enrollment-roadmap.txt

ANIMA Working Group                                        M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Informational                            7 October 2020
Expires: 10 April 2021


            Device Enrollment in IETF protocols -- A Roadmap
                 draft-richardson-enrollment-roadmap-03

Abstract

   This document provides an overview of enrollment or imprinting
   mechanisms in current IETF protocols.

   This document is being worked on in the ANIMA-WG, and on github at:
   https://github.com/anima-wg/enrollment-roadmap

Status of This Memo

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

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   This Internet-Draft will expire on 10 April 2021.

Copyright Notice

   Copyright (c) 2020 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
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Components of enrollment solutions  . . . . . . . . . . . . .   3
   3.  Map of Enrollment solution  . . . . . . . . . . . . . . . . .   4
   4.  Components  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  generic voucher semantics . . . . . . . . . . . . . . . .   6
     4.2.  constrained voucher . . . . . . . . . . . . . . . . . . .   6
     4.3.  JSON format voucher . . . . . . . . . . . . . . . . . . .   6
     4.4.  COSE-8152 . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.5.  standard signature (CMS)  . . . . . . . . . . . . . . . .   6
     4.6.  EDHOC . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.7.  EST-COAPS 2/DTLS sec(urity) . . . . . . . . . . . . . . .   6
     4.8.  EST-HTTPS TLS sec(urity)  . . . . . . . . . . . . . . . .   7
     4.9.  constrained object security (OSCORE)  . . . . . . . . . .   7
     4.10. ultra-constrained enrollment  . . . . . . . . . . . . . .   7
     4.11. Pledge traffic proxy mechanisms . . . . . . . . . . . . .   7
       4.11.1.  COAP proxy,stateless . . . . . . . . . . . . . . . .   7
     4.12. DTLS proxy  . . . . . . . . . . . . . . . . . . . . . . .   8
     4.13. IPIP proxy,stateless  . . . . . . . . . . . . . . . . . .   8
     4.14. circuit proxy stateful  . . . . . . . . . . . . . . . . .   8
   5.  call-home ssh/tls/usbkey  . . . . . . . . . . . . . . . . . .   8
   6.  manufacturer authorized signing authority (MASA)  . . . . . .   8
   7.  Enrollment Mechanisms . . . . . . . . . . . . . . . . . . . .   8
     7.1.  NETCONF . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.2.  BRSKI . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.3.  Transition to Constrained Bootstrap . . . . . . . . . . .  10
     7.4.  Cloud-based Registrars  . . . . . . . . . . . . . . . . .  10
     7.5.  BRSKY Asynchronous Enrollment . . . . . . . . . . . . . .  10
     7.6.  6tisch Zero Touch . . . . . . . . . . . . . . . . . . . .  11
     7.7.  6tisch minimal security . . . . . . . . . . . . . . . . .  11
   8.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   9.  OPEN ISSUE  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  12
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     13.2.  Informative References . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   There are numerous mechanisms being proposed to solve the problem of
   securely introducing a new devices into an existing managed network.

   This document provides an overview of the different mechanisms
   showing what technologies are common.



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   The document starts with a diagram showing the various components and
   how they go together to form five enrollment scenarios.

2.  Components of enrollment solutions

   This diagram is taken from [I-D.ietf-anima-bootstrapping-keyinfra],
   which is where this work started.

                                              +------------------------+
      +--------------Drop Ship--------------->| Vendor Service         |
      |                                       +------------------------+
      |                                       | M anufacturer|         |
      |                                       | A uthorized  |Ownership|
      |                                       | S igning     |Tracker  |
      |                                       | A uthority   |         |
      |                                       +--------------+---------+
      |                                                      ^
      |                                                      |  BRSKI-
      V                                                      |   MASA
   +-------+     ............................................|...
   |       |     .                                           |  .
   |       |     .  +------------+       +-----------+       |  .
   |       |     .  |            |       |           |       |  .
   |Pledge |     .  |   Circuit  |       | Domain    <-------+  .
   |       |     .  |   Proxy    |       | Registrar |          .
   |       <-------->............<-------> (PKI RA)  |          .
   |       |        |        BRSKI-EST   |           |          .
   |       |     .  |            |       +-----+-----+          .
   |IDevID |     .  +------------+             | EST RFC7030    .
   |       |     .           +-----------------+----------+     .
   |       |     .           | Key Infrastructure         |     .
   |       |     .           | (e.g. PKI Certificate      |     .
   +-------+     .           |       Authority)           |     .
                 .           +----------------------------+     .
                 .                                              .
                 ................................................
                               "Domain" components

   Five major components are described:

   1.  pledge: The node that is attempting to enroll.

