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Versions: (draft-ietf-6tisch-dtsecurity-secure-join) 00 01 02 03 04

6tisch Working Group                                       M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Informational                             July 08, 2019
Expires: January 9, 2020


                 6tisch Zero-Touch Secure Join protocol
             draft-ietf-6tisch-dtsecurity-zerotouch-join-04

Abstract

   This document describes a Zero-touch Secure Join (ZSJ) 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 here is an
   augmentation to the one-touch mechanism described in
   [I-D.ietf-6tisch-minimal-security], and is a profile of the
   constrained voucher mechanism [I-D.ietf-anima-constrained-voucher].

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 https://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 January 9, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Prior Bootstrapping Approaches  . . . . . . . . . . . . .   5
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
     1.3.  Scope of solution . . . . . . . . . . . . . . . . . . . .   6
     1.4.  Leveraging the new key infrastructure / next steps  . . .   7
       1.4.1.  Key Distribution Process  . . . . . . . . . . . . . .   7
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   7
     2.1.  Behavior of a Pledge  . . . . . . . . . . . . . . . . . .   7
     2.2.  Secure Imprinting using Vouchers  . . . . . . . . . . . .   9
     2.3.  Initial Device Identifier . . . . . . . . . . . . . . . .   9
     2.4.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .  10
     2.5.  Architectural Components  . . . . . . . . . . . . . . . .  12
       2.5.1.  Pledge  . . . . . . . . . . . . . . . . . . . . . . .  12
       2.5.2.  Stateless IPIP Join Proxy . . . . . . . . . . . . . .  12
       2.5.3.  Domain Registrar  . . . . . . . . . . . . . . . . . .  12
       2.5.4.  Manufacturer Service  . . . . . . . . . . . . . . . .  12
     2.6.  Certificate Time Validation . . . . . . . . . . . . . . .  12
       2.6.1.  Lack of realtime clock  . . . . . . . . . . . . . . .  13
     2.7.  Cloud Registrar . . . . . . . . . . . . . . . . . . . . .  13
     2.8.  Determining the MASA to contact . . . . . . . . . . . . .  13
   3.  Voucher-Request artifact  . . . . . . . . . . . . . . . . . .  13
   4.  Proxying details (Pledge - Proxy - Registrar) . . . . . . . .  13
   5.  Proxy details . . . . . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Pledge discovery of Proxy . . . . . . . . . . . . . . . .  14
     5.2.  HTTPS proxy connection to Registrar . . . . . . . . . . .  14
     5.3.  Proxy discovery of Registrar  . . . . . . . . . . . . . .  14
   6.  Protocol Details (Pledge - Registrar - MASA)  . . . . . . . .  15
     6.1.  BRSKI-EST (D)TLS establishment details  . . . . . . . . .  15
       6.1.1.  BRSKI-EST CoAP estasblishment details . . . . . . . .  15
       6.1.2.  BRSKI-EST CoAP/EDHOC estasblishment details . . . . .  15
     6.2.  Pledge Requests Voucher from the Registrar  . . . . . . .  17
     6.3.  Registrar Requests Voucher from MASA  . . . . . . . . . .  17
       6.3.1.  MASA renewal of expired vouchers  . . . . . . . . . .  18
       6.3.2.  MASA verification of voucher-request signature
               consistency . . . . . . . . . . . . . . . . . . . . .  18
       6.3.3.  MASA authentication of registrar (certificate)  . . .  18
       6.3.4.  MASA revocation checking of registrar (certificate) .  18
       6.3.5.  MASA verification of pledge prior-signed-voucher-
               request . . . . . . . . . . . . . . . . . . . . . . .  18
       6.3.6.  MASA pinning of registrar . . . . . . . . . . . . . .  19
       6.3.7.  MASA nonce handling . . . . . . . . . . . . . . . . .  19



