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Bootstrapping Remote Secure Key Infrastructures (BRSKI)

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8995.
Authors Max Pritikin , Michael Richardson , Toerless Eckert , Michael H. Behringer , Kent Watsen
Last updated 2019-10-28 (Latest revision 2019-09-19)
Replaces draft-pritikin-anima-bootstrapping-keyinfra
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Toerless Eckert
Shepherd write-up Show Last changed 2018-08-21
IESG IESG state Became RFC 8995 (Proposed Standard)
Consensus boilerplate Yes
Telechat date (None)
Needs 7 more YES or NO OBJECTION positions to pass.
Responsible AD Ignas Bagdonas
Send notices to "Toerless Eckert" <>
IANA IANA review state Version Changed - Review Needed
ANIMA WG                                                     M. Pritikin
Internet-Draft                                                     Cisco
Intended status: Standards Track                           M. Richardson
Expires: April 30, 2020                                        Sandelman
                                                               T. Eckert
                                                           Futurewei USA
                                                            M. Behringer

                                                               K. Watsen
                                                         Watsen Networks
                                                        October 28, 2019

        Bootstrapping Remote Secure Key Infrastructures (BRSKI)


   This document specifies automated bootstrapping of an Autonomic
   Control Plane.  To do this a Secure Key Infrastructure is
   bootstrapped.  This is done using manufacturer-installed X.509
   certificates, in combination with a manufacturer's authorizing
   service, both online and offline.  We call this process the
   Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol.
   Bootstrapping a new device can occur using a routable address and a
   cloud service, or using only link-local connectivity, or on limited/
   disconnected networks.  Support for deployment models with less
   stringent security requirements is included.  Bootstrapping is
   complete when the cryptographic identity of the new key
   infrastructure is successfully deployed to the device.  The
   established secure connection can be used to deploy a locally issued
   certificate to the device as well.

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

   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."

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   This Internet-Draft will expire on April 30, 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
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.  Prior Bootstrapping Approaches  . . . . . . . . . . . . .   6
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   7
     1.3.  Scope of solution . . . . . . . . . . . . . . . . . . . .  10
       1.3.1.  Support environment . . . . . . . . . . . . . . . . .  10
       1.3.2.  Constrained environments  . . . . . . . . . . . . . .  11
       1.3.3.  Network Access Controls . . . . . . . . . . . . . . .  12
       1.3.4.  Bootstrapping is not Booting  . . . . . . . . . . . .  12
     1.4.  Leveraging the new key infrastructure / next steps  . . .  12
     1.5.  Requirements for Autonomic Network Infrastructure (ANI)
           devices . . . . . . . . . . . . . . . . . . . . . . . . .  13
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .  13
     2.1.  Behavior of a Pledge  . . . . . . . . . . . . . . . . . .  15
     2.2.  Secure Imprinting using Vouchers  . . . . . . . . . . . .  16
     2.3.  Initial Device Identifier . . . . . . . . . . . . . . . .  17
       2.3.1.  Identification of the Pledge  . . . . . . . . . . . .  18
       2.3.2.  MASA URI extension  . . . . . . . . . . . . . . . . .  18
     2.4.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .  20
     2.5.  Architectural Components  . . . . . . . . . . . . . . . .  23
       2.5.1.  Pledge  . . . . . . . . . . . . . . . . . . . . . . .  23
       2.5.2.  Join Proxy  . . . . . . . . . . . . . . . . . . . . .  23
       2.5.3.  Domain Registrar  . . . . . . . . . . . . . . . . . .  23
       2.5.4.  Manufacturer Service  . . . . . . . . . . . . . . . .  23
       2.5.5.  Public Key Infrastructure (PKI) . . . . . . . . . . .  24
     2.6.  Certificate Time Validation . . . . . . . . . . . . . . .  24
       2.6.1.  Lack of realtime clock  . . . . . . . . . . . . . . .  24
       2.6.2.  Infinite Lifetime of IDevID . . . . . . . . . . . . .  24
     2.7.  Cloud Registrar . . . . . . . . . . . . . . . . . . . . .  25
     2.8.  Determining the MASA to contact . . . . . . . . . . . . .  25

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   3.  Voucher-Request artifact  . . . . . . . . . . . . . . . . . .  26
     3.1.  Nonceless Voucher Requests  . . . . . . . . . . . . . . .  27
     3.2.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .  27
     3.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  27
     3.4.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  29
   4.  Proxying details (Pledge - Proxy -
       Registrar)  . . . . . . . . . . . . . . . . . . . . . . . . .  32
     4.1.  Pledge discovery of Proxy . . . . . . . . . . . . . . . .  33
       4.1.1.  Proxy GRASP announcements . . . . . . . . . . . . . .  35
     4.2.  CoAP connection to Registrar  . . . . . . . . . . . . . .  36
     4.3.  Proxy discovery and communication of Registrar  . . . . .  36
   5.  Protocol Details (Pledge - Registrar - MASA)  . . . . . . . .  38
     5.1.  BRSKI-EST TLS establishment details . . . . . . . . . . .  39
     5.2.  Pledge Requests Voucher from the Registrar  . . . . . . .  40
     5.3.  Registrar Authorization of
           Pledge  . . . . . . . . . . . . . . . . . . . . . . . . .  42
     5.4.  BRSKI-MASA TLS establishment details  . . . . . . . . . .  43
       5.4.1.  MASA authentication of
               customer Registrar  . . . . . . . . . . . . . . . . .  43
     5.5.  Registrar Requests Voucher from MASA  . . . . . . . . . .  44
       5.5.1.  MASA renewal of expired vouchers  . . . . . . . . . .  46
       5.5.2.  MASA pinning of registrar . . . . . . . . . . . . . .  46
       5.5.3.  MASA checking of voucher request signature  . . . . .  46
       5.5.4.  MASA verification of domain registrar . . . . . . . .  47
       5.5.5.  MASA verification of pledge prior-signed-voucher-
               request . . . . . . . . . . . . . . . . . . . . . . .  48
       5.5.6.  MASA nonce handling . . . . . . . . . . . . . . . . .  48
     5.6.  MASA and Registrar Voucher Response . . . . . . . . . . .  48
       5.6.1.  Pledge voucher verification . . . . . . . . . . . . .  51
       5.6.2.  Pledge authentication of provisional TLS connection .  52
     5.7.  Pledge BRSKI Status Telemetry . . . . . . . . . . . . . .  53
     5.8.  Registrar audit-log request . . . . . . . . . . . . . . .  54
       5.8.1.  MASA audit log response . . . . . . . . . . . . . . .  55
       5.8.2.  Calculation of domainID . . . . . . . . . . . . . . .  58
       5.8.3.  Registrar audit log verification  . . . . . . . . . .  58
     5.9.  EST Integration for PKI bootstrapping . . . . . . . . . .  60
       5.9.1.  EST Distribution of CA Certificates . . . . . . . . .  60
       5.9.2.  EST CSR Attributes  . . . . . . . . . . . . . . . . .  60
       5.9.3.  EST Client Certificate Request  . . . . . . . . . . .  61
       5.9.4.  Enrollment Status Telemetry . . . . . . . . . . . . .  61
       5.9.5.  Multiple certificates . . . . . . . . . . . . . . . .  62
       5.9.6.  EST over CoAP . . . . . . . . . . . . . . . . . . . .  62
   6.  Clarification of transfer-encoding  . . . . . . . . . . . . .  63
   7.  Reduced security operational modes  . . . . . . . . . . . . .  63
     7.1.  Trust Model . . . . . . . . . . . . . . . . . . . . . . .  63
     7.2.  Pledge security reductions  . . . . . . . . . . . . . . .  64
     7.3.  Registrar security reductions . . . . . . . . . . . . . .  65
     7.4.  MASA security reductions  . . . . . . . . . . . . . . . .  66

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       7.4.1.  Issuing Nonceless vouchers  . . . . . . . . . . . . .  66
       7.4.2.  Trusting Owners on First Use  . . . . . . . . . . . .  67
       7.4.3.  Updating or extending voucher trust anchors . . . . .  67
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  69
     8.1.  The IETF XML Registry . . . . . . . . . . . . . . . . . .  69
     8.2.  Well-known EST registration . . . . . . . . . . . . . . .  69
     8.3.  PKIX Registry . . . . . . . . . . . . . . . . . . . . . .  69
     8.4.  Pledge BRSKI Status Telemetry . . . . . . . . . . . . . .  69
     8.5.  DNS Service Names . . . . . . . . . . . . . . . . . . . .  70
     8.6.  MUD File Extension for the MASA . . . . . . . . . . . . .  70
   9.  Applicability to the Autonomic Control Plane (ACP)  . . . . .  70
     9.1.  Operational Requirements  . . . . . . . . . . . . . . . .  71
       9.1.1.  MASA Operational Requirements . . . . . . . . . . . .  72
       9.1.2.  Domain Owner Operational Requirements . . . . . . . .  72
       9.1.3.  Device Operational Requirements . . . . . . . . . . .  73
   10. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  73
     10.1.  MASA audit log . . . . . . . . . . . . . . . . . . . . .  73
     10.2.  What BRSKI-EST reveals . . . . . . . . . . . . . . . . .  74
     10.3.  What BRSKI-MASA reveals to the manufacturer  . . . . . .  75
     10.4.  Manufacturers and Used or Stolen Equipment . . . . . . .  77
     10.5.  Manufacturers and Grey market equipment  . . . . . . . .  78
     10.6.  Some mitigations for meddling by manufacturers . . . . .  79
     10.7.  Death of a manufacturer  . . . . . . . . . . . . . . . .  80
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  80
     11.1.  Denial of Service (DoS) against MASA . . . . . . . . . .  81
     11.2.  Availability of good random numbers  . . . . . . . . . .  82
     11.3.  Freshness in Voucher-Requests  . . . . . . . . . . . . .  82
     11.4.  Trusting manufacturers . . . . . . . . . . . . . . . . .  83
     11.5.  Manufacturer Maintenance of trust anchors  . . . . . . .  84
       11.5.1.  Compromise of Manufacturer IDevID signing keys . . .  86
       11.5.2.  Compromise of MASA signing keys  . . . . . . . . . .  86
       11.5.3.  Compromise of MASA web service . . . . . . . . . . .  88
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  89
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  89
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  89
     13.2.  Informative References . . . . . . . . . . . . . . . . .  93
   Appendix A.  IPv4 and non-ANI operations  . . . . . . . . . . . .  96
     A.1.  IPv4 Link Local addresses . . . . . . . . . . . . . . . .  96
     A.2.  Use of DHCPv4 . . . . . . . . . . . . . . . . . . . . . .  96
   Appendix B.  mDNS / DNSSD proxy discovery options . . . . . . . .  97
   Appendix C.  MUD Extension  . . . . . . . . . . . . . . . . . . .  97
   Appendix D.  Example Vouchers . . . . . . . . . . . . . . . . . . 100
     D.1.  Keys involved . . . . . . . . . . . . . . . . . . . . . . 100
       D.1.1.  MASA key pair for voucher signatures  . . . . . . . . 100
       D.1.2.  Manufacturer key pair for IDevID signatures . . . . . 100
       D.1.3.  Registrar key pair  . . . . . . . . . . . . . . . . . 101
       D.1.4.  Pledge key pair . . . . . . . . . . . . . . . . . . . 103
     D.2.  Example process . . . . . . . . . . . . . . . . . . . . . 104

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       D.2.1.  Pledge to Registrar . . . . . . . . . . . . . . . . . 105
       D.2.2.  Registrar to MASA . . . . . . . . . . . . . . . . . . 108
       D.2.3.  MASA to Registrar . . . . . . . . . . . . . . . . . . 113
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 117

1.  Introduction

   The Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol
   provides a solution for secure zero-touch (automated) bootstrap of
   new (unconfigured) devices that are called pledges in this document.
   Pledges have an IDevID installed in them at the factory.

   "BRSKI" is pronounced like "brewski", a colloquial term for beer in
   Canada and parts of the US-midwest. [brewski]

   This document primarily provides for the needs of the ISP and
   Enterprise focused ANIMA Autonomic Control Plane (ACP)
   [I-D.ietf-anima-autonomic-control-plane].  This bootstrap process
   satisfies the [RFC7575] requirements of section 3.3 of making all
   operations secure by default.  Other users of the BRSKI protocol will
   need to provide separate applicability statements that include
   privacy and security considerations appropriate to that deployment.
   Section 9 explains the detailed applicability for this the ACP usage.

   The BRSKI protocol requires a significant amount of communication
   between manufacturer and owner: in its default modes it provides a
   cryptographic transfer of control to the initial owner.  In its
   strongest modes, it leverages sales channel information to identify
   the owner in advance.  Resale of devices is possible, provided that
   the manufacturer is willing to authorize the transfer.  Mechanisms to
   enable transfers of ownership without manufacturer authorization are
   not included in this version of the protocol, but could be designed
   into future versions.

   This document describes how pledges discover (or are discovered by)
   an element of the network domain to which the pledge belongs that
   will perform the bootstrap.  This element (device) is called the
   registrar.  Before any other operation, pledge and registrar need to
   establish mutual trust:

   1.  Registrar authenticating the pledge: "Who is this device?  What
       is its identity?"

   2.  Registrar authorizing the pledge: "Is it mine?  Do I want it?
       What are the chances it has been compromised?"

   3.  Pledge authenticating the registrar: "What is this registrar's

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   4.  Pledge authorizing the registrar: "Should I join this network?"

   This document details protocols and messages to answer the above
   questions.  It uses a TLS connection and an PKIX-shaped (X.509v3)
   certificate (an IEEE 802.1AR [IDevID] IDevID) of the pledge to answer
   points 1 and 2.  It uses a new artifact called a "voucher" that the
   registrar receives from a "Manufacturer Authorized Signing Authority"
   (MASA) and passes to the pledge to answer points 3 and 4.

   A proxy provides very limited connectivity between the pledge and the

   The syntactic details of vouchers are described in detail in
   [RFC8366].  This document details automated protocol mechanisms to
   obtain vouchers, including the definition of a 'voucher-request'
   message that is a minor extension to the voucher format (see
   Section 3) defined by [RFC8366].

   BRSKI results in the pledge storing an X.509 root certificate
   sufficient for verifying the registrar identity.  In the process a
   TLS connection is established that can be directly used for
   Enrollment over Secure Transport (EST).  In effect BRSKI provides an
   automated mechanism for the "Bootstrap Distribution of CA
   Certificates" described in [RFC7030] Section 4.1.1 wherein the pledge
   "MUST [...] engage a human user to authorize the CA certificate using
   out-of-band" information.  With BRSKI the pledge now can automate
   this process using the voucher.  Integration with a complete EST
   enrollment is optional but trivial.

   BRSKI is agile enough to support bootstrapping alternative key
   infrastructures, such as a symmetric key solutions, but no such
   system is described in this document.

1.1.  Prior Bootstrapping Approaches

   To literally "pull yourself up by the bootstraps" is an impossible
   action.  Similarly the secure establishment of a key infrastructure
   without external help is also an impossibility.  Today it is commonly
   accepted that the initial connections between nodes are insecure,
   until key distribution is complete, or that domain-specific keying
   material (often pre-shared keys, including mechanisms like SIM cards)
   is pre-provisioned on each new device in a costly and non-scalable
   manner.  Existing automated mechanisms are known as non-secured
   'Trust on First Use' (TOFU) [RFC7435], 'resurrecting duckling'
   [Stajano99theresurrecting] or 'pre-staging'.

   Another prior approach has been to try and minimize user actions
   during bootstrapping, but not eliminate all user-actions.  The

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   original EST protocol [RFC7030] does reduce user actions during
   bootstrap but does not provide solutions for how the following
   protocol steps can be made autonomic (not involving user actions):

   o  using the Implicit Trust Anchor [RFC7030] database to authenticate
      an owner specific service (not an autonomic solution because the
      URL must be securely distributed),

   o  engaging a human user to authorize the CA certificate using out-
      of-band data (not an autonomic solution because the human user is

   o  using a configured Explicit TA database (not an autonomic solution
      because the distribution of an explicit TA database is not

   o  and using a Certificate-Less TLS mutual authentication method (not
      an autonomic solution because the distribution of symmetric key
      material is not autonomic).

   These "touch" methods do not meet the requirements for zero-touch.

   There are "call home" technologies where the pledge first establishes
   a connection to a well known manufacturer service using a common
   client-server authentication model.  After mutual authentication,
   appropriate credentials to authenticate the target domain are
   transferred to the pledge.  This creates several problems and

   o  the pledge requires realtime connectivity to the manufacturer

   o  the domain identity is exposed to the manufacturer service (this
      is a privacy concern),

   o  the manufacturer is responsible for making the authorization
      decisions (this is a liability concern),

   BRSKI addresses these issues by defining extensions to the EST
   protocol for the automated distribution of vouchers.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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   The following terms are defined for clarity:

   ANI:  The Autonomic Network Infrastructure as defined by
      [I-D.ietf-anima-reference-model].  This document details specific
      requirements for pledges, proxies and registrars when they are
      part of an ANI.

   Circuit Proxy:  A stateful implementation of the join proxy.  This is
      the assumed type of proxy.

   drop-ship:  The physical distribution of equipment containing the
      "factory default" configuration to a final destination.  In zero-
      touch scenarios there is no staging or pre-configuration during

   Domain:  The set of entities that share a common local trust anchor.
      This includes the proxy, registrar, Domain Certificate Authority,
      Management components and any existing entity that is already a
      member of the domain.

   domainID:  The domain IDentity is a unique value based upon the
      Registrar CA's certificate.  Section 5.8.2 specifies how it is

   Domain CA:  The domain Certification Authority (CA) provides
      certification functionalities to the domain.  At a minimum it
      provides certification functionalities to a registrar and manages
      the private key that defines the domain.  Optionally, it certifies
      all elements.

   enrollment:  The process where a device presents key material to a
      network and acquires a network-specific identity.  For example
      when a certificate signing request is presented to a certification
      authority and a certificate is obtained in response.

   imprint:  The process where a device obtains the cryptographic key
      material to identify and trust future interactions with a network.
      This term is taken from Konrad Lorenz's work in biology with new
      ducklings: during a critical period, the duckling would assume
      that anything that looks like a mother duck is in fact their
      mother.  An equivalent for a device is to obtain the fingerprint
      of the network's root certification authority certificate.  A
      device that imprints on an attacker suffers a similar fate to a
      duckling that imprints on a hungry wolf.  Securely imprinting is a
      primary focus of this document [imprinting].  The analogy to
      Lorenz's work was first noted in [Stajano99theresurrecting].

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   IDevID:  An Initial Device Identity X.509 certificate installed by
      the vendor on new equipment.  This is a term from 802.1AR [IDevID]

   IPIP Proxy:  A stateless proxy alternative.

   Join Proxy:  A domain entity that helps the pledge join the domain.
      A join proxy facilitates communication for devices that find
      themselves in an environment where they are not provided
      connectivity until after they are validated as members of the
      domain.  For simplicity this document sometimes uses the term of
      'proxy' to indicate the join proxy.  The pledge is unaware that
      they are communicating with a proxy rather than directly with a

   Join Registrar (and Coordinator):  A representative of the domain
      that is configured, perhaps autonomically, to decide whether a new
      device is allowed to join the domain.  The administrator of the
      domain interfaces with a "join registrar (and coordinator)" to
      control this process.  Typically a join registrar is "inside" its
      domain.  For simplicity this document often refers to this as just
      "registrar".  Within [I-D.ietf-anima-reference-model] this is
      referred to as the "join registrar autonomic service agent".
      Other communities use the abbreviation "JRC".

   LDevID:  A Local Device Identity X.509 certificate installed by the
      owner of the equipment.  This is a term from 802.1AR [IDevID]

   manufacturer:  the term manufacturer is used throughout this document
      to be the entity that created the device.  This is typically the
      "original equipment manufacturer" or OEM, but in more complex
      situations it could be a "value added retailer" (VAR), or possibly
      even a systems integrator.  In general, it a goal of BRSKI to
      eliminate small distinctions between different sales channels.
      The reason for this is that it permits a single device, with a
      uniform firmware load, to be shipped directly to all customers.
      This eliminates costs for the manufacturer.  This also reduces the
      number of products supported in the field increasing the chance
      that firmware will be more up to date.

   MASA Audit-Log:  A list of previous owners maintained by the MASA on
      a per device (per pledge) basis.  Described in Section 5.8.1.

   MASA Service:  A third-party Manufacturer Authorized Signing
      Authority (MASA) service on the global Internet.  The MASA signs
      vouchers.  It also provides a repository for audit-log information
      of privacy protected bootstrapping events.  It does not track

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   nonced:  a voucher (or request) that contains a nonce (the normal

   nonceless:  a voucher (or request) that does not contain a nonce,
      relying upon accurate clocks for expiration, or which does not

   offline:  When an architectural component cannot perform realtime
      communications with a peer, either due to network connectivity or
      because the peer is turned off, the operation is said to be
      occurring offline.

   Ownership Tracker:  An Ownership Tracker service on the global
      Internet.  The Ownership Tracker uses business processes to
      accurately track ownership of all devices shipped against domains
      that have purchased them.  Although optional, this component
      allows vendors to provide additional value in cases where their
      sales and distribution channels allow for accurately tracking of
      such ownership.  Ownership tracking information is indicated in
      vouchers as described in [RFC8366]

   Pledge:  The prospective (unconfigured) device, which has an identity
      installed at the factory.

   (Public) Key Infrastructure:  The collection of systems and processes
      that sustain the activities of a public key system.  The registrar
      acts as an [RFC5280] and [RFC5272] (see section 7) "Registration

   TOFU:  Trust on First Use. Used similarly to [RFC7435].  This is
      where a pledge device makes no security decisions but rather
      simply trusts the first registrar it is contacted by.  This is
      also known as the "resurrecting duckling" model.

   Voucher:  A signed artifact from the MASA that indicates to a pledge
      the cryptographic identity of the registrar it should trust.
      There are different types of vouchers depending on how that trust
      is asserted.  Multiple voucher types are defined in [RFC8366]

1.3.  Scope of solution

1.3.1.  Support environment

   This solution (BRSKI) can support large router platforms with multi-
   gigabit inter-connections, mounted in controlled access data centers.
   But this solution is not exclusive to large equipment: it is intended
   to scale to thousands of devices located in hostile environments,
   such as ISP provided CPE devices which are drop-shipped to the end

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   user.  The situation where an order is fulfilled from distributed
   warehouse from a common stock and shipped directly to the target
   location at the request of a domain owner is explicitly supported.
   That stock ("SKU") could be provided to a number of potential domain
   owners, and the eventual domain owner will not know a-priori which
   device will go to which location.

   The bootstrapping process can take minutes to complete depending on
   the network infrastructure and device processing speed.  The network
   communication itself is not optimized for speed; for privacy reasons,
   the discovery process allows for the pledge to avoid announcing its
   presence through broadcasting.

   Nomadic or mobile devices often need to acquire credentials to access
   the network at the new location.  An example of this is mobile phone
   roaming among network operators, or even between cell towers.  This
   is usually called handoff.  BRSKI does not provide a low-latency
   handoff which is usually a requirement in such situations.  For these
   solutions BRSKI can be used to create a relationship (an LDevID) with
   the "home" domain owner.  The resulting credentials are then used to
   provide credentials more appropriate for a low-latency handoff.

1.3.2.  Constrained environments

   Questions have been posed as to whether this solution is suitable in
   general for Internet of Things (IoT) networks.  This depends on the
   capabilities of the devices in question.  The terminology of
   [RFC7228] is best used to describe the boundaries.

   The solution described in this document is aimed in general at non-
   constrained (i.e., class 2+ [RFC7228]) devices operating on a non-
   Challenged network.  The entire solution as described here is not
   intended to be useable as-is by constrained devices operating on
   challenged networks (such as 802.15.4 Low-power Lossy Networks

   Specifically, there are protocol aspects described here that might
   result in congestion collapse or energy-exhaustion of intermediate
   battery powered routers in an LLN.  Those types of networks should
   not use this solution.  These limitations are predominately related
   to the large credential and key sizes required for device
   authentication.  Defining symmetric key techniques that meet the
   operational requirements is out-of-scope but the underlying protocol
   operations (TLS handshake and signing structures) have sufficient
   algorithm agility to support such techniques when defined.

