H. Tschofenig
                                                        D. Kroeselberg
                                                               Siemens
                                                               Y. Ohba
                                                               Toshiba
                                                            F. Bersani
                                                    France Telecom R&D
   Document: draft-tschofenig-eap-ikev2-06.txt
   Expires: November 18, 2005                                May 2005


                          EAP IKEv2 Method
                             (EAP-IKEv2)

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on November 18, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract


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   EAP-IKEv2 is an EAP method which reuses the cryptography and the
   payloads of IKEv2, creating a flexible EAP method that supports
   both symmetric and asymmetric authentication, as well as a
   combination of both. This EAP method offers the security benefits
   of IKEv2 authentication and key agreement without the goal of
   establishing IPsec security associations.













































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   Table of Contents

   1. Introduction..................................................3
   2. IKEv2 and EAP-IKEv2 Overview..................................4
   3. Terminology...................................................5
   4. Protocol overview.............................................5
   5. Identities used in EAP-IKEv2..................................8
   6. Packet Format.................................................9
   7. Retransmission...............................................11
   8. Key derivation...............................................11
   9. Error Handling...............................................13
   10. Fast Reconnect..............................................14
   11. Channel Binding.............................................16
      11.1 Channel Binding Procedure in Full Authentication........16
      11.2 Channel Binding Procedure in Fast Reconnect.............17
      11.3 Channel Binding Error Indication........................17
      11.4 Notify Payload Types for Channel Binding................18
      11.5 Examples................................................19
   12. Security Considerations.....................................23
      12.1 General Considerations..................................23
      12.2 Security Claims.........................................23
   13. Open Issues.................................................25
   14. Normative References........................................26
   15. Informative References......................................26
   Acknowledgments.................................................27
   Author's Addresses..............................................27
   Intellectual Property Statement.................................28
   Disclaimer of Validity..........................................28
   Copyright Statement.............................................29
   Acknowledgment..................................................29


1. Introduction

   This document specifies the EAP-IKEv2 authentication method. The
   main design goal for EAP-IKEv2 is to provide a flexible and
   efficient EAP method which makes the IKEv2 protocol's features
   available for scenarios using EAP-based authentication.
   The main advantage of EAP-IKEv2 is that it does not define a new
   cryptographic protocol, but re-uses the IKEv2 authentication
   exchanges, and thereby provides strong, well-analyzed,
   cryptographic properties as well as broad flexibility.

   EAP-IKEv2 especially provides an efficient shared-secret method
   offering a high security level, and allows for password-derived
   shared secrets while protecting from password-guessing attacks.





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   EAP-IKEv2 provides mutual authentication between EAP peers. This
   may be based on either symmetric methods using pre-shared keys,
   or on asymmetric methods based on public/private key pairs,
   Certificates and CRLs. It is possible to use different types of
   authentication for the different directions, e.g. the server uses
   certificate-based authentication whereas the client uses a
   symmetric-key method.
   IKEv2 supports two-phased authentication schemes by establishing
   a server-authenticated secure tunnel and subsequently protecting
   an EAP authentication allowing for legacy client authentication
   methods. EAP-IKEv2, however, does not support this optional
   tunneling feature of IKEv2 in this version, which allows to
   increase the EAP-IKEv2 method performance and to decrease
   implementation complexity.

   A non-goal of EAP-IKEv2 (and basically the major difference to
   plain IKEv2) is the establishment of IPsec security associations,
   as this would not make much sense in the standard AAA three-party
   scenario, consisting of an EAP peer, an authenticator (NAS) and
   a back-end authentication server terminating EAP. IPsec SA
   establishment may be required locally (i.e., between the EAP peer
   and some access server). However, SA establishment within an EAP
   method would only provide SAs between the EAP peer and the back-end
   authentication server. Other approaches as, e.g., the IETF PANA
   framework are considered more appropriate in this case.


2. IKEv2 and EAP-IKEv2 Overview

   IKEv2 [Kau04] is a protocol which consists of two exchanges:

   (1) an authentication and key exchange protocol which establishes
   an IKE-SA.

   (2) messages and payloads which focus on the negotiation of
   parameters in order to establish IPsec security associations
   (i.e., Child-SAs). These payloads contain algorithm parameters
   and traffic selector fields.

   In addition to the above-mentioned parts IKEv2 also includes some
   payloads and messages which allow configuration parameters to be
   exchanged primarily for remote access scenarios.

   The EAP-IKEv2 method defined by this document uses the IKEv2
   payloads and messages used for the initial IKEv2 exchange which
   establishes an IKE-SA.

   IKEv2 provides an improvement over IKEv1 [RFC2409] as described
   in Appendix A of [Kau04]. Important for this document are the


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   reduced number of initial exchanges, decreased latency of the
   initial exchange, and some other fixes (e.g., hash problem). IKEv2
   is a cryptographically sound protocol that has received a
   considerable amount of expert review and that benefits from a long
   practical experience with IKE.
   The goal of EAP-IKEv2 is to inherit these properties within an
   efficient, secure EAP method.

   In addition, IKEv2 provides authentication and key exchange
   capabilities which allow an entity to use symmetric as well as
   asymmetric authentication within a single protocol. Such
   flexibility is considered important for an EAP method and is
   provided by EAP-IKEv2.

   [Per03] provides a good tutorial for IKEv2 design decisions.

   EAP-IKEv2 provides a secure fragmentation mechanism in which
   integrity protection is performed for each fragment of an IKEv2
   message.