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     6.4.  MASA Voucher Response . . . . . . . . . . . . . . . . . .  19
       6.4.1.  Pledge voucher verification . . . . . . . . . . . . .  19
       6.4.2.  Pledge authentication of provisional TLS connection .  20
     6.5.  Pledge Voucher Status Telemetry . . . . . . . . . . . . .  20
     6.6.  Registrar audit log request . . . . . . . . . . . . . . .  20
       6.6.1.  MASA audit log response . . . . . . . . . . . . . . .  20
       6.6.2.  Registrar audit log verification  . . . . . . . . . .  20
       6.6.3.  EST CSR Attributes  . . . . . . . . . . . . . . . . .  20
       6.6.4.  EST Client Certificate Request  . . . . . . . . . . .  20
       6.6.5.  Enrollment Status Telemetry . . . . . . . . . . . . .  21
       6.6.6.  Multiple certificates . . . . . . . . . . . . . . . .  21
       6.6.7.  EST over CoAP . . . . . . . . . . . . . . . . . . . .  21
     6.7.  Use of Secure Transport for Minimal Join  . . . . . . . .  21
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   8.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  21
     8.1.  Privacy Considerations for Production network . . . . . .  22
     8.2.  Privacy Considerations for New Pledges  . . . . . . . . .  22
       8.2.1.  EUI-64 derived address for join time IID  . . . . . .  23
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  23
     9.1.  Security of MASA voucher signing key(s) . . . . . . . . .  23
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  23
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  23
     11.2.  Informative References . . . . . . . . . . . . . . . . .  26
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  27

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.

   The mechanism described in [I-D.ietf-anima-bootstrapping-keyinfra]
   has been adapted in [I-D.ietf-anima-constrained-voucher] to produce a
   protocol that is suited for constrained devices and constrained
   networks such as 6tisch.  The above document/protocol is referred by
   by it's acronym: BRSKI and constrained-BRSKI.  The pronounciation of
   which is "brew-ski", a common north american slang for beer with a



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   pseudo-polish ending.  This constrained protocol is called Zero-touch
   Secure Join.

   This document is a profile of [I-D.ietf-anima-constrained-voucher].
   It uses COSE signatures of CBOR voucher [RFC8366] artifacts, and it
   uses [I-D.selander-ace-cose-ecdhe] as a Lightweight authenticated key
   exchange protocol.

   [I-D.ietf-anima-constrained-voucher] has options for CMS signatures
   of CBOR vouchers, and for using DTLS.  The protocol described in this
   document does not make use those options.

   Like [I-D.ietf-anima-bootstrapping-keyinfra], 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 where such an operator exists.

   This document builds upon the "one-touch" provisioning described in
   [I-D.ietf-6tisch-minimal-security], reusing the OSCOAP Join Request
   mechanism when appropriate, but preceeding it with the EDHOC key
   agreement protocol.

   As a second option, a certificate may be deployed using the
   constrained version of [RFC7030] EST described in
   [I-D.ietf-ace-coap-est].

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

   o  HTTP is replaced with CoAP.

   o  TLS (HTTPS) is replaced with 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 COSE
      signature

   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 CoAP based
      stateless proxy mechanism described in
      [I-D.ietf-6tisch-minimal-security] section 7.1 is used.




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

   o  nonce-full vouchers are encouraged, but off-line nonce-less
      operation is also supported, however, the resulting vouchers would
      have infinite life.

   802.1AR Client certificates are retained, but optionally are
   specified by reference rather than value (Work in Progress).

   It is expected that the back-end network operator infrastructure
   would be able to bootstrap ANIMA BRSKI-type devices over ethernet,
   while also being able bootstrap 6tisch devices over 802.15.4 with few
   changes.

1.1.  Prior Bootstrapping Approaches

   Constrained devices as used in industrial control systems are usually
   installed (or replaced) by technicians with expertise in the
   equipment being serviced, not in secure enrollment of devices.

   Devices therefore are typically pre-configured in advance, marked for
   a particular factory, assembly line, or even down to the specific
   machine.  It is not uncommon for manufacturers to have a unique
   product (stock keeping unit -SKU) for each customer as the part will
   be loaded with customer specifc security configuration.  The
   resulting customer-specific parts are hard to inventory and very
   expensive to provide spares for.  Should a part be delivered to the
   wrong customer, determining the reason for inability to configure is
   difficult and time consuming.

   End-user actions to configure the part at the time of installation,
   aside from being error prone, also suffer from requiring a part that
   has a user interface.

