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Versions: 00 01 02                                                      
6lo                                                     B. Sarikaya, Ed.
Internet-Draft                                                Huawei USA
Intended status: Standards Track                                  F. Xia
Expires: September 10, 2015                Huawei Technologies Co., Ltd.
                                                         P. Thubert, Ed.
                                                                   Cisco
                                                           March 9, 2015


   Lightweight and Secure Neighbor Discovery for Low-power and Lossy
                                Networks
                      draft-sarikaya-6lo-cga-nd-02

Abstract

   This document defines a lightweight and secure version of 6LoWPAN
   Neighbor Discovery for application in low-power and lossy networks.
   Cryptographically Generated Address and digital signatures are
   calculated using Elliptic Curve Cryptography, so that the
   cryptographic operations are suitable for low power devices.  An
   optimal version of this protocol is also specified which supports
   faster CGA calculation and multi-hop operation.  A node computes a
   Cryptographically Generated Address to be used as a Unique Interface
   ID, and associate all its Registered Addresses with that Unique
   Interface ID in place of the EUI-64 that is used in RFC 6775 to
   uniquely identify the interface of the Registered Address.  Once an
   address is registered with a cryptographic unique ID, only the owner
   of that ID can modify the state in the 6LR and 6LBR regarding the
   Registered Address.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 10, 2015.





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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  New and Modified Options  . . . . . . . . . . . . . . . . . .   5
     4.1.  Modified Address Registration Option  . . . . . . . . . .   5
     4.2.  CGA Parameters and Digital Signature Option . . . . . . .   6
     4.3.  Digital Signature Option  . . . . . . . . . . . . . . . .   8
     4.4.  Calculation of the Digital Signature and CGA Using ECC  .  10
   5.  Protocol Interactions . . . . . . . . . . . . . . . . . . . .  10
   6.  Optimizations . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.2.  Protocol Operations . . . . . . . . . . . . . . . . . . .  14
     6.3.  Multihop Operation  . . . . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   8.  IANA considerations . . . . . . . . . . . . . . . . . . . . .  16
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative references . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Neighbor discovery for IPv6 [RFC4861] and stateless address
   autoconfiguration [RFC4862], together referred to as neighbor
   discovery protocols (NDP), are defined for regular hosts operating
   with wired/wireless links.  These protocols are not suitable and
   require optimizations for resource constrained, low power hosts
   operating with lossy wireless links.  Neighbor Discovery
   optimizations for 6LoWPAN networks include simple optimizations such
   as a host address registration feature using the address registration



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   option (ARO) which is sent in unicast Neighbor Solicitation (NS) and
   Neighbor Advertisement (NA) messages [RFC6775].  With 6LoWPAN ND
   [RFC6775], the ARO option includes a EUI-64 address to uniquely
   identify the interface of the Registered Address on the registering
   device, so as to correlate further registrations for a same address
   and avoid address duplication.  The EUI-64 address is not secured and
   its ownership cannot be verified.  It results that any device
   claiming the same EUI-64 address may take over a registration and
   attract the traffic for that address.

   Neighbor Discovery Protocols (NDP) are not secure especially when
   physical security on the link is not assured and vulnerable to
   attacks defined in [RFC3756].  Secure neighbor discovery protocol
   (SEND) is defined to secure NDP [RFC3971].  Cryptographically
   Generated Addresses (CGA) are used in SEND [RFC3972].  SEND mandates
   the use of the RSA signature algorithm which is computationally heavy
   and not suitable to use for low-power and resource constrained nodes.
   The use of an RSA public key and signature leads to long message
   sizes not suitable to use in low-bit rate, short range, asymmetric
   and non-transitive links such as IEEE 802.15.4.

   In this document, we extend 6LoWPAN ND with CGA; but as opposed to
   SEND, the cryptographic address is not necessarily used as Interface
   ID (IID) in an IPv6 address but as a correlator associated to the
   registration of the IPv6 address.  This approach is made possible
   with 6LoWPAN ND [RFC6775], where the 6LR and the 6LBR maintain a
   state for each Registered Address.  If a CGA is associated with an
   original 6LoWPAN ND registration and stored in the registration
   state, then it can be used to validate that any update to the
   registration state is made by the owner of that CGA.