3. Terminology

   This document does not introduce new terms other than those defined
   in [RFC3748] or in [Kau04].

   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 [RFC2119].


4. Protocol overview

   This section provides some overview over EAP-IKEv2 message
   exchanges. Note that some mandatory IKEv2 payloads are omitted,
   or profiled (such as SAi2 and SAr2), as it is not supported to
   establish IPsec (ESP, AH) SAs in EAP-IKEv2.

   IKEv2 uses the same protocol message exchanges for both symmetric
   and asymmetric authentication. The difference lies only in the
   computation of the AUTH payload. See Section 2.15 of [Kau04] for
   more information about the details of the AUTH payload
   computation. It is even possible to combine symmetric (e.g., from
   the client to the server) with asymmetric authentication (e.g.,
   from the server to the client) in a single protocol exchange.
   Figure 1 depicts such a protocol exchange.

   Message exchanges are reused from [Kau04], and are adapted. Since
   this document does not describe frameworks or particular


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   architectures the message exchange takes place between two parties
   - between the Initiator (I) and the Responder (R). In the context
   of EAP the Initiator takes the role of the EAP server and the
   responder matches the EAP peer.

   The first message flow shows the EAP-IKEv2 full successful
   exchange. The core EAP-IKEv2 exchange (message (3) - (6)) consists
   of four messages (two round trips)_only. The first two messages
   constitute the standard EAP identity exchange and are optional;
   they are not required in case the EAP server is known. In the
   exchange, the EAP server (B) takes the role of the IKEv2 initiator
   and the EAP peer (A) acts as the IKEv2 responder.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR(A,0), SAi1, KEi, Ni)

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SAr1, KEr, Nr, [CERTREQ])

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,], AUTH})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDr, [CERT,] AUTH})

   7) A <-- B: EAP-Success

             Figure 1: EAP-IKEv2 successful message flow


   Figure 2 shows the message flow in case the EAP peer fails to
   authenticate the EAP server.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR(A,0), SAi1, KEi, Ni)

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SAr1, KEr, Nr, [CERTREQ])

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,], AUTH})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(


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            HDR(A,B), SK {N(AUTHENTICATION_FAILED)})

   7) A <-- B: EAP-Failure

        Figure 2: EAP-IKEv2 with failed server authentication


   Figure 3 shows the message flow in case the EAP server fails to
   authenticate the EAP peer. The EAP peer MUST send an empty
   EAP-IKEv2 informational message in reply to the EAP server's error
   indication. The EAP server answers with an EAP-Failure.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR(A,0), SAi1, KEi, Ni)

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SAr1, KEr, Nr, [CERTREQ])

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,], AUTH})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDr, [CERT,] AUTH})

   7) A <-- B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(AUTHENTICATION_FAILED)})

   8) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {})

   9) A <-- B: EAP-Failure

        Figure 3: EAP-IKEv2 with failed client authentication


   Since the goal of this EAP method is not to establish an IPsec SA
   some payloads used in IKEv2 are omitted. In particularly the
   following messages and payloads SHOULD not be sent:

   - Traffic Selector (TS) payloads
   - SA payloads that carry SA proposals for protocol IDs other than
   1(IKE), i.e., SA payloads with protocol ID 2 (ESP) or 3 (AH)
   - ESN (extended sequence number) transforms

   Some of these messages and payloads are optional in IKEv2.



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   In general it does not make sense to directly negotiate IPsec SAs
   within EAP-IKEv2, as such SAs are not required between the EAP
   endpoints and as SAs cannot be transferred to different AAA
   entities by standard AAA protocols.

   Consequently, mechanisms and payloads that are not supported by
   EAP-IKEv2 are:
   - ECN Notifications as specified in section 2.24 of [Kau04].
   - IKE-specific port handling
   - NAT traversal

   Since the EAP server acts as the initiator of the initial IKEv2
   exchange, a number of optional payloads used for realizing
   specific features in IKEv2 are not supported by EAP-IKEv2, as they
   are intended for the client side (e.g. for corporate access
   scenarios) in plain IKEv2. These payloads MUST not be sent by an
   EAP-IKEv2 entity. EAP-IKEv2 entities receiving such payloads MUST
   respond with the appropriate error messages as defined in [Kau04].
   These payloads are:
   - Configuration (CFG) payloads as specified in 3.15 of [Kau04].
   These payloads MUST not be sent by an EAP-IKEv2 implementation.
   EAP-IKEv2 entities receiving such payloads MUST ignore
   configuration payloads as described for minimal implementations
   in 3.15 of [Kau04].
   - EAP payloads as specified in section 3.16 of [Kau04]. These
   payloads allow to run an inner EAP exchange for secure legacy
   authentication through an IKE SA. EAP-IKEv2 implementations
   acting as initiator MUST include and AUTH payload in the initial
   IKE_AUTH message (message 3 of the initial IKE exchange).
   EAP-IKEv2 implementations receiving initial IKE_AUTH messages as
   responders that indicate the initiator's desire to start extended
   authentication MUST be answered with an AUTHENTICATION_FAILED
   notification as the response.

   IKEv2 provides optional functionality for additional DoS
   protection by adding a roundtrip to the initial exchanges, see
   section 2.xx of [Kau04]. As this is intended to protect the IKEv2
   responder but in EAP-IKEv2 the EAP server takes the role of the
   initiator, it is not recommended to use this feature of IKEv2 for
   server protection.


