6lo                                                          B. Sarikaya, Ed. Sarikaya
Internet-Draft                                                Huawei USA
Updates: 6775 (if approved)                                   P. Thubert
Intended status: Standards Track                                   Cisco
Expires: November 16, 25, 2017                                      M. Sethi, Ed. Sethi
                                                                Ericsson
                                                            May 15, 24, 2017

 Address Protected Neighbor Discovery for Low-power and Lossy Networks
                        draft-ietf-6lo-ap-nd-01
                        draft-ietf-6lo-ap-nd-02

Abstract

   This document defines an extension to 6LoWPAN Neighbor Discovery.
   This extension is designed for low-power and lossy network
   environments and it supports multi-hop operation. Discovery, RFC
   6775.  Nodes supporting this extension compute a Cryptographically cryptographic Owner
   Unique Interface ID and associate it with one or more of their
   Registered Addresses.  The
   Cryptographic ID (Crypto-ID) uniquely identifies the owner of the
   Registered Address.  It is used in place of the EUI-64 address that
   is specified in RFC 6775.  Once an address is registered with a
   Cryptographic ID, only the owner of that ID can modify the anchor
   state information of the Registered Address in the 6LR Address, and 6LBR. Source Address
   Validation can be enforced.

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 November 16, 25, 2017.

Copyright Notice

   Copyright (c) 2017 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  . .  Updating RFC 6775 . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Protocol Interactions .  New Fields and Options  . . . . . . . . . . . . . . . . . . .   5
     4.1.  Overview  . .  New Crypto-ID . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Updating RFC 6775  Updated EARO  . . . . . . . . . . . . . . . . . . . .   7
       4.2.1. . .   6
     4.3.  New Crypto-ID Calculation Parameters Option . . . . . . . . . . . . .   7
   5.  Protocol Overview . . . . . .  10
     4.3. . . . . . . . . . . . . . . . .   8
     5.1.  Protocol Scope  . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  Protocol Flows  . . . . . . . . . . . . . . . . . . . . .   9
     5.3.  Multihop Operation  . . . . . . . . . . . . . . . . . . .  13
   5.  11
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   6.  12
   7.  IANA considerations . . . . . . . . . . . . . . . . . . . . .  14
   7.  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   8.  13
   9.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .  14
   9.  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     9.2.  13
     10.2.  Informative references . . . . . . . . . . . . . . . . .  14
   Appendix A.  Requirements Addressed in this Document  . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Neighbor discovery for IPv6 [RFC4861] and stateless address
   autoconfiguration [RFC4862] and their extensions are together collectively
   referred to as neighbor
   discovery protocols (NDP).  They are defined for regular hosts that
   have sufficient memory and computation capabilities.  These protocols
   are however not suitable for resource-constrained devices.
   Therefore, they require adaptation the IPv6 Neighbor Discovery Protocol (IPv6 NDP).  In
   order to work on resource-constrained
   hosts operating enable IPv6 NDP operations over a constrained low-power and
   lossy network (LLN).  Neighbor (LLN), "Neighbor Discovery optimizations for 6LoWPAN networks include simple
   optimizations such as
   networks" [RFC6775] (6LoWPAN ND), reduces the use of multicast in the
   original protocol and introduces a unicast host address registration feature.  This
   feature uses the address
   technique.  The registration option mechanism leverages a new Address
   Registration Option (ARO) which that is sent carried in the unicast Neighbor
   Solicitation (NS) and Neighbor Advertisement (NA) messages [RFC6775].

   With between
   the 6LoWPAN ND [RFC6775], Node (6LN) and the ARO option includes a EUI-64 interface
   ID to uniquely identify the interface of 6LoWPAN Router (6LR), as well as the Registered
   Duplicate Address on
   the registering device, so as to correlate further registrations for Request (DAR) and Duplicate Address Confirmation
   (DAC) messages between the same address 6LR and avoid address duplication.  The EUI-64 interface
   ID the 6LoWPAN Border Router (6LBR),
   which is not secure and its ownership cannot be verified.  Consequently,
   any device claiming the same EUI-64 interface ID may take over an
   existing registration and attract central repository of all the traffic for that address. registered addresses in
   its domain.

   The
   address registration mechanism in 6LoWPAN ND [RFC6775] is limited was created for
   the original purpose of Duplicate Address Detection (DAD), whereby
   use of an address would be granted as it does long as the address is not
   require
   already present in the subnet (first come first serve).  In order to
   validate address ownership, the registration mechanism enables the
   6LR and 6LBR to correlate further claims for a node registered address
   from the device to prove its ownership which it is granted with a Owner Unique Interface
   IDentifier (OUID).  With 6LoWPAN ND, the OUID is derived from the MAC
   address of the EUI-64 Interface ID. device (EUI-64), which can be spoofed.  Therefore, any
   node connected to the subnet and aware of the
   registered address to EUI-64 interface ID a registered-address-to-
   OUID mapping may effectively fake the same interface ID and OUID, steal an address.