   To achieve this, this specification replaces the EUI-64 address, that
   is used in 6LoWPAN ND to avoid address duplication, with a CGA
   address whose ownership can be verified; it also provides new means
   for the 6LR to validate ownership of the CGA address by the
   registering device.  A node generates one 64-bit CGA address and uses
   it as Unique Interface ID in the registration of (one or more of) its
   addresses with the 6LR, which it attaches to and uses as default
   router.  The 6LR validates ownership of the CGA address typically
   upon creation or update of a registration state, for instance
   following an apparent movement from a point of attachment to another.
   The ARO option is modified to indicate that the Unique Interface ID
   is CGA-based, and through the DAR/DAC exchange, the 6LBR is kept
   aware that this is the case and whether the 6LR has verified the
   claim.

   CGA generation is based on elliptic curve cryptography (ECC)and
   signature is calculated using elliptic curve digital signature



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   algorithm (ECDSA) known to be lightweight, leading to much smaller
   packet sizes.  The resulting protocol is called Lightweight Secure
   Neighbor Discovery Protocol (LSEND).

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].

   Readers are expected to be familiar with all the terms and concepts
   that are discussed in [RFC3971], [RFC3972], "neighbor Discovery for
   IP version 6" [RFC4861], "IPv6 over Low-Power Wireless Personal Area
   Networks (6LoWPANs): Overview, Assumptions, Problem Statement, and
   Goals" [RFC4919], neighbor Discovery Optimization for Low-power and
   Lossy Networks [RFC6775] where the 6LoWPAN Router (6LR) and the
   6LoWPAN Border Router (6LBR) are introduced, and
   [I-D.chakrabarti-nordmark-6man-efficient-nd], which proposes an
   evolution of [RFC6775] for a larger applicability.

   The draft also conforms to the terms and models described in
   [RFC5889] and uses the vocabulary and the concepts defined in
   [RFC4291] for the IPv6 Architecture.

3.  Requirements

   In this section we state requirements of a secure neighbor discovery
   protocol for low-power and lossy networks.

   The protocol MUST be based on the Neighbor Discovery Optimization for
   Low-power and Lossy Networks protocol defined in [RFC6775] due to the
   host-initiated interactions to allow for sleeping hosts, elimination
   of multicast-based address resolution for hosts, etc.

   New options to be added to Neighbor Solicitation messages MUST lead
   to small packet sizes.  Smaller packet sizes facilitate low-power
   transmission by resource constrained nodes on lossy links.

   CGA generation, signature and key hash calculation MUST avoid the use
   of SHA-1 which is known to have security flaws.  In this document, we
   use SHA-2 instead of SHA-1 and thus avoid SHA-1's flaws.

   Public key and signature sizes MUST be minimized and signature
   calculation MUST be lightweight.  In this document we adopt ECC and
   ECDSA with the P-256 curve in order to meet this requirement.

   The support of the registration mechanism SHOULD be extended to more
   LLN links than IEEE 802.15.4, matching at least the LLN links for



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   which a 6lo "IPv6 over foo" specification exists, as well as Low-
   Power Wi-Fi.

   As part of this extension, a mechanism to compute a unique Identifier
   should be provided, with the capability to form a Link- Local Address
   that SHOULD be unique at least within the LLN connected to a 6LBR
   discovered by ND in each node within the LLN.

   The Address Registration Option used in the ND registration SHOULD be
   extended to carry the relevant forms of Unique Interface IDentifier.

   The Neighbour Discovery should specify the formation of a site-local
   address that follows the security recommendations from [RFC7217].

4.  New and Modified Options

4.1.  Modified Address Registration Option

   The ARO option is modified to transport a CGA-based Unique Interface
   ID.

         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    |    Status     |   Reserved    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Res | IDS |T|      TID      |     Registration Lifetime     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~         Unique Interface Identifier (variable length)         ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Track Forwarding, Transport Mode

   Fields:

   Type:         33 [RFC6775]

   Length:       8-bit unsigned integer.  Defined in [RFC6775].  The
                 length of the option (including the type and length
                 fields) in units of 8 bytes.  The value 0 is invalid.