   2.  proxy: A node that is within one layer-2 hop of the pledge that
       is helping.

   3.  domain registrar: the Join Registrar/Coordinator (JRC) that will
       determine eligibility of the pledge.




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   4.  MASA: the representative of the manufacturer that has a pre-
       established trust relationship with the pledge.

   5.  the domain PKI (if any)

3.  Map of Enrollment solution













































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                                                 .-------------------.
                                                 .   generic (YANG)  .
                                .----------------. voucher semantics .
                                |                '-------------------'
                                |                       .---
                                |                       |
     6tisch      6tisch     Tran|ition to               |
     minimal      zero       Con|trained                |
     security    touch        Bo|tstrap      BRSKI      | Netconf
   .----------..-----------..---|-------..------------. |-------------.
   |          ||           ||   v       ||            | v             |
   |          ||..................................................... |
   |          ||. constrained voucher      .  JSON format voucher   . |
   |          ||.      (anima)             .       (RFC8366)        . |
   |          ||..................................................... |
   |          ||           ||           ||            | |             |
   |          |.............|  ...................................... |
   |          |. COSE      .|  . standard signature (CMS - RFC5652) . |
   |          |. rfc8152   .|  ...................................... |
   |          |.............|           ||            | |             |
   |          ||          ............................| |             |
   |          |.........  .  EST-COAPS  .. EST-HTTPS .| |             |
   |          |. EDHOC .  . w/DTLS sec. .. TLS sec.  .| |             |
   |..................................................| |             |
   |. constrained object . ||           ||            | |             |
   |. security (OSCORE)  . ||           ||            | |.............|
   |...................... ||           ||............| |. call-home .|
   |          ||           ||.........  ||. circuit  .| |.  ssh/tls  .|
   |........................|. DTLS  .  ||.  proxy   .| |.  .usbkey  .|
   |. CoAP proxy,stateless .|. proxy .  ||. stateful .| |.............|
   |..................................................| |             |
   |          ||.     IPIP proxy,stateless           .| |             |
   |          ||......................................| |             |
   '----------''-----------''-----------''------------' '-------------'
                     ^            ^             ^              ^
                     |             \            |              |
                     |              '.          .--------------'
                     |               |          |
                     |               |          |
                     |               |  .--------------.
                     |               |  . manufacturer .
                     |               |  . authorized   .
                     '---------------|--. signing      .
                                        . authority    .
                                        . (MASA)       .
                                        '--------------'





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4.  Components

4.1.  generic voucher semantics

   The abstract semantics of the voucher, described in YANG, are in
   [RFC8366].

4.2.  constrained voucher

   The semantics of the constrained voucher, represented in CBOR, are
   described in [I-D.ietf-anima-constrained-voucher].

4.3.  JSON format voucher

   The semantics of the basic voucher, represented in JSON, are
   described in [RFC8366].

4.4.  COSE-8152

   In constrained systems the voucher is signed using the COSE mechanism
   described in [RFC8152].  This is to be replaced with
   [I-D.ietf-cose-rfc8152bis-algs] (now in RFC-EDITOR Q) and
   [I-D.ietf-cose-rfc8152bis-struct] (in WGLC, being revised to remove
   countersignatures).

4.5.  standard signature (CMS)

   In un-constrained systems the voucher is signed using the
   Cryptographic Message Syntax (CMS) described in [RFC5652].

4.6.  EDHOC

   On constrained and challenged networks, the session key management
   can be formed by [I-D.ietf-lake-edhoc].

   This document has a WG called LAKE.