   In this document, we extend 6LoWPAN ND to protect the address
   ownership with cryptographic material, but as opposed to Secure
   Neighbor Discovery (SEND) [RFC3971] and Cryptographically Generated
   Addresses (CGAs) [RFC3972], the cryptographic material generated is
   not embedded in the Interface ID (IID) as an IPv6 address.  Instead,
   attract the generated cryptographic ID is used as traffic for that address towards a correlator associated
   with the different Node.  In
   order to allow a more secured registration of mechanism, the IP address.  This approach is made
   possible with "Update to
   6LoWPAN ND [RFC6775], where ND" [I-D.ietf-6lo-rfc6775-update] opens the 6LR and semantics of the 6LBR
   maintain state information for each Registered Address.  If a
   cryptographic ID is associated with the first 6LoWPAN ND
   registration, then it can be used to validate any future updates to
   the registration.

   In order
   ARO option and allows to achieve this ownership verification, in transport alternate forms of OUIDs.

   With this extension specification, the EUI-64 interface ID used in 6LoWPAN ND is replaced
   with cryptographic material whose ownership can be verified.  The
   extension also provides new means for the 6LR to validate ownership
   of the registration, and thus, the ownership of registered address.
   The resulting protocol is called Protected Address Registration
   protocol (ND-PAR).

   In ND-PAR, a node typically 6LN generates one 64-bit a cryptographic ID
   (Crypto-ID) (Crypto-
   ID) and uses places it as Unique Interface ID in the OUID field in the registration of one (or
   more) of its addresses with the 6LR, which 6LR(s) that it attaches to and uses as default router.
   router(s).  Proof of ownership of the cryptographic ID (Crypto-ID) is
   passed with the first registration to a given 6LR, and enforced at
   the 6LR, in a new Crypto-ID Parameters Option (CIPO).  The 6LR
   validates ownership of the cryptographic ID typically upon the creation or update of a
   registration state, for instance following an apparent movement from one point of
   attachment to another.  The ARO option is modified to carry or a change in the
   Unique Interface ID, anchor information, such as
   Link-Layer Address and through the DAR/DAC exchange.

   Compared with SeND, this specification saves ~1Kbyte in every NS/NA
   message.  Also SeND requires one associated Layer-2 cryptographic material.

   The protected address per IPv6
   address.  This specification separates the cryptographic identifier
   from registration protocol proposed in this document
   enables the IPv6 address so enforcement of Source Address Validation (SAVI)
   [RFC7039], which ensures that only the correct owner uses a node can have more than one IPv6
   registered address protected by the same cryptographic identifier.  SeND forces in the IPv6 source address to be cryptographic since it integrates the CGA as
   an IID. 6LoWPAN derives the field in IPv6 address from other things like packets.  With
   this specification, a
   short address in 802.15.4 6LN that sources a packet has to enable use a better compression.

2.  Terminology 6LR to
   which the source address of the packet is registered to forward the
   packet.  The 6LR maintains state information for the registered
   addressed along with the MAC address, and link-layer cryptographic
   key associated with that node.  In SAVI-enforcement mode, the 6LR
   allows only packets from a connected Host if the connected Host owns
   the registration of the source address of the packet.

   The 6lo adaptation layer framework ([RFC4944], [RFC6282]) expects
   that a device forms its IPv6 addresses based on Layer-2 address, so
   as to enable a better compression.  This is incompatible with "Secure
   Neighbor Discovery (SEND)" [RFC3971] and "Cryptographically Generated
   Addresses (CGAs)" [RFC3972], which derive the Interface ID (IID) in
   the IPv6 addresses from cryptographic material.  "Privacy
   Considerations for IPv6 Address Generation Mechanisms"
   [I-D.ietf-6man-ipv6-address-generation-privacy] places additional
   recommendations on the way addresses should be formed and renewed.

   This specification allows a device to form and register addresses at
   will, without a constraint on the way the address is formed or the
   number of addresses that are registered in parallel.  It enables to
   protect multiple addresses with a single cryptographic material and
   to send the proof only once to a given 6LR for multiple addresses and
   refresher registrations.

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], [RFC4861], [RFC4919],
   [RFC6775], and [I-D.ietf-6lo-backbone-router] which proposes an
   evolution of [RFC6775] for wider applicability.

   This document defines Crypto-ID as an identifier of variable size
   which in most cases is 64 bits long.  It is generated using
   cryptographic means explained later in this document.

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

   This document uses [RFC7102] for Terminology in Low power And Lossy
   Networks.

3.  Requirements

   In  Updating RFC 6775

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

   o node SHOULD use a cryptographic identifier
   (Crypto-ID) as OUID in its registration; the Crypto-ID is calculated
   as described in Section 4.1.  The protocol MUST be based on fact that a OUID is a Crypto-ID is
   indicated in a new 'C' flag in the Neighbor Discovery Optimization NS(ARO) message.

