Internet DRAFT - draft-xia-csi-symmetric-key

draft-xia-csi-symmetric-key






Network Working Group                                             F. Xia
Internet-Draft                                                    Huawei
Expires: December 22, 2008                                   S. Krishnan
                                                       Ericsson Research
                                                               W. Haddad
                                                                Qualcomm
                                                             J-M. Combes
                                                         Orange Labs R&D
                                                           Chunqiang. Li
                                                                  Huawei
                                                           June 20, 2008


       Distributing a Symmetric Neighbor Discovery Key Using SEND
                   draft-xia-csi-symmetric-key-00.txt

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Abstract

   In this document, a method for provisioning a shared key from the
   router to the host is defined to protect Neighbor Discovery(ND)
   signaling between the router and the host.  The host sends a Router
   Solicitation(RS) message with ND Shared Key Request Option to the
   router.  The router encrypts a ND shared key using the host's SEcure
   Neighbor Discovery(SEND) public key and sends it back to the host
   through a Router Advertisement(RA) message.  The host decrypts the ND
   shared key using the matching private key.  The Neighbor Discovery
   shared key is then used for protecting the following Neighbor
   Discovery signaling between the router and the host.  The Router
   Solicitation and Router Advertisement message exchanges are required
   to have SEND security.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Operation Description  . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Sending Router Solicitations . . . . . . . . . . . . . . .  4
     3.2.  Receiving Router Solicitations and Sending  Router
           Advertisements . . . . . . . . . . . . . . . . . . . . . .  4
     3.3.  Receiving Router Advertisements  . . . . . . . . . . . . .  5
     3.4.  ND operation secured by a shared key . . . . . . . . . . .  5
     3.5.  Key Generation and Lifetime  . . . . . . . . . . . . . . .  6
   4.  Message Formats  . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  ND Shared Key Request Option . . . . . . . . . . . . . . .  6
     4.2.  ND Shared Key Reply Option . . . . . . . . . . . . . . . .  7
     4.3.  Neighbor Discovery Authenticator Option  . . . . . . . . .  8
   5.  IANA consideration . . . . . . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     8.2.  Informative references . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13












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1.  Introduction

   IPv6 nodes use Neighbor Discovery(ND) protocol [RFC4861] to discover
   other nodes on the link, to determine their link-layer addresses, to
   find routers, and to maintain reachability information about the
   paths to active neighbors.  [RFC3971] specifies security mechanisms
   for ND, that is, Secure Neighbor Discovery (SEND) protocol in which
   Cryptographically Generated Addresses (CGA) [RFC3972] are used.

   The construction and verification of the RSA Signature option in SEND
   operation is computationally expensive.  In the ND context, however,
   hosts typically only have to perform a few signature operations as
   they enter a link, a few operations as they find a new on-link peer
   with which to communicate, or Neighbor Unreachability Detection with
   existing neighbors.  Routers are required to perform a larger number
   of operations, particularly when the frequency of router
   advertisements is high due to mobility requirements.  Scalability
   issue arises when hundreds , even thousands of hosts attach to a
   router.

   In the same way, IPv6 over Low-Power Wireless Personal Area Networks
   (6LoWPANs) have similar constraints.  It is recommended that ND
   signalling exchanges occur between the 6lowpan host and the PAN
   coordinator, which is a router in [I-D.chakrabarti-6lowpan-ipv6-nd].
   Another point is 6lowpan hosts may not be able to do asymmetric
   cryptography all the time because of power/computing consumption.

   In this document, a lightweight mechanism is defined by which a
   shared key for securing ND exchanges between the host and the router
   is provisioned on the host by the router.  The mechanism described in
   the document utilizes SEND [RFC3971] public/private key pair to
   encrypt/decrypt a ND shared key sent from the router to the host.
   Once the ND shared key is provisioned, all ND exchanges occurring
   between the host and the router are protected by Message
   Authentication Codes (MAC) which generally requires much less
   computational operation.  This main idea of the document is in line
   with [I-D.ietf-mipshop-handover-key] in which shared handover key is
   used for protecting handover signaling between a mobile node and an
   access router.