5. Identities used in EAP-IKEv2

   A number of different places allow to convey identity information
   in IKEv2, when combined with EAP. This section describes their
   function within the different exchanges of EAP-IKEv2. Note that
   EAP-IKEv2 does not introduce more identities than other



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   non-tunneling EAP methods. Figure 4 shows which identities are
   used during the individual phases of the protocol.

    +-------+       +-------------+   +---------+
    |Client |       |Front-End    |   |AAA      |
    |       |       |Authenticator|   |Server   |
    +-------+       +-------------+   +---------+

          EAP/Identity-Request
        <---------------------
    (a)   EAP/Identity-Response
        ---------------------------------->

           Tunnel-Establishment
    (b)    (Identities of IKEv2 are used)
           Server (Network) Authentication
        <----------------------------------
                      ...
        ---------------------------------->

               Figure 4: Identities used in EAP-IKEv2

   a) The first part of the (outer) EAP message exchange provides
   information about the identities of the EAP endpoints. This
   message exchange mainly is an identity request/response. This
   exchange is optional if the EAP server is known already or can be
   learned by other means.

   b) Identities exchanged within EAP-IKEv2 for both the initiator
   and the responder. The initiator identity is often associated with
   a user identity such as a fully-qualified RFC 822 email address.
   The identity of the responder might be a FQDN. The identity is of
   importance for authorization.

   For carrying identities in EAP-IKEv2, implementations MUST follow
   the rules given in [Kau04], section 3.5, i.e., MUST be configurable
   to send at least one of ID_IPV4_ADDR, ID_FQDN, ID_RFC822_ADDR, or
   ID_KEY_ID, and MUST be configurable to accept all of these types.
   Implementations SHOULD be capable of generating and accepting all
   of these types.


6. Packet Format

   The IKEv2 payloads, which are defined in [Kau04], are embedded into
   the Data field of the standard EAP Request/Response packets. The
   Code, Identifier, Length and Type field is described in [RFC3748].
   The Type-Data field carries a one byte Flags field following the



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   IKEv2 payloads. Each IKEv2 payload starts with a header field HDR
   (see [Kau04]).

   The packet format is shown in Figure 5.

      0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Code      |   Identifier  |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |   Flags       |       Message Length          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Message Length          |       Data ...                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Integrity Checksum Data                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 5: Packet Format


   No additional packet formats other than those defined in [Kau04]
   are required for this EAP method.

   The Flags field is used for fragmentation support. The S and F bits
   are reserved for future use.

   Currently five bits of the eight bit flags field are defined. The
   remaining bits are set to zero.

    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |S F L M I 0 0 0|
   +-+-+-+-+-+-+-+-+

   S = (reserved)
   F = (reserved)
   L = Length included
   M = More fragments
   I = Integrity Checksum Data included

   EAP-IKEv2 messages which have neither the S nor the F flag set
   contain regular IKEv2 message payloads inside the Data field.

   With regard to fragmentation we follow the suggestions and
   descriptions given in Section 2.8 of [PS+03]: The L indicates that
   a length field is present and the M flag indicates fragments. The
   L flag MUST be set for the first fragment and the M flag MUST be
   set on all fragments expect for the last one. Each fragment sent
   must subsequently be acknowledged.


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   The Message Length field is four octets long and present only if
   the L bit is set. This field provides the total message length that
   is being fragmented (i.e., the length of the Data field.).

   The Integrity Checksum Data is the cryptographic checksum of the
   entire EAP message starting with the Code field through the Data
   field.  This field presents only if the I bit is set.  The field
   immediately follows the Data field without adding any padding
   octet before or after itself.  The checksum MUST be computed for
   each fragment (including the case where the entire IKEv2 message
   is carried in a single fragment) by using the same key (i.e., SK_ai
   or SK_ar) that is used for computing the checksum for the IKEv2
   Encrypted payload in the encapsulated IKEv2 message.  The
   Integrity Checksum Data field is omitted for other packets.  To
   minimize DoS   attacks on fragmented packets, messages that are
   not protected SHOULD NOT be fragmented.  Note that IKE_SA_INIT
   messages are the only ones that are not encrypted or integrity
   protected, however, such messages are not likely to be fragmented
   since they do not carry certificates.

   The EAP Type for this EAP method is <TBD>.


7. Retransmission

   Since EAP authenticators support a timer-based retransmission
   mechanism for EAP Requests and EAP peers retransmit the last valid
   EAP Response when receiving a duplicate EAP Request message, IKEv2
   messages MUST NOT be retransmitted based on timers, when used as
   EAP authentication method.


8. Key derivation

   The EAP-IKEv2 method described in this document generates session
   keys. On the one hand, these session keys are used within the
   IKE-SA, for protection of EAP-IKEv2 payloads, e.g., AUTH exchanges
   or notifications. On the other hand, additional keys are derived
   to be exported as part of the EAP keying framework [AS+05] (i.e.,
   MSK, EMSK and IV). It is good cryptographic security practice to
   use different keys for different "applications". Hence we suggest
   reusing of the key derivation function suggested in Section 2.17
   of [Kau04] to create keying material KEYMAT.

   The key derivation function defined is KEYMAT = prf+(SK_d, Ni |
   Nr), where Ni and Nr are the Nonces from the IKE_SA_INIT exchange.




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   Since the required amount of keying material is greater than the
   size of the output of the prf algorithm the prf is used iteratively.
   Section 2.13 of [Kau04] describes this mechanism in detail.