   The imprint protocol described here could, however, be used by non-
   energy constrained devices joining a non-constrained network (for

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   instance, smart light bulbs are usually mains powered, and speak
   802.11).  It could also be used by non-constrained devices across a
   non-energy constrained, but challenged network (such as 802.15.4).
   The certificate contents, and the process by which the four questions
   above are resolved do apply to constrained devices.  It is simply the
   actual on-the-wire imprint protocol that could be inappropriate.

1.3.3.  Network Access Controls

   This document presumes that network access control has either already
   occurred, is not required, or is integrated by the proxy and
   registrar in such a way that the device itself does not need to be
   aware of the details.  Although the use of an X.509 Initial Device
   Identity is consistent with IEEE 802.1AR [IDevID], and allows for
   alignment with 802.1X network access control methods, its use here is
   for pledge authentication rather than network access control.
   Integrating this protocol with network access control, perhaps as an
   Extensible Authentication Protocol (EAP) method (see [RFC3748]), is

1.3.4.  Bootstrapping is not Booting

   This document describes "bootstrapping" as the protocol used to
   obtain a local trust anchor.  It is expected that this trust anchor,
   along with any additional configuration information subsequently
   installed, is persisted on the device across system restarts
   ("booting").  Bootstrapping occurs only infrequently such as when a
   device is transferred to a new owner or has been reset to factory
   default settings.

1.4.  Leveraging the new key infrastructure / next steps

   As a result of the protocol described herein, the bootstrapped
   devices have the Domain CA trust anchor in common.  An end entity
   certificate has optionally been issued from the Domain CA.  This
   makes it possible to securely deploy functionalities across the
   domain, e.g:

   o  Device management.

   o  Routing authentication.

   o  Service discovery.

   The major intended benefit is that it possible to use the credentials
   deployed by this protocol to secure the Autonomic Control Plane (ACP)

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1.5.  Requirements for Autonomic Network Infrastructure (ANI) devices

   The BRSKI protocol can be used in a number of environments.  Some of
   the options in this document are the result of requirements that are
   out of the ANI scope.  This section defines the base requirements for
   ANI devices.

   For devices that intend to become part of an Autonomic Network
   Infrastructure (ANI) ([I-D.ietf-anima-reference-model]) that includes
   an Autonomic Control Plane
   ([I-D.ietf-anima-autonomic-control-plane]), the BRSKI protocol MUST
   be implemented.

   The pledge must perform discovery of the proxy as described in
   Section 4.1 using Generic Autonomic Signaling Protocol (GRASP)'s DULL
   [I-D.ietf-anima-grasp] M_FLOOD announcements.

   Upon successfully validating a voucher artifact, a status telemetry
   MUST be returned.  See Section 5.7.

   An ANIMA ANI pledge MUST implement the EST automation extensions
   described in Section 5.9.  They supplement the [RFC7030] EST to
   better support automated devices that do not have an end user.

   The ANI Join Registrar Autonomic Service Agent (ASA) MUST support all
   the BRSKI and above listed EST operations.

   All ANI devices SHOULD support the BRSKI proxy function, using
   circuit proxies over the ACP.  (See Section 4.3)

2.  Architectural Overview

   The logical elements of the bootstrapping framework are described in
   this section.  Figure 1 provides a simplified overview of the

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

                      Figure 1: Architecture Overview

   We assume a multi-vendor network.  In such an environment there could
   be a Manufacturer Service for each manufacturer that supports devices
   following this document's specification, or an integrator could
   provide a generic service authorized by multiple manufacturers.  It
   is unlikely that an integrator could provide Ownership Tracking
   services for multiple manufacturers due to the required sales channel
   integrations necessary to track ownership.

   The domain is the managed network infrastructure with a Key
   Infrastructure the pledge is joining.  The domain provides initial
   device connectivity sufficient for bootstrapping through a proxy.
   The domain registrar authenticates the pledge, makes authorization
   decisions, and distributes vouchers obtained from the Manufacturer
   Service.  Optionally the registrar also acts as a PKI Certification

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2.1.  Behavior of a Pledge

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

                 /  Factory   \
                 \  default   /
                | (1) Discover |
   +------------>              |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (2) Identify |
   ^------------+              |
   | rejected   +------+-------+
   |                   |
   |            +------v-------+
   |            | (3) Request  |
   |            |     Join     |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (4) Imprint  |
   ^------------+              |
   | Bad MASA   +------+-------+
   | response          |  send Voucher Status Telemetry
   |            +------v-------+
   |            | (5) Enroll   |<---+ (non-error HTTP codes  )
   ^------------+              |\___/ (e.g. 202 'Retry-After')
   | Enroll     +------+-------+
   | Failure           |
   |              -----v------
   |             /  Enrolled  \
   ^------------+             |
    Factory      \------------/

                      Figure 2: Pledge State Diagram

   State descriptions for the pledge are as follows:

   1.  Discover a communication channel to a registrar.

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   2.  Identify itself.  This is done by presenting an X.509 IDevID
       credential to the discovered registrar (via the proxy) in a TLS
       handshake.  (The registrar credentials are only provisionally
       accepted at this time).

   3.  Request to join the discovered registrar.  A unique nonce is
       included ensuring that any responses can be associated with this
       particular bootstrapping attempt.

   4.  Imprint on the registrar.  This requires verification of the
       manufacturer-service-provided voucher.  A voucher contains
       sufficient information for the pledge to complete authentication
       of a registrar.  This document details this step in depth.

   5.  Enroll.  After imprint an authenticated TLS (HTTPS) connection
       exists between pledge and registrar.  Enrollment over Secure
       Transport (EST) [RFC7030] can then be used to obtain a domain
       certificate from a registrar.

   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.

   This specification details integration with EST enrollment so that
   pledges can optionally obtain a locally issued certificate, although
   any Representational State Transfer (REST) (see [REST]) interface
   could be integrated in future work.

2.2.  Secure Imprinting using Vouchers

   A voucher is a cryptographically protected artifact (using a digital
   signature) to the pledge device authorizing a zero-touch imprint on
   the registrar domain.

   The format and cryptographic mechanism of vouchers is described in
   detail in [RFC8366].

   Vouchers provide a flexible mechanism to secure imprinting: the
   pledge device only imprints when a voucher can be validated.  At the
   lowest security levels the MASA can indiscriminately issue vouchers
   and log claims of ownership by domains.  At the highest security
   levels issuance of vouchers can be integrated with complex sales
   channel integrations that are beyond the scope of this document.  The
   sales channel integration would verify actual (legal) ownership of
   the pledge by the domain.  This provides the flexibility for a number
   of use cases via a single common protocol mechanism on the pledge and
   registrar devices that are to be widely deployed in the field.  The
   MASA services have the flexibility to leverage either the currently

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   defined claim mechanisms or to experiment with higher or lower
   security levels.

   Vouchers provide a signed but non-encrypted communication channel
   among the pledge, the MASA, and the registrar.  The registrar
   maintains control over the transport and policy decisions, allowing
   the local security policy of the domain network to be enforced.

2.3.  Initial Device Identifier

   Pledge authentication and pledge voucher-request signing is via a
   PKIX-shaped certificate installed during the manufacturing process.
   This is the 802.1AR Initial Device Identifier (IDevID), and it
   provides a basis for authenticating the pledge during the protocol
   exchanges described here.  There is no requirement for a common root
   PKI hierarchy.  Each device manufacturer can generate its own root
   certificate.  Specifically, the IDevID enables:

   1.  Uniquely identifying the pledge by the Distinguished Name (DN)
       and subjectAltName (SAN) parameters in the IDevID.  The unique
       identification of a pledge in the voucher objects are derived
       from those parameters as described below.  Section 10.3 discusses
       privacy implications of the identifier.

   2.  Provides a cryptographic authentication of the pledge to the
       Registrar (see Section 5.3).

   3.  Secure auto-discovery of the pledge's MASA by the registrar (see
       Section 2.8).

   4.  Signing of voucher-request by the pledge's IDevID (see
       Section 3).

   5.  Provides a cryptographic authentication of the pledge to the MASA
       (see Section 5.5.5).

   Section 7.2.13 (2009 edition) and section 8.10.3 (2018 edition) of
   [IDevID] discusses keyUsage and extendedKeyUsage extensions in the
   IDevID certificate.  [IDevID] acknowledges that adding restrictions
   in the certificate limits applicability of these long-lived
   certificates.  This specification emphasizes this point, and
   therefore RECOMMENDS that no key usage restrictions be included.
   This is consistent with [RFC5280] section, which does not
   require key usage restrictions for end entity certificates.

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2.3.1.  Identification of the Pledge

   In the context of BRSKI, pledges have a 1:1 relationship with a
   "serial-number".  This serial-number is used both in the "serial-
   number" field of voucher or voucher-requests (see Section 3) and in
   local policies on registrar or MASA (see Section 5).

   The serialNumber fields is defined in [RFC5280].  That specification
   allows for the field to be omitted if there is a good technical
   reason.  IDevID certificates for use with this protocol are REQUIRED
   to include the "serialNumber" attribute with the device's unique
   serial number (from [IDevID] section 7.2.8, and [RFC5280] section's list of standard attributes).

   The serialNumber field is used as follows by the pledge to build the
   "serial-number" that is placed in the voucher-request.  In order to
   build it, the fields need to be converted into a serial-number of
   "type string".

   An example of a printable form of the "serialNumber" field is
   provided in [RFC4519] section 2.31 ("WI-3005").  That section further
   provides equality and syntax attributes.

   Due to the reality of existing device identity provisioning
   processes, some manufacturers have stored serial-numbers in other
   fields.  Registrar's SHOULD be configurable, on a per-manufacturer
   basis, to look for serial-number equivalents in other fields.

   As explained in Section 5.5 the Registrar MUST extract the serial-
   number again itself from the pledge's TLS certificate.  It can
   consult the serial-number in the pledge-request if there are any
   possible confusion about the source of the serial-number.

2.3.2.  MASA URI extension

   This document defines a new PKIX non-critical certificate extension
   to carry the MASA URI.  This extension is intended to be used in the
   IDevID certificate.  The URI is represented as described in
   Section 7.4 of [RFC5280].

   The URI provides the authority information.  The BRSKI "/.well-known"
   tree ([RFC5785]) is described in Section 5.

   A complete URI MAY be in this extension, including the 'scheme',
   'authority', and 'path', The complete URI will typically be used in
   diagnostic or experimental situations.  Typically, (and in
   consideration to constrained systems), this SHOULD be reduced to only

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   the 'authority', in which case a scheme of "https://" ([RFC7230]
   section 2.7.3) and 'path' of "/.well-known/est" is to be assumed.

   The registrar can assume that only the 'authority' is present in the
   extension, if there are no slash ("/") characters in the extension.

   Section 7.4 of [RFC5280] calls out various schemes that MUST be
   supported, including LDAP, HTTP and FTP.  However, the registrar MUST
   use HTTPS for the BRSKI-MASA connection.

   The new extension is identified as follows:


   MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
   internet(1) security(5) mechanisms(5) pkix(7)
   id-mod(0) id-mod-MASAURLExtn2016(TBD) }


   -- EXPORTS ALL --

   FROM PKIX-CommonTypes-2009
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0)
       id-mod-pkixCommon-02(57) }

   id-pe FROM PKIX1Explicit-2009
     { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-mod(0)
        id-mod-pkix1-explicit-02(51) } ;

   MASACertExtensions EXTENSION ::= { ext-MASAURL, ... }
   IDENTIFIED BY id-pe-masa-url }

   id-pe-masa-url OBJECT IDENTIFIER ::= { id-pe TBD }

   MASAURLSyntax ::= IA5String



                      Figure 3: MASAURL ASN.1 Module

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   The choice of id-pe is based on guidance found in Section 4.2.2 of
   [RFC5280], "These extensions may be used to direct applications to
   on-line information about the issuer or the subject".  The MASA URL
   is precisely that: online information about the particular subject.

2.4.  Protocol Flow

   A representative flow is shown in Figure 4

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   +--------+         +---------+    +------------+     +------------+
   | Pledge |         | Circuit |    | Domain     |     | Vendor     |
   |        |         | Join    |    | Registrar  |     | Service    |
   |        |         | Proxy   |    |  (JRC)     |     | (MASA)     |
   +--------+         +---------+    +------------+     +------------+
     |                     |                   |           Internet |
   [discover]              |                   |                    |
     |<-RFC4862 IPv6 addr  |                   |                    |
     |<-RFC3927 IPv4 addr  | Appendix A        |  Legend            |
     |-++++++++++++++++++->|                   |  C - circuit       |
     | optional: mDNS query| Appendix B        |      join proxy    |
     | RFC6763/RFC6762 (+) |                   |  P - provisional   |
     |<-++++++++++++++++++-|                   |    TLS connection  |
     | GRASP M_FLOOD       |                   |                    |
     |   periodic broadcast|                   |                    |
   [identity]              |                   |                    |
     |<------------------->C<----------------->|                    |
     |         TLS via the Join Proxy          |                    |
     |<--Registrar TLS server authentication---|                    |
   [PROVISIONAL accept of server cert]         |                    |
     P---X.509 client authentication---------->|                    |
   [request join]                              |                    |
     P---Voucher Request(w/nonce for voucher)->|                    |
     P                  /-------------------   |                    |
     P                  |                 [accept device?]          |
     P                  |                 [contact Vendor]          |
     P                  |                      |--Pledge ID-------->|
     P                  |                      |--Domain ID-------->|
     P                  |                      |--optional:nonce--->|
     P              optional:                  |     [extract DomainID]
     P        can occur in advance             |     [update audit log]
     P            if nonceleess                |                    |
     P                  |                      |<- voucher ---------|
     P                  \-------------------   | w/nonce if provided|
     P<------voucher---------------------------|                    |
   [imprint]                                   |                    |
     |-------voucher status telemetry--------->|                    |
     |                                         |<-device audit log--|
     |                             [verify audit log and voucher]   |
     |<--------------------------------------->|                    |
   [enroll]                                    |                    |
     | Continue with RFC7030 enrollment        |                    |
     | using now bidirectionally authenticated |                    |
     | TLS session.                            |                    |
   [enrolled]                                  |                    |

                 Figure 4: Protocol Time Sequence Diagram

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   On initial bootstrap, a new device (the pledge) uses a local service
   autodiscovery (GRASP or mDNS) to locate a join proxy.  The join proxy
   connects the pledge to a local registrar (the JRC).

   Having found a candidate registrar, the fledgling pledge sends some
   information about itself to the registrar, including its serial
   number in the form of a voucher request and its device identity
   certificate (IDevID) as part of the TLS session.

   The registrar can determine whether it expected such a device to
   appear, and locates a MASA.  The location of the MASA is usually
   found in an extension in the IDevID.  Having determined that the MASA
   is suitable, the entire information from the initial voucher request
   (including device serial number) is transmitted over the internet in
   a TLS protected channel to the manufacturer, along with information
   about the registrar/owner.

   The manufacturer can then apply policy based on the provided
   information, as well as other sources of information (such as sales
   records), to decide whether to approve the claim by the registrar to
   own the device; if the claim is accepted, a voucher is issued that
   directs the device to accept its new owner.

   The voucher is returned to the registrar, but not immediately to the
   device -- the registrar has an opportunity to examine the voucher,
   the MASA's audit-logs, and other sources of information to determine
   whether the device has been tampered with, and whether the bootstrap
   should be accepted.

   No filtering of information is possible in the signed voucher, so
   this is a binary yes-or-no decision.  If the registrar accepts the
   voucher as a proper one for its device, the voucher is returned to
   the pledge for imprinting.

   The voucher also includes a trust anchor that the pledge uses as
   representing the owner.  This is used to successfully bootstrap from
   an environment where only the manufacturer has built-in trust by the
   device into an environment where the owner now has a PKI footprint on
   the device.

   When BRSKI is followed with EST this single footprint is further
   leveraged into the full owner's PKI and a LDevID for the device.
   Subsequent reporting steps provide flows of information to indicate
   success/failure of the process.

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2.5.  Architectural Components

2.5.1.  Pledge

   The pledge is the device that is attempting to join.  The pledge can
   talk to the Join Proxy using link-local network connectivity.  In
   most cases, the pledge has no other connectivity until the pledge
   completes the enrollment process and receives some kind of network

2.5.2.  Join Proxy

   The join proxy provides HTTPS connectivity between the pledge and the
   registrar.  A circuit proxy mechanism is described in Section 4.
   Additional mechanisms, including a CoAP mechanism and a stateless
   IPIP mechanism are the subject of future work.

2.5.3.  Domain Registrar

   The domain's registrar operates as the BRSKI-MASA client when
   requesting vouchers from the MASA (see Section 5.4).  The registrar
   operates as the BRSKI-EST server when pledges request vouchers (see
   Section 5.1).  The registrar operates as the BRSKI-EST server
   "Registration Authority" if the pledge requests an end entity
   certificate over the BRSKI-EST connection (see Section 5.9).

   The registrar uses an Implicit Trust Anchor database for
   authenticating the BRSKI-MASA connection's MASA TLS Server
   Certificate.  Configuration or distribution of trust anchors is out-
   of-scope for this specification.

   The registrar uses a different Implicit Trust Anchor database for
   authenticating the BRSKI-EST connection's Pledge TLS Client
   Certificate.  Configuration or distribution of the BRSKI-EST client
   trust anchors is out-of-scope of this specification.  Note that the
   trust anchors in/excluded from the database will affect which
   manufacturers' devices are acceptable to the registrar as pledges,
   and can also be used to limit the set of MASAs that are trusted for

2.5.4.  Manufacturer Service

   The Manufacturer Service provides two logically separate functions:
   the Manufacturer Authorized Signing Authority (MASA) described in
   Section 5.5 and Section 5.6, and an ownership tracking/auditing
   function described in Section 5.7 and Section 5.8.

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2.5.5.  Public Key Infrastructure (PKI)

   The Public Key Infrastructure (PKI) administers certificates for the
   domain of concern, providing the trust anchor(s) for it and allowing
   enrollment of pledges with domain certificates.

   The voucher provides a method for the distribution of a single PKI
   trust anchor (as the "pinned-domain-cert").  A distribution of the
   full set of current trust anchors is possible using the optional EST

   The domain's registrar acts as an [RFC5272] Registration Authority,
   requesting certificates for pledges from the Key Infrastructure.

   The expectations of the PKI are unchanged from EST [RFC7030].  This
   document does not place any additional architectural requirements on
   the Public Key Infrastructure.

2.6.  Certificate Time Validation

2.6.1.  Lack of realtime clock

   Many devices when bootstrapping do not have knowledge of the current
   time.  Mechanisms such as Network Time Protocols cannot be secured
   until bootstrapping is complete.  Therefore bootstrapping is defined
   with a framework that does not require knowledge of the current time.
   A pledge MAY ignore all time stamps in the voucher and in the
   certificate validity periods if it does not know the current time.

   The pledge is exposed to dates in the following five places:
   registrar certificate notBefore, registrar certificate notAfter,
   voucher created-on, and voucher expires-on.  Additionally, CMS
   signatures contain a signingTime.

   A pledge with a real time clock in which it has confidence in, MUST
   check the above time fields in all certificates and signatures that
   ir processes.

   If the voucher contains a nonce then the pledge MUST confirm the
   nonce matches the original pledge voucher-request.  This ensures the
   voucher is fresh.  See Section 5.2.

2.6.2.  Infinite Lifetime of IDevID

   [RFC5280] explains that long lived pledge certificates "SHOULD be
   assigned the GeneralizedTime value of 99991231235959Z" for the
   notAfter field.

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   Some deployed IDevID management systems are not compliant with the
   802.1AR requirement for infinite lifetimes, and put in typical <= 3
   year certificate lifetimes.  Registrars SHOULD be configurable on a
   per-manufacturer basis to ignore pledge lifetimes when they did not
   follow the RFC5280 recommendations.

2.7.  Cloud Registrar

   There exist operationally open networks wherein devices gain
   unauthenticated access to the Internet at large.  In these use cases
   the management domain for the device needs to be discovered within
   the larger Internet.  The case where a device can boot and get access
   to larger Internet are less likely within the ANIMA ACP scope but may
   be more important in the future.  In the ANIMA ACP scope, new devices
   will be quarantined behind a Join Proxy.

   There are additionally some greenfield situations involving an
   entirely new installation where a device may have some kind of
   management uplink that it can use (such as via 3G network for
   instance).  In such a future situation, the device might use this
   management interface to learn that it should configure itself to
   become the local registrar.

   In order to support these scenarios, the pledge MAY contact a well
   known URI of a cloud registrar if a local registrar cannot be
   discovered or if the pledge's target use cases do not include a local

   If the pledge uses a well known URI for contacting a cloud registrar
   a manufacturer-assigned Implicit Trust Anchor database (see
   [RFC7030]) MUST be used to authenticate that service as described in
   [RFC6125].  The use of a DNS-ID for validation is appropriate, and it
   may include wildcard components on the left-mode side.  This is
   consistent with the human user configuration of an EST server URI in
   [RFC7030] which also depends on RFC6125.

2.8.  Determining the MASA to contact

   The registrar needs to be able to contact a MASA that is trusted by
   the pledge in order to obtain vouchers.  There are three mechanisms

   The device's Initial Device Identifier (IDevID) will normally contain
   the MASA URL as detailed in Section 2.3.  This is the RECOMMENDED

   If the registrar is integrated with [RFC8520] and the pledge IDevID
   contains the id-pe-mud-url then the registrar MAY attempt to obtain

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   the MASA URL from the MUD file.  The MUD file extension for the MASA
   URL is defined in Appendix C.

   It can be operationally difficult to ensure the necessary X.509
   extensions are in the pledge's IDevID due to the difficulty of
   aligning current pledge manufacturing with software releases and
   development.  As a final fallback the registrar MAY be manually
   configured or distributed with a MASA URL for each manufacturer.
   Note that the registrar can only select the configured MASA URL based
   on the trust anchor -- so manufacturers can only leverage this
   approach if they ensure a single MASA URL works for all pledges
   associated with each trust anchor.

3.  Voucher-Request artifact

   Voucher-requests are how vouchers are requested.  The semantics of
   the voucher-request are described below, in the YANG model.

   A pledge forms the "pledge voucher-request", signs it with it's
   IDevID and submits it to the registrar.

   The registrar in turn forms the "registrar voucher-request", signs it
   with it's Registrar keypair and submits it to the MASA.

   The "proximity-registrar-cert" leaf is used in the pledge voucher-
   requests.  This provides a method for the pledge to assert the
   registrar's proximity.

   This network proximity results from the following properties in the
   ACP context: the pledge is connected to the Join Proxy (Section 4)
   using a Link-Local IPv6 connection.  While the Join Proxy does not
   participate in any meaningful sense in the cryptography of the TLS
   connection (such as via a Channel Binding), the Registrar can observe
   that the connection is via the private ACP (ULA) address of the join
   proxy, and could not come from outside the ACP.  The Pledge must
   therefore be at most one IPv6 Link-Local hop away from an existing
   node on the ACP.

   Other users of BRSKI will need to define other kinds of assertions if
   the network proximity described above does not match their needs.

   The "prior-signed-voucher-request" leaf is used in registrar voucher-
   requests.  If present, it is the signed pledge voucher-request
   artifact.  This provides a method for the registrar to forward the
   pledge's signed request to the MASA.  This completes transmission of
   the signed "proximity-registrar-cert" leaf.

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   Unless otherwise signaled (outside the voucher-request artifact), the
   signing structure is as defined for vouchers, see [RFC8366].

3.1.  Nonceless Voucher Requests

   A registrar MAY also retrieve nonceless vouchers by sending nonceless
   voucher-requests to the MASA in order to obtain vouchers for use when
   the registrar does not have connectivity to the MASA.  No "prior-
   signed-voucher-request" leaf would be included.  The registrar will
   also need to know the serial number of the pledge.  This document
   does not provide a mechanism for the registrar to learn that in an
   automated fashion.  Typically this will be done via scanning of bar-
   code or QR-code on packaging, or via some sales channel integration.