   This specification also introduces a new option, the CIPO, that is
   used to prove ownership of the Crypto-ID.  A node that registers for Low-power and Lossy Networks protocol defined in [RFC6775].
      RFC6775 utilizes optimizations such as host-initiated interactions
      for sleeping resource-constrained hosts and elimination of
      multicast address resolution.

   o  New options to be added
   the first time to Neighbor Solicitation messages MUST
      lead a 6LR SHOULD place a CIPO option to small packet sizes, especially compared with existing
      protocols such as SEcure Neighbor Discovery (SEND).  Smaller
      packet sizes facilitate low-power transmission by resource-
      constrained nodes on lossy links.

   o  The support for this its
   registration mechanism SHOULD be extensible but is not expected to more LLN links than IEEE 802.15.4 only.  Support for at least place the LLN links option in the next
   periodic refresher registrations for which that address, or for the
   registration of other addresses with the same OUID.  When a 6lo "IPv6 over foo" specification
      exists, as well 6LR
   receives a NS(ARO) registration with a new Crypto-ID as Low-Power Wi-Fi a OUID, then
   it SHOULD be possible.

   o  As part of this extension, challenge by responding with a mechanism to compute NA(ARO) with a unique
      Identifier should status of
   "Proof requested".  This whole process MAY be provided with skipped in networks
   where there is no or ultra low expectations of mobility.

   The challenge will also be triggered in the capability to form case of a Link
      Local registration
   for which the Source Link-Layer Address is not consistent with a
   state that SHOULD be unique already exists either at least within the LLN
      connected to a 6LR or the 6LBR.

   o  The Address Registration Option used  In the
   latter case, the 6LBR returns a status of "Proof requested" in the ND registration SHOULD
      be extended
   DAR/DAC exchange, which is echoed by the 6LR in the NA (ARO) back to carry
   the relevant forms of Unique Interface
      IDentifier.

   o  The Neighbour Discovery registering node.  This flow should specify the formation of not alter a site-
      local address that follows preexisting state
   in the security recommendations from
      [RFC7217].

4.  Protocol Interactions

   Protected address and registration neighbor discovery protocol (ND-
   PAR) modifies Neighbor Discovery Optimization for Low-power and Lossy
   Networks [RFC6775] as explained in this section.

4.1.  Overview

   The scope of 6LR or 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 6LBR.

   Upon a 6LBR per [RFC6775].

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

                       Figure 1: Basic Configuration

   The 6LBR maintains NA(ARO) with a registration state for all devices in status of "Proof requested", the
   attached LLN, and, in conjunction registering
   node SHOULD retry its registration with the first-hop router (the
   6LR), is in a position to validate uniqueness and grant CIPO option that proves its
   ownership of
   an IPv6 address before it can be used in the LLN.  This is a
   fundamental difference Crypto-ID.

   If the 6LR cannot validate the proof, it responds with a classical network that relies on IPv6
   address auto-configuration [RFC4862], where there is no guarantee status of
   ownership from the network, and any IPv6 Neighbor Discovery packet
   must be individually secured [RFC3971].

   In
   "Incorrect Proof".  Upon a mesh network, NA(ARO) with a status of "Incorrect
   Proof", the registering node SHOULD NOT use this Crypto-ID for
   registering with that 6LR anymore.

4.  New Fields and Options

4.1.  New Crypto-ID

   Elliptic Curve Cryptography (ECC) is directly connected to used in the host device.
   This specification expects that calculation of the peer-wise layer-2 security
   Crypto-ID.  The digital signature is
   deployed so that all the packets from a particular host are securely
   identifiable constructed by using the 6LR.  The 6LR may be multiple hops away from the
   6LBR.  Packets are routed between 6LN's
   private key over its EUI-64 (MAC) address.  The signature value is
   computed using the 6LR ECDSA signature algorithm and the 6LBR via other
   6LRs.  This specification expects that a chain of trust hash function
   used is
   established so that a packet that was validated SHA-256 [RFC6234].  Public Key is the most important
   parameter in CGA Parameters (sent by 6LN in an NS message).  ECC
   Public Key could be in uncompressed form or in compressed form where
   the first 6LR octet of the OCTET STRING is 0x04 and 0x02 or 0x03,
   respectively.  Point compression can
   be safely routed further reduce the key size by
   about 32 octets.

   First, the next 6LRs modifier is set to the 6LBR.

   [I-D.ietf-6tisch-architecture] suggests a random or pseudo-random 128-bit
   value.  Next, concatenate from left to use of RPL [RFC6550] as
   the routing protocol between right the 6LRs modifier, 9 zero
   octets and the 6LBR, and leveraging a
   backbone router [I-D.ietf-6lo-backbone-router] ECC public key.  SHA-256 algorithm is applied on the
   concatenation.  The 112 leftmost bits of the hash value is taken.
   Concatenate from left to extend right the modifier value, the LLN in a
   larger multilink subnet [RFC4903].  In that model, a registration
   flow happens as shown in Figure 2.  Note that network beyond prefix
   and the 6LBR encoded public key.  NIST P-256 is out executed on the
   concatenation.  The leftmost bits of scope for the result is used as the
   Crypto-ID.  With this document.

