6tisch Zero-Touch Secure Join protocol
draft-ietf-6tisch-dtsecurity-zerotouch-join-00

6tisch Working Group                                       M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Informational                                   B. Damm
Expires: March 1, 2018                            Silver Spring Networks
                                                         August 28, 2017


                 6tisch Zero-Touch Secure Join protocol
             draft-ietf-6tisch-dtsecurity-zerotouch-join-00

Abstract

   This document describes a zero-touch mechanism to enroll a new device
   (the "pledge") into a IEEE802.15.4 TSCH network using the 6tisch
   signaling mechanisms.  The resulting device will obtain a domain
   specific credential that can be used with either 802.15.9 per-host
   pair keying protocols, or to obtain the network-wide key from a
   coordinator.  The mechanism describe her is an augmentation to the
   one-touch mechanism described in [I-D.ietf-6tisch-minimal-security].

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 March 1, 2018.

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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
     1.2.  Other Bootstrapping Approaches  . . . . . . . . . . . . .   6
     1.3.  Scope of solution . . . . . . . . . . . . . . . . . . . .   6
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   6
     2.1.  Secure Imprinting using Vouchers  . . . . . . . . . . . .   6
     2.2.  Initial Device Identifier . . . . . . . . . . . . . . . .   7
     2.3.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Lack of realtime clock  . . . . . . . . . . . . . . . . .   9
     2.5.  Cloud Registrar . . . . . . . . . . . . . . . . . . . . .   9
   3.  Protocol Details  . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Discovery . . . . . . . . . . . . . . . . . . . . . . . .  10
       3.1.1.  Proxy Discovery Protocol Details  . . . . . . . . . .  10
       3.1.2.  Registrar Discovery Protocol Details  . . . . . . . .  10
     3.2.  Pledge Requests Voucher from the Registrar  . . . . . . .  10
     3.3.  Registrar Requests Voucher from MASA  . . . . . . . . . .  13
     3.4.  Voucher Response  . . . . . . . . . . . . . . . . . . . .  13
       3.4.1.  Completing authentication of Provisional TLS
               connection  . . . . . . . . . . . . . . . . . . . . .  13
     3.5.  Voucher Status Telemetry  . . . . . . . . . . . . . . . .  13
     3.6.  MASA authorization log Request  . . . . . . . . . . . . .  14
       3.6.1.  MASA authorization log Response . . . . . . . . . . .  14
     3.7.  EST Integration for PKI bootstrapping . . . . . . . . . .  14
       3.7.1.  EST Distribution of CA Certificates . . . . . . . . .  14
       3.7.2.  EST CSR Attributes  . . . . . . . . . . . . . . . . .  14
       3.7.3.  EST Client Certificate Request  . . . . . . . . . . .  14
       3.7.4.  Enrollment Status Telemetry . . . . . . . . . . . . .  14
       3.7.5.  EST over CoAP . . . . . . . . . . . . . . . . . . . .  14
   4.  Reduced security operational modes  . . . . . . . . . . . . .  14
     4.1.  Trust Model . . . . . . . . . . . . . . . . . . . . . . .  14
     4.2.  Pledge security reductions  . . . . . . . . . . . . . . .  14
     4.3.  Registrar security reductions . . . . . . . . . . . . . .  15
     4.4.  MASA security reductions  . . . . . . . . . . . . . . . .  15
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
     5.1.  MIME-Type Registry  . . . . . . . . . . . . . . . . . . .  15
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
     6.1.  Security of MASA voucher signing key(s) . . . . . . . . .  15
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  15
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19



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   Appendix A.  One-Touch Assumptions  . . . . . . . . . . . . . . .  20
     A.1.  Factory provided credentials (if any) . . . . . . . . . .  20
       A.1.1.  Credentials to be introduced  . . . . . . . . . . . .  21
     A.2.  Network Assumptions . . . . . . . . . . . . . . . . . . .  21
       A.2.1.  Security above and below IP . . . . . . . . . . . . .  21
       A.2.2.  Join network assumptions  . . . . . . . . . . . . . .  22
       A.2.3.  Number and cost of round trips  . . . . . . . . . . .  22
       A.2.4.  Size of packets, number of fragments  . . . . . . . .  22
     A.3.  Target end-state for join process . . . . . . . . . . . .  22
   Appendix B.  Join Protocol  . . . . . . . . . . . . . . . . . . .  23
     B.1.  Key Agreement process . . . . . . . . . . . . . . . . . .  23
     B.2.  Provisional Enrollment process  . . . . . . . . . . . . .  24
     B.3.  Key Distribution Process  . . . . . . . . . . . . . . . .  25
   Appendix C.  YANG model for BRSKI objects . . . . . . . . . . . .  25
     C.1.  Description of Pledge States in Join Process  . . . . . .  26
   Appendix D.  Definition of managed objects for zero-touch
                bootstrap  . . . . . . . . . . . . . . . . . . . . .  26
   Appendix E.  Privacy Considerations . . . . . . . . . . . . . . .  27
     E.1.  Privacy Considerations for Production network . . . . . .  27
     E.2.  Privacy Considerations for New Pledges  . . . . . . . . .  27
       E.2.1.  EUI-64 derived address for join time IID  . . . . . .  28
     E.3.  Privacy Considerations for Join Assistant . . . . . . . .  28
   Appendix F.  Security Considerations  . . . . . . . . . . . . . .  28
   Appendix G.  IANA Considerations  . . . . . . . . . . . . . . . .  28
   Appendix H.  Protocol Definition  . . . . . . . . . . . . . . . .  28
   Appendix I.  Acknowledgements . . . . . . . . . . . . . . . . . .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  28

1.  Introduction

   Enrollment of new nodes into LLNs present unique challenges.  The
   constrained nodes has no user interfaces, and even if they did,
   configuring thousands of such nodes manually is undesireable from a
   human resources issue, as well as the difficulty in getting
   consistent results.