3.2.  Tree Diagram

   The following tree diagram illustrates a high-level view of a
   voucher-request document.  The voucher-request builds upon the
   voucher artifact described in [RFC8366].  The tree diagram is
   described in [RFC8340].  Each node in the diagram is fully described
   by the YANG module in Section 3.4.  Please review the YANG module for
   a detailed description of the voucher-request format.

   module: ietf-voucher-request

     grouping voucher-request-grouping
       +---- voucher
          +---- created-on?                      yang:date-and-time
          +---- expires-on?                      yang:date-and-time
          +---- assertion?                       enumeration
          +---- serial-number                    string
          +---- idevid-issuer?                   binary
          +---- pinned-domain-cert?              binary
          +---- domain-cert-revocation-checks?   boolean
          +---- nonce?                           binary
          +---- last-renewal-date?               yang:date-and-time
          +---- prior-signed-voucher-request?    binary
          +---- proximity-registrar-cert?        binary

              Figure 5: YANG Tree diagram for Voucher-Request

3.3.  Examples

   This section provides voucher-request examples for illustration
   purposes.  These examples show the JSON prior to CMS wrapping.  JSON
   encoding rules specify that any binary content by base64 encoded
   ([RFC4648]).  The contents of the certificate have been elided to

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   save space.  For detailed examples, see Appendix D.2.  These examples
   conform to the encoding rules defined in [RFC7951].

   Example (1)  The following example illustrates a pledge voucher-
                request.  The assertion leaf is indicated as 'proximity'
                and the registrar's TLS server certificate is included
                in the 'proximity-registrar-cert' leaf.  See
                Section 5.2.

       "ietf-voucher-request:voucher": {
           "assertion": "proximity",
           "nonce": "62a2e7693d82fcda2624de58fb6722e5",
           "serial-number" : "JADA123456789",
           "created-on": "2017-01-01T00:00:00.000Z",
           "proximity-registrar-cert": "base64encodedvalue=="

         Figure 6: JSON representation of example Voucher-Request

   Example (2)  The following example illustrates a registrar voucher-
                request.  The 'prior-signed-voucher-request' leaf is
                populated with the pledge's voucher-request (such as the
                prior example).  The pledge's voucher-request is a
                binary CMS signed object.  In the JSON encoding used
                here it must be base64 encoded.  The nonce and assertion
                have been carried forward from the pledge request to the
                registrar request.  The serial-number is extracted from
                the pledge's Client Certificate from the TLS connection.
                See Section 5.5.

       "ietf-voucher-request:voucher": {
           "assertion" : "proximity",
           "nonce": "62a2e7693d82fcda2624de58fb6722e5",
           "created-on": "2017-01-01T00:00:02.000Z",
           "idevid-issuer": "base64encodedvalue==",
           "serial-number": "JADA123456789",
           "prior-signed-voucher-request": "base64encodedvalue=="

   Figure 7: JSON representation of example Prior-Signed Voucher-Request

   Example (3)  The following example illustrates a registrar voucher-
                request.  The 'prior-signed-voucher-request' leaf is not
                populated with the pledge's voucher-request nor is the

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                nonce leaf.  This form might be used by a registrar
                requesting a voucher when the pledge can not communicate
                with the registrar (such as when it is powered down, or
                still in packaging), and therefore could not submit a
                nonce.  This scenario is most useful when the registrar
                is aware that it will not be able to reach the MASA
                during deployment.  See Section 5.5.

       "ietf-voucher-request:voucher": {
           "created-on":    "2017-01-01T00:00:02.000Z",
           "idevid-issuer": "base64encodedvalue==",
           "serial-number": "JADA123456789"

         Figure 8: JSON representation of Offline Voucher-Request

3.4.  YANG Module

   Following is a YANG [RFC7950] module formally extending the [RFC8366]
   voucher into a voucher-request.

<CODE BEGINS> file "ietf-voucher-request@2018-02-14.yang"
module ietf-voucher-request {
  yang-version 1.1;

  prefix "vcr";

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

    reference "RFC 8366: Voucher Profile for Bootstrapping Protocols";

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   "IETF ANIMA Working Group";

   "WG Web:   <>
    WG List:  <>
    Author:   Kent Watsen
    Author:   Michael H. Behringer
    Author:   Toerless Eckert
    Author:   Max Pritikin
    Author:   Michael Richardson

   "This module defines the format for a voucher request.
    It is a superset of the voucher itself.
    It provides content to the MASA for consideration
    during a voucher request.

    The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
    'MAY', and 'OPTIONAL' in this document are to be interpreted as
    described in BCP 14 RFC2119 RFC8174 when, and only when, they
    appear in all capitals, as shown here.

    Copyright (c) 2019 IETF Trust and the persons identified as
    authors of the code. All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, is permitted pursuant to, and subject to the license
    terms contained in, the Simplified BSD License set forth in Section
    4.c of the IETF Trust's Legal Provisions Relating to IETF Documents

    This version of this YANG module is part of RFC XXXX; see the RFC
    itself for full legal notices.";

  revision "2018-02-14" {
     "Initial version";
     "RFC XXXX: Voucher Profile for Bootstrapping Protocols";

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  // Top-level statement
  rc:yang-data voucher-request-artifact {
    uses voucher-request-grouping;

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

    uses vch:voucher-artifact-grouping {
      refine "voucher/created-on" {
        mandatory false;

      refine "voucher/pinned-domain-cert" {
        mandatory false;

      refine "voucher/domain-cert-revocation-checks" {
        description "The domain-cert-revocation-checks field
                     is not valid in a voucher request, and
                     any occurence MUST be ignored";

      refine "voucher/assertion" {
        mandatory false;
        description "Any assertion included in registrar voucher
              requests SHOULD be ignored by the MASA.";

      augment "voucher"  {
          "Adds leaf nodes appropriate for requesting vouchers.";

        leaf prior-signed-voucher-request {
          type binary;
            "If it is necessary to change a voucher, or re-sign and
             forward a voucher that was previously provided along a
             protocol path, then the previously signed voucher SHOULD be
             included in this field.

             For example, a pledge might sign a voucher request
             with a proximity-registrar-cert, and the registrar
             then includes it as the prior-signed-voucher-request field.
             This is a simple mechanism for a chain of trusted
             parties to change a voucher request, while

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             maintaining the prior signature information.

             The Registrar and MASA MAY examine the prior signed
             voucher information for the
             purposes of policy decisions. For example this information
             could be useful to a MASA to determine that both pledge and
             registrar agree on proximity assertions. The MASA SHOULD
             remove all prior-signed-voucher-request information when
             signing a voucher for imprinting so as to minimize the
             final voucher size.";

        leaf proximity-registrar-cert {
          type binary;
            "An X.509 v3 certificate structure as specified by RFC 5280,
             Section 4 encoded using the ASN.1 distinguished encoding
             rules (DER), as specified in ITU-T X.690.

             The first certificate in the Registrar TLS server
             certificate_list sequence  (the end-entity TLS certificate,
             see [RFC8446]) presented by the Registrar to the Pledge.
             This MUST be populated in a Pledge's voucher request when a
             proximity assertion is requested.";



                 Figure 9: YANG module for Voucher-Request

4.  Proxying details (Pledge - Proxy - Registrar)

   This section is normative for uses with an ANIMA ACP.  The use of
   GRASP mechanism is part of the ACP.  Other users of BRSKI will need
   to define an equivalent proxy mechanism, and an equivalent mechanism
   to configure the proxy.

   The role of the proxy is to facilitate communications.  The proxy
   forwards packets between the pledge and a registrar that has been
   provisioned to the proxy via full GRASP ACP discovery.

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   This section defines a stateful proxy mechanism which is referred to
   as a "circuit" proxy.  This is a form of Application Level Gateway
   ([RFC2663] section 2.9).

   The proxy does not terminate the TLS handshake: it passes streams of
   bytes onward without examination.  A proxy MUST NOT assume any
   specific TLS version.  Please see [RFC8446] section 9.3 for details
   on TLS invariants.

   A Registrar can directly provide the proxy announcements described
   below, in which case the announced port can point directly to the
   Registrar itself.  In this scenario the pledge is unaware that there
   is no proxying occurring.  This is useful for Registrars which are
   servicing pledges on directly connected networks.

   As a result of the proxy Discovery process in Section 4.1.1, the port
   number exposed by the proxy does not need to be well known, or
   require an IANA allocation.

   During the discovery of the Registrar by the Join Proxy, the Join
   Proxy will also learn which kinds of proxy mechanisms are available.
   This will allow the Join Proxy to use the lowest impact mechanism
   which the Join Proxy and Registrar have in common.

   In order to permit the proxy functionality to be implemented on the
   maximum variety of devices the chosen mechanism should use the
   minimum amount of state on the proxy device.  While many devices in
   the ANIMA target space will be rather large routers, the proxy
   function is likely to be implemented in the control plane CPU of such
   a device, with available capabilities for the proxy function similar
   to many class 2 IoT devices.

   The document [I-D.richardson-anima-state-for-joinrouter] provides a
   more extensive analysis and background of the alternative proxy

4.1.  Pledge discovery of Proxy

   The result of discovery is a logical communication with a registrar,
   through a proxy.  The proxy is transparent to the pledge.  The
   communication between the pledge and Join Proxy is over IPv6 Link-
   Local addresses.

   To discover the proxy the pledge performs the following actions:

   1.  MUST: Obtains a local address using IPv6 methods as described in
       [RFC4862] IPv6 Stateless Address AutoConfiguration.  Use of
       [RFC4941] temporary addresses is encouraged.  To limit pervasive

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       monitoring ( [RFC7258]), a new temporary address MAY use a short
       lifetime (that is, set TEMP_PREFERRED_LIFETIME to be short).
       Pledges will generally prefer use of IPv6 Link-Local addresses,
       and discovery of proxy will be by Link-Local mechanisms.  IPv4
       methods are described in Appendix A

   2.  MUST: Listen for GRASP M_FLOOD ([I-D.ietf-anima-grasp])
       announcements of the objective: "AN_Proxy".  See section
       Section 4.1.1 for the details of the objective.  The pledge MAY
       listen concurrently for other sources of information, see
       Appendix B.

   Once a proxy is discovered the pledge communicates with a registrar
   through the proxy using the bootstrapping protocol defined in
   Section 5.

   While the GRASP M_FLOOD mechanism is passive for the pledge, the non-
   normative other methods (mDNS, and IPv4 methods) described Appendix B
   are active.  The pledge SHOULD run those methods in parallel with
   listening to for the M_FLOOD.  The active methods SHOULD back-off by
   doubling to a maximum of one hour to avoid overloading the network
   with discovery attempts.  Detection of change of physical link status
   (Ethernet carrier for instance) SHOULD reset the back off timers.

   The pledge could discover more than one proxy on a given physical
   interface.  The pledge can have a multitude of physical interfaces as
   well: a layer-2/3 Ethernet switch may have hundreds of physical

   Each possible proxy offer SHOULD be attempted up to the point where a
   valid voucher is received: while there are many ways in which the
   attempt may fail, it does not succeed until the voucher has been

   The connection attempts via a single proxy SHOULD exponentially back-
   off to a maximum of one hour to avoid overloading the network
   infrastructure.  The back-off timer for each MUST be independent of
   other connection attempts.

   Connection attempts SHOULD be run in parallel to avoid head of queue
   problems wherein an attacker running a fake proxy or registrar could
   perform protocol actions intentionally slowly.  Connection attempts
   to different proxies SHOULD be sent with an interval of 3 to 5s.  The
   pledge SHOULD continue to listen to for additional GRASP M_FLOOD
   messages during the connection attempts.

   Each connection attempt through a distinct Join Proxy MUST have a
   unique nonce in the voucher-request.

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   Once a connection to a registrar is established (e.g. establishment
   of a TLS session key) there are expectations of more timely
   responses, see Section 5.2.

   Once all discovered services are attempted (assuming that none
   succeeded) the device MUST return to listening for GRASP M_FLOOD.  It
   SHOULD periodically retry any manufacturer-specific mechanisms.  The
   pledge MAY prioritize selection order as appropriate for the
   anticipated environment.

4.1.1.  Proxy GRASP announcements

   A proxy uses the DULL GRASP M_FLOOD mechanism to announce itself.
   This announcement can be within the same message as the ACP
   announcement detailed in [I-D.ietf-anima-autonomic-control-plane].

   The formal Concise Data Definition Language (CDDL) [RFC8610]
   definition is:

 flood-message = [M_FLOOD, session-id, initiator, ttl,
                  +[objective, (locator-option / [])]]

 objective = ["AN_Proxy", objective-flags, loop-count,

 ttl             = 180000     ; 180,000 ms (3 minutes)
 initiator = ACP address to contact Registrar
 objective-flags   = sync-only  ; as in GRASP spec
 sync-only         =  4         ; M_FLOOD only requires synchronization
 loop-count        =  1         ; one hop only
 objective-value   =  any       ; none

 locator-option    = [ O_IPv6_LOCATOR, ipv6-address,
                     transport-proto, port-number ]
 ipv6-address      = the v6 LL of the Proxy
 $transport-proto /= IPPROTO_TCP   ; note this can be any value from the
                                  ; IANA protocol registry, as per
                                  ; [GRASP] section, note 3.
 port-number      = selected by Proxy

           Figure 10: CDDL definition of Proxy Discovery message

   Here is an example M_FLOOD announcing a proxy at fe80::1, on TCP port

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  [M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000,
              ["AN_Proxy", 4, 1, ""],
                h'fe800000000000000000000000000001', IPPROTO_TCP, 4443]]

               Figure 11: Example of Proxy Discovery message

   On a small network the Registrar MAY include the GRASP M_FLOOD
   announcements to locally connected networks.

   The $transport-proto above indicates the method that the pledge-
   proxy-registrar will use.  The TCP method described here is
   mandatory, and other proxy methods, such as CoAP methods not defined
   in this document are optional.  Other methods MUST NOT be enabled
   unless the Join Registrar ASA indicates support for them in it's own

4.2.  CoAP connection to Registrar

   The use of CoAP to connect from pledge to registrar is out of scope
   for this document, and is described in future work.  See

4.3.  Proxy discovery and communication of Registrar

   The registrar SHOULD announce itself so that proxies can find it and
   determine what kind of connections can be terminated.

   The registrar announces itself using ACP instance of GRASP using
   M_FLOOD messages.  A registrar may announce any convenient port
   number, including using a stock port 443.  ANI proxies MUST support
   GRASP discovery of registrars.

   The M_FLOOD is formatted as follows:

  [M_FLOOD, 12340815, h'fda379a6f6ee00000200000064000001', 180000,
              ["AN_join_registrar", 4, 255, "EST-TLS"],
                h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443]]

         Figure 12: An example of a Registrar announcement message

   The formal CDDL definition is:

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   flood-message = [M_FLOOD, session-id, initiator, ttl,
                    +[objective, (locator-option / [])]]

   objective = ["AN_join_registrar", objective-flags, loop-count,

   initiator = ACP address to contact Registrar
   objective-flags = sync-only  ; as in GRASP spec
   sync-only =  4               ; M_FLOOD only requires synchronization
   loop-count      = 255        ; mandatory maximum
   objective-value = text       ; name of the (list of) of supported
                                ; protocols: "EST-TLS" for RFC7030.

       Figure 13: CDDL definition for Registrar announcement message

   The M_FLOOD message MUST be sent periodically.  The default period
   SHOULD be 60 seconds, the value SHOULD be operator configurable but
   SHOULD NOT be smaller than 60 seconds.  The frequency of sending MUST
   be such that the aggregate amount of periodic M_FLOODs from all
   flooding sources cause only negligible traffic across the ACP.

   Here are some examples of locators for illustrative purposes.  Only
   the first one ($transport-protocol = 6, TCP) is defined in this
   document and is mandatory to implement.

   locator1  = [O_IPv6_LOCATOR, fd45:1345::6789, 6,  443]
   locator2  = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683]
   locator3  = [O_IPv6_LOCATOR, fe80::1234, 41, nil]

   A protocol of 6 indicates that TCP proxying on the indicated port is

   Registrars MUST announce the set of protocols that they support.
   They MUST support TCP traffic.

   Registrars MUST accept HTTPS/EST traffic on the TCP ports indicated.

   Registrars MUST support ANI TLS circuit proxy and therefore BRSKI
   across HTTPS/TLS native across the ACP.

   In the ANI, the Autonomic Control Plane (ACP) secured instance of
   GRASP ([I-D.ietf-anima-grasp]) MUST be used for discovery of ANI
   registrar ACP addresses and ports by ANI proxies.  The TCP leg of the
   proxy connection between ANI proxy and ANI registrar therefore also
   runs across the ACP.

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5.  Protocol Details (Pledge - Registrar - MASA)

   The pledge MUST initiate BRSKI after boot if it is unconfigured.  The
   pledge MUST NOT automatically initiate BRSKI if it has been
   configured or is in the process of being configured.

   BRSKI is described as extensions to EST [RFC7030].  The goal of these
   extensions is to reduce the number of TLS connections and crypto
   operations required on the pledge.  The registrar implements the
   BRSKI REST interface within the same "/.well-known" URI tree as the
   existing EST URIs as described in EST [RFC7030] section 3.2.2.  The
   communication channel between the pledge and the registrar is
   referred to as "BRSKI-EST" (see Figure 1).

   The communication channel between the registrar and MASA is similarly
   described as extensions to EST within the same "/.well-known" tree.
   For clarity this channel is referred to as "BRSKI-MASA".  (See
   Figure 1).

   The MASA URI is "https://" authority "/.well-known/est".

   BRSKI uses existing CMS message formats for existing EST operations.
   BRSKI uses JSON [RFC8259] for all new operations defined here, and
   voucher formats.  In all places where a binary value must be carried
   in a JSON string, the use of base64 format ([RFC4648] section 4) is
   to be used, as per [RFC7951] section 6.6.

   While EST section 3.2 does not insist upon use of HTTP persistent
   connections ([RFC7230] section 6.3), BRSKI-EST connections SHOULD use
   persistent connections.  The intention of this guidance is to ensure
   the provisional TLS state occurs only once, and that the subsequent
   resolution of the provision state is not subject to a MITM attack
   during a critical phase.

   If non-persistent connections are used, then both the pledge and the
   registrar MUST remember the certificates seen, and also sent for the
   first connection.  They MUST check each subsequent connections for
   the same certificates, and each end MUST use the same certificates as
   well.  This places a difficult restriction on rolling certificates on
   the Registrar.

   Summarized automation extensions for the BRSKI-EST flow are:

   o  The pledge either attempts concurrent connections via each
      discovered proxy, or it times out quickly and tries connections in
      series, as explained at the end of Section 5.1.

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   o  The pledge provisionally accepts the registrar certificate during
      the TLS handshake as detailed in Section 5.1.

   o  The pledge requests a voucher using the new REST calls described
      below.  This voucher is then validated.

   o  The pledge completes authentication of the server certificate as
      detailed in Section 5.6.1.  This moves the BRSKI-EST TLS
      connection out of the provisional state.

   o  Mandatory bootstrap steps conclude with voucher status telemetry
      (see Section 5.7).

   The BRSKI-EST TLS connection can now be used for EST enrollment.

   The extensions for a registrar (equivalent to EST server) are:

   o  Client authentication is automated using Initial Device Identity
      (IDevID) as per the EST certificate based client authentication.
      The subject field's DN encoding MUST include the "serialNumber"
      attribute with the device's unique serial number as explained in
      Section 2.3.1

   o  The registrar requests and validates the voucher from the MASA.

   o  The registrar forwards the voucher to the pledge when requested.

   o  The registrar performs log verifications (described in
      Section 5.8.3) in addition to local authorization checks before
      accepting optional pledge device enrollment requests.

5.1.  BRSKI-EST TLS establishment details

   The pledge establishes the TLS connection with the registrar through
   the circuit proxy (see Section 4) but the TLS handshake is with the
   registrar.  The BRSKI-EST pledge is the TLS client and the BRSKI-EST
   registrar is the TLS server.  All security associations established
   are between the pledge and the registrar regardless of proxy

   Use of TLS 1.3 (or newer) is encouraged.  TLS 1.2 or newer is
   REQUIRED on the Pledge side.  TLS 1.3 (or newer) SHOULD be available
   on the Registrar server interface, and the Registrar client
   interface, but TLS 1.2 MAY be used.  TLS 1.3 (or newer) SHOULD be
   available on the MASA server interface, but TLS 1.2 MAY be used.

   Establishment of the BRSKI-EST TLS connection is as specified in EST
   [RFC7030] section 4.1.1 "Bootstrap Distribution of CA Certificates"

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   [RFC7030] wherein the client is authenticated with the IDevID
   certificate, and the EST server (the registrar) is provisionally
   authenticated with an unverified server certificate.  Configuration
   or distribution of the trust anchor database used for validating the
   IDevID certificate is out-of-scope of this specification.  Note that
   the trust anchors in/excluded from the database will affect which
   manufacturers' devices are acceptable to the registrar as pledges,
   and can also be used to limit the set of MASAs that are trusted for

   The signatures in the certificate MUST be validated even if a signing
   key can not (yet) be validated.  The certificate (or chain) MUST be
   retained for later validation.

   A self-signed certificate for the Registrar is acceptable as the
   voucher can validate it upon successful enrollment.

   The pledge performs input validation of all data received until a
   voucher is verified as specified in Section 5.6.1 and the TLS
   connection leaves the provisional state.  Until these operations are
   complete the pledge could be communicating with an attacker.

   The pledge code needs to be written with the assumption that all data
   is being transmitted at this point to an unauthenticated peer, and
   that received data, while inside a TLS connection, MUST be considered
   untrusted.  This particularly applies to HTTP headers and CMS
   structures that make up the voucher.

   A pledge that can connect to multiple Registrars concurrently SHOULD
   do so.  Some devices may be unable to do so for lack of threading, or
   resource issues.  Concurrent connections defeat attempts by a
   malicious proxy from causing a TCP Slowloris-like attack (see

   A pledge that can not maintain as many connections as there are
   eligible proxies will need to rotate among the various choices,
   terminating connections that do not appear to be making progress.  If
   no connection is making progress after 5 seconds then the pledge
   SHOULD drop the oldest connection and go on to a different proxy: the
   proxy that has been communicated with least recently.  If there were
   no other proxies discovered, the pledge MAY continue to wait, as long
   as it is concurrently listening for new proxy announcements.

5.2.  Pledge Requests Voucher from the Registrar

   When the pledge bootstraps it makes a request for a voucher from a

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   This is done with an HTTPS POST using the operation path value of

   The pledge voucher-request Content-Type is:

   application/voucher-cms+json  [RFC8366] defines a "YANG-defined JSON
      document that has been signed using a CMS structure", and the
      voucher-request described in Section 3 is created in the same way.
      The media type is the same as defined in [RFC8366].  This is also
      used for the pledge voucher-request.  The pledge MUST sign the
      request using the Section 2.3 credential.

   Registrar implementations SHOULD anticipate future media types but of
   course will simply fail the request if those types are not yet known.

   The pledge SHOULD include an [RFC7231] section 5.3.2 "Accept" header
   field indicating the acceptable media type for the voucher response.
   The "application/voucher-cms+json" media type is defined in [RFC8366]
   but constrained voucher formats are expected in the future.
   Registrars and MASA are expected to be flexible in what they accept.

   The pledge populates the voucher-request fields as follows:

   created-on:  Pledges that have a realtime clock are RECOMMENDED to
      populate this field with the current date and time in yang:date-
      and-time format.  This provides additional information to the
      MASA.  Pledges that have no real-time clocks MAY omit this field.

   nonce:  The pledge voucher-request MUST contain a cryptographically
      strong random or pseudo-random number nonce (see [RFC4086] section
      6.2).  As the nonce is usually generated very early in the boot
      sequence there is a concern that the same nonce might generated
      across multiple boots, or after a factory reset.  Difference
      nonces MUST NOT generated for each bootstrapping attempt, whether
      in series or concurrently.  The freshness of this nonce mitigates
      against the lack of real-time clock as explained in Section 2.6.1.

   assertion:  The pledge indicates support for the mechanism described
      in this document, by putting the value "proximity" in the voucher-
      request, and MUST include the "proximity-registrar-cert" field

   proximity-registrar-cert:  In a pledge voucher-request this is the
      first certificate in the TLS server 'certificate_list' sequence
      (see [RFC5246]) presented by the registrar to the pledge.  That
      is, it is the end-entity certificate.  This MUST be populated in a
      pledge voucher-request.

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   serial-number  The serial number of the pledge is included in the
      voucher-request from the Pledge.  This value is included as a
      sanity check only, but it is not to be forwarded by the Registrar
      as described in Section 5.5.