1.2.  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],
   [I-D.ietf-anima-bootstrapping-keyinfra] and
   [I-D.ietf-anima-constrained-voucher].  The following terms are



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   imported: drop ship, imprint, enrollment, pledge, join proxy,
   ownership voucher, and join registrar/coordinator (JRC).  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"

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.

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




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   [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.

1.4.  Leveraging the new key infrastructure / next steps

   In constrained networks, it is unlikely that an ACP be formed.  This
   document does not preclude such a thing, but it is not mandated.

   The resulting secure channel SHOULD be used just to distribute
   network-wide keys using a protocol such as
   [I-D.ietf-6tisch-minimal-security].

   As a more complex, but but more secure alternative the resulting
   secure channel MAY be instead used to do an enrollment of an LDevID
   as in BRSKI.  The resulting certificate is used to do per-pair keying
   such as described by {{ieee802159}.

   XXX - this document does not yet provide a way to signal which mode
   the pledge should do.

1.4.1.  Key Distribution Process

   In addition to being used for the initial enrollment process, the
   secure channel SHOULD be kept open to use for network rekeying.  The
   CoJP protocol described in [I-D.ietf-6tisch-minimal-security]
   includes a mechanism for rekeys in section 8.4.3.1.

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 desireable.  The CoAP based
   stateless proxy mechanism described in
   [I-D.ietf-6tisch-minimal-security] section 7.1 MUST be used.

2.1.  Behavior of a Pledge

   The pledge goes through a series of steps which are outlined here at
   a high level.









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                +--------------+
                |   Factory    |
                |   default    |
                +------+-------+
                       |
                +------v-------+
                | (1) Discover |
   +------------>              |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (2) Identity |
   ^------------+              |
   | rejected   +------+-------+
   |                   |
   |            +------v-------+
   |            | (3) Request  |
   |            |     Join     |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (4) Imprint  |
   ^------------+              |
   | Bad MASA   +------+-------+
   | response          |  send Voucher Status Telemetry
   |            +------v-------+
   |            | (5) Enroll   |
   ^------------+              |
   | Enroll     +------+-------+
   | Failure           |
   |            +------v-------+
   |            | (6) Enrolled |
   ^------------+              |
    Factory     +--------------+
    reset

   State descriptions for the pledge are as follows:

   1.  Discover a communication channel to a Registrar.  This is done by
       listening for beacons as described by
       [I-D.richardson-anima-6join-discovery]

   2.  Identify itself.  This is done by presenting an X.509 IDevID
       credential to the discovered Registrar (via the Proxy) in the
       EDHOC handshake.  The certificate MAY be presented by reference.
       (The Registrar credentials are only provisionally accepted at
       this time).




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       The registrar identifies itself using a raw public key, while the
       the pledge identifies itself to the registrar using an IDevID
       credential.

   3.  Requests to Join the discovered Registrar.  A unique nonce SHOULD
       be included ensuring that any responses can be associated with
       this particular bootstrapping attempt.

   4.  Imprint on the Registrar.  This requires verification of the
       vendor service (MASA) provided voucher.  A voucher contains
       sufficient information for the Pledge to complete authentication
       of a Registrar.  The voucher is signed by the vendor (MASA) using
       a raw public key, previously installed into the pledge at
       manufacturing time.

   5.  Optionally Enroll.  By accepting the domain specific information
       from a Registrar, and by obtaining a domain certificate from a
       Registrar using a standard enrollment protocol, e.g.  Enrollment
       over Secure Transport (EST) [RFC7030].

   6.  The Pledge is now a member of, and can be managed by, the domain
       and will only repeat the discovery aspects of bootstrapping if it
       is returned to factory default settings.

2.2.  Secure Imprinting using Vouchers

   As in BRSKI, there is a voucher mechanism based upon [RFC8366].  The
   format and cryptographic mechansim of the constrained vouchers is
   described in detail in [I-D.ietf-anima-constrained-voucher].

   COSE signed vouchers and voucher-requests are MANDATORY.

2.3.  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 initial algorithms are the ECDSA
   P-256 (secp256v1).  Newer devices SHOULD begin to appear using EdDSA
   curves using the 25519 curves.