   This document is about a standard way to introduce new nodes into a
   6tisch network that does not involve any direct manipulation of the
   nodes themselves.  This act has been called "zero-touch"
   provisioning, and it does not occur by chance, but requires
   coordination between the manufacturer of the node, the service
   operator running the LLN, and the installers actually taking the
   devices out of the shipping boxes.

   This document is a constrained profile of
   [I-D.ietf-anima-bootstrapping-keyinfra].  The above document/protocol
   is referred by by it's acronym: BRSKI.  The pronounciation of which




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   is "brew-ski", a common north american slang for beer with a pseudo-
   polish ending.

   This document follows the same structure as it's parent in order to
   emphasize the similarities, but specializes a number of things to
   constrained networks of constrained devices.  Like ANIMA's BRSKI, the
   networks which are in scope for this protocol are deployed by a
   professional operator.  The deterministic mechanisms which have been
   designed into 6tisch have been created to satisfy the operational
   needs of industrial settings.

   This document builds upon the "one-touch" provisioning described in
   [I-D.ietf-6tisch-minimal-security], reusing the OSCOAP Join Request
   mechanism when appropriate.  In addition, it uses the CoAP adaption
   of EST defined in [I-D.vanderstok-ace-coap-est] in an identical way.

   Otherwise, this document follows BRSKI with the following high-level
   changes:

   o  HTTP is replaced with CoAP.

   o  TLS (HTTPS) is replaced with either DTLS+CoAP, or EDHOC/
      OSCOAP+CoAP

   o  the domain-registrar anchor certificate is replaced with a Raw
      Public Key (RPK) using [RFC7250].

   o  the PKCS7 signed JSON voucher format is replaced with CWT

   o  the GRASP discovery mechanism for the Proxy is replaced with an
      announcement in the Enhanced Beacon
      [I-D.richardson-6tisch-join-enhanced-beacon]

   o  the TCP circuit proxy mechanism is not used.  The IPIP mechanism
      if mandatory to implement when deployed with DTLS, while the CoAP
      based stateless proxy mechanism is used for OSCOAP/EDHOC.

   o  real time clocks are assumed to be impossible, so expiry dates in
      ownership vouchers are never used

   o  nonce-full vouchers are encouraged, but off-line nonce-less
      operation is also supported

   802.1AR Client certificates are retained, but optionally are
   specified by reference rather than value.

   It is expected that the back-end network operator infrastructure
   would be able to bootstrap ANIMA BRSKI-type devices over ethernet,



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   while also being able bootstrap 6tisch devices over 802.15.4 with few
   changes.

1.1.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119] and indicate requirement levels for compliant STuPiD
   implementations.

   The reader is expected to be familiar with the terms and concepts
   defined in [I-D.ietf-6tisch-terminology], [RFC7252],
   [I-D.ietf-core-object-security], and
   [I-D.ietf-anima-bootstrapping-keyinfra].  The following terms are
   imported: drop ship, imprint, enrollment, pledge, join proxy,
   ownership voucher, join registrar/coordinator.  The following terms
   are repeated here for readability, but this document is not
   authoritative for their definition:

   pledge  the prospective device, which has the identity provided to at
      the factory.  Neither the device nor the network knows if the
      device yet knows if this device belongs with this network.

   Joined Node  the prospective device, after having completing the join
      process, often just called a Node.

   Join Proxy (JP):  a stateless relay that provides connectivity
      between the pledge and the join registrar/coordinator.

   Join Registrar/Coordinator (JRC):  central entity responsible for
      authentication and authorization of joining nodes.

   Audit Token  A signed token from the manufacturer authorized signing
      authority indicating that the bootstrapping event has been
      successfully logged.  This has been referred to as an
      "authorization token" indicating that it authorizes bootstrapping
      to proceed.

   Ownership Voucher  A signed voucher from the vendor vouching that a
      specific domain "owns" the new entity as defined in
      [I-D.ietf-anima-voucher].

   MIC  manufacturer installed certificate.  An [ieee802-1AR] identity.
      Not to be confused with a (cryptographic) "Message Integrity
      Check"





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1.2.  Other Bootstrapping Approaches

   BRSKI describes a more general, more flexible approach for
   bootstrapping devices into an ISP or Enterprise network.

   [I-D.ietf-6tisch-minimal-security] provides an extremely streamlined
   approach to enrolling from hundreds to thousands of devices into a
   network, provided that a unique secret key can be installed in each
   device.

1.3.  Scope of solution

   The solution described in this document is appropriate to enrolling
   between hundreds to hundreds of thousands of diverse devices into a
   network without any prior contact with the devices.  The devices
   could be shipped by the manufacturer directly to the customer site
   without ever being seen by the operator of the network.  As described
   in BRSKI, in the audit-mode of operation the device will be claimed
   by the first network that sees it.  In the tracked owner mode of
   operation, sales channel integration provides a strong connection
   that the operator of the network is the legitimate owner of the
   device.

2.  Architectural Overview

   Section 2 of BRSKI has a diagram with all of the components shown
   together.  There are no significant changes to the diagram.