   According to [AS+05] the keying material of MSK, EMSK and IV have
   to be at minimum 64, 64 and 64 octets long.

   The produced keying material for MSK, EMSK and IV MUST be at least
   the minimum size (i.e., 64 octets).  The keying material KEYMAT
   is split into the MSK, EMSK and IV part.


   Figure 6 describes the keying hierarchy of EAP-IKEv2 graphically.
   This figure is adopted from Figure 2 of [AS+05].

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++      ---+
   |                                                          |         ^
   |                      EAP-IKEv2 Method                    |         |
   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++  +------------------+ |         |
   | |  EAP-IKEv2 Diffie-Hellmann     |  | EAP-IKEv2 prot.  | |         |
   | |  derived and authenticated key |  | session specific | |         |
   | |           SK_d                 |  | state (Nonce i,j)| |         |
   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++  +-------------+----+ |         |
   |                   |                               |      |   Local |
   |                   |                               |      |  to EAP |
   |                   |                               |      |  Method |
   |                   |                               |      |         |
   |                   |                               |      |         |
   |                   |                               |      |         |
   |                   |                               |      |         |
   |                   +---------------+-------------+ |      |         |
   |                   |               |             | |      |         |
   |               +-+-+-+-+-++  +-+-+-+-+-++  +-+-+-+-+-++   |         |
   |               | MSK      |  |EMSK      |  | IV       |   |         |
   |               |Derivation|  |Derivation|  |Derivation|   |         |
   |               +-+-+-+-+-++  +-+-+-+-+-++  +-+-+-+-+-++   |         |
   |                     |             |             |        |         V
   +-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-++-+-+-+-+-------+-+-+----+      ---+
                         |             |             |                  ^
                         |MSK          |EMSK         |IV                |
                         |             |             |                  |
                         |             |             |         Exported |
                         |             |             |           by EAP |
                         V             V             V           Method |
                    +-+-+-+-+-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+          |
                    |   AAA  Key Derivation |  | Known       |          |
                    |   Naming & Binding    |  |(Not Secret) |          |
                    +-+-+-+-+-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+          V



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     Legend:

     MSK = Master Session Key (512 Bit)
     EMSK = Extended Master Session Key (512 Bit)
     SK_d = Session key derived by EAP-IKEv2
     IV   = Initialization Vector

   Figure 6: EAP-IKEv2 Keying Hierarchy


9. Error Handling

   As described in the IKEv2 specification, there are many kinds of
   errors that can occur during IKE processing (i.e., processing the
   Data field of EAP-IKEv2 Request and Response messages) and
   detailed processing rules.  EAP-IKEv2 follows the error handling
   rules specified in the IKEv2 specification for errors on the Data
   field of EAP-IKEv2 messages, with the following additional rules:

   For an IKEv2 error that triggers an initiation of an IKEv2 exchange
   (i.e., an INFORMATIONAL exchange), an EAP-IKEv2 message that
   contains the IKEv2 request that is generated for the IKEv2 exchange
   MUST be sent to the peering entity.  In this case, the EAP message
   that caused the IKEv2 error MUST be treated as a valid EAP message.

   For an IKEv2 error for which the IKEv2 message that caused the error
   is discarded without triggering an initiation of an IKEv2
   exchange, the EAP message that carries the erroneous IKEv2 message
   MUST be treated as an invalid EAP message and discarded as if it
   were not received at EAP layer.

   For an error occurred outside the Data field of EAP-IKEv2 messages,
   including defragmentation failures, integrity check failures,
   errors in Flag and Message Length fields, the EAP message that
   caused the error MUST be treated as an invalid EAP message and
   discarded as if it were not received at EAP layer.

   When the EAP-IKEv2 method runs on a backend EAP server, an
   outstanding EAP Request is not retransmitted based on timer and
   thus there is a possibility of EAP conversation stall when the EAP
   server receives an invalid EAP Response.  To avoid this, the EAP
   server MAY retransmit the outstanding EAP Request in response to
   an invalid EAP Response.  Alternatively, the EAP server MAY send
   a new EAP Request in response to an invalid EAP Response with
   assigning a new Identifier and putting the last transmitted IKEv2
   message in the Data field.





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10. Fast Reconnect

   EAP-IKEv2 supports fast reconnect, i.e., a successful reconnect
   exchange creates a new IKE-SA by using an IKE CHILD_SA exchange.
   The purpose of a re-authentication exchange is to allow for
   efficient re-keying based on the existing IKE-SA in situations
   where (depending on the given security policy) no full
   authentication is required in case of an existing EAP-IKEv2
   security context.
   The fast reconnect exchange uses the IKE-SA rekeying as specified
   in section 2.18 of [Kau04]. However, the exchanges for EAP-IKEv2
   do not use rekeying payloads other than IKE SAs:
   - The TS (traffic selector) payloads SHOULD not be sent by
   EAP-IKEv2 implementations.
   - The [N] payload (REKEY_SA notification) SHOULD not be sent by
   EAP-IKEv2 implementations.

   During fast re-authentication, the new IKE_SA is computed as
   specified in [Kau04], section 2.18. The new keying material
   derived from this IKE_SA is computed as in an initial EAP-IKEv2
   authentication exchange.
   Fast re-authentication allows for an optional new Diffie-Hellman
   exchange.