    6LoWPAN Node        6LR             6LBR
     (RPL leaf)       (router)         (root)
         |               |               |
         |  6LoWPAN ND   |6LoWPAN ND+RPL | Efficient ND
         |   LLN link    |Route-Over mesh|  IPv6 link
         |               |               |
         |  NS(ARO)      |               |
         |-------------->|               |
         | 6LoWPAN ND    | DAR (then DAO)|
         |               |-------------->|
         |               |               |
         |               |               |
         |               |               |
         |               |               |
         |               |               |
         |               | specification, the last 64 bits are retained,
   but it could be expanded to more bits in the future by increasing the
   size of the OUID field.

   In respecting the cryptographic algorithm agility [RFC7696], Curve
   25519 [RFC7748] can also be used instead of NIST P-256.  This is
   indicated by 6LN by setting the Crypto Type field in the CIPO option
   to a value of 1.  If 6LBR does not support Curve 25519, it will set
   Crypto Type field to zero.  This means that the default algorithm
   (NIST P-256) will be used.

4.2.  Updated EARO

       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   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | DAC Reserved  |C|T|     TID       |     Registration Lifetime     |               |<--------------|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  NA(ARO)                                                               |
      +          Owner Unique ID (EUI-64 or equivalent)               +
      |
         |<--------------|                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: (Re-)Registration Flow over Multi-Link Subnet

   A new device that joins the network auto-configures an address and
   performs an initial registration to an on-link 6LR with an NS message
   that carries a new 1: Enhanced Address Registration Option (ARO) [RFC6775].

   Type:

      33

   Length:

      8-bit unsigned integer.  The
   6LR validates length of the address with option (including the central 6LBR using a DAR/DAC
   exchange,
      type and length fields) in units of 8 bytes.

   Status:

      8-bit unsigned integer.  Indicates the 6LR confirms (or denies) the address ownership with
   an NA message that also carries an Address Registration Option.

   The status of a registration mechanism in [RFC6775] was created for
      the original
   purpose of Duplicate Address Detection (DAD), whereby use of an
   address would NA response.  MUST be granted as long as the address is not already
   present set to 0 in NS messages.  This
      specification leverages values introduced in the subnet.  But [RFC6775] Update to 6LoWPAN
      ND [I-D.ietf-6lo-rfc6775-update], such as 5: Proof Requested, and
      does not require that the 6LR
   use the registration for source address validation (SAVI) [RFC7039].

   Protected address registration protocol proposed in this document
   enforces SAVI.  With this we ensure that only the correct owner uses
   the registered address in the source address field.  Therefore a
   destination node can trust that the source is the real owner without
   using SeND.  All packets destined for a node go through the 6LR additional values to
   which it be defined.

   Reserved:

      This field is attached.  The 6LR maintains state information for the
   registered addressed along with the MAC address, and link-layer
   cryptographic key associated with that node.  The 6LR therefore only
   delivers packets to the real owner based on its state information.

   In order to validate address ownership, the registration mechanism
   (that goes all the way unused.  It MUST be initialized to zero by the 6LBR with the DAR/DAC) enables
      sender and MUST be ignored by the 6LBR
   to correlate further claims for receiver.

   C:

      This specification introduces a registered address from the device
   to C bit, which it is granted, based on set to indicate
      that the Owner Unique ID field contains a Crypto-ID.

   T and TID:

      Defined in [I-D.ietf-6lo-rfc6775-update].

   Owner Unique Interface IDentifier (UID).
   This UID is derived from the MAC address of the device (EUI-64). ID:

      When using this specification, this field contains a Crypto-ID.

4.3.  New Crypto-ID Parameters Option

   This document uses specification introduces a randomly generated value as an alternate UID for new option, the registration.  Proof Crypto-ID Parameters
   Option (CIPO), that carries the 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 crypto-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     |   Pad Length  |  Crypto Type  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                      Modifier (16 octets)                     +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                    Subnet Prefix (8 octets)                   +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                                                               |
      +                  Public Key (variable length)                 +
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                           Padding                             .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 2: Crypto-ID Parameters Option

   Type:

      CIPO, to be assigned by IANA.

   Length:

      The length of the source address option in units of 8 octets.

   Pad Length:

      The length of the packet.

   In a multihop 6LoWPAN, the registration with Crypto-ID is propagated
   to 6LBR as described Padding field.

   Crypto Type:

      The type of cryptographic algorithm used in Section 4.3.  If a chain calculation Crypto-ID.
      Default value of trust is present
   between the 6LR and the 6LBR, then there all zeros indicate NIST P-256.  A value of 1 is no need to propagate the
   proof
      assigned for Curve 25519.  New values may be defined later.

   Modifier:

      128 bit random value.

   Subnet Prefix:

      64 bit subnet prefix.

   Public Key:

      ECC public key of ownership to the 6LBR.  All 6LN.

   Padding:

      A variable-length field making the 6LBR needs to know is that
   this particular UID is randomly generated, so as to enforce that any
   update via option length a different 6LR is also random.