   The use of a circuit proxy is not mandated.  Instead the IPIP
   mechanism described in appendix C ("IPIP Join Proxy mechanism")
   SHOULD be be used instead as it supports both DTLS, EDHOC and OSCOAP
   protocols.  The CoAP proxy mechanism MAY be implemented instead: the
   decision depends upon the capabilities of the Registrar and the
   proxy.  A mechanism is included for the Registrar to announce it's
   capabilities (XXX).

2.1.  Secure Imprinting using Vouchers

   As in BRSKI, the format and cryptographic mechansim of vouchers is
   described in detail in [I-D.ietf-anima-voucher].  As described in
   section YYY, the physical format for vouchers in this document
   differs from that of BRSKI, in that it uses
   [I-D.ietf-ace-cbor-web-token] to encode the voucher and to sign it.








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2.2.  Initial Device Identifier

   The essential component of the zero-touch operation is that the
   pledge is provisioned with an 802.1AR (PKIX) certificate installed
   during the manufacturing process.

   It is expected that constrained devices will use a signature
   algorithm corresponding to the hardware acceleration that they have,
   if they have any.  The anticipated algorithms are the ECDSA P-256
   (secp256p1) as SHOULD-, while newer devices SHOLD+ begin to appear
   using EdDSA curves using the 25519 curves.  (EDNOTE details here)

   There are a number of simplications detailed later on in this
   document designed to eliminate the need for an ASN.1 parser in the
   pledge.

   The pledge should consider it's 802.1AR certificate to be an opaque
   blob of bytes, to be inserted into protocols at appropriate places.
   The pledge SHOULD have access to it's public and private keys in the
   most useable native format for computation.

   The pledge MUST have the public key of the MASA built in a
   manufacturer time.  This is a seemingly identical requirement as for
   BRSKI, but rather than being an abstract trust anchor that can be
   augmented with a certificate chain, the pledge MUST be provided with
   the Raw Public Key that the MASA will use to sign vouchers for that
   pledge.

   There are a number of security concerns with use of a single MASA
   signing key, and section Section 6.1 addresses some of them with some
   operational suggestions.

   BRSKI places some clear requirements upon the contents of the IDevID,
   but leaves the exact origin of the voucher serial-number open.  This
   document restricts the process to being the hwSerialNum OCTET STRING.
   As CWT can handle binary formats, no base64 encoding is necessary.

   The use of the MASA-URL extension is encouraged if the certificate is
   sent at all.

   [[EDNOTE here belongs text about sending only a reference to the
   IDevID rather than the entire certificate]]

2.3.  Protocol Flow

   The diagram from BRSKI is reproduced with some edits:

    +--------+         +---------+    +------------+     +------------+



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    | Pledge |         | IPIP    |    | Domain     |     | Vendor     |
    |        |         | Proxy   |    | Registrar  |     | Service    |
    |        |         |         |    |            |     | (Internet  |
    +--------+         +---------+    +------------+     +------------+
      |                     |                   |                    |
      |<-RFC4862 IPv6 adr   |                   |                    |
      |                     |                   |                    |
      |<--------------------|                   |                    |
      | Enhanced Beacon     |                   |                    |
      |   periodic broadcast|                   |                    |
      |                     |                   |                    |
      |<------------------->C<----------------->|                    |
      |             DTLS via the IPIP    Proxy  |                    |
      |<--Registrar DTLS server authentication--|                    |
    [PROVISIONAL accept of server cert]         |                    |
      P---X.509 client authentication---------->|                    |
      P                     |                   |                    |
      P---Voucher Request (include nonce)------>|                    |
      P                     |                   |                    |
      P                     |                   |                    |
      P                     |              [accept device?]          |
      P                     |              [contact Vendor]          |
      P                     |                   |--Pledge ID-------->|
      P                     |                   |--Domain ID-------->|
      P                     |                   |--nonce------------>|
      P                     |                   |     [extract DomainID]
      P                     |                   |                    |
      P                     |                   |     [update audit log]
      P                     |                   |                    |
      P                     |                   |                    |
      P                     |                   |                    |
      P                     |                   |                    |
      P                     |                   |                    |
      P                     |                   |<-device audit log--|
      P                     |                   |<- voucher ---------|
      P                     |                   |                    |
      P                     |                   |                    |
      P                     |       [verify audit log and voucher]   |
      P                     |                   |                    |
      P<------voucher---------------------------|                    |
    [verify voucher ]       |                   |                    |
    [verify provisional cert|                   |                    |
      |                     |                   |                    |
      |<--------------------------------------->|                    |
      | Continue with RFC7030 enrollment        |                    |
      | using now bidirectionally authenticated |                    |
      | DTLS session.       |                   |                    |
      |                     |                   |                    |



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      |                     |                   |                    |
      |                     |                   |                    |

   Noteable changes are:

   1.  no IPv4 support/options.

   2.  no mDNS steps, 6tisch only uses Enhanced Beacon

   3.  nonce-full option is always recommended

2.4.  Lack of realtime clock

   For the constrained situation it is assumed that devices have no real
   time clock.  These nodes do have access to a monotonically increasing
   clock that will not go backwards in the form of the Absolute Sequence
   Number.  Synchronization to the ASN is required in order to transmit/
   receive data and most nodes will maintain it in hardware.

   The heuristic described in BRSKI under this section SHOULD be applied
   if there are dates in the CWT format voucher.

   Voucher requests SHOULD include a nonce.  For devices intended for
   off-line deployment, the vouchers will have been generated in advance
   and no nonce-ful operation will not be possible.

2.5.  Cloud Registrar

   In 6tisch, the pledge never has network connectivity until it is
   enrolled, so no alternate registrar is ever possible.