   The CoAP-EST layer on top is described by [I-D.ietf-ace-coap-est]

4.7.  EST-COAPS 2/DTLS sec(urity)

   On unconstrained networks, the session key management is provided by
   [RFC6347].  The CoAP-EST layer on top is described by
   [I-D.ietf-ace-coap-est], which is in the RFC-EDITOR Q, waiting for
   DTLS 1.3.

   The ACE WG adopted this document, and published it.




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4.8.  EST-HTTPS TLS sec(urity)

   On unconstrained networks with unconstrained nodes, the EST layer and
   session key management is described by [RFC7030] as modified by
   [I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI).

   BRSKI is in the RFC-EDITOR Q, waiting for
   [I-D.ietf-anima-autonomic-control-plane], which is awaiting IESG go-
   ahead.

4.9.  constrained object security (OSCORE)

   On constained networks with constrained nodes, the CoAP transactions
   are secured by [I-D.ietf-core-object-security] using symmetric keys.
   The symmetric key may be pre-shared (for 6tisch minimal security), or
   MAY be derived using EDHOC.

4.10.  ultra-constrained enrollment

   The document [I-D.selander-ace-ake-authz].  Version -01 expired in
   September 2020, but is expected to be reposted for discussion in the
   ACE WG.

4.11.  Pledge traffic proxy mechanisms

   Traffic between the Pledge and the JRC does not flow directly as the
   pledge does not typically have a globally reachable address, nor does
   it have any network access keys (whether WEP, WPA, 802.1x, or
   802.15.4 keys).

   Communication between the pledge and JRC is mediated by a proxy.
   This is primarily to protect the network against attacks.  The proxy
   mechanism is provided by as many nodes as can afford to as a benefit
   to the network, and therefore MUST be as light weight as possible.

   There are therefore stateless mechanisms and stateful mechanisms.
   The costs of the various methods is analysized in
   [I-D.richardson-anima-state-for-joinrouter].

4.11.1.  COAP proxy,stateless

   The CoAP proxy mechanism uses the OSCORE Context Hint to statelessly
   store the address of the proxy within the CoAP structure.  It is
   described in [I-D.ietf-6tisch-minimal-security].







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4.12.  DTLS proxy

   A DTLS specific mechanism for COAPS, is described in
   [I-D.vanderstok-anima-constrained-join-proxy].

4.13.  IPIP proxy,stateless

   An IPIP proxy mechanism uses a layer of IP-in-IP header (protocol 98)
   to encapsulate the traffic between Join Proxy and JRC.  It has some
   complexities to implement on typical POSIX platforms.

   At one point, it was described in
   [I-D.ietf-6tisch-dtsecurity-zerotouch-join], in an Appendix.  Another
   home for the text is desired.

4.14.  circuit proxy stateful

   The circuit proxy method utilitizes either an application layer
   gateway (which in canonical 1990-era implementation requires a
   process per connection), or the use of NAT66.  It maintains some
   state for each connection whether TCP or UDP.

   It is this most expensive and most easily abused, but also the most
   widely available, code-wise.

5.  call-home ssh/tls/usbkey

   The NETCONF call-home mechanism assumes that the device can get basic
   connectivity, enough for an out "outgoing" TCP connection to the
   manufacturer.

6.  manufacturer authorized signing authority (MASA)

   The MASA is the manufacturers anchor of the manufacturer/pledge trust
   relationship that is established at the factory where the pledge is
   built.

7.  Enrollment Mechanisms

7.1.  NETCONF

   The NETCONF WG is describing this in [I-D.ietf-netconf-zerotouch]
   document.








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   The NETCONF Zerotouch mechanism provides configuration and ownership
   information by having the pledge "call home" to a location determined
   by a mix of local hints (DHCPv4, DHCPv6, and mDNS), as well as built-
   in anchors.  Additionally, ownership vouchers can be alternatively
   distributed by portable storage such as USB key.

   Upon reaching a validated call-home server, Zerotouch typically
   "reverses" the connection providing either an SSH or TLS connection
   _to_ the pledge device such that it can be configured automatically.

   Zerotouch relies upon either open or very easy access to network
   connectivity, along with the ability to make an outgoing TCP
   connection to the Internet, or to the provided local configuration
   agent.