   The following exchange provides fast reconnect for EAP-IKEv2,
   where A is the EAP peer (IKE responder) and B is the EAP server
   (IKE initiator):

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
               HDR, SK {SA, Ni, [KEi]})

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
               HDR, SK {SA, Nr, [KEr]})

   5) A <-- B: EAP-Success

                Figure 7: Fast Reconnect Message Flow

   The first two messages constitute the standard EAP identity
   exchange and are optional; they are not required in case the EAP
   server is known.

   Figure 8 shows the fast reconnect message flow in case the EAP peer
   fails to re-authenticate the EAP server.



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   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2
            (HDR, SK {SA, Ni, [KEi]})

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
               HDR, SK {N(AUTHENTICATION_FAILED)})

   5) A <-- B: EAP-Failure

                 Figure 8: EAP-IKEv2 fast reconnect
                   (server authentication failed)


   Figure 9 shows the fast reconnect message flow in case the EAP
   server fails to re-authenticate the EAP peer. The EAP peer MUST
   send an empty EAP-IKEv2 informational message in reply to the EAP
   server's error indication. The EAP server answers with an
   EAP-Failure.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
               HDR, SK {SA, Ni, [KEi]})

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
               HDR, SK {SA, Nr, [KEr]})

   5) A <-- B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(AUTHENTICATION_FAILED)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {})

   7) A <-- B: EAP-Failure

                 Figure 9: EAP-IKEv2 fast reconnect
                   (client authentication failed)



   IKE_SAs do not have lifetimes. Such lifetimes are therefore set
   by local policies of the peers. Typically the peer setting the
   shorter lifetime will therefore trigger the reconnect procedure.



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   Note: IKEv2 supports fast rekeying to be initiated by both peers.
   In EAP-IKEv2, the EAP server initiates the rekeying as this results
   in the most efficient message flow. If the client initiates fast
   rekeying, it needs to indicate this to the network by appropriate
   out-of-band (e.g. link-layer) means.


11. Channel Binding

   EAP-IKEv2 provides a channel binding functionality [RFC3784] in
   order for the EAP peer and EAP server to make sure that the both
   entities are given the same network access attributes such as
   Calling-Station-Id, Called-Station-Id, and NAS-Port-Type by the
   NAS. This is achieved by using Notify payloads to exchange
   attribute data between the EAP peer and EAP server.

   A Notify payload that carries a null channel binding attribute is
   referred to as a channel binding request.  A Notify payload which
   contains a non-null channel binding attribute and is sent in
   response to a channel binding request is referred to as a channel
   binding response.  A pair of channel binding request and channel
   binding response constitutes a channel binding exchange.  A
   distinct Notify payload type is used for a particular type of
   channel binding attribute, which is referred to as a channel
   binding attribute type. It is allowed to carry multiple channel
   binding requests and/or responses with different channel binding
   attribute types in a single IKEv2 message.  A set of channel binding
   exchanges performed in a single round of EAP-IKEv2 full
   authentication or fast reconnect is referred to as a channel
   binding procedure.

   A Notify payload that is used for reporting an error occurred
   during a channel binding exchange is referred to as a channel
   binding error indication.

   EAP-IKEv2 offers a protected result indication mechanism (see
   section 12.2). To receive protected result indication, the EAP
   server MUST initiate a channel binding exchange as specified in
   Figure 10, message 5. As a result of this channel binding exchange,
   the client will receive a protected result indication, because the
   server will initiate an informational exchange as part of the
   channel binding procedure (messages 7 and 8) through the new IKE-SA
   that results from a successful reconnect procedure.

11.1 Channel Binding Procedure in Full Authentication

   In the case of EAP-IKEv2 full authentication procedure, the
   channel binding procedure is performed in the following way.



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   The EAP peer MAY include one or more channel binding request in
   an IKE_SA_INIT response. The EAP server MAY include one or more
   channel binding request in an IKE_AUTH request. When the EAP server
   receives an IKE_SA_INIT response with one or more channel binding
   request, it MUST include the corresponding channel binding
   response(s) an IKE_AUTH request (in addition to its channel
   binding request(s) if any). When the EAP peer receives an IKE_AUTH
   request with one or more channel binding request, it MUST include
   the corresponding channel binding response(s) in an IKE_AUTH
   response.

   When the EAP server successfully validates all the channel binding
   response(s) sent by the EAP server, it initiates an INFORMATIONAL
   exchange, where an empty payload is used in both INFORMATIONAL
   request and INFORMATIONAL response.  This exchange serves as a
   protected success indication.  After completion of this
   INFORMATIONAL exchange, the EAP server sends Success message.

11.2 Channel Binding Procedure in Fast Reconnect

   In the case of EAP-IKEv2 fast reconnect, the channel binding
   procedure is performed in the following way.

   In the pair of CREATE_CHILD_SA exchange, the EAP peer and/or the
   EAP server MAY include one or more channel binding request, one
   for each channel binding attribute that needs validation.  When
   the EAP peer receives a CREATE_CHILD_SA request with containing
   one or more channel binding request, it MUST contain channel
   binding response(s) in the CREATE_CHILD_SA response, as well as
   its channel binding request(s) if any.  This piggybacking is
   possible because the CREATE_CHILD_SA exchange is protected with
   the old IKE_SA.  When the EAP server receives a CREATE_CHILD_SA
   response, if it has one or more channel binding response to send
   to the EAP peer, it initiates an INFORMATIONAL exchange
   immediately after completion of the CREATE_CHILD_SA exchange,
   where one or more channel binding response is carried in the
   INFORMATIONAL request.  If the EAP peer successfully validates the
   channel binding response(s), it MUST respond with an empty
   INFORMATIONAL response.  This exchange serves as a protected
   success indication.  After completion of this INFORMATIONAL
   exchange, the EAP server sends Success message.