3.  Protocol Details

   BRSKI is specified to run over HTTPS.  This document respecifies it
   to run over CoAP with either DTLS or EDHOC-provided OSCOAP security.
   There is an emerging (hybrid) possibility of DTLS-providing the
   OSCOAP security, but such a specification does not yet exist.

   [I-D.vanderstok-ace-coap-est] specifies that CoAP specifies the use
   of CoAP Block-Wise Transfer ("Block") [RFC7959] to fragment EST
   messages at the application layer.

   BRSKI introduces the concept of a provisional state for EST.  The
   same situation must also be added to DTLS: a situation where the
   connection is active but the identity of the Registar has not yet
   been confirmed.  The DTLS MUST validate that the exchange has been
   signed by the Raw Public Key that is presented by the Server, even
   though there is as yet no trust in that key.  Such a key is often



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   available through APIs that provide for channel binding, such as
   described in [RFC5056].

   As in [I-D.vanderstok-ace-coap-est], support for Observe CoAP options
   [RFC7641] with BRSKI is not supported in the current BRSKI/EST
   message flows.  Observe options could be used by the server to notify
   clients about a change in the cacerts or csr attributes (resources)
   and might be an area of future work.

   Redirection as described in [RFC7030] section 3.2.1 is NOT supported.

3.1.  Discovery

   Only IPv6 operations using Link-Local addresses are supported.  Use
   of a temporary address is NOT encouraged as the critial resource on
   the Proxy device is the number of Neighbour Cache Entries that can be
   used for untrusted pledge entries.

3.1.1.  Proxy Discovery Protocol Details

   The Proxy is discovered using the enhanced beacon defined in
   [I-D.richardson-6tisch-join-enhanced-beacon].

3.1.2.  Registrar Discovery Protocol Details

   The Registrar is not discovered by the Proxy.  Any device that is
   expected to be able to operate as a Registrar MAY be told the address
   of the Registrar when that device joins the network.  The address MAY
   be included in the [I-D.ietf-6tisch-minimal-security] Join Response.
   If the address is NOT included, then Proxy may assume that the
   Registrar can be found at the DODAG root, which is well known in the
   6tisch's use of the RPL protocol.

3.2.  Pledge Requests Voucher from the Registrar

   The voucher request and response as defined by BRSKI is modified
   slightly.  In order to simplify the pledge, the use of a certificate
   (and chain) for the Registrar is not supported.  Instead the newly
   defined pinned-domain-subject-public-key-info must contain the (raw)
   public key info for the Registrar.  It MUST be byte for byte
   identical to that which is transmitted by the Registrar during the
   TLS ServerCertificate handshake.

   BRSKI permits the voucher request to be signed or unsigned.  This
   document defines the voucher request to be unsigned.

 /* -*- c -*- */
 module ietf-cwt-voucher {



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   yang-version 1.1;

   namespace
     "urn:ietf:params:xml:ns:yang:ietf-cwt-voucher";
   prefix "vcwt";

   import ietf-restconf {
     prefix rc;
     description
       "This import statement is only present to access
        the yang-data extension defined in RFC 8040.";
     reference "RFC 8040: RESTCONF Protocol";
   }

   import ietf-voucher {
     prefix "v";
   }

   organization
    "IETF 6tisch Working Group";

   contact
    "WG Web:   <http://tools.ietf.org/wg/6tisch/>
     WG List:  <mailto:6tisch@ietf.org>
     Author:   Michael Richardson
               <mailto:mcr+ietf@sandelman.ca>";

   description
    "This module defines the format for a voucher, which is produced by
     a pledge's manufacturer or delegate (MASA) to securely assign one
     or more pledges to an 'owner', so that the pledges may establish a
     secure connection to the owner's network infrastructure.

     This version provides a very restricted subset appropriate
     for very constrained devices.
     In particular, it assumes that nonce-ful operation is
     always required, that expiration dates are rather weak, as no
     clocks can be assumed, and that the Registrar is identified
     by a pinned Raw Public Key.

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
     'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in
     the module text are to be interpreted as described in RFC 2119.";

   revision "YYYY-MM-DD" {
     description
      "Initial version";
     reference



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      "RFC XXXX: Voucher Profile for Constrained Devices";
   }

   // Grouping defined for future usage
   grouping voucher-cwt-grouping {
     description
       "Grouping to allow reuse/extensions in future work.";

     uses v:voucher-artifact-grouping {
       augment "voucher" {
         description "Base the CWT voucher upon the regular one";
         leaf pinned-domain-subject-public-key-info {
           type binary;
           description
             "The pinned-domain-subject replaces the
          pinned-domain-certificate in constrained uses of
          the voucher.  The pinned-domain-public-key-info is the
          Raw Public Key of the Registrar. This field is encoded
          as specified in RFC7250, section 3.
          The ECDSA algorithm MUST be supported.
          The EdDSA algorithm as specified in
          draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
          Support for the DSA algorithm is not recommended.
          Support for the RSA algorithm is a MAY.";
         }
       }
     }
   }
 }

   This definition, translated via the rules in
   [I-D.ietf-core-yang-cbor] produces the following CDDL for an unsigned
   voucher (request):


















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This is a PLACEHOLDER for a CDDL definition derived from the YANG model.
SID experimental base 60100 is used.

dictionary keys are:
60100      ietf-cwt-voucher
60101      assertion
60102      created-on
60103      domain-cert-revocation-checks
60104      expires-on
60105      idevid-issuer
60106      last-renewal-date
60107      nonce
60108      pinned-domain-cert
60109      pinned-domain-subject-public-key-info
60110      prior-signed-voucher
60111      serial-number





3.3.  Registrar Requests Voucher from MASA

   There are no change from BRSKI, as this step is between two non-
   constrained devices.  The format of the voucher is CWT, which implies
   changes to both the Registrar and the MASA, but semantically the
   content is the same.