   The manufacturer will always know what algorithms are available in
   the Pledge, and will use an appropriate one.  The other components
   that need to evaluate the IDevID (the Registrar and MASA) are
   expected to support all common algorithms.



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   The JRC is expected to be an easily updated appliance that can learn
   about new algorithms with a regular maintenance cycle.

   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 the underlying 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 protocol optimizes for network bandwidth,
   and does not transfer the public key or certificate chain used to
   validate the voucher in-band.

   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.

   This use of a direct key has drawbacks, section Section 9.1 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 MASA-URL extension MANDATORY.  The inclusion of a MUD URL
   [RFC8520] is strongly recommended.

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

2.4.  Protocol Flow

   This diagram from BRSKI is reproduced with some edits:

    +--------+         +---------+    +------------+     +------------+
    | Pledge |         | IPIP    |    | Domain     |     | Vendor     |
    |        |         | Proxy   |    | Registrar  |     | Service    |
    |        |         |         |    | (JRC)      |     | (MASA)     |
    +--------+         +---------+    +------------+     +------------+
      |                     |                   |                    |
      |<-RFC4862 IPv6 adr   |                   |                    |
      |                     |                   |                    |



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      |<--------------------|                   |                    |
      | Enhanced Beacon     |                   |                    |
      |   periodic broadcast|                   |                    |
      |                     |                   |                    |
      |<------------------->C<----------------->|                    |
      |<--Registrar EDHOC server authentication-|                    |
    [PROVISIONAL accept of server RPK ]         |                    |
      P-------- 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 EST-COAPS enrollment      |                    |
      | using now bidirectionally authenticated |                    |
      |                     |                   |                    |
      |<--------------------------------------->|                    |
      |  Use 6tisch-minimal-security join request                    |

   Noteable changes are:

   1.  no IPv4 support/options.

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




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   3.  nonce-full option is always mandatory

2.5.  Architectural Components

   The bootstrap process includes the following architectural
   components:

2.5.1.  Pledge

   The Pledge is the device which is attempting to join.  Until the
   pledge completes the enrollment process, it has network connectivity
   only to the Proxy.

2.5.2.  Stateless IPIP Join Proxy

   The stateless CoAP provides CoAP connectivity between the pledge and
   the registrar.  The stateless CoAP proxy mechanism is described in
   [I-D.ietf-6tisch-minimal-security].

2.5.3.  Domain Registrar

   The Domain Registrar (having the formal name Join Registrar/
   Coordinator (JRC)), operates as a CMC Registrar, terminating the
   CoAP-EST and BRSKI connections.  The Registrar is manually configured
   or distributed with a list of trust anchors necessary to authenticate
   any Pledge device expected on the network.  The Registrar
   communicates with the Vendor supplied MASA to establish ownership.

   The JRC is typically located on the 6LBR/DODAG root, but it may be
   located elsewhere, provided IP level connectivity can be established.
   The 6LBR may also provide a proxy or relay function to connect to the
   actual registrar in addition to the IPIP proxy described above.  The
   existence of such an additional proxy is a private matter, and this
   documents assumes without loss of generality that the registrar is
   co-located with the 6LBR.

2.5.4.  Manufacturer Service

   The Manufacturer Service provides two logically seperate functions:
   the Manufacturer Authorized Signing Authority (MASA), and an
   ownership tracking/auditing function.  This function is identical to
   that used by BRSKI, except that a different format voucher is used.

2.6.  Certificate Time Validation







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2.6.1.  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 COSE 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.

2.7.  Cloud Registrar

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

2.8.  Determining the MASA to contact

   There are no changes from BRSKI: the IDevID provided by the pledge
   will contain a MASA URL extension.

3.  Voucher-Request artifact

   The voucher-request artifact is defined in
   [I-D.ietf-anima-constrained-voucher] section 6.1.

   For the 6tisch ZSJ protocol defined in this document, only COSE
   signed vouchers as described in [I-D.ietf-anima-constrained-voucher]
   section 6.3.2 are supported.

4.  Proxying details (Pledge - Proxy - Registrar)

   The voucher-request artifact is defined in
   [I-D.ietf-anima-constrained-voucher].