   The solution is based on and compatible with SEND operation.


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 [RFC2119].



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   The terminology and messages in this document are based on the
   definitions in [RFC3971], in addition to the ones defined below.
   ND shared key :  A key is shared between a router and a host, and
      used to protect ND signaling between the router and the host.



3.  Operation Description

3.1.  Sending Router Solicitations

   According to SEND [RFC3971], the CGA option MUST be present in Router
   Solicitation(RS) messages unless they are sent with the unspecified
   source address.  In this document, RS message with a CGA source
   address is used for a ND shared key request.

   The host MUST send a RS containing a ND Shared Key Request Option
   defined in Section 4.1 with the SEND's public key.  A CGA for the
   host MUST be the source address of the packet, and the host MUST
   include the SEND CGA Option and SEND Signature Option with the
   packet, as specified in [RFC3971].  The SEND signature covers all
   fields in the RS, including the 128 bit source and destination
   addresses and ICMP checksum as described in [RFC3971], except for the
   Signature Option itself.  The host also sets the authentication
   Algorithm Type (AT) field in the ND Shared Key Request Option to the
   host's preferred authentication algorithm.  The SEND Nonce MUST also
   be included for anti-replay protection.

3.2.  Receiving Router Solicitations and Sending  Router Advertisements

   When the router receives a RS from the host protected with SEND and
   including a ND Shared Key Request Option, the router MUST first
   validate the RS using SEND as described in [RFC3971].  If the RS can
   not be validated, the router MUST NOT include a ND Shared Key Reply
   Option Section 4.2 in the reply.

   If the RS is validated, the router MUST then determine whether the
   CGA is already associated with a ND shared key.  If the CGA is
   associated with an existing key, the router MUST return the existing
   key to the host.  If the CGA does not have a ND shared key, the
   router MUST construct a ND shared key as described in Section 3.5.
   The router MUST encrypt the key with the host's SEND public key.  The
   router MUST insert the encrypted ND shared key into a ND Shared Key
   Reply Option and MUST attach the option to the RA.  The lifetime of
   the key MUST also be included in the ND Shared Key Reply Option.  The
   router SHOULD set the AT field of the ND Shared Key Option to the
   MN's preferred algorithm type indicated in the AT field of the ND
   Shared Key Request Option, if it is supported; otherwise, the router



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   MUST select an authentication algorithm which is of equivalent
   strength or stronger and set the field to that.  The router MUST also
   include the SEND nonce from the RS for anti- replay protection.  The
   router MUST use the CGA constructed from its certified key as the
   source address for the RA and include a SEND CGA Option and a SEND
   Signature Option with the SEND signature of the message.  The SEND
   signature covers all fields in the RA, including the 128 bit source
   and destination addresses and ICMP checksum as described in
   [RFC3971], except for the Signature Option itself.  The RA is then
   unicast back to the host.  The ND shared key MUST be stored by the
   router for future use, indexed by the host's CGA, and the
   authentication AT and a lifetime MUST be recorded with the key.

3.3.  Receiving Router Advertisements

   Upon receipt of one or more RA secured with SEND and having the ND
   Shared Key Reply Option, the host MUST first validate the RA as
   described in [RFC3971].  Normally the host will have obtained the
   router's certification path to validate an RA prior to sending the RS
   and the host MUST check to ensure that the key used to sign the RA is
   the router's certified public key.  If the host does not have the
   router's certification path cached, it MUST use the SEND
   Certification Path Solicitation (CPS) / Certification Path
   Advertisement (CPA) messages to obtain the certification path to
   validate the key.  If the message is not signed by a certified key ,
   the message MUST be dropped.