   The manufacturer will know what algorithms are supported by the
   pledge, and will issue a 406 (Conflict) error to the Registrar if the
   Registar's public key format is not supported by the pledge.

3.4.  Voucher Response

   The voucher response MUST have an additional header called: "pinned-
   domain-rpk".

3.4.1.  Completing authentication of Provisional TLS connection

   In order to simplify the pledge as much as possible, the voucher
   response

3.5.  Voucher Status Telemetry

   XXX






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3.6.  MASA authorization log Request

   XXX

3.6.1.  MASA authorization log Response

   XXX

3.7.  EST Integration for PKI bootstrapping

   XXX

3.7.1.  EST Distribution of CA Certificates

   XXX

3.7.2.  EST CSR Attributes

   XXX

3.7.3.  EST Client Certificate Request

   XXX

3.7.4.  Enrollment Status Telemetry

   XXX

3.7.5.  EST over CoAP

   XXX

4.  Reduced security operational modes

   XXX

4.1.  Trust Model

   XXX

4.2.  Pledge security reductions

   XXX








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4.3.  Registrar security reductions

   XXX

4.4.  MASA security reductions

   XXX

5.  IANA Considerations

   XXX

5.1.  MIME-Type Registry

   XXX

6.  Security Considerations

6.1.  Security of MASA voucher signing key(s)

7.  Privacy Considerations

   XXX

8.  Acknowledgements

9.  References

9.1.  Normative References

   [cullenCiscoPhoneDeploy]
              Jennings, C., "Transitive Trust Enrollment for Constrained
              Devices", 2012, <http://www.lix.polytechnique.fr/hipercom/
              SmartObjectSecurity/papers/CullenJennings.pdf>.

   [I-D.ietf-6lo-privacy-considerations]
              Thaler, D., "Privacy Considerations for IPv6 Adaptation
              Layer Mechanisms", draft-ietf-6lo-privacy-
              considerations-04 (work in progress), October 2016.

   [I-D.ietf-6tisch-minimal]
              Vilajosana, X., Pister, K., and T. Watteyne, "Minimal
              6TiSCH Configuration", draft-ietf-6tisch-minimal-21 (work
              in progress), February 2017.







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   [I-D.ietf-6tisch-minimal-security]
              Vucinic, M., Simon, J., Pister, K., and M. Richardson,
              "Minimal Security Framework for 6TiSCH", draft-ietf-
              6tisch-minimal-security-03 (work in progress), June 2017.

   [I-D.ietf-6tisch-terminology]
              Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
              "Terminology in IPv6 over the TSCH mode of IEEE
              802.15.4e", draft-ietf-6tisch-terminology-09 (work in
              progress), June 2017.

   [I-D.ietf-ace-cbor-web-token]
              Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
              "CBOR Web Token (CWT)", draft-ietf-ace-cbor-web-token-08
              (work in progress), August 2017.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
              S., and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-07 (work in progress), July 2017.

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-15 (work in progress), July 2017.

   [I-D.ietf-anima-voucher]
              Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "Voucher Profile for Bootstrapping Protocols", draft-ietf-
              anima-voucher-05 (work in progress), August 2017.

   [I-D.ietf-core-comi]
              Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
              Management Interface", draft-ietf-core-comi-01 (work in
              progress), July 2017.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security of CoAP (OSCOAP)", draft-ietf-core-
              object-security-04 (work in progress), July 2017.

   [I-D.ietf-core-yang-cbor]
              Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A.
              Minaburo, "CBOR Encoding of Data Modeled with YANG",
              draft-ietf-core-yang-cbor-05 (work in progress), August
              2017.




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   [I-D.ietf-netconf-keystore]
              Watsen, K., "Keystore Model", draft-ietf-netconf-
              keystore-02 (work in progress), June 2017.

   [I-D.richardson-6tisch-join-enhanced-beacon]
              Dujovne, D. and M. Richardson, "IEEE802.15.4 Informational
              Element encapsulation of 6tisch Join Information", draft-
              richardson-6tisch-join-enhanced-beacon-02 (work in
              progress), July 2017.

   [I-D.richardson-6tisch-minimal-rekey]
              Richardson, M., "Minimal Security rekeying mechanism for
              6TiSCH", draft-richardson-6tisch-minimal-rekey-02 (work in
              progress), August 2017.

   [I-D.richardson-anima-6join-discovery]
              Richardson, M., "GRASP discovery of Registrar by Join
              Assistant", draft-richardson-anima-6join-discovery-00
              (work in progress), October 2016.

   [I-D.selander-ace-cose-ecdhe]
              Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
              Diffie-Hellman Over COSE (EDHOC)", draft-selander-ace-
              cose-ecdhe-07 (work in progress), July 2017.

   [I-D.vanderstok-ace-coap-est]
              Kumar, S., Stok, P., Kampanakis, P., Furuhed, M., and S.
              Raza, "EST over secure CoAP (EST-coaps)", draft-
              vanderstok-ace-coap-est-02 (work in progress), June 2017.

   [iec62591]
              IEC, ., "62591:2016 Industrial networks - Wireless
              communication network and communication profiles -
              WirelessHART", 2016, <https://webstore.iec.ch/
              publication/24433>.

   [ieee802-1AR]
              IEEE Standard, ., "IEEE 802.1AR Secure Device Identifier",
              2009, <http://standards.ieee.org/findstds/
              standard/802.1AR-2009.html>.