   Status:       8-bit unsigned integer.  Extended from [RFC6775].
                 Indicates the status of a registration in the NA
                 response.  MUST be set to 0 in NS messages.  A new
                 status for req-proof of to-be-defined-by-iana (4




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                 suggested) indicates that the cryptographic material
                 that proves the CGA ownership is requested in a new NS.

   Reserved:     8 bits.  This field is unused.  It MUST be initialized
                 to zero by the sender and MUST be ignored by the
                 receiver.

   Res:          4 bits.  This field is unused.  It MUST be initialized
                 to zero by the sender and MUST be ignored by the
                 receiver.

   IDS:          Identifier name Space.  Indicates the name space for
                 the Unique Interface Identifier.  IDS of 0 means EUI-64
                 UID.  A new IDS to be assigned by IANA (a value of 2 is
                 suggested) is defined for CGA-based Unique Interface
                 ID.

   T bit:        1 bit flag.  Set if the TID octet is valid.

   TID:          8-bit integer.  It is a transaction id maintained by
                 the host and used by the 6LR to indicate the
                 registration that is being validated

   Registration Lifetime:  16-bit unsigned integer.  Defined in
                 [RFC6775].  The amount of time in a unit of 60 seconds
                 that the router should retain the Neighbor Cache entry
                 for the sender of the NS that includes this option.  A
                 value of zero means to remove the registration.

   Unique Interface Identifier:  8 bytes.  May be CGA-based with this
                 specification.

4.2.  CGA Parameters and Digital Signature Option

   This option contains both CGA parameters and the digital signature.

   A summary of the CGA Parameters and Digital Signature Option format
   is shown below.













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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     |   Pad  Length |  Sig. Length  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                        CGA Parameters                         .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                       Digital Signature                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                           Padding                             .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      TBA1 for CGA Parameters and Digital Signature

   Length

      The length of the option (including the Type, Length, Pad Length,
      Signature Length, CGA Parameters, Digital Signature and Padding
      fields) in units of 8 octets.

   Pad Length

      The length of the Padding field.

   Sig Length

      The length of the Digital Signature field.

   CGA Parameters

      The CGA Parameters field is variable-length containing the CGA
      Parameters data structure described in Section 4 of [RFC3972].




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   Digital Signature

      The Digital Signature field is a variable length field containing
      a Elliptic Curve Digital Signature Algorithm (ECDSA) signature
      (with SHA-256 and P-256 curve of [FIPS-186-3]).  Digital signature
      is constructed as explained in Section 4.4.

   Padding

      The Padding field contains a variable-length field making the CGA
      Parameters and Digital Signature Option length a multiple of 8.

4.3.  Digital Signature Option

   This option contains the digital signature.

   A summary of the Digital Signature Option format is shown below.
   Note that this option has the same format as RSA Signature Option
   defined in [RFC3971].  The differences are that Digital Signature
   field carries an ECDSA signature not an RSA signature, and in
   calculating Key Hash field SHA-2 is used instead of SHA-1.

   In the sequence of octets to be signed using the sender's private key
   includes 128-bit CGA Message Type tag.  In LSEND, CGA Message Type
   tag of 0xE8C47FB7FD2BB885DAB2D31A0F2808B4 MUST be used.


























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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            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                          Key Hash                             |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                       Digital Signature                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                           Padding                             .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      TBA2 for Digital Signature

   Length

      The length of the option (including the Type, Length, Reserved,
      Key Hash, Digital Signature and Padding fields) in units of 8
      octets.

   Key Hash

      The Key Hash field is a 128-bit field containing the most
      significant (leftmost) 128 bits of a SHA-2 hash of the public key
      used for constructing the signature.  This is the same as in
      [RFC3971] except for SHA-1 which has been replaced by SHA-2.

   Digital Signature

      Same as in Section 4.2.

   Padding





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      The Padding field contains a variable-length field containing as
      many bytes long as remain after the end of the signature.

4.4.  Calculation of the Digital Signature and CGA Using ECC

   Due to the use of Elliptic Curve Cryptography, the following
   modifications are needed to [RFC3971] and [RFC3972].