4.2.  Updating RFC 6775

   Protocol interactions are multiple of 8,
      containing as defined in Figure 2.  The Crypto-ID is
   calculated many octets as described specified in Section 4.2.1. the Pad Length field.

5.  Protocol Overview

5.1.  Protocol Scope

   The Target Address field in NS message scope of the present work is set 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].

   The 6LBR maintains a registration state for all devices in the prefix
   concatenated
   attached LLN, and, in conjunction with the node's address.  This address does not need
   duplicate address detection as Crypto-ID first-hop router (the
   6LR), is globally unique.  So in a
   host cannot steal position to validate uniqueness and grant ownership of
   an IPv6 address that is already registered unless before it has
   the key used for generating the Crypto-ID.  The same Crypto-ID can
   thus be used to protect multiple addresses e.g. when the node
   receives a different prefix.

   Local or on-link protocol interactions are shown in Figure 3.
   Crypto-ID and ARO are passed to and stored by the 6LR/6LBR on the
   first NS and not sent again in the next NS.  The operation starts LLN.  This is a
   fundamental difference with 6LR sending a Router Advertisement (RA) message to 6LN.

   The 6LR/6LBR ensures first-come/first-serve by storing classical network that relies on IPv6
   address auto-configuration [RFC4862], where there is no guarantee of
   ownership from the ARO network, and any IPv6 Neighbor Discovery packet
   must be individually secured [RFC3971].

               ---+-------- ............
                  |      External Network
                  |
               +-----+
               |     | 6LBR
               +-----+
             o    o   o
      o     o   o     o
         o   o LLN   o    o     o
            o   o   o       (6LR)
                    o         (6LN)

                       Figure 3: Basic Configuration

   In a mesh network, the Crypto-ID correlated to the node being registered.  The node 6LR is
   free directly connected to claim any address it likes as long as it is the first to make
   such a claim.  The node becomes owner of host device.
   This specification expects that address and the address peer-wise layer-2 security is bound to the Crypto-ID in
   deployed so that all the 6LR/6LBR registry.  This procedure
   avoids packets from a particular host are securely
   identifiable by the constrained device to compute multiple keys for multiple
   addresses. 6LR.  The registration process allows the node to tie all 6LR may be multiple hops away from the
   addresses to
   6LBR.  Packets are routed between the same Crypto-ID 6LR and have the 6LR/6LBR enforce first-
   come first-serve after that.

   A condition where a 6LN uses multiple IPv6 addresses may happen when the node moves at 6LBR via other
   6LRs.  This specification expects that a different place and receives chain of trust is
   established so that a different prefix.
   In this scenario, packet that was validated by the node uses first 6LR can
   be safely routed by the same Crypto-ID next 6LRs to protect its new
   IPv6 address.  This prevents other nodes from stealing the address
   and trying 6LBR.

5.2.  Protocol Flows

   The 6TiSCH Architecture [I-D.ietf-6tisch-architecture] suggests to
   use it of RPL [RFC6550] as their source address.

   Note that if the device that moves always forms new MAC and IP
   address [RFC6775], then this new address can be used for
   registration.  In case of a collision of routing protocol between the new MAC 6LRs and therefore IP
   address, the node can easily form a new IPv6 address.  This is one
   case where the use of Crypto-ID would not be needed.  Crypto-ID or
   ND-PAR should be activated when the IP address is claimed at another
   place, or for
   6LBR.  In that model, a different MAC address at the same place, e.g. for MAC
   address privacy [I-D.ietf-6man-ipv6-address-generation-privacy].

         6LN registration flow happens as shown in
   Figure 4.

    6LoWPAN Node        6LR             6LBR
     (RPL leaf)       (router)       (RPL root)
         |               |               |
         |
          |<------------------- RA --------------------------|  6LoWPAN ND   |  6LoWPAN ND   |
          |----------- NS with ARO and Crypto-ID ----------->|
         |               |
          |<---------- NA with ARO (status=req-proof) -------|               |
         |
          |----------- NS with ARO and Crypto-ID ----------->|               |               |
          |<---------------- NA with ARO --------------------|
         |  NS(ARO)      |
          ...                                              ...               |
         |-------------->|               |
          |------------ NS with ARO and Crypto-ID ---------->|
         | 6LoWPAN ND    | DAR           |
         |
          |<---------------- NA with ARO --------------------|
          ...                                              ...               |-------------->|
         |               |(then RPL DAO) |
         |               |               |
         |               | DAC           |
         |               |<--------------|
         |  NA(ARO)      |               |
         |<--------------|               |
         |               |
          |----------- NS with ARO and Crypto-ID ----------->|               |
         |               |               |
          |<---------------- NA with ARO --------------------|

                     Figure 3: On-link Protocol Operation

   Elliptic Curve Cryptography (ECC) is used in the calculation of
   cryptographic identifier (Crypto-ID).  The digital signature is
   constructed by using the 6LN's private key over its EUI-64 (MAC)
   address.  The signature value is computed using 4: (Re-)Registration Flow

   A new device that joins the ECDSA signature
   algorithm network auto-configures an address and the hash function used is SHA-256 [RFC6234].  Public
   Key is the most important parameter in CGA Parameters (sent by 6LN in
   performs an initial registration to an on-link 6LR with an NS message).  ECC Public Key could be in uncompressed form or in
   compressed form where the first octet of message
   that carries an Address Registration Option (ARO) [RFC6775].  The 6LR
   validates the OCTET STRING is 0x04 and
   0x02 or 0x03, respectively.  Point compression can further reduce address with the
   key size by about 32 octets.