   All other fields MAY be omitted in the pledge voucher-request.

   An example JSON payload of a pledge voucher-request is in Section 3.3
   Example 1.

   The registrar confirms that the assertion is 'proximity' and that
   pinned 'proximity-registrar-cert' is the Registrar's certificate.  If
   this validation fails, then there is an On-Path Attacker (MITM), and
   the connection MUST be closed after the returning an HTTP 401 error

5.3.  Registrar Authorization of Pledge

   In a fully automated network all devices must be securely identified
   and authorized to join the domain.

   A Registrar accepts or declines a request to join the domain, based
   on the authenticated identity presented.  For different networks,
   examples of automated acceptance may include:

   o  allow any device of a specific type (as determined by the X.509

   o  allow any device from a specific vendor (as determined by the
      X.509 IDevID),

   o  allow a specific device from a vendor (as determined by the X.509
      IDevID) against a domain white list.  (The mechanism for checking
      a shared white list potentially used by multiple Registrars is out
      of scope).

   If validation fails the registrar SHOULD respond with the HTTP 404
   error code.  If the voucher-request is in an unknown format, then an
   HTTP 406 error code is more appropriate.  A situation that could be
   resolved with administrative action (such as adding a vendor to a
   whitelist) MAY be responded with an 403 HTTP error code.

   If authorization is successful the registrar obtains a voucher from
   the MASA service (see Section 5.5) and returns that MASA signed
   voucher to the pledge as described in Section 5.6.

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5.4.  BRSKI-MASA TLS establishment details

   The BRSKI-MASA TLS connection is a 'normal' TLS connection
   appropriate for HTTPS REST interfaces.  The registrar initiates the
   connection and uses the MASA URL obtained as described in
   Section 2.8.  The mechanisms in [RFC6125] SHOULD be used
   authentication of the MASA using a DNS-ID that matches that which is
   found in the IDevID.  Registrars MAY include a mechanism to override
   the MASA URL on a manufacturer-by-manufacturer basis, and within that
   override it is appropriate to provide alternate anchors.  This will
   typically used by some vendors to establish explicit (or private)
   trust anchors for validating their MASA that is part of a sales
   channel integration.

   Use of TLS 1.3 (or newer) is encouraged.  TLS 1.2 or newer is
   REQUIRED.  TLS 1.3 (or newer) SHOULD be available.

   As described in [RFC7030], the MASA and the registrars SHOULD be
   prepared to support TLS client certificate authentication and/or HTTP
   Basic or Digest authentication.  This connection MAY also have no
   client authentication at all.

   Registrars SHOULD permit trust anchors to be pre-configured on a per-
   vendor(MASA) basis.  Registrars SHOULD include the ability to
   configure a TLS ClientCertificate on a per-MASA basis, or to use no
   client certificate.  Registrars SHOULD also permit HTTP Basic and
   Digest authentication to be configured.

   The authentication of the BRSKI-MASA connection does not change the
   voucher-request process, as voucher-requests are already signed by
   the registrar.  Instead, this authentication provides access control
   to the audit-log as described in Section 5.8.

   Implementors are advised that contacting the MASA is to establish a
   secured API connection with a web service and that there are a number
   of authentication models being explored within the industry.
   Registrars are RECOMMENDED to fail gracefully and generate useful
   administrative notifications or logs in the advent of unexpected HTTP
   401 (Unauthorized) responses from the MASA.

5.4.1.  MASA authentication of customer Registrar

   Providing per-customer options requires that the customer's registrar
   be uniquely identified.  This can be done by any stateless method
   that HTTPS supports such as with HTTP Basic or Digest authentication
   (that is using a password), but the use of TLS Client Certificate
   authentication is RECOMMENDED.

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   Stateful methods involving API tokens, or HTTP Cookies, are not

   It is expected that the setup and configuration of per-customer
   Client Certificates is done as part of a sales ordering process.

   The use of public PKI (i.e.  WebPKI) End-Entity Certificates to
   identify the Registrar is reasonable, and if done universally this
   would permit a MASA to identify a customers' Registrar simply by a

   The use of DANE records in DNSSEC signed zones would also permit use
   of a FQDN to identify customer Registrars.

   A third (and simplest, but least flexible) mechanism would be for the
   MASA to simply store the Registrar's certificate pinned in a

   A MASA without any supply chain integration can simply accept
   Registrars without any authentication, or can accept them on a blind
   Trust-on-First-Use basis as described in Section 7.4.2.

   This document does not make a specific recommendation on how the MASA
   authenticates the Registrar as there are likely different tradeoffs
   in different environments and product values.  Even within the ANIMA
   ACP applicability, there is a significant difference between supply
   chain logistics for $100 CPE devices and $100,000 core routers.

5.5.  Registrar Requests Voucher from MASA

   When a registrar receives a pledge voucher-request it in turn submits
   a registrar voucher-request to the MASA service via an HTTPS
   interface ([RFC7231]).

   This is done with an HTTP POST using the operation path value of

   The voucher media type "application/voucher-cms+json" is defined in
   [RFC8366] and is also used for the registrar voucher-request.  It is
   a JSON document that has been signed using a CMS structure.  The
   registrar MUST sign the registrar voucher-request.  The entire
   registrar certificate chain, up to and including the Domain CA, MUST
   be included in the CMS structure.

   MASA impementations SHOULD anticipate future media types but of
   course will simply fail the request if those types are not yet known.

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   The Registrar SHOULD include an [RFC7231] section 5.3.2 "Accept"
   header field indicating the response media types that are acceptable.
   This list SHOULD be the entire list presented to the Registrar in the
   Pledge's original request (see Section 5.2) but MAY be a subset.
   MASA's are expected to be flexible in what they accept.

   The registrar populates the voucher-request fields as follows:

   created-on:  The Registrars SHOULD populate this field with the
      current date and time when the Registrar formed this voucher
      request.  This field provides additional information to the MASA.

   nonce:  This value, if present, is copied from the pledge voucher-
      request.  The registrar voucher-request MAY omit the nonce as per
      Section 3.1.

   serial-number:  The serial number of the pledge the registrar would
      like a voucher for.  The registrar determines this value by
      parsing the authenticated pledge IDevID certificate.  See
      Section 2.3.  The registrar MUST verify that the serial number
      field it parsed matches the serial number field the pledge
      provided in its voucher-request.  This provides a sanity check
      useful for detecting error conditions and logging.  The registrar
      MUST NOT simply copy the serial number field from a pledge voucher
      request as that field is claimed but not certified.

   idevid-issuer:  The Issuer value from the pledge IDevID certificate
      is included to ensure unique interpretation of the serial-number.
      In the case of nonceless (offline) voucher-request, then an
      appropriate value needs to be configured from the same out-of-band
      source as the serial-number.

   prior-signed-voucher-request:  The signed pledge voucher-request
      SHOULD be included in the registrar voucher-request.  The entire
      CMS signed structure is to be included, base64 encoded for
      transport in the JSON structure.

   A nonceless registrar voucher-request MAY be submitted to the MASA.
   Doing so allows the registrar to request a voucher when the pledge is
   offline, or when the registrar anticipates not being able to connect
   to the MASA while the pledge is being deployed.  Some use cases
   require the registrar to learn the appropriate IDevID SerialNumber
   field and appropriate 'Accept header field' values from the physical
   device labeling or from the sales channel (out-of-scope for this

   All other fields MAY be omitted in the registrar voucher-request.

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   The "proximity-registrar-cert" field MUST NOT be present in the
   registrar voucher-request.

   Example JSON payloads of registrar voucher-requests are in
   Section 3.3 Examples 2 through 4.

   The MASA verifies that the registrar voucher-request is internally
   consistent but does not necessarily authenticate the registrar
   certificate since the registrar MAY be unknown to the MASA in
   advance.  The MASA performs the actions and validation checks
   described in the following sub-sections before issuing a voucher.

5.5.1.  MASA renewal of expired vouchers

   As described in [RFC8366] vouchers are normally short lived to avoid
   revocation issues.  If the request is for a previous (expired)
   voucher using the same registrar (that is, a Registrar with the same
   Domain CA) then the request for a renewed voucher SHOULD be
   automatically authorized.  The MASA has sufficient information to
   determine this by examining the request, the registrar
   authentication, and the existing audit-log.  The issuance of a
   renewed voucher is logged as detailed in Section 5.6.

   To inform the MASA that existing vouchers are not to be renewed one
   can update or revoke the registrar credentials used to authorize the
   request (see Section 5.5.4 and Section 5.5.3).  More flexible methods
   will likely involve sales channel integration and authorizations
   (details are out-of-scope of this document).

5.5.2.  MASA pinning of registrar

   The registrar's certificate chain is extracted from the signature
   method.  The entire registrar certificate chain was included in the
   CMS structure, as specified in Section 5.5.  This CA certificate will
   be used to populate the "pinned-domain-cert" of the voucher being

   If this domain CA is unknown to the MASA, then it is to be considered
   a temporary trust anchor for the rest of the steps in this section.
   The intention is not to authenticate the message as having come from
   a fully validated origin, but to establish the consistency of the
   domain PKI.

5.5.3.  MASA checking of voucher request signature

   As described in Section 5.5.2, the MASA has extracted Registrar's
   domain CA.  This is used to validate the CMS signature ([RFC5652]) on
   the voucher-request.

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   Normal PKIX revocation checking is assumed during voucher-request
   signature validation.  This CA certificate MAY have Certificate
   Revocation List distribution points, or Online Certificate Status
   Protocol (OCSP) information ([RFC6960]).  If they are present, the
   MASA MUST be able to reach the relevant servers belonging to the
   Registrar's domain CA to perform the revocation checks.

   The use of OCSP Stapling is preferred.

5.5.4.  MASA verification of domain registrar

   The MASA MUST verify that the registrar voucher-request is signed by
   a registrar.  This is confirmed by verifying that the id-kp-cmcRA
   extended key usage extension field (as detailed in EST RFC7030
   section 3.6.1) exists in the certificate of the entity that signed
   the registrar voucher-request.  This verification is only a
   consistency check that the unauthenticated domain CA intended the
   voucher-request signer to be a registrar.  Performing this check
   provides value to the domain PKI by assuring the domain administrator
   that the MASA service will only respect claims from authorized
   Registration Authorities of the domain.

   Even when a domain CA is authenticated to the MASA, and there is
   strong sales channel integration to understand who the legitimate
   owner is, the above cmcRC check prevents arbitrary End-Entity
   certificates (such as an LDevID certificate) from having vouchers
   issued against them.

   Other cases of inappropriate voucher issuance are detected by
   examination of the audit log.

   If a nonceless voucher-request is submitted the MASA MUST
   authenticate the registrar as described in either EST [RFC7030]
   section 3.2.3, section 3.3.2, or by validating the registrar's
   certificate used to sign the registrar voucher-request using a
   configured trust anchor.  Any of these methods reduce the risk of
   DDoS attacks and provide an authenticated identity as an input to
   sales channel integration and authorizations (details are out-of-
   scope of this document).

   In the nonced case, validation of the Registrar's identity (via TLS
   Client Certificate or HTTP authentication) MAY be omitted if the
   device policy is to accept audit-only vouchers.

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

   The MASA MAY verify that the registrar voucher-request includes the
   'prior-signed-voucher-request' field.  If so the prior-signed-
   voucher-request MUST include a 'proximity-registrar-cert' that is
   consistent with the certificate used to sign the registrar voucher-
   request.  Additionally the voucher-request serial-number leaf MUST
   match the pledge serial-number that the MASA extracts from the
   signing certificate of the prior-signed-voucher-request.  The
   consistency check described above is checking that the 'proximity-
   registrar-cert' SPKI fingerprint exists within the registrar voucher-
   request CMS signature's certificate chain.  This is substantially the
   same as the pin validation described in in [RFC7469] section 2.6,
   paragraph three.

   If these checks succeed the MASA updates the voucher and audit-log
   assertion leafs with the "proximity" assertion, as defined by
   [RFC8366] section 5.3.

5.5.6.  MASA nonce handling

   The MASA does not verify the nonce itself.  If the registrar voucher-
   request contains a nonce, and the prior-signed-voucher-request
   exists, then the MASA MUST verify that the nonce is consistent.
   (Recall from above that the voucher-request might not contain a
   nonce, see Section 5.5 and Section 5.5.4).

   The MASA populates the audit-log with the nonce that was verified.
   If a nonceless voucher is issued, then the audit-log is to be
   populated with the JSON value "null".

5.6.  MASA and Registrar Voucher Response

   The MASA voucher response to the registrar is forwarded without
   changes to the pledge; therefore this section applies to both the
   MASA and the registrar.  The HTTP signaling described applies to both
   the MASA and registrar responses.

   When a voucher request arrives at the registrar, if it has a cached
   response from the MASA for the corresponding registrar voucher-
   request, that cached response can be used according to local policy;
   otherwise the registrar constructs a new registrar voucher-request
   and sends it to the MASA.

   Registrar evaluation of the voucher itself is purely for transparency
   and audit purposes to further inform log verification (see
   Section 5.8.3) and therefore a registrar could accept future voucher
   formats that are opaque to the registrar.

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   If the voucher-request is successful, the server (MASA responding to
   registrar or registrar responding to pledge) response MUST contain an
   HTTP 200 response code.  The server MUST answer with a suitable 4xx
   or 5xx HTTP [RFC7230] error code when a problem occurs.  In this
   case, the response data from the MASA MUST be a plaintext human-
   readable (UTF-8) error message containing explanatory information
   describing why the request was rejected.

   The registrar MAY respond with an HTTP 202 ("the request has been
   accepted for processing, but the processing has not been completed")
   as described in EST [RFC7030] section 4.2.3 wherein the client "MUST
   wait at least the specified 'Retry-After' time before repeating the
   same request".  (see [RFC7231] section 6.6.4) The pledge is
   RECOMMENDED to provide local feedback (blinked LED etc) during this
   wait cycle if mechanisms for this are available.  To prevent an
   attacker registrar from significantly delaying bootstrapping the
   pledge MUST limit the 'Retry-After' time to 60 seconds.  Ideally the
   pledge would keep track of the appropriate Retry-After header field
   values for any number of outstanding registrars but this would
   involve a state table on the pledge.  Instead the pledge MAY ignore
   the exact Retry-After value in favor of a single hard coded value (a
   registrar that is unable to complete the transaction after the first
   60 seconds has another chance a minute later).  A pledge SHOULD only
   maintain a 202 retry-state for up to 4 days, which is longer than a
   long weekend, after which time the enrollment attempt fails and the
   pledge returns to discovery state.

   A pledge that retries a request after receiving a 202 message MUST
   resend the same voucher-request.  It MUST NOT sign a new voucher-
   request each time, and in particular, it MUST NOT change the nonce

   In order to avoid infinite redirect loops, which a malicious
   registrar might do in order to keep the pledge from discovering the
   correct registrar, the pledge MUST NOT follow more than one
   redirection (3xx code) to another web origins.  EST supports
   redirection but requires user input; this change allows the pledge to
   follow a single redirection without a user interaction.

   A 403 (Forbidden) response is appropriate if the voucher-request is
   not signed correctly, stale, or if the pledge has another outstanding
   voucher that cannot be overridden.

   A 404 (Not Found) response is appropriate when the request is for a
   device that is not known to the MASA.

   A 406 (Not Acceptable) response is appropriate if a voucher of the
   desired type or using the desired algorithms (as indicated by the

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   Accept: header fields, and algorithms used in the signature) cannot
   be issued such as because the MASA knows the pledge cannot process
   that type.  The registrar SHOULD use this response if it determines
   the pledge is unacceptable due to inventory control, MASA audit-logs,
   or any other reason.

   A 415 (Unsupported Media Type) response is appropriate for a request
   that has a voucher-request or Accept: value that is not understood.

   The voucher response format is as indicated in the submitted Accept
   header fields or based on the MASA's prior understanding of proper
   format for this Pledge.  Only the [RFC8366] "application/voucher-
   cms+json" media type is defined at this time.  The syntactic details
   of vouchers are described in detail in [RFC8366].  Figure 14 shows a
   sample of the contents of a voucher.

     "ietf-voucher:voucher": {
       "nonce": "62a2e7693d82fcda2624de58fb6722e5",
       "assertion": "logged",
       "pinned-domain-cert": "base64encodedvalue==",
       "serial-number": "JADA123456789"

                       Figure 14: An example voucher

   The MASA populates the voucher fields as follows:

   nonce:  The nonce from the pledge if available.  See Section 5.5.6.

   assertion:  The method used to verify the relationship between pledge
      and registrar.  See Section 5.5.5.

   pinned-domain-cert:  The domain CA cert.  See Section 5.5.2.  This
      figure is illustrative, for an example, see Appendix D.2

   serial-number:  The serial-number as provided in the voucher-request.
      Also see Section 5.5.5.

   domain-cert-revocation-checks:  Set as appropriate for the pledge's
      capabilities and as documented in [RFC8366].  The MASA MAY set
      this field to 'false' since setting it to 'true' would require
      that revocation information be available to the pledge and this
      document does not make normative requirements for [RFC6961] or
      equivalent integrations.

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   expires-on:  This is set for nonceless vouchers.  The MASA ensures
      the voucher lifetime is consistent with any revocation or pinned-
      domain-cert consistency checks the pledge might perform.  See
      section Section 2.6.1.  There are three times to consider: (a) a
      configured voucher lifetime in the MASA, (b) the expiry time for
      the registrar's certificate, (c) any certificate revocation
      information (CRL) lifetime.  The expires-on field SHOULD be before
      the earliest of these three values.  Typically (b) will be some
      significant time in the future, but (c) will typically be short
      (on the order of a week or less).  The RECOMMENDED period for (a)
      is on the order of 20 minutes, so it will typically determine the
      lifespan of the resulting voucher.  20 minutes is sufficient time
      to reach the post-provisional state in the pledge, at which point
      there is an established trust relationship between pledge and
      registrar.  The subsequent operations can take as long as required
      from that point onwards.  The lifetime of the voucher has no
      impact on the lifespan of the ownership relationship.

   Whenever a voucher is issued the MASA MUST update the audit-log
   sufficiently to generate the response as described in Section 5.8.1.
   The internal state requirements to maintain the audit-log are out-of-

5.6.1.  Pledge voucher verification

   The pledge MUST verify the voucher signature using the manufacturer-
   installed trust anchor(s) associated with the manufacturer's MASA
   (this is likely included in the pledge's firmware).  Management of
   the manufacturer-installed trust anchor(s) is out-of-scope of this
   document; this protocol does not update these trust anchor(s).

   The pledge MUST verify the serial-number field of the signed voucher
   matches the pledge's own serial-number.

   The pledge MUST verify the nonce information in the voucher.  If
   present, the nonce in the voucher must match the nonce the pledge
   submitted to the registrar; vouchers with no nonce can also be
   accepted (according to local policy, see Section 7.2.

   The pledge MUST be prepared to parse and fail gracefully from a
   voucher response that does not contain a 'pinned-domain-cert' field.
   Such a thing indicates a failure to enroll in this domain, and the
   pledge MUST attempt joining with other available Join Proxy.

   The pledge MUST be prepared to ignore additional fields that it does
   not recognize.

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5.6.2.  Pledge authentication of provisional TLS connection

   The 'pinned-domain-cert' element of the voucher contains the domain
   CA's public key.  The pledge MUST use the 'pinned-domain-cert' trust
   anchor to immediately complete authentication of the provisional TLS

   If a registrar's credentials cannot be verified using the pinned-
   domain-cert trust anchor from the voucher then the TLS connection is
   immediately discarded and the pledge abandons attempts to bootstrap
   with this discovered registrar.  The pledge SHOULD send voucher
   status telemetry (described below) before closing the TLS connection.
   The pledge MUST attempt to enroll using any other proxies it has
   found.  It SHOULD return to the same proxy again after unsuccessful
   attempts with other proxies.  Attempts should be made repeated at
   intervals according to the backoff timer described earlier.  Attempts
   SHOULD be repeated as failure may be the result of a temporary
   inconsistency (an inconsistently rolled registrar key, or some other
   mis-configuration).  The inconsistency could also be the result an
   active MITM attack on the EST connection.

   The registrar MUST use a certificate that chains to the pinned-
   domain-cert as its TLS server certificate.

   The pledge's PKIX path validation of a registrar certificate's
   validity period information is as described in Section 2.6.1.  Once
   the PKIX path validation is successful the TLS connection is no
   longer provisional.

   The pinned-domain-cert MAY be installed as an trust anchor for future
   operations such as enrollment (e.g.  [RFC7030] as recommended) or
   trust anchor management or raw protocols that do not need full PKI
   based key management.  It can be used to authenticate any dynamically
   discovered EST server that contain the id-kp-cmcRA extended key usage
   extension as detailed in EST RFC7030 section 3.6.1; but to reduce
   system complexity the pledge SHOULD avoid additional discovery
   operations.  Instead the pledge SHOULD communicate directly with the
   registrar as the EST server.  The 'pinned-domain-cert' is not a
   complete distribution of the [RFC7030] section 4.1.3 CA Certificate
   Response, which is an additional justification for the recommendation
   to proceed with EST key management operations.  Once a full CA
   Certificate Response is obtained it is more authoritative for the
   domain than the limited 'pinned-domain-cert' response.

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5.7.  Pledge BRSKI Status Telemetry

   The domain is expected to provide indications to the system
   administrators concerning device lifecycle status.  To facilitate
   this it needs telemetry information concerning the device's status.

   To indicate pledge status regarding the voucher, the pledge MUST post
   a status message to the Registrar.

   The posted data media type: application/json

   The client sends an HTTP POST to the server at the URI ".well-

   The format and semantics described below are for version 1.  A
   version field is included to permit significant changes to this
   feedback in the future.  A Registrar that receives a status message
   with a version larger than it knows about SHOULD log the contents and
   alert a human.

   The Status field indicates if the voucher was acceptable.  Boolean
   values are acceptable, where "true" indicates the voucher was

   If the voucher was not acceptable the Reason string indicates why.
   In the failure case this message may be sent to an unauthenticated,
   potentially malicious registrar and therefore the Reason string
   SHOULD NOT provide information beneficial to an attacker.  The
   operational benefit of this telemetry information is balanced against
   the operational costs of not recording that an voucher was ignored by
   a client the registrar expected to continue joining the domain.

   The reason-context attribute is an arbitrary JSON object (literal
   value or hash of values) which provides additional information
   specific to this pledge.  The contents of this field are not subject
   to standardization.

   The version and status fields MUST be present.  The Reason field
   SHOULD be present whenever the status field is false.  The Reason-
   Context field is optional.

   The keys to this JSON object are case-sensitive and MUST be
   lowercase.  Figure 15 shows an example JSON.

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       "reason":"Informative human readable message",
       "reason-context": { "additional" : "JSON" }

                    Figure 15: Example Status Telemetry

   The server SHOULD respond with an HTTP 200 but MAY simply fail with
   an HTTP 404 error.  The client ignores any response.  Within the
   server logs the server SHOULD capture this telemetry information.

   Additional standard JSON fields in this POST MAY be added, see
   Section 8.4.  A server that sees unknown fields should log them, but
   otherwise ignore them.

5.8.  Registrar audit-log request

   After receiving the pledge status telemetry Section 5.7, the
   registrar SHOULD request the MASA audit-log from the MASA service.

   This is done with an HTTP POST using the operation path value of

   The registrar SHOULD HTTP POST the same registrar voucher-request as
   it did when requesting a voucher (using the same Content-Type).  It
   is posted to the /requestauditlog URI instead.  The "idevid-issuer"
   and "serial-number" informs the MASA which log is requested so the
   appropriate log can be prepared for the response.  Using the same
   media type and message minimizes cryptographic and message operations
   although it results in additional network traffic.  The relying MASA
   implementation MAY leverage internal state to associate this request
   with the original, and by now already validated, voucher-request so
   as to avoid an extra crypto validation.

   A registrar MAY request logs at future times.  If the registrar
   generates a new request then the MASA is forced to perform the
   additional cryptographic operations to verify the new request.

   A MASA that receives a request for a device that does not exist, or
   for which the requesting owner was never an owner returns an HTTP 404
   ("Not found") code.