   The digital signature is constructed by using the sender's private
   key over the same sequence of octets specified in Section 5.2 of
   [RFC3971] up to all neighbor discovery protocol options preceding the
   Digital Signature option containing the ECC-based signature.  The
   signature value is computed using the ECDSA signature algorithm as
   defined in [SEC1] and hash function SHA-256.

   Public Key is the most important parameter in CGA Parameters defined
   in Section 4.2.  Public Key MUST be DER-encoded ASN.1 structure of
   the type SubjectPublicKeyInfo formatted as ECC Public Key.  The
   AlgorithmIdentifier, contained in ASN.1 structure of type
   SubjectPublicKeyInfo, MUST be the (unrestricted) id- ecPublicKey
   algorithm identifier, which is OID 1.2.840.10045.2.1, and the
   subjectPublicKey MUST be formatted as an ECC Public Key, specified in
   Section 2.2 of [RFC5480].

   Note that the ECC key lengths are determined by the namedCurves
   parameter stored in ECParameters field of the AlgorithmIdentifier.
   The named curve to use is secp256r1 corresponding to P-256 which is
   OID 1.2.840.10045.3.1.7 [SEC2].

   ECC Public Key could be in uncompressed form or in compressed form
   where the first octet of the OCTET STRING is 0x04 and 0x02 or 0x03,
   respectively.  Point compression using secp256r1 reduces the key size
   by 32 octets.  In LSEND, point compression MUST be supported.

5.  Protocol Interactions

   Lightweight Secure Neighbor Discovery for Low-power and Lossy
   Networks (LSEND for LLN) modifies Neighbor Discovery Optimization for
   Low-power and Lossy Networks [RFC6775] as explained in this section.
   Protocol interactions are shown in Figure 1.

   6LoWPAN Nodes (6LN, or simply "nodes") receive RAs from adjacent 6LRs
   and generate their own cryptographically generated addresses using
   elliptic curve cryptography as explained in Section 4.4.  The node
   sends a neighbor solicitation (NS) message with the address
   registration option (ARO) to 6LR.  Such a NS is called an address
   registration NS.




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  6LN                                                       6LR
   |                                                         |
   |<-----------------------RA-------------------------------|
   |                                                         |
   |---------------NS with ARO and CGA UID   --------------->|
   |                                                         |
   |<-----------------------NA with ARO (status=req-proof) --|
   |                                                         |
   |---------------NS with ARO and Digital Signature Option->|
   |                                                         |
   |<-----------------------NA with ARO----------------------|
   |                                                         |
   ...
   |                                                         |
   |---------------NS with ARO and CGA UID   --------------->|
   |                                                         |                                                          |
   |<-----------------------NA with ARO----------------------|
   ...
   |                                                         |
   |---------------NS with ARO and CGA UID   --------------->|
   |                                                         |                                                          |
   |<-----------------------NA with ARO----------------------|


                Figure 1: Lightweight SEND for LLN Protocol

6.  Optimizations

   In this section we present optimizations to the base LSEND defined
   above.  We use EUI-64 identifier instead of source address in CGA
   calculations.  We also extend LSEND operation to 6LoWPAN multihop
   network.

6.1.  Overview

   The scope of the present work is a 6LoWPAN Low Power Lossy Network
   (LLN), typically a stub network connected to a larger IP network via
   a Border Router called a 6LBR per [RFC6775].













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               ---+-------- ............ ------------
                  |      External Network       |
                  |
               +-----+
               |     | LLN Border
               |     | router
               +-----+
             o    o   o
      o     o   o     o
         o   o LLN   o    o     o
            o   o   o       o
                    o

                       Figure 2: Basic Configuration

   The 6LBR maintains a registration state for all devices in the
   attached LLN, and, in conjunction with the first-hop router (the
   6LR), is in position to validate uniqueness and grant ownership of an
   IPv6 address before it can be used in the LLN.  This is a fundamental
   difference with a classical network that relies on IPv6 address auto-
   configuration [RFC4862], where there is no guarantee of ownership
   from the network, and any IPv6 Neighbor Discovery packet must be
   individually secured [RFC3971].