   The 6tisch use of the constrained version differs from the non-
   constrained version in two ways:

   1.  it does not include the proximity-registrar-cert, but rather uses
       the proximity-registrar-subjet-public-key-info entry.  This
       accomodates the use of a raw public key to identify the
       registrar.





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   2.  the pledge uses the proximity-registrar-subject-public-key-info
       to verify the raw public key for the JRC.

   An appendix of [I-D.ietf-anima-constrained-voucher] shows example
   requests and responses.

5.  Proxy details

   The role of the Proxy is to facilitate communication.  In the
   constrained situation the proxy needs to be stateless as there is
   very little ram in constrained nodes, and none can be allocated to
   keep state for an unlimited number of potential pledges.

5.1.  Pledge discovery of Proxy

   In BRSKI, the pledge discovers the proxy via use of a GRASP M_FLOOD
   messages sent by the proxy.  In 6tisch ZSJ, the existence of the
   proxy is announced by the Enhanced Beacon message described in
   [I-D.richardson-6tisch-enrollment-enhanced-beacon].  The proxy as
   described by [I-D.ietf-6tisch-minimal-security] section 10 is to be
   used in an identical fashion when EDHOC and OSCOAP are used.

5.2.  HTTPS proxy connection to Registrar

   HTTPS connections are not used between the Pledge, Proxy and
   Registrar.  The Proxy relays CoAP packets and does not interpret or
   terminate CoAP connections.

   HTTPS is still used between the Registrar and MASA!

5.3.  Proxy discovery of Registrar

   In BRSKI, the proxy autonomically discovers the Registrar by
   listening for GRASP messages.

   In the constrained network, the proxies are optionally configured
   with the address of the JRC by the Join Response in in
   [I-D.ietf-6tisch-minimal-security] section 9.3.2.  (As described in
   that section, the address of the registrar otherwise defaults to be
   that of the DODAG root)

   Whether or not a 6LR will announce itself as a possible Join Proxy is
   outside the scope of this document.








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6.  Protocol Details (Pledge - Registrar - MASA)

   BRSKI is specified to run over HTTPS.  This document respecifies it
   to run over CoAP with either DTLS or EDHOC-provided OSCOAP security.

   BRSKI introduces the concept of a provisional state for EST.

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

   As in [I-D.ietf-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.

6.1.  BRSKI-EST (D)TLS establishment details

   6tisch ZSJ does not use TLS.  The connection is CoAP with EDHOC
   security.

6.1.1.  BRSKI-EST CoAP estasblishment details

   The details in the BRSKI document apply directly to use of DTLS.

   The registrar SHOULD authenticate itself with a raw public key.  A
   256 bit ECDSA raw public key is RECOMMENDED.  Pledges SHOULD support
   EDDSA keys if they contain hardware that supports doing so
   efficiently.

   TBD: the Pledge needs to signal what kind of Raw Public Key it
   supports before the Registrar sends its ServerCertificate.  Can SNI
   be used to do this?

   The pledge SHOULD authenticate itself with the built-in IDevID
   certificate as a ClientCertificate.

6.1.2.  BRSKI-EST CoAP/EDHOC estasblishment details

   [I-D.selander-ace-cose-ecdhe] details how to use EDHOC.  The EDHOC
   description identifiers a party U (the initiator), and a party V.
   The Pledge is the party U, and the JRC is the party V.




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   The communication from the Pledge is via CoAP via the Join Proxy.
   The Join proxy relays traffic to the JRC, and using the mechanism
   described in [I-D.ietf-6tisch-minimal-security] section 5.1.  This is
   designed so that the Join Proxy does not need to know if it is
   performing the one-touch enrollment described in
   [I-D.ietf-6tisch-minimal-security] or the zero-touch enrollment
   protocol described in this document.  A network could consist of a
   mix of nodes of each type.

   As generating ephemeral keys is expensive for a low-resource Pledge,
   the use of a common E_U by the Pledge for multiple enrollment
   attempts (should the first turn out to be the wrong network) is
   encouraged.

   The first communication detailed in [I-D.ietf-ace-coap-est] is to
   query the "/.well-known/core" resource to request the Link for EST.
   This is where the initial CoAP request is to sent.