   It is reasonable for a Registrar, that the MASA does not believe to
   be the current owner, to request the audit-log.  There are probably
   reasons for this which are hard to predict in advance.  For instance,
   such a registrar may not be aware that the device has been resold; it

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   may be that the device has been resold inappropriately, and this is
   how the original owner will learn of the occurance.  It is also
   possible that the device legitimately spends time in two different

   Rather than returning the audit-log as a response to the POST (with a
   return code 200), the MASA MAY instead return a 201 ("Created")
   response ([RFC7231] sections 6.3.2 and 7.1), with the URL to the
   prepared (and idempotent, therefore cachable) audit response in the
   Location: header field.

   In order to avoid enumeration of device audit-logs, MASA that return
   URLs SHOULD take care to make the returned URL unguessable.
   [W3C.WD-capability-urls-20140218] provides very good additional
   guidance.  For instance, rather than returning URLs containing a
   database number such as or the EUI
   of the device such,
   the MASA SHOULD return a randomly generated value (a "slug" in web
   parlance).  The value is used to find the relevant database entry.

   A MASA that returns a code 200 MAY also include a Location: header
   for future reference by the registrar.

5.8.1.  MASA audit log response

   A log data file is returned consisting of all log entries associated
   with the device selected by the IDevID presented in the request.  The
   audit log may be abridged by removal of old or repeated values as
   explained below.  The returned data is in JSON format ([RFC8259]),
   and the Content-Type SHOULD be "application/json".

   The following CDDL ([RFC8610]) explains the structure of the JSON
   format audit-log response:

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   audit-log-response = {
     "version": uint,
     "events": [ + event ]
     "truncation": {
       ? "nonced duplicates": uint,
       ? "nonceless duplicates": uint,
       ? "arbitrary": uint,

   event = {
     "date": text,
     "domainID": text,
     "nonce": text / null,
     "assertion": "verified" / "logged" / "proximity",
     ? "truncated": uint,

                  Figure 16: CDDL for audit-log response

   As an abstract example:

       "truncation": {
           "nonced duplicates": "0",
           "nonceless duplicates": "1",
           "arbitrary": "2"

                 Figure 17: Example of audit-log response

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   The domainID is a binary SubjectKeyIdentifier value calculated
   according to Section 5.8.2.  It is encoded once in base64 in order to
   be transported in this JSON container.

   The date is in [RFC3339] format, which is consistent with typical
   JavaScript usage of JSON.

   The truncation structure MAY be omitted if all values are zero.  Any
   counter missing from the truncation structure is the be assumed to be

   The nonce is a string, as provided in the voucher-request, and used
   in the voucher.  If no nonce was placed in the resulting voucher,
   then a value of null SHOULD be used in preference to omitting the
   entry.  While the nonce is often created as a base64 encoded random
   series of bytes, this should not be assumed.

   Distribution of a large log is less than ideal.  This structure can
   be optimized as follows: Nonced or Nonceless entries for the same
   domainID MAY be abridged from the log leaving only the single most
   recent nonced or nonceless entry for that domainID.  In the case of
   truncation the 'event' truncation value SHOULD contain a count of the
   number of events for this domainID that were omitted.  The log SHOULD
   NOT be further reduced but there could exist operational situation
   where maintaining the full log is not possible.  In such situations
   the log MAY be arbitrarily abridged for length, with the number of
   removed entries indicated as 'arbitrary'.

   If the truncation count exceeds 1024 then the MASA MAY use this value
   without further incrementing it.

   A log where duplicate entries for the same domain have been omitted
   ("nonced duplicates" and/or "nonceless duplicates) could still be
   acceptable for informed decisions.  A log that has had "arbitrary"
   truncations is less acceptable but manufacturer transparency is
   better than hidden truncations.

   A registrar that sees a version value greater than 1 indicates an
   audit log format that has been enhanced with additional information.
   No information will be removed in future versions; should an
   incompatible change be desired in the future, then a new HTTP end
   point will be used.

   This document specifies a simple log format as provided by the MASA
   service to the registrar.  This format could be improved by
   distributed consensus technologies that integrate vouchers with
   technologies such as block-chain or hash trees or optimized logging
   approaches.  Doing so is out of the scope of this document but is an

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   anticipated improvement for future work.  As such, the registrar
   SHOULD anticipate new kinds of responses, and SHOULD provide operator
   controls to indicate how to process unknown responses.

5.8.2.  Calculation of domainID

   The domainID is a binary value (a BIT STRING) that uniquely
   identifies a Registrar by the "pinned-domain-cert"

   If the "pinned-domain-cert" certificate includes the
   SubjectKeyIdentifier (Section [RFC5280]), then it is to be
   used as the domainID.  If not, the SPKI Fingerprint as described in
   [RFC7469] section 2.4 is to be used.  This value needs to be
   calculated by both MASA (to populate the audit-log), and by the
   Registrar (to recognize itself in the audit log).

   [RFC5280] section does not mandate that the
   SubjectKeyIdentifier extension be present in non-CA certificates.  It
   is RECOMMENDED that Registrar certificates (even if self-signed),
   always include the SubjectKeyIdentifier to be used as a domainID.

   The domainID is determined from the certificate chain associated with
   the pinned-domain-cert and is used to update the audit-log.

5.8.3.  Registrar audit log verification

   Each time the Manufacturer Authorized Signing Authority (MASA) issues
   a voucher, it appends details of the assignment to an internal audit
   log for that device.  The internal audit log is processed when
   responding to requests for details as described in Section 5.8.  The
   contents of the audit log can express a variety of trust levels, and
   this section explains what kind of trust a registrar can derive from
   the entries.

   While the audit log provides a list of vouchers that were issued by
   the MASA, the vouchers are issued in response to voucher-requests,
   and it is the contents of the voucher-requests which determines how
   meaningful the audit log entries are.

   A registrar SHOULD use the log information to make an informed
   decision regarding the continued bootstrapping of the pledge.  The
   exact policy is out of scope of this document as it depends on the
   security requirements within the registrar domain.  Equipment that is
   purchased pre-owned can be expected to have an extensive history.
   The following discussion is provided to help explain the value of
   each log element:

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   date:  The date field provides the registrar an opportunity to divide
      the log around known events such as the purchase date.  Depending
      on context known to the registrar or administrator events before/
      after certain dates can have different levels of importance.  For
      example for equipment that is expected to be new, and thus have no
      history, it would be a surprise to find prior entries.

   domainID:  If the log includes an unexpected domainID then the pledge
      could have imprinted on an unexpected domain.  The registrar can
      be expected to use a variety of techniques to define "unexpected"
      ranging from white lists of prior domains to anomaly detection
      (e.g. "this device was previously bound to a different domain than
      any other device deployed").  Log entries can also be compared
      against local history logs in search of discrepancies (e.g. "this
      device was re-deployed some number of times internally but the
      external audit log shows additional re-deployments our internal
      logs are unaware of").

   nonce:  Nonceless entries mean the logged domainID could
      theoretically trigger a reset of the pledge and then take over
      management by using the existing nonceless voucher.

   assertion:  The assertion leaf in the voucher and audit log indicates
      why the MASA issued the voucher.  A "verified" entry means that
      the MASA issued the associated voucher as a result of positive
      verification of ownership but this can still be problematic for
      registrar's that expected only new (not pre-owned) pledges.  A
      "logged" assertion informs the registrar that the prior vouchers
      were issued with minimal verification.  A "proximity" assertion
      assures the registrar that the pledge was truly communicating with
      the prior domain and thus provides assurance that the prior domain
      really has deployed the pledge.

   A relatively simple policy is to white list known (internal or
   external) domainIDs, and require all vouchers to have a nonce.  An
   alternative is to require that all nonceless vouchers be from a
   subset (e.g. only internal) of domainIDs.  If the policy is violated
   a simple action is to revoke any locally issued credentials for the
   pledge in question or to refuse to forward the voucher.  The
   Registrar MUST then refuse any EST actions, and SHOULD inform a human
   via a log.  A registrar MAY be configured to ignore (i.e. override
   the above policy) the history of the device but it is RECOMMENDED
   that this only be configured if hardware assisted (i.e.  TPM
   anchored) Network Endpoint Assessment (NEA) [RFC5209] is supported.

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5.9.  EST Integration for PKI bootstrapping

   The pledge SHOULD follow the BRSKI operations with EST enrollment
   operations including "CA Certificates Request", "CSR Attributes" and
   "Client Certificate Request" or "Server-Side Key Generation", etc.
   This is a relatively seamless integration since BRSKI API calls
   provide an automated alternative to the manual bootstrapping method
   described in [RFC7030].  As noted above, use of HTTP persistent
   connections simplifies the pledge state machine.

   Although EST allows clients to obtain multiple certificates by
   sending multiple Certificate Signing Requests (CSR) requests, BRSKI
   does not support this mechanism directly.  This is because BRSKI
   pledges MUST use the CSR Attributes request ([RFC7030] section 4.5).
   The registrar MUST validate the CSR against the expected attributes.
   This implies that client requests will "look the same" and therefore
   result in a single logical certificate being issued even if the
   client were to make multiple requests.  Registrars MAY contain more
   complex logic but doing so is out-of-scope of this specification.
   BRSKI does not signal any enhancement or restriction to this

5.9.1.  EST Distribution of CA Certificates

   The pledge SHOULD request the full EST Distribution of CA
   Certificates message.  See RFC7030, section 4.1.

   This ensures that the pledge has the complete set of current CA
   certificates beyond the pinned-domain-cert (see Section 5.6.2 for a
   discussion of the limitations inherent in having a single certificate
   instead of a full CA Certificates response.)  Although these
   limitations are acceptable during initial bootstrapping, they are not
   appropriate for ongoing PKIX end entity certificate validation.

5.9.2.  EST CSR Attributes

   Automated bootstrapping occurs without local administrative
   configuration of the pledge.  In some deployments it is plausible
   that the pledge generates a certificate request containing only
   identity information known to the pledge (essentially the X.509
   IDevID information) and ultimately receives a certificate containing
   domain specific identity information.  Conceptually the CA has
   complete control over all fields issued in the end entity
   certificate.  Realistically this is operationally difficult with the
   current status of PKI certificate authority deployments, where the
   CSR is submitted to the CA via a number of non-standard protocols.
   Even with all standardized protocols used, it could operationally be
   problematic to expect that service specific certificate fields can be

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   created by a CA that is likely operated by a group that has no
   insight into different network services/protocols used.  For example,
   the CA could even be outsourced.

   To alleviate these operational difficulties, the pledge MUST request
   the EST "CSR Attributes" from the EST server and the EST server needs
   to be able to reply with the attributes necessary for use of the
   certificate in its intended protocols/services.  This approach allows
   for minimal CA integrations and instead the local infrastructure (EST
   server) informs the pledge of the proper fields to include in the
   generated CSR (such as rfc822Name).  This approach is beneficial to
   automated bootstrapping in the widest number of environments.

   In networks using the BRSKI enrolled certificate to authenticate the
   ACP (Autonomic Control Plane), the EST CSR attributes MUST include
   the ACP Domain Information Fields defined in
   [I-D.ietf-anima-autonomic-control-plane] section 6.1.1.

   The registrar MUST also confirm that the resulting CSR is formatted
   as indicated before forwarding the request to a CA.  If the registrar
   is communicating with the CA using a protocol such as full CMC, which
   provides mechanisms to override the CSR attributes, then these
   mechanisms MAY be used even if the client ignores CSR Attribute

5.9.3.  EST Client Certificate Request

   The pledge MUST request a new client certificate.  See RFC7030,
   section 4.2.

5.9.4.  Enrollment Status Telemetry

   For automated bootstrapping of devices, the administrative elements
   providing bootstrapping also provide indications to the system
   administrators concerning device lifecycle status.  This might
   include information concerning attempted bootstrapping messages seen
   by the client.  The MASA provides logs and status of credential
   enrollment.  [RFC7030] assumes an end user and therefore does not
   include a final success indication back to the server.  This is
   insufficient for automated use cases.

   In order to communicate this indicator, the client HTTP POSTs the
   following to the server at the new EST endpoint at "/.well-known/est/

   To indicate successful enrollment the client SHOULD first re-
   establish the EST TLS session using the newly obtained credentials.
   TLS 1.2 supports doing this in-band, but TLS 1.3 does not.  The

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   client SHOULD therefore close the existing TLS connection, and start
   a new one.

   In the case of a FAIL, the Reason string indicates why the most
   recent enrollment failed.

   The reason-context attribute is an arbitrary JSON object (literal
   value or hash of values) which provides additional information
   specific to the failure to unroll from this pledge.  The contents of
   this field are not subject to standardization.

   In the case of a SUCCESS the Reason string is omitted.

   An example status report can be seen below.  It is sent with with the
   media type: application/json

       "Reason":"Informative human readable message",
       "reason-context": { "additional" : "JSON" }

               Figure 18: Example of enrollment status POST

   The server SHOULD respond with an HTTP 200 but MAY simply fail with
   an HTTP 404 error.

   Within the server logs the server MUST capture if this message was
   received over an TLS session with a matching client certificate.

5.9.5.  Multiple certificates

   Pledges that require multiple certificates could establish direct EST
   connections to the registrar.

5.9.6.  EST over CoAP

   This document describes extensions to EST for the purposes of
   bootstrapping of remote key infrastructures.  Bootstrapping is
   relevant for CoAP enrollment discussions as well.  The definition of
   EST and BRSKI over CoAP is not discussed within this document beyond
   ensuring proxy support for CoAP operations.  Instead it is
   anticipated that a definition of CoAP mappings will occur in
   subsequent documents such as [I-D.ietf-ace-coap-est] and that CoAP
   mappings for BRSKI will be discussed either there or in future work.

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6.  Clarification of transfer-encoding

   [RFC7030] defines its endpoints to include a "Content-Transfer-
   Encoding" heading, and the payloads to be [RFC4648] Base64 encoded

   When used within BRSKI, the original RFC7030 EST endpoints remain
   Base64 encoded, but the new BRSKI end points which send and receive
   binary artifacts (specifically, "/.well-known/est/requestvoucher")
   are binary.  That is, no encoding is used.

   In the BRSKI context, the EST "Content-Transfer-Encoding" header
   field if present, SHOULD be ignored.  This header field does not need
   to be included.

7.  Reduced security operational modes

   A common requirement of bootstrapping is to support less secure
   operational modes for support specific use cases.  This section
   suggests a range of mechanisms that would alter the security
   assurance of BRSKI to accommodate alternative deployment
   architectures and mitigate lifecycle management issues identified in
   Section 10.  They are presented here as informative (non-normative)
   design guidance for future standardization activities.  Section 9
   provides standardization applicability statements for the ANIMA ACP.
   Other users would be expected that subsets of these mechanisms could
   be profiled with an accompanying applicability statements similar to
   the one described in Section 9.

   This section is considered non-normative in the generality of the
   protocol.  Use of the suggested mechanisms here MUST be detailed in
   specific profiles of BRSKI, such as in Section 9.

7.1.  Trust Model

   This section explains the trust relationships detailed in
   Section 2.4:

   +--------+         +---------+    +------------+     +------------+
   | Pledge |         | Join    |    | Domain     |     |Manufacturer|
   |        |         | Proxy   |    | Registrar  |     | Service    |
   |        |         |         |    |            |     | (Internet) |
   +--------+         +---------+    +------------+     +------------+

   Figure 10

   Pledge:  The pledge could be compromised and providing an attack
      vector for malware.  The entity is trusted to only imprint using

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      secure methods described in this document.  Additional endpoint
      assessment techniques are RECOMMENDED but are out-of-scope of this

   Join Proxy:  Provides proxy functionalities but is not involved in
      security considerations.

   Registrar:  When interacting with a MASA a registrar makes all
      decisions.  For Ownership Audit Vouchers (see [RFC8366]) the
      registrar is provided an opportunity to accept MASA decisions.

   Vendor Service, MASA:  This form of manufacturer service is trusted
      to accurately log all claim attempts and to provide authoritative
      log information to registrars.  The MASA does not know which
      devices are associated with which domains.  These claims could be
      strengthened by using cryptographic log techniques to provide
      append only, cryptographic assured, publicly auditable logs.

   Vendor Service, Ownership Validation:  This form of manufacturer
      service is trusted to accurately know which device is owned by
      which domain.

7.2.  Pledge security reductions

   The following is a list of alternative behaviours that the pledge can
   be programmed to implement.  These behaviours are not mutually
   exclusive, nor are they dependent upon each other.  Some of these
   methods enable offline and emergency (touch based) deployment use
   cases.  Normative language is used as these behaviours are referenced
   in later sections in a normative fashion.

   1.  The pledge MUST accept nonceless vouchers.  This allows for a use
       case where the registrar can not connect to the MASA at the
       deployment time.  Logging and validity periods address the
       security considerations of supporting these use cases.

   2.  Many devices already support "trust on first use" for physical
       interfaces such as console ports.  This document does not change
       that reality.  Devices supporting this protocol MUST NOT support
       "trust on first use" on network interfaces.  This is because
       "trust on first use" over network interfaces would undermine the
       logging based security protections provided by this

   3.  The pledge MAY have an operational mode where it skips voucher
       validation one time.  For example if a physical button is
       depressed during the bootstrapping operation.  This can be useful
       if the manufacturer service is unavailable.  This behavior SHOULD

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       be available via local configuration or physical presence methods
       (such as use of a serial/craft console) to ensure new entities
       can always be deployed even when autonomic methods fail.  This
       allows for unsecured imprint.

   4.  A craft/serial console could include a command such as "est-
       enroll [2001:db8:0:1]:443" that begins the EST process from the
       point after the voucher is validated.  This process SHOULD
       include server certificate verification using an on-screen

   It is RECOMMENDED that "trust on first use" or any method of skipping
   voucher validation (including use of craft serial console) only be
   available if hardware assisted Network Endpoint Assessment (NEA:
   [RFC5209]) is supported.  This recommendation ensures that domain
   network monitoring can detect inappropriate use of offline or
   emergency deployment procedures when voucher-based bootstrapping is
   not used.

7.3.  Registrar security reductions

   A registrar can choose to accept devices using less secure methods.
   They MUST NOT be the default behavior.  These methods may be
   acceptable in situations where threat models indicate that low
   security is adequate.  This includes situations where security
   decisions are being made by the local administrator:

   1.  A registrar MAY choose to accept all devices, or all devices of a
       particular type, at the administrator's discretion.  This could
       occur when informing all registrars of unique identifiers of new
       entities might be operationally difficult.

   2.  A registrar MAY choose to accept devices that claim a unique
       identity without the benefit of authenticating that claimed
       identity.  This could occur when the pledge does not include an
       X.509 IDevID factory installed credential.  New Entities without
       an X.509 IDevID credential MAY form the Section 5.2 request using
       the Section 5.5 format to ensure the pledge's serial number
       information is provided to the registrar (this includes the
       IDevID AuthorityKeyIdentifier value, which would be statically
       configured on the pledge.)  The pledge MAY refuse to provide a
       TLS client certificate (as one is not available.)  The pledge
       SHOULD support HTTP-based or certificate-less TLS authentication
       as described in EST RFC7030 section 3.3.2.  A registrar MUST NOT
       accept unauthenticated New Entities unless it has been configured
       to do so by an administrator that has verified that only expected
       new entities can communicate with a registrar (presumably via a
       physically secured perimeter.)

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   3.  A registrar MAY submit a nonceless voucher-requests to the MASA
       service (by not including a nonce in the voucher-request.)  The
       resulting vouchers can then be stored by the registrar until they
       are needed during bootstrapping operations.  This is for use
       cases where the target network is protected by an air gap and
       therefore cannot contact the MASA service during pledge

   4.  A registrar MAY ignore unrecognized nonceless log entries.  This
       could occur when used equipment is purchased with a valid history
       being deployed in air gap networks that required offline

   5.  A registrar MAY accept voucher formats of future types that can
       not be parsed by the Registrar.  This reduces the Registrar's
       visibility into the exact voucher contents but does not change
       the protocol operations.

7.4.  MASA security reductions

   Lower security modes chosen by the MASA service affect all device
   deployments unless the lower-security behavior is tied to specific
   device identities.  The modes described below can be applied to
   specific devices via knowledge of what devices were sold.  They can
   also be bound to specific customers (independent of the device
   identity) by authenticating the customer's Registrar.

7.4.1.  Issuing Nonceless vouchers

   A MASA has the option of not including a nonce in the voucher, and/or
   not requiring one to be present in the voucher-request.  This results
   in distribution of a voucher that may never expire and in effect
   makes the specified Domain an always trusted entity to the pledge
   during any subsequent bootstrapping attempts.  That a nonceless
   voucher was issued is captured in the log information so that the
   registrar can make appropriate security decisions when a pledge joins
   the Domain.  Nonceless vouchers are useful to support use cases where
   registrars might not be online during actual device deployment.

   While a nonceless voucher may include an expiry date, a typical use
   for a nonceless voucher is for it to be long-lived.  If the device
   can be trusted to have an accurate clock (the MASA will know), then a
   nonceless voucher CAN be issued with a limited lifetime.

   A more typical case for a nonceless voucher is for use with offline
   onboarding scenarios where it is not possible to pass a fresh
   voucher-request to the MASA.  The use of a long-lived voucher also

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   eliminates concern about the availability of the MASA many years in
   the future.  Thus many nonceless vouchers will have no expiry dates.

   Thus, the long lived nonceless voucher does not require the proof
   that the device is online.  Issuing such a thing is only accepted
   when the registrar is authenticated by the MASA and the MASA is
   authorized to provide this functionality to this customer.  The MASA
   is RECOMMENDED to use this functionality only in concert with an
   enhanced level of ownership tracking, the details of which are out of
   scope for this document.

   If the pledge device is known to have a real-time-clock that is set
   from the factory, use of a voucher validity period is RECOMMENDED.

7.4.2.  Trusting Owners on First Use

   A MASA has the option of not verifying ownership before responding
   with a voucher.  This is expected to be a common operational model
   because doing so relieves the manufacturer providing MASA services
   from having to track ownership during shipping and supply chain and
   allows for a very low overhead MASA service.  A registrar uses the
   audit log information as a defense in depth strategy to ensure that
   this does not occur unexpectedly (for example when purchasing new
   equipment the registrar would throw an error if any audit log
   information is reported.)  The MASA SHOULD verify the 'prior-signed-
   voucher-request' information for pledges that support that
   functionality.  This provides a proof-of-proximity check that reduces
   the need for ownership verification.  The proof-of-proximity comes
   from the assumption that the pledge and Join Proxy are on the same
   link-local connection.

   A MASA that practices Trust-on-First-Use (TOFU) for Registrar
   identity may wish to annotate the origin of the connection by IP
   address or netblock, and restrict future use of that identity from
   other locations.  A MASA that does this SHOULD take care to not
   create nuisance situations for itself when a customer has multiple
   registrars, or uses outgoing IPv4 NAT44 connections that change

7.4.3.  Updating or extending voucher trust anchors

   This section deals with the problem of a MASA that is no longer
   available due to a failed business, or the situation where a MASA is
   uncooperative to a secondary sale.

   A manufacturer could offer a management mechanism that allows the
   list of voucher verification trust anchors to be extended.
   [I-D.ietf-netconf-keystore] is one such interface that could be

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   implemented using YANG.  Pretty much any configuration mechanism used
   today could be extended to provide the needed additional update.  A
   manufacturer could even decide to install the domain CA trust anchors
   received during the EST "cacerts" step as voucher verification
   anchors.  Some additional signals will be needed to clearly identify
   which keys have voucher validation authority from among those signed
   by the domain CA.  This is future work.

   With the above change to the list of anchors, vouchers can be issued
   by an alternate MASA.  This could be the previous owner (the seller),
   or some other trusted third party who is mediating the sale.  If it
   was a third party, then the seller would need to have taken steps to
   introduce the third party configuration to the device prior
   disconnection.  The third party (e.g. a wholesaler of used equipment)
   could however use a mechanism described in Section 7.2 to take
   control of the device after receiving it physically.  This would
   permit the third party to act as the MASA for future onboarding
   actions.  As the IDevID certificate probably can not be replaced, the
   new owner's Registrar would have to support an override of the MASA

   To be useful for resale or other transfers of ownership one of two
   situations will need to occur.  The simplest is that the device is
   not put through any kind of factory default/reset before going
   through onboarding again.  Some other secure, physical signal would
   be needed to initiate it.  This is most suitable for redeploying a
   device within the same Enterprise.  This would entail having previous
   configuration in the system until entirely replaced by the new owner,
   and represents some level of risk.