   Zerotouch is seen as an updated version of TR-69 by some, appropriate
   for configuration of residential appliances which are drop-shiped by
   ISPs or other service providers to homes.  That is not the only
   targetted use.

7.2.  BRSKI

   The ANIMA WG is describing BRSKI in
   [I-D.ietf-anima-bootstrapping-keyinfra] document.

   The ANIMA WG does enrollment with the aim of creating a secure
   channel with a public-key infrastructure (PKI) Registrar.  The
   secured channel is used to perform Enrollment over Secure Transport
   (EST, RFC7030).  The real goal is the enrollment a new device which
   was probably been drop-shipped into ANIMA's Autonomic Control Plane.

   That is, after the pledge has been assigned a certificate within the
   (autonomic) domain, the device (no longer a pledge) will then form
   secure channels (typically using IKEv2 to key an IPsec channel).  On
   top of that channel a routing protocol (RPL) is run to form the
   Autonomic Control Plane (ACP).  The ACP is then used as a management
   network with which to configure the new device.

   BRSKI is therefore step one of a number of steps, the ultimate goal
   of which is to bring the pledge into the ACP as a new device.

   BRSKI itself does not provide for any direct keying of the network
   (802.11 WEP/WPA, or 802.15.4 security).  The provision of a domain
   certificate at each node can, however, be used to do that kind of
   keying: for instance 802.15.9 provides for use of HIP and IKEv2 to
   key 802.15.4 networks.





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7.3.  Transition to Constrained Bootstrap

   It is distinguished from BRSKI in that it uses DTLS (rather than TLS)
   and constrained (CBOR) vouchers.  It is distinguished from 6tisch
   Zero Touch in that uses CMS to sign rather than COSE.

   The ACE WG has adopted [I-D.ietf-ace-coap-est], but this is not a
   sufficient.

   The constrained version of BRSKI is current described as part of
   [I-D.ietf-anima-constrained-voucher].

   The use of this technology slice is attractive to IoT deployments
   where the devices are not battery powered (lighting for instance, AMI
   for electric meters).  In such situations, the processors in each
   device have significantly more resources, and in particular far more
   code space available.  The use of DTLS to secure application traffic
   (as described in the ACE documents) is already common, and so reuse
   of DTLS is desireable from a code point of view.

   However, the network capacity is still limited so TCP and CBOR are
   still important.  The network may also contain extremely constrained
   devices (kinetically powered light switches for n instance).

7.4.  Cloud-based Registrars

   BRSKI depends upon a local join proxy to direct the pledge device to
   the location of the Registrar.  Not only does this require that a
   join proxy be widely available, but it also assumes that the owner is
   able to operate a Registrar.

   [I-D.friel-anima-brski-cloud] deals with two use cases:

   1.  where there is a Registrar, but no join proxy.  A redirection
       through a manufacturer or VAR operated register points the device
       to a Registrar located on the Internet.

   2.  where there is no Registrar (yet), but the network operator does
       have an RFC7030 EST server.  The cloud registrar provides a
       voucher connecting the pledge to the appropriate EST server.

7.5.  BRSKY Asynchronous Enrollment

   BRSKI depends the join proxy being available in the location where
   the devices are installed, and for that proxy to also be able to
   communicate to the Registrar (possibly over the Internet).





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   In a number of environments, such as new construction, a number of
   devices need to go through an onboarding process, but there is no
   connectivity available.  (Possibly not even LTE/3G due to metal
   walls, lack of towers, etc.).

   The [I-D.ietf-anima-brski-async-enroll] proposes two amendments to
   BRSKI:

   1.  the use of CMP rather than EST for enrollment, which eliminates
       the need to keep a live TLS connection between pledge and
       Registrar.

   2.  a discovery, store-and-forward mechanism for moving voucher
       requests and vouchers between the Registrar and Pledge, including
       a batch mechanism that aims to reduce the amount of walking that
       an installer might have to do.

7.6.  6tisch Zero Touch

   The 6tisch WG is describing this in
   [I-D.ietf-6tisch-dtsecurity-zerotouch-join] document.