   [ieee802154]
              IEEE Standard, ., "802.15.4-2015 - IEEE Standard for Low-
              Rate Wireless Personal Area Networks (WPANs)", 2015,
              <http://standards.ieee.org/findstds/
              standard/802.15.4-2015.html>.





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   [ieee802159]
              IEEE Standard, ., "802.15.9-2016 - IEEE Approved Draft
              Recommended Practice for Transport of Key Management
              Protocol (KMP) Datagrams", 2016,
              <http://standards.ieee.org/findstds/
              standard/802.15.9-2016.html>.

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

   [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,
              <https://www.rfc-editor.org/info/rfc6775>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013, <https://www.rfc-
              editor.org/info/rfc7030>.

   [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, <https://www.rfc-
              editor.org/info/rfc7217>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014, <https://www.rfc-
              editor.org/info/rfc7228>.

   [RFC7250]  Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
              Weiler, S., and T. Kivinen, "Using Raw Public Keys in
              Transport Layer Security (TLS) and Datagram Transport
              Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
              June 2014, <https://www.rfc-editor.org/info/rfc7250>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014, <https://www.rfc-
              editor.org/info/rfc7252>.







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   [RFC7959]  Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
              the Constrained Application Protocol (CoAP)", RFC 7959,
              DOI 10.17487/RFC7959, August 2016, <https://www.rfc-
              editor.org/info/rfc7959>.

9.2.  Informative References

   [duckling]
              Stajano, F. and R. Anderson, "The resurrecting duckling:
              security issues for ad-hoc wireless networks", 1999,
              <https://www.cl.cam.ac.uk/~fms27/papers/1999-StajanoAnd-
              duckling.pdf>.

   [I-D.ietf-ace-actors]
              Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
              architecture for authorization in constrained
              environments", draft-ietf-ace-actors-05 (work in
              progress), March 2017.

   [I-D.ietf-core-sid]
              Veillette, M., Pelov, A., Turner, R., Minaburo, A., and A.
              Somaraju, "YANG Schema Item iDentifier (SID)", draft-ietf-
              core-sid-01 (work in progress), May 2017.

   [I-D.ietf-roll-useofrplinfo]
              Robles, I., Richardson, M., and P. Thubert, "When to use
              RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
              useofrplinfo-16 (work in progress), July 2017.

   [ISA100]   "The Technology Behind the ISA100.11a Standard", June
              2010, <http://www.isa100wci.org/Documents/PDF/
              The-Technology-Behind-ISA100-11a-v-3_pptx>.

   [PFS]      Wikipedia, ., "Forward Secrecy", August 2016,
              <https://en.wikipedia.org/w/
              index.php?title=Forward_secrecy&oldid=731318899>.

   [pledge]   Dictionary.com, ., "Dictionary.com Unabridged", 2015,
              <http://dictionary.reference.com/browse/pledge>.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <https://www.rfc-editor.org/info/rfc4191>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006, <https://www.rfc-
              editor.org/info/rfc4655>.



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   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure
              Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
              <https://www.rfc-editor.org/info/rfc5056>.

   [RFC7554]  Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
              IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
              Internet of Things (IoT): Problem Statement", RFC 7554,
              DOI 10.17487/RFC7554, May 2015, <https://www.rfc-
              editor.org/info/rfc7554>.

   [RFC7641]  Hartke, K., "Observing Resources in the Constrained
              Application Protocol (CoAP)", RFC 7641,
              DOI 10.17487/RFC7641, September 2015, <https://www.rfc-
              editor.org/info/rfc7641>.

   [RFC7731]  Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
              and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
              February 2016, <https://www.rfc-editor.org/info/rfc7731>.

9.3.  URIs

   [2] mailto:6tisch@ietf.org

   [3] mailto:mcr+ietf@sandelman.ca

Appendix A.  One-Touch Assumptions

   This document interacts with the one-touch solution described in
   [I-D.ietf-6tisch-minimal-security].

A.1.  Factory provided credentials (if any)

   When a manufacturer installed certificate is provided as the IDevID,
   it SHOULD contain a number of fields.
   [I-D.ietf-anima-bootstrapping-keyinfra] provides a detailed set of
   requirements.

   A manufacturer unique serial number MUST be provided in the
   serialNumber SubjectAltName extension, and MAY be repeated in the
   Common Name.  There are no sequential or numeric requirements on the
   serialNumber, it may be any unique value that the manufacturer wants
   to use.  The serialNumber SHOULD be printed on the packaging and/or
   on the device in a discrete way so that failures can be physically
   traced to the relevant device.







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A.1.1.  Credentials to be introduced

   The goal of the bootstrap process is to introduce one or more new
   locally relevant credentials:

   1.  a certificate signed by a local certificate authority/registrar.
       This is the LDevID of [ieee802-1AR].

   2.  alternatively, a network-wide key to be used to secure L2
       traffic.

   3.  alternatively, a network-wide key to be used to authenticate per-
       peer keying of L2 traffic using a mechanism such as provided by
       [ieee802159].

A.2.  Network Assumptions

   This document is about enrollment of constrained devices [RFC7228] to
   a constrained network.  Constrained networks is such as [ieee802154],
   and in particular the time-slotted, channel hopping (tsch) mode,
   feature low bandwidths, and limited opportunities to transmit.  A key
   feature of these networks is that receivers are only listening at
   certain times.