   In a route-over mesh network, the 6LR is directly connected to the
   host device; this specification expects that peer-wise Layer-2
   security is deployed so that all the packets from a particular host
   are identified as such by the 6LR.  The 6LR may be multiple hops away
   from the 6LBR.  Packets are routed between the 6LR and the 6LBR via
   other 6LRs; this specification expects that a chain of trust is
   established so that a packet that was validated by the first 6LR can
   be safely routed by the next 6LRs and 6LBR.

   The [I-D.ietf-6tisch-architecture] suggests to use RPL [RFC6550] as
   the routing protocol between the 6LRs and the 6LBR, and to leverage
   [I-D.chakrabarti-nordmark-6man-efficient-nd] to extend the LLN in a
   larger multilink subnet [RFC4903].  In that model, a registration
   flow happens as shown in Figure 3:













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    6LoWPAN Node        6LR             6LBR            6BBR
     (RPL leaf)       (router)         (root)
         |               |               |               |
         |  6LoWPAN ND   |6LoWPAN ND+RPL | Efficient ND  | IPv6 ND
         |   LLN link    |Route-Over mesh|  IPv6 link    | Backbone
         |               |               |               |
         |  NS(ARO)      |               |               |
         |-------------->|               |               |
         | 6LoWPAN ND    | DAR (then DAO)|               |
         |               |-------------->|               |
         |               |               |  NS(ARO)      |
         |               |               |-------------->|
         |               |               |               | DAD
         |               |               |               |------>
         |               |               |               |
         |               |               |  NA(ARO)      |
         |               |               |<--------------|
         |               | DAC           |               |
         |               |<--------------|               |
         |  NA(ARO)      |               |               |
         |<--------------|               |               |


          Figure 3: (Re-)Registration Flow over Multi-Link Subnet

   A new device that joins the network auto-configures and address and
   performs an initial registration to an on-link 6LR with an NS message
   that carries a new Address Registration Option (ARO) [RFC6775].  The
   6LR validates with address with the central 6LBR using a DAR/DAC
   exchange, and the 6LR confirms (or infirms) the address ownership
   with an NA message that also carries an Address Registration Option.

   The registration mechanism in [RFC6775] was created for the original
   purpose of Duplicate Address Detection (DAD), whereby use of an
   address would be granted as long as the address is not already
   present in the subnet.  But [RFC6775] does not require that the 6LR
   use the registration for source address validation (SAVI).

   In order to validate address ownership, that mechanism enables the
   6LBR to correlate further claims for a registered address with the
   device to which it is granted, based on a Unique Interface IDentifier
   (UID) that is derived from the MAC address of the device (EUI-64).

   The limit of the mechanism in [RFC6775] is that it does not enable to
   prove the UID itself, so any node connected to the subnet and aware
   of the address/UID mapping may effectively fake the same UID and
   steal an address.




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   This draft uses a Cryptographically Generated Address (CGA) [RFC3972]
   as an alternate UID for the registration.  Proof of ownership of the
   UID is passed with the first registration to a given 6LR, and
   enforced at the 6LR, which validates the proof.  With this new
   operation, the 6LR allows only packets from a connected host if the
   connected host owns the registration of the source address of the
   packet.

   If a chain of trust is present between the 6LR and the 6LBR, then
   there is no need to propagate the proof of ownership to the 6LBR.
   All the 6LBR need to know is that this particular UID is based on
   CGA, so as to enforce that any update via a different 6LR is also
   based on CGA.

6.2.  Protocol Operations

   Digital signature and CGA are calculated over EUI-64 or interface id
   of the node.  It is only done initially at once not repeated with
   every message the node sends.  The calculation does not change even
   if the node has a new address since EUI-64 does not change.  This
   means that this CGA can be used to claim multiple targets.  The
   calculation is ECC based as described in Section 4.4.