   The host MUST use it's private key to decrypt the ND shared key.  The
   host MUST use the returned authentication AT indicated in the RA.
   The host MUST index the ND shared keys with the router's CGA, and the
   algorithm type and the lifetime are also stored.

   When the host moves from a router to another router, it is possible
   that the new router has no any idea about the ND Shared Key which is
   provided by the old one.  A solution is that the host erases the ND
   shared key and re-use CGA after a certain number of NS
   retransmissions.

3.4.  ND operation secured by a shared key

   When the host sends Neighbor Solicitation (NS), Neighbor
   Advertisement (NA), Router Solicitation(RS) to the router, the host
   SHOULD check if there is a ND shared key for the router.  The host
   SHOULD utilize the shared key and the corresponding authentication
   algorithm type to generate an authenticator for the message if a ND
   shared key exists; otherwise, the host behaves according to[RFC3971],
   or requests a ND shared key using the procedure defined in this
   document.  The authenticator is conveyed in Neighbor Discovery



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   Authenticator Option defined in Section 4.3.

   When the router sends Neighbor Solicitation (NS), Neighbor
   Advertisement (NA), Router Solicitation(RS), Redirect, Router
   Advertisement(RA) to the host, the router SHOULD check if there is a
   ND shared key for the host.  The router SHOULD utilize the shared key
   and the corresponding authentication algorithm to generate an
   authenticator for the message if a ND shared key exists;
   otherwise,the router behaves according to [RFC3971].  The
   authenticator is conveyed in Neighbor Discovery Authenticator Option
   defined in Section 4.3.

3.5.  Key Generation and Lifetime

   The router MUST randomly generate a key having sufficient strength to
   match the authentication algorithm.  Some authentication algorithms
   specify a required key size.  The router MUST generate a unique key
   along with a lifetime for each CGA public key of a host.

   Before the lifetime expires, the host SHOULD apply for a new ND
   shared key using the procedure defined in this document.  Once the ND
   shared key expires, the host and the router SHOULD discard the key.


4.  Message Formats

4.1.  ND Shared Key Request Option

   The ND Shared Key Request Option is a IPv6 Neighbor Discovery
   [RFC4861] option in TLV format.  The ND Shared Key Request Option is
   included in the RS message along with the SEND CGA Option, RSA
   Signature Option, and Nonce Option.



















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       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |    Length     |     AT        |   Reserved    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Reserved                                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Fields:

         Type:       To be assigned by IANA.

         Length:     The length of the option in units of 8 octets,
                     including the Type and Length fields. The value 0
                     is invalid. The receiver MUST discard a message
                     that contains this value.

         AT:         authentication Algorithm Type
                     1  HMAC_SHA1
                     2  HMAC_SHA256
                     3  MD5


         Reserved:   A 40-bit field reserved for future use.


4.2.  ND Shared Key Reply Option

   ND Shared Key Reply Option is a IPv6 Neighbor Discovery [RFC4861]
   option in TLV format.  The Reply Option is included in the RA message
   along with the SEND CGA Option, RSA Signature Option, and Nonce
   Option.



















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       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |    Length     |      AT       |   Reserved    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Key Lifetime        |                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                                                               |
       .                                                               .
       .                    Encrypted ND Shared Key                    .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Fields:

         Type:       To be assigned by IANA.

         Length:     The length of the option in units of 8 octets,
                     including the Type and Length fields. The value 0
                     is invalid. The receiver MUST discard a message
                     that contains this value.

         AT:         authentication Algorithm Type
                     1  HMAC_SHA1
                     2  HMAC_SHA256
                     3  MD5

         Reserved:   A 8-bit field reserved for future use.  The value
                     MUST be initialized to zero by the sender and MUST
                     be ignored by the receiver.

         Key Lifetime:
                     lifetime of the ND shared key, in seconds.

         Encrypted ND Shared Key:

                     The shared key, encrypted with the host's
                     ND shared key  encryption  public  key,  using  the
                     RSAES-PKCS1-v1_5 format [RFC3447].