   The JRC MAY replace it's E_V ephermal key on a periodic basis, or
   even for every communication session.

   The Pledge's ID_U is the Pledge's IDevID.  It is transmitted in an
   x5bag [I-D.schaad-cose-x509].  An x5u (URL) MAY be used.  An x5t
   (hash) MAY also be used and would be the smallest, but the Registrar
   may not know where to find the Pledge's IDevID unless the JRC has
   been preloaded will all the IDevIDs via out-of-band mechanism.  It is
   impossible for the Pledge to know if the JRC has been loaded in such
   a way so x5t is discouraged for general use.

   The JRC's ID_V is the JRC's Raw Public Key. It is transmitted as a
   key in COSE's YYY parameter.

   The initial Mandatory to Implement (MTI) of an HKDF of SHA2-256, an
   AEAD based upon AES-CCM-16-64-128, a signature verification of
   TBD:BBBB, and signature generation of TBD:BBBB.  The Pledge proposes
   a set of algorithms that it supports, and Pledge need not support
   more than one combination.

   JRCs are expected to run on non-constrained servers, and are expected
   to support the above initial as MTI, and any subsequent ones that
   become common.

   A JRC SHOULD support all available algorithms for a significant
   amount of time.

   Even when algorithms become weak or suspect, it is likely that it
   will still have to perform secure join for older devices.  A JRC that
   responds to such an older device might not in the end accept the



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   device into the network, but it is important that it be able to audit
   the event and communicate the event to an operator.

   While EDHOC supports sending additional data in the message_3, in the
   constrained network situation, it is anticipated that the size of the
   this message will already be large, and no additional data is to be
   sent.

   A COAP confirmable message SHOULD be used.

   [I-D.ietf-6tisch-minimal-security] section 6 details how to setup
   OSCORE context given a shared key derived by EDHOC.

   The registrar SHOULD authenticate itself with a raw public key.

   The pledge SHOULD authenticate itself with the built-in IDevID
   certificate.

6.2.  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
   proximity-registrar-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 mandates that all voucher requests be signed.

6.3.  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-request and voucher response is COSE, 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.  It is
   however, too late for the Registar to use a different key, but at
   least it can log a reason for a failure.





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   It is likely that the ZSJ-BRSKI-EST connection has already failed,
   and this step is never reached.

6.3.1.  MASA renewal of expired vouchers

   There are assumed to be no useful real-time clocks on constrained
   devices, so all vouchers are in effect infinite duration.  Pledges
   will use nonces for freshness, and a request for a new voucher with a
   new voucher for the same Registrar is not unusual.

   A token-bucket system SHOULD be used such that no more than 24
   vouchers are issued per-day, but more than one voucher can be issued
   in a one hour period.  Tokens should not accumulate for more than one
   day.

6.3.2.  MASA verification of voucher-request signature consistency

   The voucher-request is signed by the Registrar using it's Raw Public
   Key.  There is no additional certificate authority to sign this key.
   The MASA MAY have this key via sales-channel integration, but in most
   cases it will be seeing the key for the first time.

   XXX-should the TLS connection from Registrar to MASA have a
   ClientCertificate?  If so, then should it use the same Public Key?
   Or a different one?

6.3.3.  MASA authentication of registrar (certificate)

   IDEA: The MASA SHOULD pin the Raw Public Key (RPK) to the IP address
   that was first used to make a request with it.  Should the RPK <-> IP
   address relationship be 1:1, 1:N, N:1?  Should we take IP address to
   mean, "IP subnet", essentially the IPv4/24, and IPv6/64?  The value
   of doing is about DDoS mitigation?

   Should above mapping be on a per-Pledge basis?

6.3.4.  MASA revocation checking of registrar (certificate)

   As the Registrar has a Raw Public Key as an identity, there is no
   meaningful standard revocation checking that can be done.  The MASA
   SHOULD have a blacklist table, and a way to add entries, but this
   process is out of scope.

6.3.5.  MASA verification of pledge prior-signed-voucher-request

   The Registrar will put the signed pledge voucher-request into it's
   voucher-request as 'prior-signed-voucher-request'.  The MASA can




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   verify the signature from the Pledge using the MASA's copy of the
   Pledge's IDevID public key.