11.3 Channel Binding Error Indication

   A channel binding error is detected by the EAP peer or EAP server
   when (i) a channel binding response is not contained in the
   expected IKEv2 message or (ii) a channel binding response is
   contained in the expected IKEv2 message but the channel binding
   attribute does not have the expected value.  Whenever a channel


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   binding error is detected, the detecting entity MUST send a channel
   binding error indication to its peering entity.  In case of (ii),
   the channel binding error indication MUST contain the channel
   binding attribute that caused the error.

   When the EAP server detects a channel binding error, a channel
   binding error indication MUST be carried in an INFORMATIONAL
   request, and the EAP peer MUST respond with an empty INFORMATIONAL
   response.
   When the EAP peer detects a channel binding error, a channel
   binding error indication MUST be carried in an IKEv2 error
   reporting message for which the R-flag of the IKEv2 header MUST
   be set. The EAP server MUST respond with EAP-Failure message when
   it receives such a channel binding error indication.

11.4 Notify Payload Types for Channel Binding

   The following Notify Payload types are defined for the purpose of
   channel binding exchange.

      CALLING_STATION_ID              TBD
          The payload data in a channel binding response of this type
          contains octet string representation of
          Calling-Station-Id value known to the EAP server by using
          an external mechanism.

      CALLED_STATION_ID               TBD
          The payload data in a channel binding response of this type
          contains octet string representation of Called-Station-Id
          value known to the EAP peer by using an external mechanism.

      NAS_PORT_TYPE                   TBD
          The payload data in a channel binding response of this type
          contains 4-octet unsigned integer value of NAS-Port-Type
          known to the EAP peer by using an external mechanism.


   The following Notify Payload types are defined for the purpose of
   reporting when there is an error in a channel binding exchange.

      INVALID_CALLING_STATION_ID      TBD

          The payload data (if non-null) contains octet string
          representation of Calling-Station-Id value that caused the
          error.

      INVALID_CALLED_STATION_ID       TBD

          The payload data (if non-null) contains octet string


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          representation of Called-Station-Id value that caused the
          error.

      INVALID_NAS_PORT_TYPE           TBD

          The payload data (if non-null) contains 4-octet unsigned
          integer value of NAS-Port-Type that caused the error.


   Table 1 shows the entity that is allowed to send a channel binding
   request for each channel binding attribute type.

      channel binding        The entity that is allowed to send
      attribute type         channel binding request
   ----------------------+---------------------------------------
      CALLING_STATION_ID     EAP server

      CALLED_STATION_ID      EAP peer

      NAS_PORT_TYPE          EAP server

      Table 1: Channel Binding Attribute Types and Requesting
               Entities


11.5 Examples

   In the figures of this section, a Notify payload tagged with '*'
   indicates a Notify payload with null data (i.e., a channel binding
   request).  a Notify payload no tagged with '*' indicates a Notify
   payload with non-null data (i.e., a channel binding response).

   Figure 10 shows an example of EAP-IKEv2 authentication sequence
   with a successful channel binding procedure.  The first two
   messages constitute the standard EAP identity exchange and are
   optional.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR(A,0), SAi1, KEi, Ni)

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SAr1, KEr, Nr, [CERTREQ,]
            N(CALLED_STATION_ID*))

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,], AUTH,


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            N(CALLED_STATION_ID),
            N(CALLING_STATION_ID*),
            N(NAS_PORT_TYPE*)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDr, [CERT,] AUTH,
            N(CALLING_STATION_ID),
            N(NAS_PORT_TYPE)})

   7) A <-- B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {})

   8) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {})

   9) A <-- B: EAP-Success

        Figure 10: EAP-IKEv2 with successful channel binding


   Figure 11 shows an example of EAP-IKEv2 authentication sequence
   when the EAP server detects an error in a channel binding
   procedure. The first two messages constitute the standard EAP
   identity exchange and are optional.  In this case, message 7) and
   8) MUST constitute an INFORMATIONAL exchange.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR(A,0), SAi1, KEi, Ni)

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SAr1, KEr, Nr, [CERTREQ,]
            N(CALLED_STATION_ID*))

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,], AUTH,
            N(CALLED_STATION_ID),
            N(CALLING_STATION_ID*),
            N(NAS_PORT_TYPE*)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDr, [CERT,] AUTH,
            N(CALLING_STATION_ID),
            N(NAS_PORT_TYPE)})

   7) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(INVALID_CALLING_STATION_ID)})


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   8) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {})

   9) A <-- B: EAP-Failure

           Figure 11: EAP-IKEv2 with channel binding error
                      (detected by EAP server)


   Figure 12 shows an example of EAP-IKEv2 authentication sequence
   when the EAP peer detects an error in a channel binding procedure.
   The first two messages constitute the standard EAP identity
   exchange and are optional.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR(A,0), SAi1, KEi, Ni)

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SAr1, KEr, Nr, [CERTREQ,]
            N(CALLED_STATION_ID*))

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,], AUTH,
            N(CALLED_STATION_ID),
            N(CALLING_STATION_ID*),
            N(NAS_PORT_TYPE*)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(INVALID_CALLED_STATION_ID)})