   Protocol interactions are as defined in Section 5.  The address
   registration NS message contains CGA Parameters and Digital Signature
   Option defined in Section 4.2.  The node MUST set the Extended Unique
   Interface IDentifier (EUI-64) field [Guide] in ARO to the
   crypotographically generated address.  The Subnet Prefix field of CGA
   Parameters MUST be set to the 64-bit prefix in the RA message
   received from 6LBR.  Source address MUST be set to the prefix
   concatenated with the node's crypotographically generated address.
   The Public Key field of CGA Parameters MUST be set to the node's ECC
   Public Key.

   CGA calculated may need to be modified before it is used as EUI-64.
   The b2 bit or U/L or "u" bit MUST be set to zero for globally unique
   and b1 bit or I/G or "g" bit MUST be set to zero for unicast before
   using it in IPv6 address as the interface identifier.  In LSEND,
   senders and receivers ignore any differences in the three leftmost
   bits and in bits 6 and 7 (i.e., the "u" and "g" bits) in the
   interface identifiers [RFC3972].

   The Target Address field in NS message is set to the prefix
   concatenated with the node's crypotographically generated address.
   This address does not need duplicate address detection as EUI-64 is
   globally unique.  So a host cannot steal an address that is already
   registered unless it has the key for the EUI-64.  The same EUI-64 can
   thus be used to protect multiple addresses e.g. when the node



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   receives a different prefix.  The node adds CGA Parameters (including
   Public Key) and Digital Signature Option defined in Section 4.2 into
   NS message.  The node sends the address registration option (ARO)
   which is set to the CGA calculated.

   Protocol interactions given in Figure 1 are modified a bit in that
   Digital Signature option with the public key and ARO are passed to
   and stored by the 6LR/6LBR on the first NS and not sent again the in
   the next NS.

   The 6LR/6LBR ensures first-come/first-serve by storing the ARO and
   the cryptographical material correlated to the target being
   registered.  Then, if the node is the first to claim any address it
   likes, then it becomes owner of that address and the address is bound
   to the CGA in the 6LR/6LBR registry.  This procedure avoids the
   constrained device to compute multiple keys for multiple addresses.
   The registration process allows the node to tie all the addresses to
   the same EUI-64 and have the 6LR/6LBR enforce first come first serve
   after that.

6.3.  Multihop Operation

   In multihop 6LoWPAN, 6LBR sends RAs with prefixes downstream and it
   is the 6LR that receives and relays them to the nodes. 6LR and 6LBR
   communicate with the ICMPv6 Duplicate Address Request (DAR) and the
   Duplicate Address Confirmation (DAC) messages.  The DAR and DAC use
   the same message format as NS and NA with different ICMPv6 type
   values.

   In LSEND we extend DAR/DAC messages to carry CGA Parameters and
   Digital Signature Option defined in Section 4.2.

   In a multihop 6LoWPAN, the node exchanges the messages shown in
   Figure 3.  6LBR must be aware of who owns an address (EUI-64) to
   defend the first user if there is an attacker on another 6LR.
   Because of this the content that the source signs and the signature
   needs to be propagated to the 6LBR in DAR message.  For this purpose
   we need the DAR message sent by 6LR to 6LBR MUST contain CGA
   Parameters and Digital Signature Option carrying the CGA that the
   node calculates and its public key.  DAR message also contains ARO.

   It is possible that occasionally, 6LR may miss the node's CGA (that
   it received in ARO) or the crypto information (that it received in
   CGA Parameters and Digital Signature Option). 6LR should be able to
   ask for it again.  This is done by restarting the exchanges shown in
   Figure 1.  The result enables 6LR to refresh CGA and public key
   information that was lost. 6LR MUST send DAR message with CGA
   Parameters and Digital Signature Option and ARO to 6LBR.  6LBR as a



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   reply forms a DAC message with the information copied from the DAR
   and the Status field is set to zero.  With this exchange, the 6LBR
   can (re)validate and store the CGA and crypto information to make
   sure that the 6LR is not a fake.

7.  Security Considerations

   The same considerations regarding the threats to the Local Link Not
   Covered (as in [RFC3971]) apply.

   The threats discussed in Section 9.2 of [RFC3971] are countered by
   the protocol described in this document as well.

   As to the attacks to the protocol itself, denial of service attacks
   that involve producing a very high number of packets are deemed
   unlikely because of the assumptions on the node capabilities in low-
   power and lossy networks.