A.2.1.  Security above and below IP

   802.15.4 networks have three kinds of layer-2 security:

   o  a network key that is shared with all nodes and is used for
      unicast and multicast.  The key may be used for privacy, and it
      may be used in some cases for authentication only (in the case of
      enhanced beacons).

   o  a series of network keys that are shared (agreed to) between pairs
      of nodes (the per-peer key)

   o  a network key that is shared with all nodes (through a group key
      management system), and is used for multicast traffic only, while
      a per-pair key is used for unicast traffic

   Setting up the credentials to bootstrap one of these kinds of
   security, (or directly configuring the key itself for the first case)
   is required.  This is the security below the IP layer.

   Security is required above the IP layer: there are three aspects
   which the credentials in the previous section are to be used.





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   o  to provide for secure connection with a Path Computation Element
      [RFC4655], or other LLC (see ({RFC7554}} section 3).

   o  to initiate a connection between a Resource Server (RS) and an
      application layer Authorization Server (AS and CAS from
      [I-D.ietf-ace-actors]).

A.2.1.1.  Perfect Forward Secrecy

   Perfert Forward Secrecy (PFS) is the property of a protocol such that
   complete knowledge of the crypto state (for instance, via a memory
   dump) at time X does not imply that data from a disjoint time Y can
   also be recovered.  ([PFS]).

   PFS is important for two reasons: one is that it offers protection
   against the compromise of a node.  It does this by changing the keys
   in a non-deterministic way.  This second property also makes it much
   easier to remove a node from the network, as any node which has not
   participated in the key changing process will find itself no longer
   connected.

A.2.2.  Join network assumptions

   The network which the new pledge will connect to will have to have
   the following properties:

   o  a known PANID.  The PANID 0xXXXX where XXXX is the assigned RFC#
      for this document is suggested.

   o  a minimal schedule with some Aloha time.  This is usually in the
      same slotframe as the Enhanced Beacon, but a pledge MUST listen
      for an unencrypted Enhanced Beacon to so that it can synchronize.

A.2.3.  Number and cost of round trips

   TBD.

A.2.4.  Size of packets, number of fragments

A.3.  Target end-state for join process

   At the end of the zero-touch join process there will be a symmetric
   key protected channel between the Join Registrar/Coordinator and the
   pledge, now known as a Joined Node.  This channel may be rekeyed via
   new exchange of asymmetric exponents (ECDH for instance),
   authenticated using the domain specific credentials created during
   the join process.




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   This channel is in the form of an OSCOAP protected connection with
   [I-D.ietf-core-comi] encoded objects.  This document includes
   definition of a [I-D.ietf-netconf-keystore] compatible objects for
   encoding of the relevant [I-D.ietf-anima-bootstrapping-keyinfra]
   objects.

Appendix B.  Join Protocol

   The pledge join protocol state machine is described in
   [I-D.ietf-6tisch-minimal-security], in section XYZ.  The pledge
   recognizes that it is in zero-touch configuration by the following
   situation:

   o  no PSK has been configured for the network in which it has joined.

   o  the pledge has no locally defined certificate (no LDevID), only an
      IDevID.

   o  the network asserts an identity that the pledge does not
      recognize.

   All of these conditions MUST be true.  If any of these are not true,
   then the pledge has either been connected to the wrong network, or it
   has already been bootstrapped into a different network, and it should
   wait until it finds that network.

   The zero-touch process consists of three stages:

   1.  the key agreement process

   2.  the provisional enrollment process

   3.  the key distribution process

B.1.  Key Agreement process

   The key agreement process is identical to
   [I-D.ietf-6tisch-minimal-security].  The process uses EDHOC with
   certificates.

   The pledge will have to trust the JRC provisionally, as described in
   [I-D.ietf-anima-bootstrapping-keyinfra], section 3.1.2, and in
   section 4.1.1 of [RFC7030].

   The JRC will be able to validate the IDevID of the pledge using the
   manufacturer's CA.





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   The pledge may not know if it is in a zero-touch or one-touch
   situation: the pledge may be able to verify the JRC based upon trust
   anchors that were installed at manufacturing time.  In that case, the
   pledge runs the simplified one-touch process.

   The pledge signals in the EDHOC message_2 if it has accepted the JRC
   certificate.  The JRC will in general, not trust the pledge with the
   network keys until it has provided the pledge with a voucher.  The
   pledge will notice the absence of the provisioning keys.

   XXX - there could be some disconnect here.  May need additional
   signals here.

B.2.  Provisional Enrollment process

   When the pledge determines that it can not verify the certificate of
   the JRC using built-in trust anchors, then it enters a provisional
   state.  In this state, it keeps the channel created by EDHOC open.

   A new EDHOC key derivation is done by the JRC and pledge using a new
   label, "6tisch-provisional".

   The pledge runs as a passive CoMI server, leaving the JRC to drive
   the enrollment process.  The JRC can interrogate the pledge in a
   variety of fashions as shown below: the process terminates when the
   JRC provides the pledge with an ownership voucher and the pledge
   leaves the provisional state.

   A typical interaction involves the following requests:






















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       +-----------+ +----------+ +-----------+ +----------+
       |           | |          | | Circuit   | | New      |
       |  Vendor   | | Registrar| |  Proxy    | | Entity   |
       |  (MASA)   | |          | |           | |          |
       ++----------+ +--+-------+ +-----------+ +----------+
        |               |     GET  request voucher       |
        |               |-------------------------------->
        |               <----------voucher-token---------|
        |/requestvoucher|                                |
        <---------------+                                |
        +--------------->                                |
        |/requestlog    |                                |
        <---------------+                                |
        +--------------->                                |
        |               |        POST voucher            |
        |               |-------------------------------->
        |               <------------2.05 OK ------------+
        |               |                                |
        |               |        POST csr attributes     |
        |               |-------------------------------->
        |               <------------2.05 OK ------------+
        |               |                                |
        |               |        GET  cert request       |
        |               |-------------------------------->
        |     ????      <------------2.05 OK ------------+
        |<--------------|              CSR               |
        |-------------->|                                |
        |               |        POST certificate        |
        |               |-------------------------------->
        |               <------------2.05 OK ------------+
        |               |                                |

B.3.  Key Distribution Process

   The key distribution process utilizes the protocol described
   [I-D.richardson-6tisch-minimal-rekey].  The process starts with the
   initial key, rather than an actual rekey.