   7) A <-- B: EAP-Failure

           Figure 12: EAP-IKEv2 with channel binding error
                       (detected by EAP peer)


   Figure 13 shows an example of EAP-IKEv2 fast reconnection sequence
   with a successful channel binding procedure.  The first two
   messages constitute the standard EAP identity exchange and are
   optional.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)



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   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR, SK {SA, Ni, [KEi,]
            N(CALLING_STATION_ID*),
            N(NAS_PORT_TYPE*)})

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(HDR, SK {SA, Nr, [KEr,]
            N(CALLED_STATION_ID*),
            N(CALLING_STATION_ID),
            N(NAS_PORT_TYPE)})

   5) A <-- B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(CALLED_STATION_ID)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(HDR(A,B), SK {})

   7) A <-- B: EAP-Success

        Figure 13: Fast reconnect with channel binding error
                          (fast reconnect)


   Figure 14 shows an example of EAP-IKEv2 fast reconnect sequence
   when the EAP server detects an error in a channel binding
   procedure. The first two messages constitute the standard EAP
   identity exchange and are optional.  In this case, message 7) and
   8) MUST constitute an INFORMATIONAL exchange.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR, SK {SA, Ni, [KEi,]
            N(CALLING_STATION_ID*),
            N(NAS_PORT_TYPE*)})

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(HDR, SK {SA, Nr, [KEr,]
            N(CALLED_STATION_ID*),
            N(CALLING_STATION_ID),
            N(NAS_PORT_TYPE)})

   5) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(INVALID_CALLING_STATION_ID)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {})

   7) A <-- B: EAP-Failure

        Figure 14: Fast reconnect with channel binding error
                      (detected by EAP server)


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   Figure 15 shows an example of EAP-IKEv2 fast reconnect sequence
   when the EAP peer detects an error in a channel binding procedure.
   The first two messages constitute the standard EAP identity
   exchange and are optional.

   1) A <-- B: EAP-Request/Identity

   2) A --> B: EAP-Response/Identity(Id)

   3) A <-- B: EAP-Request/EAP-Type=EAP-IKEv2(HDR, SK {SA, Ni, [KEi,]
            N(CALLING_STATION_ID*),
            N(NAS_PORT_TYPE*)})

   4) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(HDR, SK {SA, Nr, [KEr,]
            N(CALLED_STATION_ID*),
            N(CALLING_STATION_ID),
            N(NAS_PORT_TYPE)})

   5) A <-- B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(CALLED_STATION_ID)})

   6) A --> B: EAP-Response/EAP-Type=EAP-IKEv2(
            HDR(A,B), SK {N(INVALID_CALLED_STATION_ID)})

   7) A <-- B: EAP-Failure

   Figure 15: Fast reconnect with channel binding error
              (detected by EAP peer)


12. Security Considerations

12.1 General Considerations

   The security of the proposed EAP method is intentionally based on
   IKEv2 [Kau04]. Therefore, the security claims of EAP-IKEv2 are
   derived from the security offered by the supported features of
   IKEv2.

12.2 Security Claims

   Authentication mechanism:
   Mutual authentication is supported based on either pre-shared
   symmetric keys or public/private key pairs. Besides certificates,
   plain public keys can be used. It is possible to use different types
   of authentication for the different directions within one
   authentication exchange. An example is the server using


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   certificate-based authentication and the client using pre-shared
   secrets.

   Password-based authentication should only be used in IKEv2 with
   extended authentication (EAP tunneling), which is not supported
   by this version of EAP-IKEv2. Without extended authentication, the
   use of passwords (i.e., password-derived shared secrets) is
   discouraged for IKEv2.
   In contrast, EAP-IKEv2 changes the roles regarding password usage:
   The EAP server acts as initiator, the remote peer as responder.
   This results in an exchange which protects user authentication
   (based on a shared secret derived from a user password) to the
   network through an already network (initiator-) authenticated,
   secured IKEv2 SA (see e.g. message 6 of Figure 1). This prevents
   an attacker from launching password-guessing attacks on the
   peer-generated AUTH value.
   Therefore, dictionary attacks are not applicable in the context
   of EAP-IKEv2 in the case the EAP peer uses a password-derived
   shared secret.

   Man-in-the-middle attacks discovered in the context of tunneled
   authentication protocols (see [AN03] and [PL+03]) are not
   applicable to EAP-IKEv2 as the extended authentication feature of
   IKEv2 is not supported. Hence, the cryptographic binding claim is
   not applicable.

   Ciphersuite negotiation is supported as specified in IKEv2 for
   IKE-SAs. The negotiation for IPsec (Child) SAs is not supported,
   as such SAs are not generated by EAP-IKEv2.

   Protected result indication as described in section 7.16 of
   [RFC3748] is optionally provided by EAP-IKEv2. In message 5 of
   figure 1 (full successful authentication) the EAP server
   authenticates to the client. Message 6 authenticates the client
   to the server, and the client by authenticating the server and by
   sending message 6 expresses that it is willing to accept access.
   The client, however, does not get a protected result indication
   from the server in this case. An attacker could potentially forge
   an EAP success/failure message which could result in DoS to the
   client. In some situations, synchronization may be achieved by
   lower layer indications.