   The 6tisch use case consists of very constrained devices with very
   constrained networks.  Code space in the devices is larger than
   typical class 2, but the devices are typically battery powered and
   wish to sleep significantly.

   The use of CBOR for vouchers, COSE to sign the vouchers saves
   significant network bandwidth and code space.  Both CBOR, COSE and
   OSCORE are typically already in use for the application support.  The
   addition of EDHOC to provide asymmetric bootstrap of OSCORE completes
   the suite of constrained security protocols.

7.7.  6tisch minimal security

   The 6tisch WG is describing this in
   [I-D.ietf-6tisch-minimal-security] document.  This mechanism does
   enrollment in a single request/response message, but requires at
   least one "touch" to pre-share symmetric keys.

   The 6tisch WG felt that the number of round trips required to do
   EDHOC, and the size of the vouchers required an even simpler
   protocol.  As existing 6tisch-type technology is typically deployed
   with network keys built-in at manufacturer time (no "drop-ship"), the
   switch from a static network key to a PSK for authenticaiton is
   considered an incremental improvement.

   All other methods are considered zero "touch".



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   [I-D.ietf-6tisch-minimal-security] is in the RFC-EDITOR Q, waiting
   for core-stateless on which is depends to leave the WG.

8.  Discussion

   A goal of this document is to provide some guidance in selecting
   which enrollment profile to use for a given scenario.  This section
   tries to provide some constrasting comments between the various
   mechanisms.

   (BUT, it does not yet do that..)

9.  OPEN ISSUE

   1.  insufficient guidance if there is no internet connection.

   2.  classes of devices where the manufacturer will never have an HSM/
       PKI. so, it will only be a self-signed key.

   3.  how does a supply-chain manage BRSKI?

10.  Security Considerations

   This document includes a tradeoff of the security attributes of the
   different protocols, and so the entire document contains security
   advice.

11.  IANA Considerations

   This document does not define any new protocols, and therefore does
   not have any IANA Considerations.

12.  Acknowledgements

   TBD

13.  References

13.1.  Normative References

   [I-D.ietf-6tisch-dtsecurity-zerotouch-join]
              Richardson, M., "6tisch Zero-Touch Secure Join protocol",
              Work in Progress, Internet-Draft, draft-ietf-6tisch-
              dtsecurity-zerotouch-join-04, 8 July 2019,
              <http://www.ietf.org/internet-drafts/draft-ietf-6tisch-
              dtsecurity-zerotouch-join-04.txt>.





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   [I-D.ietf-6tisch-minimal-security]
              Vucinic, M., Simon, J., Pister, K., and M. Richardson,
              "Constrained Join Protocol (CoJP) for 6TiSCH", Work in
              Progress, Internet-Draft, draft-ietf-6tisch-minimal-
              security-15, 10 December 2019, <http://www.ietf.org/
              internet-drafts/draft-ietf-6tisch-minimal-security-
              15.txt>.

   [I-D.ietf-ace-coap-est]
              Stok, P., Kampanakis, P., Richardson, M., and S. Raza,
              "EST over secure CoAP (EST-coaps)", Work in Progress,
              Internet-Draft, draft-ietf-ace-coap-est-18, 6 January
              2020, <http://www.ietf.org/internet-drafts/draft-ietf-ace-
              coap-est-18.txt>.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
              and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", Work in Progress, Internet-
              Draft, draft-ietf-anima-bootstrapping-keyinfra-44, 21
              September 2020, <http://www.ietf.org/internet-drafts/
              draft-ietf-anima-bootstrapping-keyinfra-44.txt>.

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", Work in
              Progress, Internet-Draft, draft-ietf-anima-constrained-
              voucher-08, 13 July 2020, <http://www.ietf.org/internet-
              drafts/draft-ietf-anima-constrained-voucher-08.txt>.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", Work in Progress, Internet-Draft, draft-ietf-
              core-object-security-16, 6 March 2019,
              <http://www.ietf.org/internet-drafts/draft-ietf-core-
              object-security-16.txt>.

   [I-D.ietf-netconf-zerotouch]
              Watsen, K., Abrahamsson, M., and I. Farrer, "Secure Zero
              Touch Provisioning (SZTP)", Work in Progress, Internet-
              Draft, draft-ietf-netconf-zerotouch-29, 15 January 2019,
              <http://www.ietf.org/internet-drafts/draft-ietf-netconf-
              zerotouch-29.txt>.