4.3.  Neighbor Discovery Authenticator Option

   This option MUST be present all ND signaling between the host and the
   router.  This option specifies how to compute and verify a MAC using
   the established ND shared key.



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       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |    Length     |         Reserved              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                     Authenticator                             .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Fields:

         Type:       To be assigned by IANA.

         Length:     The length of the option in units of 8 octets,
                     including the Type and Length fields. The value 0
                     is invalid. The receiver MUST discard a message
                     that contains this value.

         Reserved:   A 8-bit field reserved for future use.  The value
                     MUST be initialized to zero by the sender and MUST
                     be ignored by the receiver.

         Authenticator:

                     cryptographic value which can be used to determine
                     that the message in question comes from the right
                     authority


   Rules for calculating the Authenticator value are the following:


         ND Data = host's source address | router's address | ICMP Data
         Authenticator = First (96, Algorithm( ND Shared Key, ND Data))



   The algorithm type for authenticator is negotiated between the host
   and the router through ND Shared Key Request Option and ND Shared Key
   Reply Option.


5.  IANA consideration

   Three new IPv6 Neighbor Discovery options, the ND Shared Key Request



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   Option, ND Shared Key Reply Option, and Neighbor Discovery
   Authenticator Option, are defined, and require IPv6 Neighbor
   Discovery option type codes from IANA.


6.  Security Considerations

   This document describes a shared key provisioning protocol for the
   Neighbor Discovery protocol.  The key provisioning protocol utilizes
   a public key of SEND.  General security considerations involving CGAs
   apply to the protocol described in this document, see [RFC4861] for a
   discussion of security considerations around CGAs.


7.  Acknowledgements

   Jean-Michel Combes is partly funded by MobiSEND, a research project
   supported by the French 'National Research Agency' (ANR).


8.  References

8.1.  Normative References

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

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
              Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC5121]  Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S.
              Madanapalli, "Transmission of IPv6 via the IPv6
              Convergence Sublayer over IEEE 802.16 Networks", RFC 5121,
              February 2008.

   [RFC3314]  Wasserman, M., "Recommendations for IPv6 in Third
              Generation Partnership Project (3GPP) Standards",
              RFC 3314, September 2002.






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8.2.  Informative references

   [I-D.ietf-mipshop-handover-key]
              Kempf, J., "Distributing a Symmetric FMIPv6 Handover Key
              using SEND", draft-ietf-mipshop-handover-key-03 (work in
              progress), October 2007.

   [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography
              Standards (PKCS) #1: RSA Cryptography Specifications
              Version 2.1", RFC 3447, February 2003.

   [I-D.chakrabarti-6lowpan-ipv6-nd]
              Chakrabarti, S. and E. Nordmark, "LowPan Neighbor
              Discovery Extensions",
              draft-chakrabarti-6lowpan-ipv6-nd-04 (work in progress),
              November 2007.



































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Authors' Addresses

   Frank Xia
   Huawei
   1700 Alma Dr. Suite 500
   Plano, TX  75075

   Phone: +1 972-509-5599
   Email: xiayangsong@huawei.com


   Suresh Krishnan
   Ericsson Research
   8400 Decarie Blvd.
   Town of Mount Royal, QC Canada

   Phone: +1 514 345 7900
   Email: Suresh.Krishnan@ericsson.com


   Wassim Haddad
   Qualcomm

   Phone:
   Email: whaddad@qualcomm.com


   Jean-Michel Combes
   Orange Labs R&D
   38 rue du General Leclerc
   Issy-les-Moulineaux Cedex 9, France  92794

   Phone:
   Email: jeanmichel.combes@gmail.com


   Chunqiang Li
   Huawei
   No.91 BaiXia Rd.
   Nanjing, China  210001

   Phone:
   Email: li.chunqiang@huawei.com








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