   After calculating its Crypto-ID, central 6LBR using a 6LN sends it along with DAR/DAC exchange,
   and the CGA
   parameters in 6LR confirms (or denies) the first NS message, see Figure 3.  In order to send
   Crypto-ID, a modified address registration option called Enhanced ownership with an NA
   message that also carries an Address Registration Option (EARO) is defined in Figure 4.  As
   defined in Option.

   In a multihop 6LoWPAN, the figure this ID registration with Crypto-ID is variable length, varying between 64 propagated
   to 128 bits.  This ID is 128 bits long only if it is used 6LBR as IPv6
   address.  This may happen when some application uses one IP address described in Section 5.3.  If a chain of trust is present
   between the device as device ID.  It would make sense in that case 6LR and the 6LBR, then there is no need to
   build a real CGA IPv6 address.  The prefix propagate the
   proof of ownership to the address would be
   obtained from prefix information option (PIO in RA) [RFC4861].

   6LN also sends some other parameters 6LBR.  All the 6LBR needs to enable know is that
   this particular OUID is randomly generated, so as to enforce that any
   update via a different 6LR is also random.

   Local or 6LBR to verify
   the Crypto-ID.  The option on-link protocol interactions are shown in Figure 5 can be used.  In 5.
   Crypto-ID and ARO are passed to and stored by the
   figure, CGA Parameters field contains 6LR/6LBR on the public key, prefix
   first NS and some
   other values.  It is a simplified form of CGA Option defined not sent again in
   [RFC3971].

4.2.1.  Crypto-ID Calculation

   First, the modifier is set to next NS.  The operation starts
   with 6LR sending a random or pseudo-random 128-bit
   value.  Next, concatenate from left Router Advertisement (RA) message to right 6LN.

   The 6LR/6LBR ensures first-come/first-serve by storing the modifier, 9 zero
   octets ARO and
   the ECC public key.  SHA-256 algorithm is applied on Crypto-ID correlated to the
   concatenation. node being registered.  The 112 leftmost bits of the hash value node is
   free to claim any address it likes as long as it is taken.
   Concatenate from left to right the modifier value, the subnet prefix
   and first to make
   such a claim.  After a successful registration, the encoded public key.  NIST P-256 is executed on node becomes the
   concatenation.  The leftmost bits
   owner of the result is used as registered address and the
   Crypto-ID.  The length address is normally 64 bits, however it could be 128
   bits.

   In respecting bound to the cryptographical algorithm agility [RFC7696], Curve
   25519 [RFC7748]
   Crypto-ID in the 6LR/6LBR registry.  This binding can also be used instead of NIST P-256.  This is
   indicated by 6LN by setting verified
   later, which prevents other nodes from stealing the Crypto Type field in CGA Parameters
   Option address and
   trying to a value of 1.  If 6LBR does not support Curve 25519, attract traffic for that address or use it
   will set Crypto Type field to zero. as their source
   address.

   A node may uses multiple IPv6 addresses at any time.  This means that the default
   algorithm (NIST P-256) will be used.

       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   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Reserved  |C|T|     TID       |     Registration Lifetime     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +          Owner Unique ID (EUI-64 condition
   may happen for privacy reasons
   [I-D.ietf-6man-ipv6-address-generation-privacy], or equivalent)               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 4: Enhanced Address Registration Option

   Type:

      TBA1

   Length:

      8-bit unsigned integer. when the node
   moves at a different place and auto-configures an new address from a
   different prefix.  In those situations, the node may use the same
   Crypto-ID to protect multiple IPv6 addresses.  The length separation of the option (including the
      type
   address and length fields) in units of 8 bytes.  The value 0 is
      invalid.  A value of 3 with the C flag set indicates a Crypto-ID
      of 128 bits.

   Status:

      8-bit unsigned integer.  Indicates the status of a registration in avoids the NA response.  MUST be set to 0 in NS messages.  See below.

   Reserved:

      This field is unused.  It MUST be initialized constrained device to zero by the
      sender and MUST be ignored by compute
   multiple keys for multiple addresses.  The registration process
   allows the receiver.

   C:

      C bit when set is used node to indicate that Owner Unique ID fields
      contains Crypto-ID.

   T and TID:

      Defined in [I-D.ietf-6lo-backbone-router].

   Owner Unique ID:

      In this specification, this field contains Crypto-ID, a variable
      length field tie all of its addresses to carry the same Crypto-ID or random UID.  This field is
      normally 64 bits long.  It could be 128 bits long if IPv6 address
      is used as and
   have the Crypto-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     |   Pad Length  |  Crypto Type  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 6LR/6LBR enforce first-come first-serve after that.

