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Versions: 00 01 02 03 04 rfc5807                                        
PANA Working Group                                               Y. Ohba
Internet-Draft                                                   Toshiba
Expires: April 27, 2009                                 October 24, 2008


   Definition of Master Key between PANA Client and Enforcement Point
                        draft-ohba-pana-pemk-02

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   This Internet-Draft will expire on April 27, 2009.

Abstract

   This document defines a master key used between a client of the
   Protocol for carrying Authentication for Network Access (PANA) and an
   enforcement point, for bootstrapping lower-layer ciphering.  The
   master key is derived from the Master Session Key of Extensible
   Authentication Protocol as a result of successful PANA
   authentication.  The master key guarantees cryptographic independence
   among enforcement points across different types of lower-layers.









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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Specification of Requirements . . . . . . . . . . . . . . . 3
   2.  PaC-EP Master Key . . . . . . . . . . . . . . . . . . . . . . . 4
     2.1.  Key Name of PEMK  . . . . . . . . . . . . . . . . . . . . . 4
     2.2.  Scope of PEMK . . . . . . . . . . . . . . . . . . . . . . . 4
     2.3.  Context of PEMK . . . . . . . . . . . . . . . . . . . . . . 5
     2.4.  Lifetime of PEMK  . . . . . . . . . . . . . . . . . . . . . 5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
     3.1.  Channel Binding . . . . . . . . . . . . . . . . . . . . . . 5
     3.2.  Guideline for distributing PEMK from PAA to EP  . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8
































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1.  Introduction

   PANA (Protocol for carrying Authentication for Network Access)
   [RFC5191] is designed to facilitate network access authentication and
   authorization of clients in access networks.  It carries EAP
   [RFC3748] between a PaC (PANA Client) and a PAA (PANA Authentication
   Agent) where the PAA functions as an authentication gateway to the
   Authentication Server (AS).  The PANA framework [RFC5193] defines an
   another entity referred to as an EP (Enforcement Point) which resides
   in the access network and allows access (data traffic) of authorized
   PaCs while preventing access by others depending on the PANA
   authentication and authorization result.  The EP and PAA may be
   implemented on the same device or separate devices.

   The EP uses non-cryptographic or cryptographic filters to selectively
   allow and discard data packets.  These filters may be applied at the
   link-layer or the IP-layer [I-D.ietf-pana-ipsec].  When cryptographic
   access control is used, a secure association protocol [RFC3748] needs
   to run between the PaC and EP.  After completion of the secure
   association protocol, link or network layer per-packet security (for
   example IPsec ESP) is enabled for integrity protection, data origin
   authentication, replay protection and optionally confidentiality
   protection.

   This document defines PaC-EP Master Key (PEMK) that is used by a
   secure association protocol as the pre-shared secret between the PaC
   and EP to enable cryptographic filters in the access network.  The
   PEMK is defined to guarantee cryptographic independence among EPs
   across different lower-layer types.  This document also describes
   guideline for distributing PEMKs from the PAA to EP.

   This document does not specify a mechanism for a PaC to know whether
   the lower-layer requires a secure association protocol or the pre-
   shared secret for the secure association protocol needs to be
   bootstrapped from PANA authentication.  Such a mechanism may be
   defined by each lower-layer protocol.

1.1.  Specification of Requirements

   In this document, several words are used to signify the requirements
   of the specification.  These words are often capitalized.  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 [RFC2119].







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2.  PaC-EP Master Key

   A PEMK (PaC-EP Master Key) is derived from the available MSK.  The
   PEMK is 64 octets in length and it is calculated as follows:

   PEMK = prf+(MSK, "IETF PEMK" | SID | KID | EPID)
          where | denotes concatenation.

   o  The prf+ function is defined in IKEv2 [RFC4306].  The pseudo-
      random function used for the prf+ function is specified in the
      PRF-Algorithm AVP carried in a PANA-Auth-Request message with 'S'
      (Start) bit set.

   o  "IETF PEMK" is the ASCII code representation of the non-NULL
      terminated string (excluding the double quotes around it).

   o  MSK is a Master Session Key generated by EAP and exported to PANA.