   The second mechanism is that there would need to be two levels of
   factory reset.  One would take the system back entirely to
   manufacturer state, including removing any added trust anchors, and
   the second (more commonly used) one would just restore the
   configuration back to a known default without erasing trust anchors.
   This weaker factory reset might leave valuable credentials on the
   device and this may be unacceptable to some owners.

   As a third option, the manufacturer's trust anchors could be entirely
   overwritten with local trust anchors.  A factory default would never
   restore those anchors.  This option comes with a lot of power, but
   also a lot of responsibility: if access to the private part of the
   new anchors are lost the manufacturer may be unable to help.

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8.  IANA Considerations

   This document requires the following IANA actions:

8.1.  The IETF XML Registry

   This document registers a URI in the "IETF XML Registry" [RFC3688].
   IANA has registered the following:

      URI: urn:ietf:params:xml:ns:yang:ietf-mud-brski-masa
      Registrant Contact: The ANIMA WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

8.2.  Well-known EST registration

   This document extends the definitions of "est" (so far defined via
   RFC7030) in the "
   well-known-uris.xhtml" registry.  IANA is asked to change the
   registration of "est" to include RFC7030 and this document.

8.3.  PKIX Registry

   IANA is requested to register the following:

   This document requests a number for id-mod-MASAURLExtn2016(TBD) from
   the pkix(7) id-mod(0) Registry.

   This document has received an early allocation from the id-pe
   registry (SMI Security for PKIX Certificate Extension) for id-pe-
   masa-url with the value 32, resulting in an OID of

8.4.  Pledge BRSKI Status Telemetry

   IANA is requested to create a new Registry entitled: "BRSKI
   Parameters", and within that Registry to create a table called:
   "Pledge BRSKI Status Telemetry Attributes".  New items can be added
   using the Specification Required.  The following items are to be in
   the initial registration, with this document (Section 5.7) as the

   o  version

   o  Status

   o  Reason

   o  reason-context

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8.5.  DNS Service Names

   IANA is requested to register the following Service Names:

   Service Name: brski-proxy
   Transport Protocol(s): tcp
   Assignee: IESG <>.
   Contact: IESG <>
   Description: The Bootstrapping Remote Secure Key
                Infrastructures Proxy
   Reference: [This document]

   Service Name: brski-registrar
   Transport Protocol(s): tcp
   Assignee: IESG <>.
   Contact: IESG <>
   Description: The Bootstrapping Remote Secure Key
                Infrastructures Registrar
   Reference: [This document]

8.6.  MUD File Extension for the MASA

   The IANA is requested to list the name "masa" in the MUD extensions
   registry defined in [RFC8520].  Its use is documented in Appendix C.

9.  Applicability to the Autonomic Control Plane (ACP)

   This document provides a solution to the requirements for secure
   bootstrap set out in Using an Autonomic Control Plane for Stable
   Connectivity of Network Operations, Administration, and Maintenance
   [RFC8368], A Reference Model for Autonomic Networking
   [I-D.ietf-anima-reference-model] and specifically the An Autonomic
   Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane], section
   3.2 (Secure Bootstrap), and section 6.1 (ACP Domain, Certificate and

   The protocol described in this document has appeal in a number of
   other non-ANIMA use cases.  Such uses of the protocol will be
   deploying into other environments with different tradeoffs of
   privacy, security, reliability and autonomy from manufacturers.  As
   such those use cases will need to provide their own applicability
   statements, and will need to address unique privacy and security
   considerations for the environments in which they are used.

   The autonomic control plane (ACP) that is bootstrapped by the BRSKI
   protocol is typically used in medium to large Internet Service
   Provider organizations.  Equivalent enterprises that have significant
   layer-3 router connectivity also will find significant benefit,

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   particularly if the Enterprise has many sites.  (A network consisting
   of primarily layer-2 is not excluded, but the adjacencies that the
   ACP will create and maintain will not reflect the topology until all
   devices participate in the ACP).

   In the ACP, the Join Proxy is found to be proximal because
   communication between the pledge and the join proxy is exclusively on
   IPv6 Link-Local addresses.  The proximity of the Join Proxy to the
   Registrar is validated by the Registrar using ANI ACP IPv6 Unique
   Local Addresses (ULA).  ULAs are not routable over the Internet, so
   as long as the Join Proxy is operating correctly the proximity
   asssertion is satisfied.  Other uses of BRSKI will need make similar
   analysis if they use proximity assertions.

   As specified in the ANIMA charter, this work "..focuses on
   professionally-managed networks."  Such a network has an operator and
   can do things like install, configure and operate the Registrar
   function.  The operator makes purchasing decisions and is aware of
   what manufacturers it expects to see on its network.

   Such an operator is also capable of performing bootstrapping of a
   device using a serial-console (craft console).  The zero-touch
   mechanism presented in this and the ACP document
   [I-D.ietf-anima-autonomic-control-plane] represents a significiant
   efficiency: in particular it reduces the need to put senior experts
   on airplanes to configure devices in person.

   There is a recognition as the technology evolves that not every
   situation may work out, and occasionally a human may still have to
   visit.  In recognition of this, some mechanisms are presented in
   Section 7.2.  The manufacturer MUST provide at least one of the one-
   touch mechanisms described that permit enrollment to be proceed
   without availability of any manufacturer server (such as the MASA).

   The BRSKI protocol is going into environments where there have
   already been quite a number of vendor proprietary management systems.
   Those are not expected to go away quickly, but rather to leverage the
   secure credentials that are provisioned by BRSKI.  The connectivity
   requirements of said management systems are provided by the ACP.

9.1.  Operational Requirements

   This section collects operational requirements based upon the three
   roles involved in BRSKI: The Manufacturer Authorized Signing
   Authority (MASA), the (Domain) Owner and the Device.  It should be
   recognized that the manufacturer may be involved in two roles, as it
   creates the software/firmware for the device, and also may be the
   operator of the MASA.

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   The requirements in this section are presented using BCP14
   ([RFC2119], [RFC8174]) language.  These do not represent new
   normative statements, just a review of a few such things in one place
   by role.  They also apply specifically to the ANIMA ACP use case.
   Other use cases likely have similar, but MAY different requirements.

9.1.1.  MASA Operational Requirements

   The manufacturer MUST arrange for an online service to be available
   called the MASA.  It MUST be available at the URL which is encoded in
   the IDevID certificate extensions described in Section 2.3.2.

   The online service MUST have access to a private key with which to
   sign [RFC8366] format voucher artifacts.  The public key,
   certificate, or certificate chain MUST be built in to the device as
   part of the firmware.

   It is RECOMMENDED that the manufacturer arrange for this signing key
   (or keys) to be escrowed according to typical software source code
   escrow practices [softwareescrow].

   The MASA accepts voucher requests from Domain Owners according to an
   operational practice appropriate for the device.  This can range from
   any domain owner (first-come first-served, on a TOFU-like basis), to
   full sales channel integration where Domain Owners need to be
   positively identified by TLS Client Certicate pinned, or HTTP
   Authentication process.  The MASA creates signed voucher artifacts
   according to a it's internally defined policies.

   The MASA MUST operate an audit log for devices that is accessible.
   The audit log is designed to be easily cacheable and the MASA MAY
   find it useful to put this content on a CDN.

9.1.2.  Domain Owner Operational Requirements

   The domain owner MUST operate an EST ([RFC7030]) server with the
   extensions described in this document.  This is the JRC or Registrar.
   This JRC/EST server MUST announce itself using GRASP within the ACP.
   This EST server will typically reside with the Network Operations
   Center for the organization.

   The domain owner MAY operate an internal certificate authority (CA)
   that is seperate from the EST server, or it MAY combine all
   activities into a single device.  The determination of the
   architecture depends upon the scale and resiliency requirements of
   the organization.  Multiple JRC instances MAY be announced into the
   ACP from multiple locations to achieve an appropriate level of

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   In order to recognize which devices and which manufacturers are
   welcome on the domain owner's network, the domain owner SHOULD
   maintain a white list of manufacturers.  This MAY extend to
   integration with purchasing departments to know the serial numbers of

   The domain owner SHOULD use the resulting overlay ACP network to
   manage devices, replacing legacy out-of-band mechanisms.

   The domain owner SHOULD operate one or more EST servers which can be
   used to renew the domain certificates (LDevIDs) which are deployed to
   devices.  These servers MAY be the same as the JRC, or MAY be a
   distinct set of devices, as approriate for resiliency.

   The organization MUST take appropriate precautions against loss of
   access to the certificate authority private key.  Hardware security
   modules and/or secret splitting are appropriate.

9.1.3.  Device Operational Requirements

   Devices MUST come with built-in trust anchors that permit the device
   to validate vouchers from the MASA.

   Device MUST come with (unique, per-device) IDevID certificates that
   include their serial numbers, and the MASA URL extension.

   Devices are expected to find Join Proxies using GRASP, and then
   connect to the JRC using the protocol described in this document.

   Once a domain owner has been validated with the voucher, devices are
   expected to enroll into the domain using EST.  Devices are then
   expected to form ACPs using IPsec over IPv6 Link-Local addresses as
   described in [I-D.ietf-anima-autonomic-control-plane]

   Once a device has been enrolled it SHOULD listen for the address of
   the JRC using GRASP, and it SHOULD enable itself as a Join Proxy, and
   announce itself on all links/interfaces using GRASP DULL.

   Devices are expected to renew their certificates before they expire.

10.  Privacy Considerations

10.1.  MASA audit log

   The MASA audit log includes the domainID for each domain a voucher
   has been issued to.  This information is closely related to the
   actual domain identity.  A MASA may need additional defenses against
   Denial of Service attacks (Section 11.1), and this may involve

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   collecting additional (unspecified here) information.  This could
   provide sufficient information for the MASA service to build a
   detailed understanding the devices that have been provisioned within
   a domain.

   There are a number of design choices that mitigate this risk.  The
   domain can maintain some privacy since it has not necessarily been
   authenticated and is not authoritatively bound to the supply chain.

   Additionally the domainID captures only the unauthenticated subject
   key identifier of the domain.  A privacy sensitive domain could
   theoretically generate a new domainID for each device being deployed.
   Similarly a privacy sensitive domain would likely purchase devices
   that support proximity assertions from a manufacturer that does not
   require sales channel integrations.  This would result in a
   significant level of privacy while maintaining the security
   characteristics provided by Registrar based audit log inspection.

10.2.  What BRSKI-EST reveals

   During the provisional phase of the BRSKI-EST connection between the
   Pledge and the Registrar, each party reveals its certificates to each
   other.  For the Pledge, this includes the serialNumber attribute, the
   MASA URL, and the identity that signed the IDevID certificate.

   TLS 1.2 reveals the certificate identities to on-path observers,
   including the Join Proxy.

   TLS 1.3 reveals the certificate identities only to the end parties,
   but as the connection is provisional, an on-path attacker (MTIM) can
   see the certificates.  This includes not just malicious attackers,
   but also Registrars that are visible to the Pledge, but which are not
   part of the intended domain.

   The certificate of the Registrar is rather arbitrary from the point
   of view of the BRSKI protocol.  As no [RFC6125] validations are
   expected to be done, the contents could be easily pseudonymized.  Any
   device that can see a join proxy would be able to connect to the
   Registrar and learn the identity of the network in question.  Even if
   the contents of the certificate are pseudonymized, it would be
   possible to correlate different connections in different locations
   belong to the same entity.  This is unlikely to present a significant
   privacy concern to ANIMA ACP uses of BRSKI, but may be a concern to
   other users of BRSKI.

   The certificate of the Pledge could be revealed by a malicious Join
   Proxy that performed a MITM attack on the provisional TLS connection.

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   Such an attacker would be able to reveal the identity of the Pledge
   to third parties if it chose to so.

   Research into a mechanism to do multi-step, multi-party authenticated
   key agreement, incorporating some kind of zero-knowledge proof would
   be valuable.  Such a mechanism would ideally avoid disclosing
   identities until pledge, registrar and MASA agree to the transaction.
   Such a mechanism would need to discover the location of the MASA
   without knowing the identity of the pledge, or the identity of the
   MASA.  This part of the problem may be unsolveable.

10.3.  What BRSKI-MASA reveals to the manufacturer

   The so-called "call-home" mechanism that occurs as part of the BRSKI-
   MASA connection standardizes what has been deemed by some as a
   sinister mechanism for corporate oversight of individuals.
   ([livingwithIoT] and [IoTstrangeThings] for a small sample).

   As the Autonomic Control Plane (ACP) usage of BRSKI is not targeted
   at individual usage of IoT devices, but rather at the Enterprise and
   ISP creation of networks in a zero-touch fashion, the "call-home"
   represents a different kind of concern.

   It needs to be re-iterated that the BRSKI-MASA mechanism only occurs
   once during the commissioning of the device.  It is well defined, and
   although encrypted with TLS, it could in theory be made auditable as
   the contents are well defined.  This connection does not occur when
   the device powers on or is restarted for normal routines.  (It is
   conceivable, but remarkably unusual, that a device could be forced to
   go through a full factory reset during an exceptional firmware update
   situation, after which enrollment would have be repeated, and a new
   connection would occur)

   The BRSKI call-home mechanism is mediated via the owner's Registrar,
   and the information that is transmitted is directly auditable by the
   device owner.  This is in stark contrast to many "call-home"
   protocols where the device autonomously calls home and uses an
   undocumented protocol.

   While the contents of the signed part of the pledge voucher request
   can not be changed, they are not encrypted at the registrar.  The
   ability to audit the messages by the owner of the network is a
   mechanism to defend against exfiltration of data by a nefarious
   pledge.  Both are, to re-iterate, encrypted by TLS while in transit.

   The BRSKI-MASA exchange reveals the following information to the

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   o  the identity of the device being enrolled.  This is revealed by
      transmission of a signed voucher-request containing the serial-
      number.  The manufacturer can usually link the serial number to a
      device model.

   o  an identity of the domain owner in the form of the domain trust
      anchor.  However, this is not a global PKI anchored name within
      the WebPKI, so this identity could be pseudonymous.  If there is
      sales channel integration, then the MASA will have authenticated
      the domain owner, either via pinned certificate, or perhaps
      another HTTP authentication method, as per Section 5.5.4.

   o  the time the device is activated,

   o  the IP address of the domain Owner's Registrar.  For ISPs and
      Enterprises, the IP address provides very clear geolocation of the
      owner.  No amount of IP address privacy extensions ([RFC4941]) can
      do anything about this, as a simple whois lookup likely identifies
      the ISP or Enterprise from the upper bits anyway.  A passive
      attacker who observes the connection definitely may conclude that
      the given enterprise/ISP is a customer of the particular equipment
      vendor.  The precise model that is being enrolled will remain

   Based upon the above information, the manufacturer is able to track a
   specific device from pseudonymous domain identity to the next
   pseudonymous domain identity.  If there is sales-channel integration,
   then the identities are not pseudonymous.

   The manufacturer knows the IP address of the Registrar, but it can
   not see the IP address of the device itself.  The manufacturer can
   not track the device to a detailed physical or network location, only
   to the location of the Registrar.  That is likely to be at the
   Enterprise or ISPs headquarters.

   The above situation is to be distinguished from a residential/
   individual person who registers a device from a manufacturer.
   Individuals do not tend to have multiple offices, and their registrar
   is likely on the same network as the device.  A manufacturer that
   sells switching/routing products to enterprises should hardly be
   surprised if additional purchases switching/routing products are
   made.  Deviations from a historical trend or an establish baseline
   would, however, be notable.

   The situation is not improved by the enterprise/ISP using
   anonymization services such as ToR [Dingledine2004], as a TLS 1.2
   connection will reveal the ClientCertificate used, clearly
   identifying the enterprise/ISP involved.  TLS 1.3 is better in this

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   regard, but an active attacker can still discover the parties
   involved by performing a Man-In-The-Middle-Attack on the first
   attempt (breaking/killing it with a TCP RST), and then letting
   subsequent connection pass through.

   A manufacturer could attempt to mix the BRSKI-MASA traffic in with
   general traffic their site by hosting the MASA behind the same (set)
   of load balancers that the companies normal marketing site is hosted
   behind.  This makes lots of sense from a straight capacity planning
   point of view as the same set of services (and the same set of
   Distributed Denial of Service mitigations) may be used.
   Unfortunately, as the BRSKI-MASA connections include TLS
   ClientCertificate exchanges, this may easily be observed in TLS 1.2,
   and a traffic analysis may reveal it even in TLS 1.3.  This does not
   make such a plan irrelevant.  There may be other organizational
   reasons to keep the marketing site (which is often subject to
   frequent re-designs, outsourcing, etc.) separate from the MASA, which
   may need to operate reliably for decades.

10.4.  Manufacturers and Used or Stolen Equipment

   As explained above, the manufacturer receives information each time
   that a device which is in factory-default mode does a zero-touch
   bootstrap, and attempts to enroll into a domain owner's registrar.

   The manufacturer is therefore in a position to decline to issue a
   voucher if it detects that the new owner is not the same as the
   previous owner.

   1.  This can be seen as a feature if the equipment is believed to
       have been stolen.  If the legitimate owner notifies the
       manufacturer of the theft, then when the new owner brings the
       device up, if they use the zero-touch mechanism, the new
       (illegitimate) owner reveals their location and identity.

   2.  In the case of Used equipment, the initial owner could inform the
       manufacturer of the sale, or the manufacturer may just permit
       resales unless told otherwise.  In which case, the transfer of
       ownership simply occurs.

   3.  A manufacturer could however decide not to issue a new voucher in
       response to a transfer of ownership.  This is essentially the
       same as the stolen case, with the manufacturer having decided
       that the sale was not legitimate.

   4.  There is a fourth case, if the manufacturer is providing
       protection against stolen devices.  The manufacturer then has a
       responsibility to protect the legitimate owner against fraudulent

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       claims that the equipment was stolen.  In the absence of such
       manufacturer protection, such a claim would cause the
       manufacturer to refuse to issue a new voucher.  Should the device
       go through a deep factory reset (for instance, replacement of a
       damaged main board component, the device would not bootstrap.

   5.  Finally, there is a fifth case: the manufacturer has decided to
       end-of-line the device, or the owner has not paid a yearly
       support amount, and the manufacturer refuses to issue new
       vouchers at that point.  This last case is not new to the
       industry: many license systems are already deployed that have
       significantly worse effect.

   This section has outlined five situations in which a manufacturer
   could use the voucher system to enforce what are clearly license
   terms.  A manufacturer that attempted to enforce license terms via
   vouchers would find it rather ineffective as the terms would only be
   enforced when the device is enrolled, and this is not (to repeat), a
   daily or even monthly occurrence.

10.5.  Manufacturers and Grey market equipment

   Manufacturers of devices often sell different products into different
   regional markets.  Which product is available in which market can be
   driven by price differentials, support issues (some markets may
   require manuals and tech-support to be done in the local language),
   government export regulation (such as whether strong crypto is
   permitted to be exported, or permitted to be used in a particular
   market).  When an domain owner obtains a device from a different
   market (they can be new) and transfers it to a different location,
   this is called a Grey Market.

   A manufacturer could decide not to issue a voucher to an enterprise/
   ISP based upon their location.  There are a number of ways which this
   could be determined: from the geolocation of the registrar, from
   sales channel knowledge about the customer, and what products are
   (un-)available in that market.  If the device has a GPS the
   coordinates of the device could even be placed into an extension of
   the voucher.

   The above actions are not illegal, and not new.  Many manufacturers
   have shipped crypto-weak (exportable) versions of firmware as the
   default on equipment for decades.  The first task of an enterprise/
   ISP has always been to login to a manufacturer system, show one's
   "entitlement" (country information, proof that support payments have
   been made), and receive either a new updated firmware, or a license
   key that will activate the correct firmware.

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   BRSKI permits the above process to automated (in an autonomic
   fashion), and therefore perhaps encourages this kind of
   differentiation by reducing the cost of doing it.

   An issue that manufacturers will need to deal with in the above
   automated process is when a device is shipped to one country with one
   set of rules (or laws or entitlements), but the domain registry is in
   another one.  Which rules apply is something will have to be worked
   out: the manufacturer could come to believe they are dealing with
   Grey market equipment, when it is simply dealing with a global

10.6.  Some mitigations for meddling by manufacturers

   The most obvious mitigation is not to buy the product.  Pick
   manufacturers that are up-front about their policies, who do not
   change them gratuitously.

   Section 7.4.3 describes some ways in which a manufacturer could
   provide a mechanism to manage the trust anchors and built-in
   certificates (IDevID) as an extension.  There are a variety of
   mechanism, and some may take a substantial amount of work to get
   exactly correct.  These mechanisms do not change the flow of the
   protocol described here, but rather allow the starting trust
   assumptions to be changed.  This is an area for future
   standardization work.

   Replacement of the voucher validation anchors (usually pointing to
   the original manufacturer's MASA) with those of the new owner permits
   the new owner to issue vouchers to subsequent owners.  This would be
   done by having the selling (old) owner to run a MASA.

   The BRSKI protocol depends upon a trust anchor on the device and an
   identity on the device.  Management of these entities facilitates a
   few new operational modes without making any changes to the BRSKI
   protocol.  Those modes include: offline modes where the domain owner
   operates an internal MASA for all devices, resell modes where the
   first domain owner becomes the MASA for the next (resold-to) domain
   owner, and services where an aggregator acquires a large variety of
   devices, and then acts as a pseudonymized MASA for a variety of
   devices from a variety of manufacturers.

   Although replacement of the IDevID is not required for all modes
   described above, a manufacturers could support such a thing.  Some
   may wish to consider replacement of the IDevID as an indication that
   the device's warrantee is terminated.  For others, the privacy
   requirements of some deployments might consider this a standard
   operating practice.

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   As discussed at the end of Section 5.8.1, new work could be done to
   use a distributed consensus technology for the audit log.  This would
   permit the audit log to continue to be useful, even when there is a
   chain of MASA due to changes of ownership.

10.7.  Death of a manufacturer

   A common concern has been that a manufacturer could go out of
   business, leaving owners of devices unable to get new vouchers for
   existing products.  Said products might have been previously
   deployed, but need to be re-initialized, they might have been
   purchased used, or they might have kept in a warehouse as long-term

   The MASA was named the Manufacturer *Authorized* Signing Authority to
   emphasize that it need not be the manufacturer itself that performs
   this.  It is anticipated that specialist service providers will come
   to exist that deal with the creation of vouchers in much the same way
   that many companies have outsourced email, advertising and janitorial

   Further, it is expected that as part of any service agreement that
   the manufacturer would arrange to escrow appropriate private keys
   such that a MASA service could be provided by a third party.  This
   has routinely been done for source code for decades.

11.  Security Considerations

   This document details a protocol for bootstrapping that balances
   operational concerns against security concerns.  As detailed in the
   introduction, and touched on again in Section 7, the protocol allows
   for reduced security modes.  These attempt to deliver additional
   control to the local administrator and owner in cases where less
   security provides operational benefits.  This section goes into more
   detail about a variety of specific considerations.

   To facilitate logging and administrative oversight, in addition to
   triggering Registrar verification of MASA logs, the pledge reports on
   voucher parsing status to the registrar.  In the case of a failure,
   this information is informative to a potentially malicious registrar.
   This is mandated anyway because of the operational benefits of an
   informed administrator in cases where the failure is indicative of a
   problem.  The registrar is RECOMMENDED to verify MASA logs if voucher
   status telemetry is not received.

   To facilitate truly limited clients EST RFC7030 section 3.3.2
   requirements that the client MUST support a client authentication
   model have been reduced in Section 7 to a statement that the

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   registrar "MAY" choose to accept devices that fail cryptographic
   authentication.  This reflects current (poor) practices in shipping
   devices without a cryptographic identity that are NOT RECOMMENDED.

   During the provisional period of the connection the pledge MUST treat
   all HTTP header and content data as untrusted data.  HTTP libraries
   are regularly exposed to non-secured HTTP traffic: mature libraries
   should not have any problems.

   Pledges might chose to engage in protocol operations with multiple
   discovered registrars in parallel.  As noted above they will only do
   so with distinct nonce values, but the end result could be multiple
   vouchers issued from the MASA if all registrars attempt to claim the
   device.  This is not a failure and the pledge choses whichever
   voucher to accept based on internal logic.  The registrars verifying
   log information will see multiple entries and take this into account
   for their analytics purposes.