6.3.6.  MASA pinning of registrar

   When the MASA creates a voucher, it puts the Registrar's Raw Public
   Key into the 'pinned-domain-subject-public-key-info' leaf of the
   voucher.

   The MASA does not include the 'pinned-domain-cert' field in such
   vouchers.

6.3.7.  MASA nonce handling

   Use of nonces is highly RECOMMENDED, but there are situations where
   not all components are connected at the same time in which the nonce
   will not be present.

   There are no significant changes from BRSKI.

6.4.  MASA Voucher Response

   As exaplained in [I-D.ietf-anima-constrained-voucher] section 6.3.2,
   when a voucher is returned by the MASA to the JRC, a public key or
   certificate container that will verify the voucher SHOULD also be
   returned.

   In order to do this, the MASA MAY return a multipart/related return,
   within that body, two items SHOULD be returned:

   1.  An application/voucher-cose+cbor body.

   2.  An application/TBD:SOMETHING containing a Raw Public Key.

   A MASA is not obligated to return the public key, and MAY return only
   the application/voucher-cose+cbor object.  In that case, the JRC will
   be unable to validate it, and will have to just audit the contents.

6.4.1.  Pledge voucher verification

   The Pledge receives the voucher from the Registrar over it's CoAP
   connection.  It verifies the signature using the MASA anchor built
   in, as in the BRSKI case.








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6.4.2.  Pledge authentication of provisional TLS connection

   The BRSKI process uses the pinned-domain-cert field of the voucher to
   validate the registrar's ServerCertificate.  In the ZeroTouch case,
   the voucher will contain a pinned-domain-subject-public-key-info
   field containing the raw public key of the certificate.  It should
   match, byte-to-byte with the raw public key ServerCertificate.

6.5.  Pledge Voucher Status Telemetry

   The voucher status telemetry report is communicated from the pledge
   to the registrar over CoAP channel.  The shortened URL is as
   described in table QQQ.

6.6.  Registrar audit log request

   There are no changes to the Registrar audit log request.

6.6.1.  MASA audit log response

   There are no changes to the MASA audit log response.

6.6.2.  Registrar audit log verification

   There are no changes to how the Registrar verifies the audit log.

6.6.3.  EST CSR Attributes

   In 6tisch, no Autonomic Control Plane will be created, so none of the
   criteria for SubjectAltname found in
   [I-D.ietf-anima-autonomic-control-plane] apply.

   The CSR Attributes request SHOULD NOT be performed.

6.6.4.  EST Client Certificate Request

   6tisch will use a certificate to:

   1.  to authenticate an 802.15.9 key agreement protocol.

   2.  to terminate an incoming DTLS or EDHOC key agreement as part of
       application data protection.

   It is recommended that the requested subjectAltName contain only the
   [RFC4514] hwSerialNum.






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6.6.5.  Enrollment Status Telemetry

   There are no changes to the status telemetry between Registrar and
   MASA.

6.6.6.  Multiple certificates

   Multiple certificates are not supported.

6.6.7.  EST over CoAP

   This document and [I-D.ietf-ace-coap-est] detail how to run EST over
   CoAP.

6.7.  Use of Secure Transport for Minimal Join

   Rather than bootstrap to a public key infrastructure, the secure
   channel MAY instead be for the minimal security join process
   described in [I-D.ietf-6tisch-minimal-security].

   The desire to do a minimal-security join process is signaled by the
   Registrar in it's voucher-request by including a 'join-process' value
   of 'minimal'.  The MASA copies this value into the voucher that is
   creates, and also logs this to the audit log.

   When the secure channel was created with EDHOC, then the keys setup
   by EDHOC are simply used by OSCORE exactly as if they had been Pre-
   Shared.  The keys derived by EDHOC SHOULD be stored by both Registrar
   and Pledge as their long term key should the join process need to be
   repeated.

7.  IANA Considerations

   No specific requests are made

8.  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.