   This protocol remains active for subsequent rekey operations.

Appendix C.  YANG model for BRSKI objects

   module ietf-6tisch-brski { yang-version 1.1;

   namespace "urn:ietf:params:xml:ns:yang:6tisch-brski"; prefix
   "ietf6brski";





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   //import ietf-yang-types { prefix yang; } //import ietf-inet-types {
   prefix inet; }

   organization "IETF 6tisch Working Group";

   contact "WG Web: http://tools.ietf.org/wg/6tisch/ WG List:
   6tisch@ietf.org [2] Author: Michael Richardson mcr+ietf@sandelman.ca
   [3]";

   description "This module defines an interface to set and retrieve
   BRSKI objects using CoMI.  This interface is used as part of an
   enrollment process for constrained nodes and networks.";

   revision "2017-03-01" { description "Initial version"; reference "RFC
   XXXX: 6tisch zero-touch bootstrap"; }

   // top-level container container ietf6brski { leaf requestnonce {
   type binary; length XX; // how big can/should it be? mandatory true;
   description "Request Nonce."; } leaf voucher { type binary;
   description "The voucher as a serialized COSE object"; }

   leaf csrattributes {
     type binary;
     description "A list of attributes that MUST be in the CSR";
   }

   leaf certificaterequest {
     type binary;
     description "A PKIX format Certificate Request";
   }

   leaf certificate {
     type binary;
     description "The LDevID certificate";
   }   } }

C.1.  Description of Pledge States in Join Process

   TBD

Appendix D.  Definition of managed objects for zero-touch bootstrap

   The following is relevant YANG for use in the bootstrap protocol.
   The objects identified are identical in format to the named objects
   from [I-D.ietf-anima-bootstrapping-keyinfra].






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Appendix E.  Privacy Considerations

   [I-D.ietf-6lo-privacy-considerations] details a number of privacy
   considerations important in Resource Constrained nodes.  There are
   two networks and three sets of constrained nodes to consider.  They
   are: 1. the production nodes on the production network.  2. the new
   pledges, which have yet to enroll, and which are on a join network.
   3. the production nodes which are also acting as proxy nodes.

E.1.  Privacy Considerations for Production network

   The details of this are out of scope for this document.

E.2.  Privacy Considerations for New Pledges

   New Pledges do not yet receive Router Advertisements with PIO
   options, and so configure link-local addresses only based upon
   layer-2 addresses using the normal SLAAC mechanisms described in
   [RFC4191].

   These link-local addresses are visible to any on-link eavesdropper
   (who is synchronized to the same Join Assistant), so regardless of
   what is chosen they can be seen.  This link-layer traffic is
   encapsulated by the Join Assistant into IPIP packets and carried to
   the JCE.  The traffic SHOULD never leave the operator's network, and
   no outside traffic should enter, so it should not be possible to do
   any ICMP scanning as described in
   [I-D.ietf-6lo-privacy-considerations].

   The join process described herein requires that some identifier
   meaningful to the network operator be communicated to the JCE via the
   Neighbor Advertisement's ARO option.  This need not be a manufacturer
   created EUI-64 as assigned by IEEE; it could be another value with
   higher entropy and less interesting vendor/device information.
   Regardless of what is chosen, it can be used to track where the
   device attaches.

   For most constrained device, network attachment occurs very
   infrequently, often only once in their lifetime, so tracking
   opportunities may be rare.

   Further, during the enrollment process, a DTLS connection connection
   will be created.  Unless TLS1.3 is used, the device identity will be
   visible to passive observers in the 802.11AR IDevID certificate that
   is sent.  Even when TLS1.3 is used, an active attacker could collect
   the information by simply connecting to the device; it would not have
   to successful complete the negotiation either, or even attempt to
   Man-In-The-Middle the device.



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   There is, at the same time, significant value in avoiding a link-
   local DAD process by using an IEEE assigned EUI-64, and there is also
   significant advantage to the operator being able to see what the
   vendor of the new device is.

E.2.1.  EUI-64 derived address for join time IID

   It is therefore suggested that the IID used in the link-local address
   used during the join process be a vendor assigned EUI-64.  After the
   join process has concluded, the device SHOULD be assigned a unique
   randomly generated long address, and a unique short address (not
   based upon the vendor EUI-64) for use at link-layer.  At that point,
   all layer-3 content is encrypted by the layer-2 key.

E.3.  Privacy Considerations for Join Assistant

Appendix F.  Security Considerations

Appendix G.  IANA Considerations

   This document allocates one value from the subregistry "Address
   Registration Option Status Values": ND_NS_JOIN_DECLINED Join
   Assistant, JOIN DECLINED (TBD-AA)

Appendix H.  Protocol Definition

Appendix I.  Acknowledgements

   Kristofer Pister helped with many non-IETF references.

Authors' Addresses

   Michael Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca


   Benjamin Damm
   Silver Spring Networks

   Email: bdamm@ssni.com









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