11.1.  Denial of Service (DoS) against MASA

   There are uses cases where the MASA could be unavailable or
   uncooperative to the Registrar.  They include active DoS attacks,
   planned and unplanned network partitions, changes to MASA policy, or
   other instances where MASA policy rejects a claim.  These introduce
   an operational risk to the Registrar owner in that MASA behavior
   might limit the ability to bootstrap a pledge device.  For example
   this might be an issue during disaster recovery.  This risk can be
   mitigated by Registrars that request and maintain long term copies of
   "nonceless" vouchers.  In that way they are guaranteed to be able to
   bootstrap their devices.

   The issuance of nonceless vouchers themselves creates a security
   concern.  If the Registrar of a previous domain can intercept
   protocol communications then it can use a previously issued nonceless
   voucher to establish management control of a pledge device even after
   having sold it.  This risk is mitigated by recording the issuance of
   such vouchers in the MASA audit log that is verified by the
   subsequent Registrar and by Pledges only bootstrapping when in a
   factory default state.  This reflects a balance between enabling MASA
   independence during future bootstrapping and the security of
   bootstrapping itself.  Registrar control over requesting and auditing
   nonceless vouchers allows device owners to choose an appropriate

   The MASA is exposed to DoS attacks wherein attackers claim an
   unbounded number of devices.  Ensuring a registrar is representative
   of a valid manufacturer customer, even without validating ownership
   of specific pledge devices, helps to mitigate this.  Pledge

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   signatures on the pledge voucher-request, as forwarded by the
   registrar in the prior-signed-voucher-request field of the registrar
   voucher-request, significantly reduce this risk by ensuring the MASA
   can confirm proximity between the pledge and the registrar making the
   request.  Supply chain integration ("know your customer") is an
   additional step that MASA providers and device vendors can explore.

11.2.  Availability of good random numbers

   Although the nonce used by the Pledge in the voucher-request does not
   require a strong cryptographic randomness, the use of TLS in all of
   the protocols in this document does.

   In particular implementations should pay attention to the advance in
   [RFC4086] section 3, particularly section 3.4.  Devices which are
   reset to factory default in order to perform a second bootstrap with
   a new owner MUST NOT seed their random number generators in the same
   way across bootstraps.

11.3.  Freshness in Voucher-Requests

   A concern has been raised that the pledge voucher-request should
   contain some content (a nonce) provided by the registrar and/or MASA
   in order for those actors to verify that the pledge voucher-request
   is fresh.

   There are a number of operational problems with getting a nonce from
   the MASA to the pledge.  It is somewhat easier to collect a random
   value from the registrar, but as the registrar is not yet vouched
   for, such a registrar nonce has little value.  There are privacy and
   logistical challenges to addressing these operational issues, so if
   such a thing were to be considered, it would have to provide some
   clear value.  This section examines the impacts of not having a fresh
   pledge voucher-request.

   Because the registrar authenticates the pledge, a full Man-in-the-
   Middle attack is not possible, despite the provisional TLS
   authentication by the pledge (see Section 5.)  Instead we examine the
   case of a fake registrar (Rm) that communicates with the pledge in
   parallel or in close time proximity with the intended registrar.
   (This scenario is intentionally supported as described in
   Section 4.1.)

   The fake registrar (Rm) can obtain a voucher signed by the MASA
   either directly or through arbitrary intermediaries.  Assuming that
   the MASA accepts the registrar voucher-request (either because Rm is
   collaborating with a legitimate registrar according to supply chain

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   information, or because the MASA is in audit-log only mode), then a
   voucher linking the pledge to the registrar Rm is issued.

   Such a voucher, when passed back to the pledge, would link the pledge
   to registrar Rm, and would permit the pledge to end the provisional
   state.  It now trusts Rm and, if it has any security vulnerabilities
   leveragable by an Rm with full administrative control, can be assumed
   to be a threat against the intended registrar.

   This flow is mitigated by the intended registrar verifying the audit
   logs available from the MASA as described in Section 5.8.  Rm might
   chose to collect a voucher-request but wait until after the intended
   registrar completes the authorization process before submitting it.
   This pledge voucher-request would be 'stale' in that it has a nonce
   that no longer matches the internal state of the pledge.  In order to
   successfully use any resulting voucher the Rm would need to remove
   the stale nonce or anticipate the pledge's future nonce state.
   Reducing the possibility of this is why the pledge is mandated to
   generate a strong random or pseudo-random number nonce.

   Additionally, in order to successfully use the resulting voucher the
   Rm would have to attack the pledge and return it to a bootstrapping
   enabled state.  This would require wiping the pledge of current
   configuration and triggering a re-bootstrapping of the pledge.  This
   is no more likely than simply taking control of the pledge directly
   but if this is a consideration the target network is RECOMMENDED to
   take the following steps:

   o  Ongoing network monitoring for unexpected bootstrapping attempts
      by pledges.

   o  Retrieval and examination of MASA log information upon the
      occurrence of any such unexpected events.  Rm will be listed in
      the logs along with nonce information for analysis.

11.4.  Trusting manufacturers

   The BRSKI extensions to EST permit a new pledge to be completely
   configured with domain specific trust anchors.  The link from built-
   in manufacturer-provided trust anchors to domain-specific trust
   anchors is mediated by the signed voucher artifact.

   If the manufacturer's IDevID signing key is not properly validated,
   then there is a risk that the network will accept a pledge that
   should not be a member of the network.  As the address of the
   manufacturer's MASA is provided in the IDevID using the extension
   from Section 2.3, the malicious pledge will have no problem
   collaborating with it's MASA to produce a completely valid voucher.

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   BRSKI does not, however, fundamentally change the trust model from
   domain owner to manufacturer.  Assuming that the pledge used its
   IDevID with RFC7030 EST and BRSKI, the domain (registrar) still needs
   to trust the manufacturer.

   Establishing this trust between domain and manufacturer is outside
   the scope of BRSKI.  There are a number of mechanisms that can
   adopted including:

   o  Manually configuring each manufacturer's trust anchor.

   o  A Trust-On-First-Use (TOFU) mechanism.  A human would be queried
      upon seeing a manufacturer's trust anchor for the first time, and
      then the trust anchor would be installed to the trusted store.
      There are risks with this; even if the key to name mapping is
      validated using something like the WebPKI, there remains the
      possibility that the name is a look alike: e.g, dem0.example. vs

   o  scanning the trust anchor from a QR code that came with the
      packaging (this is really a manual TOFU mechanism)

   o  some sales integration process where trust anchors are provided as
      part of the sales process, probably included in a digital packing
      "slip", or a sales invoice.

   o  consortium membership, where all manufacturers of a particular
      device category (e.g, a light bulb, or a cable-modem) are signed
      by an certificate authority specifically for this.  This is done
      by CableLabs today.  It is used for authentication and
      authorization as part of TR-79: [docsisroot] and [TR069].

   The existing WebPKI provides a reasonable anchor between manufacturer
   name and public key.  It authenticates the key.  It does not provide
   a reasonable authorization for the manufacturer, so it is not
   directly useable on it's own.

11.5.  Manufacturer Maintenance of trust anchors

   BRSKI depends upon the manufacturer building in trust anchors to the
   pledge device.  The voucher artifact which is signed by the MASA will
   be validated by the pledge using that anchor.  This implies that the
   manufacturer needs to maintain access to a signing key that the
   pledge can validate.

   The manufacturer will need to maintain the ability to make signatures
   that can be validated for the lifetime that the device could be
   onboarded.  Whether this onboarding lifetime is less than the device

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   lifetime depends upon how the device is used.  An inventory of
   devices kept in a warehouse as spares might not be onboarded for many

   There are good cryptographic hygiene reasons why a manufacturer would
   not want to maintain access to a private key for many decades.  A
   manufacturer in that situation can leverage a long-term certificate
   authority anchor, built-in to the pledge, and then a certificate
   chain may be incorporated using the normal CMS certificate set.  This
   may increase the size of the voucher artifacts, but that is not a
   significant issues in non-constrained environments.

   There are a few other operational variations that manufacturers could
   consider.  For instance, there is no reason that every device need
   have the same set of trust anchors pre-installed.  Devices built in
   different factories, or on different days, or any other consideration
   could have different trust anchors built in, and the record of which
   batch the device is in would be recorded in the asset database.  The
   manufacturer would then know which anchor to sign an artifact

   Aside from the concern about long-term access to private keys, a
   major limiting factor for the shelf-life of many devices will be the
   age of the cryptographic algorithms included.  A device produced in
   2019 will have hardware and software capable of validating algorithms
   common in 2019, and will have no defense against attacks (both
   quantum and von-neuman brute force attacks) which have not yet been
   invented.  This concern is orthogonal to the concern about access to
   private keys, but this concern likely dominates and limits the
   lifespan of a device in a warehouse.  If any update to firmware to
   support new cryptographic mechanism were possible (while the device
   was in a warehouse), updates to trust anchors would also be done at
   the same time.

   The set of standard operating procedures for maintaining high value
   private keys is well documented.  For instance, the WebPKI provides a
   number of options for audits at [cabforumaudit], and the DNSSEC root
   operations are well documented at [dnssecroot].

   It is not clear if Manufacturers will take this level of precaution,
   or how strong the economic incentives are to maintain an appropriate
   level of security.

   This next section examines the risk due to a compromised manufacturer
   IDevID signing key.  This is followed by examination of the risk due
   to a compromised MASA key.  The third section sections below examines
   the situation where MASA web server itself is under attacker control,

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   but that the MASA signing key itself is safe in a not-directly
   connected hardware module.

11.5.1.  Compromise of Manufacturer IDevID signing keys

   An attacker that has access to the key that the manufacturer uses to
   sign IDevID certificates can create counterfeit devices.  Such
   devices can claim to be from a particular manufacturer, but be
   entirely different devices: Trojan horses in effect.

   As the attacker controls the MASA URL in the certificate, the
   registrar can be convinced to talk to the attackers' MASA.  The
   Registrar does not need to be in any kind of promiscuous mode to be

   In addition to creating fake devices, the attacker may also be able
   to issue revocations for existing certificates if the IDevID
   certificate process relies upon CRL lists that are distributed.

   There does not otherwise seem to be any risk from this compromise to
   devices which are already deployed, or which are sitting locally in
   boxes waiting for deployment (local spares).  The issue is that
   operators will be unable to trust devices which have been in an
   uncontrolled warehouse as they do not know if those are real devices.

11.5.2.  Compromise of MASA signing keys

   There are two periods of time in which to consider: when the MASA key
   has fallen into the hands of an attacker, and after the MASA
   recognizes that the key has been compromised.  Attacker opportunties with compromised MASA key

   An attacker that has access to the MASA signing key could create
   vouchers.  These vouchers could be for existing deployed devices, or
   for devices which are still in a warehouse.  In order to exploit
   these vouchers two things need to occur: the device has to go through
   a factory default boot cycle, and the registrar has to be convinced
   to contact the attacker's MASA.

   If the attacker controls a Registrar which is visible to the device,
   then there is no difficulty in delivery of the false voucher.  A
   possible practical example of an attack like this would be in a data
   center, at an ISP peering point (whether a public IX, or a private
   peering point).  In such a situation, there are already cables
   attached to the equipment that lead to other devices (the peers at
   the IX), and through those links, the false voucher could be
   delivered.  The difficult part would be get the device put through a

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   factory reset.  This might be accomplished through social engineering
   of data center staff.  Most locked cages have ventilation holes, and
   possibly a long "paperclip" could reach through to depress a factory
   reset button.  Once such a piece of ISP equipment has been
   compromised, it could be used to compromise equipment that was
   connected to (through long haul links even), assuming that those
   pieces of equipment could also be forced through a factory reset.

   The above scenario seems rather unlikely as it requires some element
   of physical access; but were there a remote exploit that did not
   cause a direct breach, but rather a fault that resulted in a factory
   reset, this could provide a reasonable path.

   The above deals with ANI uses of BRSKI.  For cases where 802.11 or
   802.15.4 is involved, the need to connect directly to the device is
   eliminated, but the need to do a factory reset is not.  Physical
   possession of the device is not required as above, provided that
   there is some way to force a factory reset.  With some consumers
   devices with low overall implementation quality, the end users might
   be familiar with needing to reset the device regularly.

   The authors are unable to come up with an attack scenario where a
   compromised voucher signature enables an attacker to introduce a
   compromised pledge into an existing operator's network.  This is the
   case because the operator controls the communication between
   Registrar and MASA, and there is no opportunity to introduce the fake
   voucher through that conduit.  Risks after key compromise is known

   Once the operator of the MASA realizes that the voucher signing key
   has been compromised it has to do a few things.

   First, it MUST issue a firmware update to all devices that had that
   key as a trust anchor, such that they will no longer trust vouchers
   from that key.  This will affect devices in the field which are
   operating, but those devices, being in operation, are not performing
   onboarding operations, so this is not a critical patch.

   Devices in boxes (in warehouses) are vulnerable, and remain
   vulnerable until patched.  An operator would be prudent to unbox the
   devices, onboard them in a safe environment, and then perform
   firmware updates.  This does not have to be done by the end-operator;
   it could be done by a distributor that stores the spares.  A
   recommended practice for high value devices (which typically have a
   <4hr service window) may be to validate the device operation on a
   regular basis anyway.

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   If the onboarding process includes attestations about firmware
   versions, then through that process the operator would be advised to
   upgrade the firmware before going into production.  Unfortunately,
   this does not help against situations where the attacker operates
   their own Registrar (as listed above).

   [RFC8366] section 6.1 explains the need for short-lived vouchers.
   The nonce guarantees freshness, and the short-lived nature of the
   voucher means that the window to deliver a fake voucher is very
   short.  A nonceless, long-lived voucher would be the only option for
   the attacker, and devices in the warehouse would be vulnerable to
   such a thing.

   A key operational recommendation is for manufacturers to sign
   nonceless, long-lived vouchers with a different key that they sign
   short-lived vouchers.  That key needs significantly better
   protection.  If both keys come from a common trust-anchor (the
   manufacturer's CA), then a compromise of the manufacturer's CA would
   compromise both keys.  Such a compromise of the manufacturer's CA
   likely compromises all keys outlined in this section.

11.5.3.  Compromise of MASA web service

   An attacker that takes over the MASA web service has a number of
   attacks.  The most obvious one is simply to take the database listing
   customers and devices and to sell this data to other attackers who
   will now know where to find potentially vulnerable devices.

   The second most obvious thing that the attacker can do is to kill the
   service, or make it operate unreliably, making customers frustrated.
   This could have a serious affect on ability to deploy new services by
   customers, and would be a significant issue during disaster recovery.

   While the compromise of the MASA web service may lead to the
   compromise of the MASA voucher signing key, if the signing occurs
   offboard (such as in a hardware signing module, HSM), then the key
   may well be safe, but control over it resides with the attacker.

   Such an attacker can issue vouchers for any device presently in
   service.  Said device still needs to be convinced to do through a
   factory reset process before an attack.

   If the attacker has access to a key that is trusted for long-lived
   nonceless vouchers, then they could issue vouchers for devices which
   are not yet in service.  This attack may be very hard to verify and
   as it would involve doing firmware updates on every device in
   warehouses (a potentially ruinously expensive process), a
   manufacturer might be reluctant to admit this possibility.

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12.  Acknowledgements

   We would like to thank the various reviewers for their input, in
   particular William Atwood, Brian Carpenter, Fuyu Eleven, Eliot Lear,
   Sergey Kasatkin, Anoop Kumar, Markus Stenberg, Peter van der Stok,
   and Thomas Werner

   Significant reviews were done by Jari Arko, Christian Huitema and
   Russ Housley.

   Henk Birkholz contributed the CDDL for the audit log response.

   This document started it's life as a two-page idea from Steinthor

   In addition, significant review comments were received by many IESG
   members, including Adam Roach, Alexey Melnikov, Alissa Cooper,
   Benjamin Kaduk, Eric Vyncke, Roman Danyliw, and Magnus Westerlund.

13.  References

13.1.  Normative References

              Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
              Control Plane (ACP)", draft-ietf-anima-autonomic-control-
              plane-20 (work in progress), July 2019.

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

   [IDevID]   "IEEE 802.1AR Secure Device Identifier", December 2009,

              International Telecommunications Union, "Information
              Technology - ASN.1 encoding rules: Specification of Basic
              Encoding Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", ITU-T Recommendation
              X.690, 1994.

   [REST]     Fielding, R., "Architectural Styles and the Design of
              Network-based Software Architectures", 2000,

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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              DOI 10.17487/RFC3927, May 2005,

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,

   [RFC4519]  Sciberras, A., Ed., "Lightweight Directory Access Protocol
              (LDAP): Schema for User Applications", RFC 4519,
              DOI 10.17487/RFC4519, June 2006,

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,

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   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,

   [RFC5386]  Williams, N. and M. Richardson, "Better-Than-Nothing
              Security: An Unauthenticated Mode of IPsec", RFC 5386,
              DOI 10.17487/RFC5386, November 2008,

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,

   [RFC5660]  Williams, N., "IPsec Channels: Connection Latching",
              RFC 5660, DOI 10.17487/RFC5660, October 2009,

   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)
              Extensions: Extension Definitions", RFC 6066,
              DOI 10.17487/RFC6066, January 2011,

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,

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   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,

   [RFC7469]  Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
              Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
              2015, <>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,

   [RFC8368]  Eckert, T., Ed. and M. Behringer, "Using an Autonomic
              Control Plane for Stable Connectivity of Network
              Operations, Administration, and Maintenance (OAM)",
              RFC 8368, DOI 10.17487/RFC8368, May 2018,

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,

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   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <>.

13.2.  Informative References

   [brewski]  "Urban Dictionary: Brewski", October 2019,

              "Information for Auditors and Assessors", August 2019,

              Dingledine, R., Mathewson, N., and P. Syverson, "Tor: the
              second-generation onion router", 2004,

              "DNSSEC Practice Statement for the Root Zone ZSK
              Operator", December 2017,

              "CableLabs Digital Certificate Issuance Service", February
              2018, <

              Stok, P., Kampanakis, P., Richardson, M., and S. Raza,
              "EST over secure CoAP (EST-coaps)", draft-ietf-ace-coap-
              est-15 (work in progress), October 2019.

              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", draft-
              ietf-anima-constrained-voucher-05 (work in progress), July

              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              and J. Nobre, "A Reference Model for Autonomic
              Networking", draft-ietf-anima-reference-model-10 (work in
              progress), November 2018.

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              Eckert, T. and M. Behringer, "Using Autonomic Control
              Plane for Stable Connectivity of Network OAM", draft-ietf-
              anima-stable-connectivity-10 (work in progress), February

              Watsen, K., "A YANG Data Model for a Keystore", draft-
              ietf-netconf-keystore-12 (work in progress), July 2019.

              Richardson, M., "Considerations for stateful vs stateless
              join router in ANIMA bootstrap", draft-richardson-anima-
              state-for-joinrouter-02 (work in progress), January 2018.

              "Wikipedia article: Imprinting", July 2015,

              "IoT of toys stranger than fiction: Cybersecurity and data
              privacy update (accessed 2018-12-02)", March 2017,

              "What is it actually like to live in a house filled with
              IoT devices? (accessed 2018-12-02)", February 2018,

   [openssl]  "OpenSSL X509 utility", September 2019,

   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations",
              RFC 2663, DOI 10.17487/RFC2663, August 1999,

   [RFC5209]  Sangster, P., Khosravi, H., Mani, M., Narayan, K., and J.
              Tardo, "Network Endpoint Assessment (NEA): Overview and
              Requirements", RFC 5209, DOI 10.17487/RFC5209, June 2008,

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   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              DOI 10.17487/RFC5785, April 2010,

   [RFC6960]  Santesson, S., Myers, M., Ankney, R., Malpani, A.,
              Galperin, S., and C. Adams, "X.509 Internet Public Key
              Infrastructure Online Certificate Status Protocol - OCSP",
              RFC 6960, DOI 10.17487/RFC6960, June 2013,

   [RFC6961]  Pettersen, Y., "The Transport Layer Security (TLS)
              Multiple Certificate Status Request Extension", RFC 6961,
              DOI 10.17487/RFC6961, June 2013,

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <>.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <>.

   [RFC7575]  Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking: Definitions and Design Goals", RFC 7575,
              DOI 10.17487/RFC7575, June 2015,

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,

   [RFC8520]  Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
              Description Specification", RFC 8520,
              DOI 10.17487/RFC8520, March 2019,

   [RFC8572]  Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
              Touch Provisioning (SZTP)", RFC 8572,
              DOI 10.17487/RFC8572, April 2019,

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              "Slowloris (computer security)", February 2019,

              "Wikipedia article: Software Escrow", October 2019,

              Stajano, F. and R. Anderson, "The resurrecting duckling:
              security issues for ad-hoc wireless networks", 1999,

   [TR069]    "TR-69: CPE WAN Management Protocol", February 2018,

              Tennison, J., "Good Practices for Capability URLs", World
              Wide Web Consortium WD WD-capability-urls-20140218,
              February 2014,

Appendix A.  IPv4 and non-ANI operations

   The secification of BRSKI in Section 4 intentionally only covers the
   mechanisms for an IPv6 pledge using Link-Local addresses.  This
   section describes non-normative extensions that can be used in other

A.1.  IPv4 Link Local addresses

   Instead of an IPv6 link-local address, an IPv4 address may be
   generated using [RFC3927] Dynamic Configuration of IPv4 Link-Local

   In the case that an IPv4 Link-Local address is formed, then the
   bootstrap process would continue as in the IPv6 case by looking for a
   (circuit) proxy.

A.2.  Use of DHCPv4

   The Plege MAY obtain an IP address via DHCP [RFC2131].  The DHCP
   provided parameters for the Domain Name System can be used to perform
   DNS operations if all local discovery attempts fail.

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Appendix B.  mDNS / DNSSD proxy discovery options

   Pledge discovery of the proxy (Section 4.1) MAY be performed with
   DNS-based Service Discovery [RFC6763] over Multicast DNS [RFC6762] to
   discover the proxy at "_brski-proxy._tcp.local.".

   Proxy discovery of the registrar (Section 4.3) MAY be performed with
   DNS-based Service Discovery over Multicast DNS to discover registrars
   by searching for the service "_brski-registrar._tcp.local.".

   To prevent unaccceptable levels of network traffic, when using mDNS,
   the congestion avoidance mechanisms specified in [RFC6762] section 7
   MUST be followed.  The pledge SHOULD listen for an unsolicited
   broadcast response as described in [RFC6762].  This allows devices to
   avoid announcing their presence via mDNS broadcasts and instead
   silently join a network by watching for periodic unsolicited
   broadcast responses.

   Discovery of registrar MAY also be performed with DNS-based service
   discovery by searching for the service "_brski-
   registrar._tcp.<domain>".  In this case the domain "" is
   discovered as described in [RFC6763] section 11 (Appendix A.2
   suggests the use of DHCP parameters).

   If no local proxy or registrar service is located using the GRASP
   mechanisms or the above mentioned DNS-based Service Discovery
   methods, the pledge MAY contact a well known manufacturer provided
   bootstrapping server by performing a DNS lookup using a well known
   URI such as "".  The details
   of the URI are manufacturer specific.  Manufacturers that leverage
   this method on the pledge are responsible for providing the registrar
   service.  Also see Section 2.7.

   The current DNS services returned during each query are maintained
   until bootstrapping is completed.  If bootstrapping fails and the
   pledge returns to the Discovery state, it picks up where it left off
   and continues attempting bootstrapping.  For example, if the first
   Multicast DNS _bootstrapks._tcp.local response doesn't work then the
   second and third responses are tried.  If these fail the pledge moves
   on to normal DNS-based Service Discovery.