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8.1.  Privacy Considerations for Production network

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

8.2.  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 Proxy into IPIP packets and carried to the
   JRC.  The traffic SHOULD never leave the operator's network, will be
   kept confidential by the layer-2 keys inside the LLN.  As no outside
   traffic can enter the join network, 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 JRC.  The
   join request with this object occurs within a secured CoAP channel,
   although the link-local address configured by the pledge will be
   visible in either the CoAP stateless proxy option (section 5.1 of
   [I-D.ietf-6tisch-minimal-security]), or in the equivalent DTLS
   stateless proxy option (reference TBD).

   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.  Once connected, the long 8-byte EUI64
   layer-2 address is usually replaced with a short JRC assigned 2-byte
   address.

   Additionally, during the enrollment process, a DTLS connection or
   EDHOC connection will be created.  TLS1.3 will keep contents of the
   certificates transmitted private while TLS 1.2 will not.  If the
   client certificate can be observed, then the device identity will be
   visible to passive observers in the 802.11AR IDevID certificate that
   is sent.

   Even when TLS 1.3 is used, an active attacker could collect the
   information by creating a rogue proxy.



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   The use of a manufacturer assigned EUI64 (whether derived from IEEE
   assignment or created through another process during manufacturing
   time) is encouraged.

8.2.1.  EUI-64 derived address for join time IID

   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 address.  At that point, all layer-3
   content is encrypted by the layer-2 key.

9.  Security Considerations

   TBD

9.1.  Security of MASA voucher signing key(s)

   TBD

10.  Acknowledgements

   Kristofer Pister helped with many non-IETF references.

11.  References

11.1.  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-security]
              Vucinic, M., Simon, J., Pister, K., and M. Richardson,
              "Minimal Security Framework for 6TiSCH", draft-ietf-
              6tisch-minimal-security-11 (work in progress), June 2019.








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   [I-D.ietf-6tisch-terminology]
              Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
              "Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4e",
              draft-ietf-6tisch-terminology-10 (work in progress), March
              2018.

   [I-D.ietf-ace-coap-est]
              Stok, P., Kampanakis, P., Richardson, M., and S. Raza,
              "EST over secure CoAP (EST-coaps)", draft-ietf-ace-coap-
              est-12 (work in progress), June 2019.

   [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-22 (work in progress), June 2019.

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", draft-
              ietf-anima-constrained-voucher-04 (work in progress), July
              2019.

   [I-D.ietf-anima-voucher]
              Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "Voucher Profile for Bootstrapping Protocols", draft-ietf-
              anima-voucher-07 (work in progress), January 2018.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", draft-ietf-core-object-security-16 (work in
              progress), March 2019.

   [I-D.richardson-6tisch-enrollment-enhanced-beacon]
              Dujovne, D. and M. Richardson, "IEEE802.15.4 Informational
              Element encapsulation of 6tisch Join and Enrollment
              Information", draft-richardson-6tisch-enrollment-enhanced-
              beacon-01 (work in progress), April 2018.

   [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-03 (work in
              progress), January 2018.






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   [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.schaad-cose-x509]
              Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Headers for carrying and referencing X.509 certificates",
              draft-schaad-cose-x509-03 (work in progress), December
              2018.

   [I-D.selander-ace-cose-ecdhe]
              Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
              Diffie-Hellman Over COSE (EDHOC)", draft-selander-ace-
              cose-ecdhe-13 (work in progress), March 2019.

   [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>.

   [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>.







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   [RFC4514]  Zeilenga, K., Ed., "Lightweight Directory Access Protocol
              (LDAP): String Representation of Distinguished Names",
              RFC 4514, DOI 10.17487/RFC4514, June 2006,
              <https://www.rfc-editor.org/info/rfc4514>.

   [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>.

   [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>.

   [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>.

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,
              <https://www.rfc-editor.org/info/rfc8366>.

11.2.  Informative References

   [I-D.ietf-anima-autonomic-control-plane]
              Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
              Control Plane (ACP)", draft-ietf-anima-autonomic-control-
              plane-19 (work in progress), March 2019.

   [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>.

   [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>.





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Internet-Draft   6tisch Zero-Touch Secure Join protocol        July 2019


   [RFC8520]  Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
              Description Specification", RFC 8520,
              DOI 10.17487/RFC8520, March 2019,
              <https://www.rfc-editor.org/info/rfc8520>.

Author's Address

   Michael Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca








































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