   Protected result indication is optionally provided as specified
   in section 11.
   If this mechanism is not used, the recommended behavior for the
   client is to assume the correct establishment of a new IKE-SA after
   sending message 6, independent of the receipt of an EAP
   success/failure. In case of unsuccessful authentication, the
   server would answer with an IKEv2 notification (which, in case of


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   the fast reconnect exchange, would be protected by the old IKE-SA).
   In case of a lost message 6, the server would retransmit message
   5, indicating the message loss to the client.
   The client implementation can minimize potential DoS risks due to
   missing protected result indications by assuming the correct
   establishment of a new IKE-SA after not receiving one of the above
   messages within a certain time window after sending message 6. In
   the fast reconnect case, the client needs to hold both the old and
   the new IKE-SA in parallel during this time window.

   Session independence is optionally provided if the fast reconnect
   exchange includes the KE payloads (new Diffie-Hellman) as
   described in section 10, Figure 7.

   Security claims:
         Ciphersuite negotiation:   Yes
         Mutual authentication:     Yes
         Integrity protection:      Yes
         Replay protection:         Yes
         Confidentiality:           Yes
         Key derivation:            Yes
         Key strength:              Variable
         Dictionary attack prot.:   Yes
         Fast reconnect:            Yes
         Crypt. binding:            N/A
         Protected result ind.:     yes
         Session independence:      yes
         Fragmentation:             Yes
         Channel binding:           Yes



13. Open Issues

   The following issues are still under consideration:

   - Notifications

   IKEv2 provides the concept of notifications to exchange messages
   at any time (e.g., dead peer detection). It remains for further
   study which of these messages are required for this EAP method.

   - supported identities

   Can the NAI be carried by the RFC822 ID type of IKEv2? Are there
   other formats to be supported? Additional profiling may be
   required in section 5.

   - tunneled method


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   To reduce the method's complexity, EAP tunneling through EAP-IKEv2
   that is in principal possible with IKEv2 is not supported. If
   tunneling support is, however, required (e.g. for sequencing), it
   is possible to develop an EAP-IKEv2-tunneled method from the
   present one. The major change would be to reverse the roles of IKEv2
   initiator and responder, as the initiator is EAP-authenticated in
   the tunneled case.
   It is not considered a good approach by the authors to have both
   the tunneled and the non-tunneled method in a single
   specification, as this would result in a rather complex method
   description. The tunneled-method EAP-IKEv2 specification, if
   required, will therefore come with a separate document.


14. Normative References

   [RFC3748] Aboba, Blunk, Carlson and Levkowetz: "Extensible
   Authentication Protocol (EAP)", RFC 3748, June 2004.

   [Kau04] C. Kaufman: "Internet Key Exchange (IKEv2) Protocol",
   internet draft, Internet Engineering Task Force, September 2004.
   Work in progress.

   [RFC2119] S. Bradner: "Key words for use in RFCs to Indicate
   Requirement Levels", RFC 2119, Internet Engineering Task Force,
   March 1997.


15. Informative References

   [AN03] N. Asokan, V. Niemi, and K. Nyberg: "Man-in-the-middle in
   tunnelled authentication", In the Proceedings of the 11th
   International Workshop on Security Protocols, Cambridge, UK,
   April 2003. To be published in the Springer-Verlag LNCS series.

   [PL+03] J. Puthenkulam, V. Lortz, A. Palekar, D. Simon, and B.
   Aboba, "The compound authentication binding problem," internet
   draft, Internet Engineering Task Force, October 2003.  Expired.

   [RFC2409] D. Harkins, D. Carrel: "The Internet Key Exchange
   (IKE)", RFC 2409, November 1998.

   [Per03] R. Perlman: "Understanding IKEv2: Tutorial, and rationale
   for decisions", internet draft, Internet Engineering Task Force,
   2003.  Expired.

   [AS+05] B. Aboba, D. Simon, J. Arkko, P. Eronen and H. Levkowetz:
   "Extensible Authentication Protocol (EAP) Key Management


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   Framework", internet draft, Internet Engineering Task Force,
   April, 2005.  Work in progress.

   [PS+03] A. Palekar, D. Simon, G. Zorn, H. Zhou and S. Josefsson:
   "Protected EAP Protocol (PEAP)", internet draft, Internet
   Engineering Task Force, July 2004.  Work in progress.


Acknowledgments

   We would like to thank Bernard Aboba, Jari Arkko, Guenther Horn,
   Paoulo Pagliusi and John Vollbrecht for their comments to this
   draft.

   Additionally we would like to thank members of the PANA design team
   (namely D. Forsberg and A. Yegin) for their comments and input to
   the initial version of the draft.

   Finally we would like to thank the members of the EAP keying design
   team for their discussion in the area of the EAP Key Management
   Framework.


Author's Addresses

   Hannes Tschofenig
   Siemens AG
   Otto-Hahn-Ring 6
   81739 Munich
   Germany
   EMail: Hannes.Tschofenig@siemens.com

   Dirk Kroeselberg
   Siemens AG
   Haidenauplatz 1
   81667 Munich
   Germany
   EMail: Dirk.Kroeselberg@siemens.com

   Yoshihiro Ohba
   Toshiba America Research, Inc.
   1 Telcordia Drive
   Piscataway, NJ 08854
   USA

   Phone: +1 732 699 5305
   EMail: yohba@tari.toshiba.com

   Florent Bersani


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   France Telecom R&D
   38, rue du General Leclerc
   Issy-Les-Moulineaux  92794 Cedex 9
   FR

   EMail: florent.bersani@francetelecom.com


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