         6LN                                                6LR
          |                                                  |
      +                                                               +
          |<------------------- RA --------------------------|
          |                                                  |
      +                      Modifier (16 octets)                     +
          |----------- NS with ARO and Crypto-ID ----------->|
          |                                                  |
      +                                                               +
          |<---------- NA with ARO (status=proof requested) -|
          |                                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |----------- NS with ARO and Crypto-ID ----------->|
          |                                                  |
      +                    Subnet Prefix (8 octets)                   +
          |<---------------- NA with ARO --------------------|
          |                                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          ...                                              ...
          |                                                  |
          |------------ NS with ARO and Crypto-ID ---------->|
          |                                                  |
      +                  Public Key (variable length)                 +
          |                                                  |
          |<---------------- NA with ARO --------------------|
          ...                                              ...
          |                                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |----------- NS with ARO and Crypto-ID ----------->|
          |                                                  |
      .                                                               .
      .                           Padding                             .
      .                                                               .
          |                                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |<---------------- NA with ARO --------------------|

                   Figure 5: CGA Parameters Option

   Type:

      TBA2

   Length:

      The length of the option in units of 8 octets.

   Pad Length:

      The length of the Padding field.

   Crypto Type:

      The type of cryptographic algorithm used in calculation Crypto-ID.
      Default value of all zeros indicate NIST P-256.  A value of 1 is
      assigned for Curve 25519.  New values may be defined later.

   Modifier:

      128 bit random value.

   Subnet Prefix:

      64 bit subnet prefix.

   Public Key:

      ECC public key of 6LN.

   Padding:

      A variable-length field making the option length a multiple of 8,
      containing as many octets as specified in the Pad Length field.

4.3. On-link Protocol Operation

5.3.  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 ND-PAR we extend DAR/DAC messages to carry cryptographically
   generated UID. OUID.  In a multihop 6LoWPAN, the node exchanges the
   messages shown in Figure 2. 4.  The 6LBR must be aware of who owns an
   address (EUI-64) to defend the first node 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 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.
   CIPO option.  DAR message also contains ARO.

   It is possible that occasionally, a 6LR may miss the node's UID OUID
   (that it received in ARO). 6LR should be able to ask for it again.
   This is done by restarting the exchanges shown in Figure 3. 5.  The
   result enables 6LR to refresh the information that was lost. 6LR MUST
   send DAR message with ARO to 6LBR.  6LBR as a 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 information to make sure that the 6LR is not a fake.

   In some cases 6LBR may use DAC message to signal to 6LR that it
   expects Crypto-ID from 6LR also asks 6LR to verify the EUI-64 6LR
   received from 6LN.  This may happen when a 6LN node is compromised
   and a fake node is sending the Crypto-ID as if it is is the node's EUI-
   64.  Note that the detection in this case can only be done by 6LBR
   not by 6LR.

6.  Security Considerations

   The observations regarding the threats to the Local Link Network in
   [RFC3971] also apply to this specification.

   This document inherits threats discussed in 6LoWPAN ND [RFC6775] and
   its update [I-D.ietf-6lo-rfc6775-update] and addresses the potential
   attacks related to address stealing and spoofing within a LLN.
   Compared with SeND, this specification saves about 1Kbyte in every
   NS/NA message.  Also, this specification separates the cryptographic
   identifier from the registered IPv6 address so that a node can have
   more than one IPv6 address protected by the same cryptographic
   identifier.  SeND forces the IPv6 address to be cryptographic since
   it integrates the node's EUI-
   64.  Note that CGA as the detection IID in this case can only be done by 6LBR
   not by 6LR.

5.  Security Considerations

   The same considerations regarding the threats to IPv6 address.  This
   specification frees the Local Link
   Network covered device to form its addresses in [RFC3971] apply. any fashion,
   so as to enable the classical 6LoWPAN compression which derives IPv6
   addresses from Layer-2 addresses, as well as privacy addresses.

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

   Collisions of Crypto-ID is a possibility that needs to be considered.
   The formula for calculating probability of a collision is 1 -
   e^{-k^2/(2n)}. If the Crypto-ID is 64-bit long, then the chance of
   finding a collision is 0.01% when the network contains 66 million
   nodes.  It is important to note that the collision is only relevant
   when this happens within one stub network (6LBR).  A collision of ID
   in ND-PAR is a rare event.  However, when such a collision does
   happen, the protocol operation is not affected, although it opens a
   window for a node to hijack an address from another.  The link-layer
   security ensures that the nodes would normally not be aware of a
   collision on the subnet.  If a malicious node is able to gain
   knowledge of a collision through other means, the only thing that it
   could do is to steal addresses from the other honest node.  This
   would be no different from what is already possible in a 6lo network
   today.

6.

7.  IANA considerations

   IANA is requested to assign two new option type values, TBA1 and TBA2 values for the CIPO
   under the subregistry "IPv6 Neighbor Discovery Option Formats".