Appendix C.  MUD Extension

   The following extension augments the MUD model to include a single
   node, as described in [RFC8520] section 3.6, using the following
   sample module that has the following tree structure:

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   module: ietf-mud-brski-masa
   augment /ietf-mud:mud:
   +--rw masa-server?   inet:uri

   The model is defined as follows:

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   <CODE BEGINS> file "ietf-mud-brski-masaurl-extension@2018-02-14.yang"
   module ietf-mud-brski-masa {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-mud-brski-masa";
     prefix ietf-mud-brski-masa;
     import ietf-mud {
       prefix ietf-mud;
     import ietf-inet-types {
       prefix inet;

       "IETF ANIMA (Autonomic Networking Integrated Model and
       Approach) Working Group";
       "WG Web:
       WG List:
       "BRSKI extension to a MUD file to indicate the
       MASA URL.";

     revision 2018-02-14 {
       "Initial revision.";
       "RFC XXXX: Manufacturer Usage Description

     augment "/ietf-mud:mud" {
       "BRSKI extension to a MUD file to indicate the
       MASA URL.";
       leaf masa-server {
         type inet:uri;
         "This value is the URI of the MASA server";

   The MUD extensions string "masa" is defined, and MUST be included in
   the extensions array of the mud container of a MUD file when this
   extension is used.

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Appendix D.  Example Vouchers

   Three entities are involved in a voucher: the MASA issues (signs) it,
   the registrar's public key is mentioned in the voucher, and the
   pledge validates it.  In order to provide reproduceable examples the
   public and private keys for an example MASA and registrar are first

D.1.  Keys involved

   The Manufacturer has a Certificate Authority that signs the pledge's
   IDevID.  In addition the Manufacturer's signing authority (the MASA)
   signs the vouchers, and that certificate must distributed to the
   devices at manufacturing time so that vouchers can be validated.

D.1.1.  MASA key pair for voucher signatures

   This private key signs vouchers:

   -----END EC PRIVATE KEY-----

   This public key validates vouchers:

   -----END CERTIFICATE-----

D.1.2.  Manufacturer key pair for IDevID signatures

   This private key signs IDevID certificates:

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   -----END EC PRIVATE KEY-----

   This public key validates IDevID certificates:

   -----END CERTIFICATE-----

D.1.3.  Registrar key pair

   The registrar key (or chain) is the representative of the domain
   owner.  This key signs registrar voucher-requests:

   -----END EC PRIVATE KEY-----

   The public key is indicated in a pledge voucher-request to show

   -----END CERTIFICATE-----

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   The registrar public certificate as decoded by openssl's x509
   utility.  Note that the registrar certificate is marked with the
   cmcRA extension.

           Version: 3 (0x2)
           Serial Number: 3 (0x3)
       Signature Algorithm: ecdsa-with-SHA384
           Issuer: DC=ca, DC=sandelman, CN=Unstrung Fountain CA
               Not Before: Sep  5 01:12:45 2017 GMT
               Not After : Sep  5 01:12:45 2019 GMT
           Subject: DC=ca, DC=sandelman, CN=localhost
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
                   ASN1 OID: prime256v1
           X509v3 extensions:
               X509v3 Basic Constraints:
       Signature Algorithm: ecdsa-with-SHA384

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D.1.4.  Pledge key pair

   The pledge has an IDevID key pair built in at manufacturing time:

   -----END EC PRIVATE KEY-----

   The public key is used by the registrar to find the MASA.  The MASA
   URL is in an extension described in Section 2.3.

   -----END CERTIFICATE-----

   The pledge public certificate as decoded by openssl's x509 utility so
   that the extensions can be seen.  This was version 1.1.1c of the
   [openssl] library and utility.  There is a second Custom Extension is
   included to provided to contain the EUI48/EUI64 that the pledge will
   configure as it's layer-2 address (this is non-normative).

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        Version: 3 (0x2)
        Serial Number: 166573225 (0x9edb4a9)
        Signature Algorithm: ecdsa-with-SHA256
        Issuer: DC = ca, DC = sandelman, CN = Unstrung Highway CA
            Not Before: Apr 24 02:16:58 2019 GMT
            Not After : Dec 31 00:00:00 2999 GMT
        Subject: serialNumber = 00-d0-e5-02-00-2d
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (256 bit)
                ASN1 OID: prime256v1
                NIST CURVE: P-256
        X509v3 extensions:
            X509v3 Subject Key Identifier:
            X509v3 Basic Constraints:
            X509v3 Subject Alternative Name:
    Signature Algorithm: ecdsa-with-SHA256

D.2.  Example process

   The JSON examples below are wrapped at 60 columns.  This results in
   strings that have newlines in them, which makes them invalid JSON as
   is.  The strings would otherwise be too long, so they need to be
   unwrapped before processing.

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D.2.1.  Pledge to Registrar

   As described in Section 5.2, the pledge will sign a pledge voucher-
   request containing the registrar's public key in the proximity-
   registrar-cert field.  The base64 has been wrapped at 60 characters
   for presentation reasons.

   -----BEGIN CMS-----
   -----END CMS-----

   file: examples/vr_00-D0-E5-02-00-2D.pkcs

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   The ASN1 decoding of the artifact:

    0:d=0  hl=4 l=1717 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1702 cons: cont [ 0 ]
   19:d=2  hl=4 l=1698 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l= 849 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l= 834 cons: cont [ 0 ]
   60:d=5  hl=4 l= 830 prim: OCTET STRING      :{"ietf-voucher-request:v
  894:d=3  hl=4 l= 520 cons: cont [ 0 ]
  898:d=4  hl=4 l= 516 cons: SEQUENCE
  902:d=5  hl=4 l= 395 cons: SEQUENCE
  906:d=6  hl=2 l=   3 cons: cont [ 0 ]
  908:d=7  hl=2 l=   1 prim: INTEGER           :02
  911:d=6  hl=2 l=   4 prim: INTEGER           :09EDB4A9
  917:d=6  hl=2 l=  10 cons: SEQUENCE
  919:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
  929:d=6  hl=2 l=  77 cons: SEQUENCE
  931:d=7  hl=2 l=  18 cons: SET
  933:d=8  hl=2 l=  16 cons: SEQUENCE
  935:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  947:d=9  hl=2 l=   2 prim: IA5STRING         :ca
  951:d=7  hl=2 l=  25 cons: SET
  953:d=8  hl=2 l=  23 cons: SEQUENCE
  955:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  967:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
  978:d=7  hl=2 l=  28 cons: SET
  980:d=8  hl=2 l=  26 cons: SEQUENCE
  982:d=9  hl=2 l=   3 prim: OBJECT            :commonName
  987:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
 1008:d=6  hl=2 l=  32 cons: SEQUENCE
 1010:d=7  hl=2 l=  13 prim: UTCTIME           :190424021658Z
 1025:d=7  hl=2 l=  15 prim: GENERALIZEDTIME   :29991231000000Z
 1042:d=6  hl=2 l=  28 cons: SEQUENCE
 1044:d=7  hl=2 l=  26 cons: SET
 1046:d=8  hl=2 l=  24 cons: SEQUENCE
 1048:d=9  hl=2 l=   3 prim: OBJECT            :serialNumber
 1053:d=9  hl=2 l=  17 prim: UTF8STRING        :00-d0-e5-02-00-2d
 1072:d=6  hl=2 l=  89 cons: SEQUENCE
 1074:d=7  hl=2 l=  19 cons: SEQUENCE
 1076:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 1085:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 1095:d=7  hl=2 l=  66 prim: BIT STRING

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 1163:d=6  hl=3 l= 135 cons: cont [ 3 ]
 1166:d=7  hl=3 l= 132 cons: SEQUENCE
 1169:d=8  hl=2 l=  29 cons: SEQUENCE
 1171:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Ident
 1176:d=9  hl=2 l=  22 prim: OCTET STRING      [HEX DUMP]:04148FC298754A
 1200:d=8  hl=2 l=   9 cons: SEQUENCE
 1202:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 1207:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 1211:d=8  hl=2 l=  43 cons: SEQUENCE
 1213:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Alternati
 1218:d=9  hl=2 l=  36 prim: OCTET STRING      [HEX DUMP]:3022A02006092B
 1256:d=8  hl=2 l=  43 cons: SEQUENCE
 1258:d=9  hl=2 l=   9 prim: OBJECT            :
 1269:d=9  hl=2 l=  30 prim: OCTET STRING      [HEX DUMP]:0C1C6D6173612E
 1301:d=5  hl=2 l=  10 cons: SEQUENCE
 1303:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1313:d=5  hl=2 l= 103 prim: BIT STRING
 1418:d=3  hl=4 l= 299 cons: SET
 1422:d=4  hl=4 l= 295 cons: SEQUENCE
 1426:d=5  hl=2 l=   1 prim: INTEGER           :01
 1429:d=5  hl=2 l=  85 cons: SEQUENCE
 1431:d=6  hl=2 l=  77 cons: SEQUENCE
 1433:d=7  hl=2 l=  18 cons: SET
 1435:d=8  hl=2 l=  16 cons: SEQUENCE
 1437:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1449:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 1453:d=7  hl=2 l=  25 cons: SET
 1455:d=8  hl=2 l=  23 cons: SEQUENCE
 1457:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1469:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 1480:d=7  hl=2 l=  28 cons: SET
 1482:d=8  hl=2 l=  26 cons: SEQUENCE
 1484:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1489:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
 1510:d=6  hl=2 l=   4 prim: INTEGER           :09EDB4A9
 1516:d=5  hl=2 l=  11 cons: SEQUENCE
 1518:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 1529:d=5  hl=2 l= 105 cons: cont [ 0 ]
 1531:d=6  hl=2 l=  24 cons: SEQUENCE
 1533:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 1544:d=7  hl=2 l=  11 cons: SET
 1546:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 1557:d=6  hl=2 l=  28 cons: SEQUENCE
 1559:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 1570:d=7  hl=2 l=  15 cons: SET
 1572:d=8  hl=2 l=  13 prim: UTCTIME           :190515212555Z
 1587:d=6  hl=2 l=  47 cons: SEQUENCE
 1589:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest

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 1600:d=7  hl=2 l=  34 cons: SET
 1602:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:1037694FEDAAB0
 1636:d=5  hl=2 l=  10 cons: SEQUENCE
 1638:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1648:d=5  hl=2 l=  71 prim: OCTET STRING      [HEX DUMP]:30450220461084

   The JSON contained in the voucher request:


D.2.2.  Registrar to MASA

   As described in Section 5.5 the registrar will sign a registrar
   voucher-request, and will include pledge's voucher request in the

   -----BEGIN CMS-----

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   -----END CMS-----

   file: examples/parboiled_vr_00_D0-E5-02-00-2D.pkcs

   The ASN1 decoding of the artifact:

    0:d=0  hl=4 l=3987 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=3972 cons: cont [ 0 ]
   19:d=2  hl=4 l=3968 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l=2516 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l=2501 cons: cont [ 0 ]
   60:d=5  hl=4 l=2497 prim: OCTET STRING      :{"ietf-voucher-request:v
 2561:d=3  hl=4 l=1090 cons: cont [ 0 ]
 2565:d=4  hl=4 l= 465 cons: SEQUENCE
 2569:d=5  hl=4 l= 342 cons: SEQUENCE
 2573:d=6  hl=2 l=   3 cons: cont [ 0 ]
 2575:d=7  hl=2 l=   1 prim: INTEGER           :02
 2578:d=6  hl=2 l=   1 prim: INTEGER           :02
 2581:d=6  hl=2 l=  10 cons: SEQUENCE
 2583:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA384
 2593:d=6  hl=2 l= 113 cons: SEQUENCE
 2595:d=7  hl=2 l=  18 cons: SET
 2597:d=8  hl=2 l=  16 cons: SEQUENCE
 2599:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent

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 2611:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 2615:d=7  hl=2 l=  25 cons: SET
 2617:d=8  hl=2 l=  23 cons: SEQUENCE
 2619:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2631:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 2642:d=7  hl=2 l=  64 cons: SET
 2644:d=8  hl=2 l=  62 cons: SEQUENCE
 2646:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 2651:d=9  hl=2 l=  55 prim: UTF8STRING        :#<SystemVariable:0x00000
 2708:d=6  hl=2 l=  30 cons: SEQUENCE
 2710:d=7  hl=2 l=  13 prim: UTCTIME           :171107234528Z
 2725:d=7  hl=2 l=  13 prim: UTCTIME           :191107234528Z
 2740:d=6  hl=2 l=  67 cons: SEQUENCE
 2742:d=7  hl=2 l=  18 cons: SET
 2744:d=8  hl=2 l=  16 cons: SEQUENCE
 2746:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2758:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 2762:d=7  hl=2 l=  25 cons: SET
 2764:d=8  hl=2 l=  23 cons: SEQUENCE
 2766:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2778:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 2789:d=7  hl=2 l=  18 cons: SET
 2791:d=8  hl=2 l=  16 cons: SEQUENCE
 2793:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 2798:d=9  hl=2 l=   9 prim: UTF8STRING        :localhost
 2809:d=6  hl=2 l=  89 cons: SEQUENCE
 2811:d=7  hl=2 l=  19 cons: SEQUENCE
 2813:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 2822:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 2832:d=7  hl=2 l=  66 prim: BIT STRING
 2900:d=6  hl=2 l=  13 cons: cont [ 3 ]
 2902:d=7  hl=2 l=  11 cons: SEQUENCE
 2904:d=8  hl=2 l=   9 cons: SEQUENCE
 2906:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 2911:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 2915:d=5  hl=2 l=  10 cons: SEQUENCE
 2917:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA384
 2927:d=5  hl=2 l= 105 prim: BIT STRING
 3034:d=4  hl=4 l= 617 cons: SEQUENCE
 3038:d=5  hl=4 l= 495 cons: SEQUENCE
 3042:d=6  hl=2 l=   3 cons: cont [ 0 ]
 3044:d=7  hl=2 l=   1 prim: INTEGER           :02
 3047:d=6  hl=2 l=   1 prim: INTEGER           :03
 3050:d=6  hl=2 l=  10 cons: SEQUENCE
 3052:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3062:d=6  hl=2 l= 109 cons: SEQUENCE
 3064:d=7  hl=2 l=  18 cons: SET
 3066:d=8  hl=2 l=  16 cons: SEQUENCE

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 3068:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3080:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3084:d=7  hl=2 l=  25 cons: SET
 3086:d=8  hl=2 l=  23 cons: SEQUENCE
 3088:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3100:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3111:d=7  hl=2 l=  60 cons: SET
 3113:d=8  hl=2 l=  58 cons: SEQUENCE
 3115:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3120:d=9  hl=2 l=  51 prim: UTF8STRING
 3173:d=6  hl=2 l=  30 cons: SEQUENCE
 3175:d=7  hl=2 l=  13 prim: UTCTIME           :190113225444Z
 3190:d=7  hl=2 l=  13 prim: UTCTIME           :210112225444Z
 3205:d=6  hl=2 l= 109 cons: SEQUENCE
 3207:d=7  hl=2 l=  18 cons: SET
 3209:d=8  hl=2 l=  16 cons: SEQUENCE
 3211:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3223:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3227:d=7  hl=2 l=  25 cons: SET
 3229:d=8  hl=2 l=  23 cons: SEQUENCE
 3231:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3243:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3254:d=7  hl=2 l=  60 cons: SET
 3256:d=8  hl=2 l=  58 cons: SEQUENCE
 3258:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3263:d=9  hl=2 l=  51 prim: UTF8STRING
 3316:d=6  hl=2 l= 118 cons: SEQUENCE
 3318:d=7  hl=2 l=  16 cons: SEQUENCE
 3320:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 3329:d=8  hl=2 l=   5 prim: OBJECT            :secp384r1
 3336:d=7  hl=2 l=  98 prim: BIT STRING
 3436:d=6  hl=2 l=  99 cons: cont [ 3 ]
 3438:d=7  hl=2 l=  97 cons: SEQUENCE
 3440:d=8  hl=2 l=  15 cons: SEQUENCE
 3442:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 3447:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 3450:d=9  hl=2 l=   5 prim: OCTET STRING      [HEX DUMP]:30030101FF
 3457:d=8  hl=2 l=  14 cons: SEQUENCE
 3459:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Key Usage
 3464:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 3467:d=9  hl=2 l=   4 prim: OCTET STRING      [HEX DUMP]:03020106
 3473:d=8  hl=2 l=  29 cons: SEQUENCE
 3475:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Ident
 3480:d=9  hl=2 l=  22 prim: OCTET STRING      [HEX DUMP]:0414B9A5F6CB11
 3504:d=8  hl=2 l=  31 cons: SEQUENCE
 3506:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Authority Key Ide
 3511:d=9  hl=2 l=  24 prim: OCTET STRING      [HEX DUMP]:30168014B9A5F6
 3537:d=5  hl=2 l=  10 cons: SEQUENCE

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 3539:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3549:d=5  hl=2 l= 104 prim: BIT STRING
 3655:d=3  hl=4 l= 332 cons: SET
 3659:d=4  hl=4 l= 328 cons: SEQUENCE
 3663:d=5  hl=2 l=   1 prim: INTEGER           :01
 3666:d=5  hl=2 l= 118 cons: SEQUENCE
 3668:d=6  hl=2 l= 113 cons: SEQUENCE
 3670:d=7  hl=2 l=  18 cons: SET
 3672:d=8  hl=2 l=  16 cons: SEQUENCE
 3674:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3686:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3690:d=7  hl=2 l=  25 cons: SET
 3692:d=8  hl=2 l=  23 cons: SEQUENCE
 3694:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3706:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3717:d=7  hl=2 l=  64 cons: SET
 3719:d=8  hl=2 l=  62 cons: SEQUENCE
 3721:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3726:d=9  hl=2 l=  55 prim: UTF8STRING        :#<SystemVariable:0x00000
 3783:d=6  hl=2 l=   1 prim: INTEGER           :02
 3786:d=5  hl=2 l=  11 cons: SEQUENCE
 3788:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 3799:d=5  hl=2 l= 105 cons: cont [ 0 ]
 3801:d=6  hl=2 l=  24 cons: SEQUENCE
 3803:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 3814:d=7  hl=2 l=  11 cons: SET
 3816:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 3827:d=6  hl=2 l=  28 cons: SEQUENCE
 3829:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 3840:d=7  hl=2 l=  15 cons: SET
 3842:d=8  hl=2 l=  13 prim: UTCTIME           :190515212555Z
 3857:d=6  hl=2 l=  47 cons: SEQUENCE
 3859:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 3870:d=7  hl=2 l=  34 cons: SET
 3872:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:50508CC996CD93
 3906:d=5  hl=2 l=  10 cons: SEQUENCE
 3908:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3918:d=5  hl=2 l=  71 prim: OCTET STRING      [HEX DUMP]:3045022006D85B

D.2.3.  MASA to Registrar

   The MASA will return a voucher to the registrar, to be relayed to the

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   -----BEGIN CMS-----
   -----END CMS-----

   file: examples/voucher_00-D0-E5-02-00-2D.pkcs

   The ASN1 decoding of the artifact:

    0:d=0  hl=4 l=1714 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1699 cons: cont [ 0 ]
   19:d=2  hl=4 l=1695 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01

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   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l= 832 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l= 817 cons: cont [ 0 ]
   60:d=5  hl=4 l= 813 prim: OCTET STRING      :{"ietf-voucher:voucher":
  877:d=3  hl=4 l= 501 cons: cont [ 0 ]
  881:d=4  hl=4 l= 497 cons: SEQUENCE
  885:d=5  hl=4 l= 376 cons: SEQUENCE
  889:d=6  hl=2 l=   3 cons: cont [ 0 ]
  891:d=7  hl=2 l=   1 prim: INTEGER           :02
  894:d=6  hl=2 l=   4 prim: INTEGER           :23CC8913
  900:d=6  hl=2 l=  10 cons: SEQUENCE
  902:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
  912:d=6  hl=2 l=  77 cons: SEQUENCE
  914:d=7  hl=2 l=  18 cons: SET
  916:d=8  hl=2 l=  16 cons: SEQUENCE
  918:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  930:d=9  hl=2 l=   2 prim: IA5STRING         :ca
  934:d=7  hl=2 l=  25 cons: SET
  936:d=8  hl=2 l=  23 cons: SEQUENCE
  938:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  950:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
  961:d=7  hl=2 l=  28 cons: SET
  963:d=8  hl=2 l=  26 cons: SEQUENCE
  965:d=9  hl=2 l=   3 prim: OBJECT            :commonName
  970:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
  991:d=6  hl=2 l=  30 cons: SEQUENCE
  993:d=7  hl=2 l=  13 prim: UTCTIME           :190423232107Z
 1008:d=7  hl=2 l=  13 prim: UTCTIME           :190524092107Z
 1023:d=6  hl=2 l= 102 cons: SEQUENCE
 1025:d=7  hl=2 l=  15 cons: SET
 1027:d=8  hl=2 l=  13 cons: SEQUENCE
 1029:d=9  hl=2 l=   3 prim: OBJECT            :countryName
 1034:d=9  hl=2 l=   6 prim: PRINTABLESTRING   :Canada
 1042:d=7  hl=2 l=  18 cons: SET
 1044:d=8  hl=2 l=  16 cons: SEQUENCE
 1046:d=9  hl=2 l=   3 prim: OBJECT            :organizationName
 1051:d=9  hl=2 l=   9 prim: UTF8STRING        :Sandelman
 1062:d=7  hl=2 l=  19 cons: SET
 1064:d=8  hl=2 l=  17 cons: SEQUENCE
 1066:d=9  hl=2 l=   3 prim: OBJECT            :organizationalUnitName
 1071:d=9  hl=2 l=  10 prim: UTF8STRING        :honeydukes
 1083:d=7  hl=2 l=  42 cons: SET
 1085:d=8  hl=2 l=  40 cons: SEQUENCE
 1087:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1092:d=9  hl=2 l=  33 prim: UTF8STRING        :masa.honeydukes.sandelma

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 1127:d=6  hl=2 l= 118 cons: SEQUENCE
 1129:d=7  hl=2 l=  16 cons: SEQUENCE
 1131:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 1140:d=8  hl=2 l=   5 prim: OBJECT            :secp384r1
 1147:d=7  hl=2 l=  98 prim: BIT STRING
 1247:d=6  hl=2 l=  16 cons: cont [ 3 ]
 1249:d=7  hl=2 l=  14 cons: SEQUENCE
 1251:d=8  hl=2 l=  12 cons: SEQUENCE
 1253:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 1258:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 1261:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 1265:d=5  hl=2 l=  10 cons: SEQUENCE
 1267:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1277:d=5  hl=2 l= 103 prim: BIT STRING
 1382:d=3  hl=4 l= 332 cons: SET
 1386:d=4  hl=4 l= 328 cons: SEQUENCE
 1390:d=5  hl=2 l=   1 prim: INTEGER           :01
 1393:d=5  hl=2 l=  85 cons: SEQUENCE
 1395:d=6  hl=2 l=  77 cons: SEQUENCE
 1397:d=7  hl=2 l=  18 cons: SET
 1399:d=8  hl=2 l=  16 cons: SEQUENCE
 1401:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1413:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 1417:d=7  hl=2 l=  25 cons: SET
 1419:d=8  hl=2 l=  23 cons: SEQUENCE
 1421:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1433:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 1444:d=7  hl=2 l=  28 cons: SET
 1446:d=8  hl=2 l=  26 cons: SEQUENCE
 1448:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1453:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
 1474:d=6  hl=2 l=   4 prim: INTEGER           :23CC8913
 1480:d=5  hl=2 l=  11 cons: SEQUENCE
 1482:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 1493:d=5  hl=2 l= 105 cons: cont [ 0 ]
 1495:d=6  hl=2 l=  24 cons: SEQUENCE
 1497:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 1508:d=7  hl=2 l=  11 cons: SET
 1510:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 1521:d=6  hl=2 l=  28 cons: SEQUENCE
 1523:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 1534:d=7  hl=2 l=  15 cons: SET
 1536:d=8  hl=2 l=  13 prim: UTCTIME           :190516025142Z
 1551:d=6  hl=2 l=  47 cons: SEQUENCE
 1553:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 1564:d=7  hl=2 l=  34 cons: SET
 1566:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:98461E22DB5423
 1600:d=5  hl=2 l=  10 cons: SEQUENCE

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 1602:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1612:d=5  hl=2 l= 104 prim: OCTET STRING      [HEX DUMP]:30660231009860

Authors' Addresses

   Max Pritikin


   Michael C. Richardson
   Sandelman Software Works


   Toerless Eckert
   Futurewei Technologies Inc.  USA
   2330 Central Expy
   Santa Clara  95050


   Michael H. Behringer


   Kent Watsen
   Watsen Networks


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