8.  IANA considerations

   This document defines two new options to be used in neighbor
   discovery protocol messages and new type values for CGA Parameters
   and Digital Signature Option (TBA1) and Digital Signature Option
   (TBA2) need to be assigned by IANA.

   This document defines 0xE8C47FB7FD2BB885DAB2D31A0F2808B4 for LSEND
   CGA Message Type Tag.

9.  Acknowledgements

   TBD.

10.  References

10.1.  Normative References

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

   [RFC3756]  Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor
              Discovery (ND) Trust Models and Threats", RFC 3756, May
              2004.

   [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.



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   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

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

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC4903]  Thaler, D., "Multi-Link Subnet Issues", RFC 4903, June
              2007.

   [RFC4919]  Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
              over Low-Power Wireless Personal Area Networks (6LoWPANs):
              Overview, Assumptions, Problem Statement, and Goals", RFC
              4919, August 2007.

   [RFC5480]  Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
              "Elliptic Curve Cryptography Subject Public Key
              Information", RFC 5480, March 2009.

   [RFC5889]  Baccelli, E. and M. Townsley, "IP Addressing Model in Ad
              Hoc Networks", RFC 5889, September 2010.

   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

   [RFC6775]  Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann,
              "Neighbor Discovery Optimization for IPv6 over Low-Power
              Wireless Personal Area Networks (6LoWPANs)", RFC 6775,
              November 2012.

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217, April 2014.

   [SEC1]     "Standards for Efficient Crtptography Group.  SEC 1:
              Elliptic Curve Cryptography Version 2.0", May 2009.

   [Guide]    "Guidelines for 64-bit global Identifier (EUI-64TM)",
              November 2012,
              <http://standards.ieee.org/develop/regauth/tut/eui64.pdf>.






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   [ANSIX9.62]
              "American National Standards Institute (ANSI), ANS
              X9.62-2005: The Elliptic Curve Digital Signature Algorithm
              (ECDSA)", November 2005.

10.2.  Informative references

   [SEC2]     "Standards for Efficient Crtptography Group.  SEC 2:
              Recommended Elliptic Curve Domain Parameters Version 2.0",
              January 2010.

   [FIPS-186-3]
              "National Institute of Standards and Technology, "Digital
              Signature Standard"", June 2009.

   [NIST-ST]  "National Institute of Standards and Technology, "NIST
              Comments on Cryptanalytic Attackts on SHA-1"", January
              2009,
              <http://csrc.nist.gov/groups/ST/hash/statement.html>.

   [I-D.rafiee-6man-ssas]
              Rafiee, H. and C. Meinel, "A Simple Secure Addressing
              Scheme for IPv6 AutoConfiguration (SSAS)", draft-rafiee-
              6man-ssas-11 (work in progress), September 2014.

   [I-D.chakrabarti-nordmark-6man-efficient-nd]
              Chakrabarti, S., Nordmark, E., Thubert, P., and M.
              Wasserman, "IPv6 Neighbor Discovery Optimizations for
              Wired and Wireless Networks", draft-chakrabarti-nordmark-
              6man-efficient-nd-07 (work in progress), February 2015.

   [I-D.ietf-6tisch-architecture]
              Thubert, P., Watteyne, T., Struik, R., and M. Richardson,
              "An Architecture for IPv6 over the TSCH mode of IEEE
              802.15.4e", draft-ietf-6tisch-architecture-06 (work in
              progress), March 2015.

Authors' Addresses

   Behcet Sarikaya (editor)
   Huawei USA
   5340 Legacy Dr. Building 3
   Plano, TX  75024

   Email: sarikaya@ieee.org






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   Frank Xia
   Huawei Technologies Co., Ltd.
   101 Software Avenue, Yuhua District
   Nanjing,  Jiangsu  210012, China

   Phone: ++86-25-56625443
   Email: xiayangsong@huawei.com


   Pascal Thubert (editor)
   Cisco Systems, Inc
   Building D
   45 Allee des Ormes - BP1200
   MOUGINS - Sophia Antipolis  06254
   FRANCE

   Phone: +33 497 23 26 34
   Email: pthubert@cisco.com

































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