   [I-D.selander-ace-cose-ecdhe]
              Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
              Diffie-Hellman Over COSE (EDHOC)", Work in Progress,



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              Internet-Draft, draft-selander-ace-cose-ecdhe-14, 11
              September 2019, <http://www.ietf.org/internet-drafts/
              draft-selander-ace-cose-ecdhe-14.txt>.

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

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/info/rfc5652>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [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>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [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>.

   [RFC8152]  Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,
              <https://www.rfc-editor.org/info/rfc8152>.

   [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>.

13.2.  Informative References




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   [I-D.friel-anima-brski-cloud]
              Friel, O., Shekh-Yusef, R., and M. Richardson, "BRSKI
              Cloud Registrar", Work in Progress, Internet-Draft, draft-
              friel-anima-brski-cloud-03, 24 September 2020,
              <http://www.ietf.org/internet-drafts/draft-friel-anima-
              brski-cloud-03.txt>.

   [I-D.ietf-anima-autonomic-control-plane]
              Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
              Control Plane (ACP)", Work in Progress, Internet-Draft,
              draft-ietf-anima-autonomic-control-plane-29, 11 September
              2020, <http://www.ietf.org/internet-drafts/draft-ietf-
              anima-autonomic-control-plane-29.txt>.

   [I-D.ietf-anima-brski-async-enroll]
              Fries, S., Brockhaus, H., and E. Lear, "Support of
              asynchronous Enrollment in BRSKI (BRSKI-AE)", Work in
              Progress, Internet-Draft, draft-ietf-anima-brski-async-
              enroll-00, 10 July 2020, <http://www.ietf.org/internet-
              drafts/draft-ietf-anima-brski-async-enroll-00.txt>.

   [I-D.ietf-cose-rfc8152bis-algs]
              Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Initial Algorithms", Work in Progress, Internet-Draft,
              draft-ietf-cose-rfc8152bis-algs-12, 24 September 2020,
              <http://www.ietf.org/internet-drafts/draft-ietf-cose-
              rfc8152bis-algs-12.txt>.

   [I-D.ietf-cose-rfc8152bis-struct]
              Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Structures and Process", Work in Progress, Internet-Draft,
              draft-ietf-cose-rfc8152bis-struct-14, 24 September 2020,
              <http://www.ietf.org/internet-drafts/draft-ietf-cose-
              rfc8152bis-struct-14.txt>.

   [I-D.ietf-lake-edhoc]
              Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
              Diffie-Hellman Over COSE (EDHOC)", Work in Progress,
              Internet-Draft, draft-ietf-lake-edhoc-01, 2 August 2020,
              <http://www.ietf.org/internet-drafts/draft-ietf-lake-
              edhoc-01.txt>.










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   [I-D.richardson-anima-state-for-joinrouter]
              Richardson, M., "Considerations for stateful vs stateless
              join router in ANIMA bootstrap", Work in Progress,
              Internet-Draft, draft-richardson-anima-state-for-
              joinrouter-03, 22 September 2020, <http://www.ietf.org/
              internet-drafts/draft-richardson-anima-state-for-
              joinrouter-03.txt>.

   [I-D.selander-ace-ake-authz]
              Selander, G., Mattsson, J., Vucinic, M., Richardson, M.,
              and A. Schellenbaum, "Lightweight Authorization for
              Authenticated Key Exchange.", Work in Progress, Internet-
              Draft, draft-selander-ace-ake-authz-01, 9 March 2020,
              <http://www.ietf.org/internet-drafts/draft-selander-ace-
              ake-authz-01.txt>.

   [I-D.vanderstok-anima-constrained-join-proxy]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Join Proxy for Bootstrapping Protocols", Work in Progress,
              Internet-Draft, draft-vanderstok-anima-constrained-join-
              proxy-04, 22 September 2020, <http://www.ietf.org/
              internet-drafts/draft-vanderstok-anima-constrained-join-
              proxy-04.txt>.

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

Author's Address

   Michael Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca


















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