   o  SID is a four-octet PANA session identifier [RFC5191].

   o  KID is the content of the PANA Key-ID AVP associated with the MSK
      [RFC5191].

   o  EPID is the identifier of the EP.  The first two octets represents
      the AddressType, which contains an Address Family defined in
      [IANAADFAM].  The remaining octets encode the address value.  The
      length of the address value is determined by the AddressType.  The
      AddressType is used to discriminate the content and format of the
      remaining octets for the address value.  The use of address family
      and address value guarantees the cryptographic independence of
      PEMKs among multiple EPs across multiple lower-layer protocols.
      How a PaC configures an EPID is out of the scope of this document.

2.1.  Key Name of PEMK

   The key name of the PEMK is defined as follows.

   PEMKname = MD5(EPID | SID | KID), where MD5 denotes Message-Digest
   algorithm 5 hash function.

2.2.  Scope of PEMK

   A PEMK is used between a PaC and an EP.  A PEMK MUST NOT be shared
   among multiple PaCs or EPs.







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2.3.  Context of PEMK

   A PEMK is used as the pre-shared key of the secure association
   protocol in the scope of the PEMK.  A PEMK MUST NOT be used for any
   other usage.

2.4.  Lifetime of PEMK

   The lifetime of a PEMK MUST be no greater than the lifetime of the
   MSK.


3.  Security Considerations

   The following considerations are specifically made to follow the AAA
   key management guidance [RFC4962].  Other AAA key management
   requirements such as key lifetime, key scope, key context and key
   name are described under Section 2.

3.1.  Channel Binding

   Since the device identifier of the EP is involved in the key
   derivation function, Channel Binding on a PEMK is made between the
   PaC and PAA at the time when the PEMK is generated.  If a malicious
   EP advertises a different device identifier than that is registered
   with the PAA, the malicious attempt will not succeed since the secure
   association protocol will fail due to the difference in the PEMK
   values calculated by the PaC and the EP.

3.2.  Guideline for distributing PEMK from PAA to EP

   When an EP is implemented on the same device as the PAA, no protocol
   needs to be used for distributing a PEMK from the PAA to the EP.  It
   is assumed that an EP is implemented on the same device as the PAA
   when the device identifier of the EP is equals to a link-layer
   address or an IP address of the PAA.  Otherwise, it is assumed that
   the EP is implemented on a separate device from the PAA.

   In the case where the EP is implemented on a separate device from the
   PAA, a protocol is needed to distribute a PEMK from the PAA to the
   EP.  Such a key distribution protocol may depend on the lower-layer
   protocol over which PANA operates.  A key distribution protocol for a
   PEMK MUST ensure that the PEMK is encrypted as well as integrity and
   replay protected, with a security association between the PAA and EP,
   where the security association MUST be cryptographically bound to the
   identities of the PAA and EP known to the PaC.





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4.  IANA Considerations

   This document has no actions for IANA.


5.  Acknowledgments

   TBD.


6.  References

6.1.  Normative References

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, "Extensible Authentication Protocol (EAP)",
              RFC 3748, June 2004.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.

   [RFC5191]  Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
              Yegin, "Protocol for Carrying Authentication for Network
              Access (PANA)", RFC 5191, May 2008.

   [IANAADFAM]
              IANA, "Address Family Numbers",
               http://www.iana.org/assignments/address-family-numbers.

6.2.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4962]  Housley, R. and B. Aboba, "Guidance for Authentication,
              Authorization, and Accounting (AAA) Key Management",
              BCP 132, RFC 4962, July 2007.

   [RFC5193]  Jayaraman, P., Lopez, R., Ohba, Y., Parthasarathy, M., and
              A. Yegin, "Protocol for Carrying Authentication for
              Network Access (PANA) Framework", RFC 5193, May 2008.

   [I-D.ietf-pana-ipsec]
              Parthasarathy, M., "PANA Enabling IPsec based Access
              Control", draft-ietf-pana-ipsec-07 (work in progress),
              July 2005.





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Author's Address

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

   Phone: +1 732 699 5365
   Email: yohba@tari.toshiba.com









































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