7.

8.  Acknowledgements

   We are grateful to Rene Struik and Robert Moskowitz for their
   comments that lead to many improvements to this document.

8.

9.  Change Log

   o  submitted version -00 as a working group draft after adoption, and
      corrected the order of authors

   o  submitted version -01 with no changes

9.

   o  submitted version -02 with these changes: Moved Requirements to
      Appendix A, Section 4.2 moved to Section 3, New section 4 on New
      Fields and Options, Section 4 changed to Protocol Overview as
      Section 5 with Protocol Scope and Flows subsections.

10.  References

9.1.

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,
              <http://www.rfc-editor.org/info/rfc3971>.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, DOI 10.17487/RFC3972, March 2005,
              <http://www.rfc-editor.org/info/rfc3972>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <http://www.rfc-editor.org/info/rfc4291>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <http://www.rfc-editor.org/info/rfc4862>.

   [RFC4903]  Thaler, D., "Multi-Link Subnet Issues",

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,
              <http://www.rfc-editor.org/info/rfc6775>.

   [I-D.ietf-6lo-rfc6775-update]
              Thubert, P., Nordmark, E., and S. Chakrabarti, "An Update
              to 6LoWPAN ND", draft-ietf-6lo-rfc6775-update-05 (work in
              progress), May 2017.

10.2.  Informative references

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,
              <http://www.rfc-editor.org/info/rfc3971>.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, DOI 10.17487/RFC3972, March 2005,
              <http://www.rfc-editor.org/info/rfc3972>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <http://www.rfc-editor.org/info/rfc4944>.

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 4903, 6282,
              DOI 10.17487/RFC4903, June 2007,
              <http://www.rfc-editor.org/info/rfc4903>. 10.17487/RFC6282, September 2011,
              <http://www.rfc-editor.org/info/rfc6282>.

   [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, DOI 10.17487/RFC4919, August 2007,
              <http://www.rfc-editor.org/info/rfc4919>.

   [RFC5889]  Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
              Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
              September 2010, <http://www.rfc-editor.org/info/rfc5889>.

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,
              <http://www.rfc-editor.org/info/rfc6234>.

   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., 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,
              DOI 10.17487/RFC6550, March 2012,
              <http://www.rfc-editor.org/info/rfc6550>.

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,
              <http://www.rfc-editor.org/info/rfc6775>.

   [RFC7102]  Vasseur, JP., "Terms Used in Routing for Low-Power and
              Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
              2014, <http://www.rfc-editor.org/info/rfc7102>.

   [RFC7039]  Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
              "Source Address Validation Improvement (SAVI) Framework",
              RFC 7039, DOI 10.17487/RFC7039, October 2013,
              <http://www.rfc-editor.org/info/rfc7039>.

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014,
              <http://www.rfc-editor.org/info/rfc7217>.

   [RFC7696]  Housley, R., "Guidelines for Cryptographic Algorithm
              Agility and Selecting Mandatory-to-Implement Algorithms",
              BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
              <http://www.rfc-editor.org/info/rfc7696>.

   [RFC7748]  Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
              for Security", RFC 7748, DOI 10.17487/RFC7748, January
              2016, <http://www.rfc-editor.org/info/rfc7748>.

9.2.  Informative references

   [I-D.ietf-6lo-backbone-router]
              Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo-
              backbone-router-03 (work in progress), January 2017.

   [I-D.ietf-6tisch-architecture]
              Thubert, P., "An Architecture for IPv6 over the TSCH mode
              of IEEE 802.15.4", draft-ietf-6tisch-architecture-11 (work
              in progress), January 2017.

   [I-D.ietf-6man-ipv6-address-generation-privacy]
              Cooper, A., Gont, F., and D. Thaler, "Privacy
              Considerations for IPv6 Address Generation Mechanisms",
              draft-ietf-6man-ipv6-address-generation-privacy-08 (work
              in progress), September 2015.

Appendix A.  Requirements Addressed in this Document

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

   o  The protocol MUST be based on the Neighbor Discovery Optimization
      for Low-power and Lossy Networks protocol defined in [RFC6775].
      RFC6775 utilizes optimizations such as host-initiated interactions
      for sleeping resource-constrained hosts and elimination of
      multicast address resolution.

   o  New options to be added to Neighbor Solicitation messages MUST
      lead to small packet sizes, especially compared with existing
      protocols such as SEcure Neighbor Discovery (SEND).  Smaller
      packet sizes facilitate low-power transmission by resource-
      constrained nodes on lossy links.

   o  The support for this registration mechanism SHOULD be extensible
      to more LLN links than IEEE 802.15.4 only.  Support for at least
      the LLN links for which a 6lo "IPv6 over foo" specification
      exists, as well as Low-Power Wi-Fi SHOULD be possible.

   o  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.

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

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

Authors' Addresses

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

   Email: sarikaya@ieee.org

   Pascal Thubert
   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

   Mohit Sethi (editor)
   Ericsson
   Hirsalantie
   Jorvas  02420

   Email: mohit@piuha.net