Admin Interface for the OSCORE Group Manager
draft-ietf-ace-oscore-gm-admin-04

Document Type Active Internet-Draft (ace WG)
Authors Marco Tiloca  , Rikard Höglund  , Peter Van der Stok  , Francesca Palombini 
Last updated 2021-10-25
Replaces draft-tiloca-ace-oscore-gm-admin
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ACE Working Group                                              M. Tiloca
Internet-Draft                                                R. Höglund
Intended status: Standards Track                                 RISE AB
Expires: 28 April 2022                                   P. van der Stok
                                                              Consultant
                                                            F. Palombini
                                                             Ericsson AB
                                                         25 October 2021

              Admin Interface for the OSCORE Group Manager
                   draft-ietf-ace-oscore-gm-admin-04

Abstract

   Group communication for CoAP can be secured using Group Object
   Security for Constrained RESTful Environments (Group OSCORE).  A
   Group Manager is responsible to handle the joining of new group
   members, as well as to manage and distribute the group keying
   material.  This document defines a RESTful admin interface at the
   Group Manager, that allows an Administrator entity to create and
   delete OSCORE groups, as well as to retrieve and update their
   configuration.  The ACE framework for Authentication and
   Authorization is used to enforce authentication and authorization of
   the Administrator at the Group Manager.  Protocol-specific transport
   profiles of ACE are used to achieve communication security, proof-of-
   possession and server authentication.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the ACE Working Group
   mailing list (ace@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/ace/.

   Source for this draft and an issue tracker can be found at
   https://github.com/ace-wg/ace-oscore-gm-admin.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   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
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   This Internet-Draft will expire on 28 April 2022.

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   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Group Administration  . . . . . . . . . . . . . . . . . . . .   6
     2.1.  Getting Access to the Group Manager . . . . . . . . . . .   7
       2.1.1.  Format of Scope . . . . . . . . . . . . . . . . . . .   8
     2.2.  Managing OSCORE Groups  . . . . . . . . . . . . . . . . .   9
     2.3.  Collection Representation . . . . . . . . . . . . . . . .  10
     2.4.  Discovery . . . . . . . . . . . . . . . . . . . . . . . .  10
   3.  Group Configurations  . . . . . . . . . . . . . . . . . . . .  10
     3.1.  Group Configuration Representation  . . . . . . . . . . .  10
       3.1.1.  Configuration Properties  . . . . . . . . . . . . . .  11
       3.1.2.  Status Properties . . . . . . . . . . . . . . . . . .  13
     3.2.  Default Values  . . . . . . . . . . . . . . . . . . . . .  14
       3.2.1.  Configuration Parameters  . . . . . . . . . . . . . .  14
       3.2.2.  Status Parameters . . . . . . . . . . . . . . . . . .  15
   4.  Interactions with the Group Manager . . . . . . . . . . . . .  15
     4.1.  Retrieve the Full List of Groups Configurations . . . . .  16
     4.2.  Retrieve a List of Group Configurations by Filters  . . .  16
     4.3.  Create a New Group Configuration  . . . . . . . . . . . .  18
     4.4.  Retrieve a Group Configuration  . . . . . . . . . . . . .  23
     4.5.  Retrieve Part of a Group Configuration by Filters . . . .  25
     4.6.  Overwrite a Group Configuration . . . . . . . . . . . . .  28
       4.6.1.  Effects on Joining Nodes  . . . . . . . . . . . . . .  31
       4.6.2.  Effects on the Group Members  . . . . . . . . . . . .  31
     4.7.  Selective Update of a Group Configuration . . . . . . . .  33

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       4.7.1.  Effects on Joining Nodes  . . . . . . . . . . . . . .  37
       4.7.2.  Effects on the Group Members  . . . . . . . . . . . .  38
     4.8.  Delete a Group Configuration  . . . . . . . . . . . . . .  38
       4.8.1.  Effects on the Group Members  . . . . . . . . . . . .  39
   5.  ACE Groupcomm Error Identifiers . . . . . . . . . . . . . . .  39
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  40
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  40
     7.1.  ACE Groupcomm Parameters  . . . . . . . . . . . . . . . .  40
     7.2.  ACE Groupcomm Errors  . . . . . . . . . . . . . . . . . .  42
     7.3.  Resource Types  . . . . . . . . . . . . . . . . . . . . .  42
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  42
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  42
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  45
   Appendix A.  Document Updates . . . . . . . . . . . . . . . . . .  46
     A.1.  Version -03 to -04  . . . . . . . . . . . . . . . . . . .  46
     A.2.  Version -02 to -03  . . . . . . . . . . . . . . . . . . .  46
     A.3.  Version -01 to -02  . . . . . . . . . . . . . . . . . . .  47
     A.4.  Version -00 to -01  . . . . . . . . . . . . . . . . . . .  47
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  47
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  47

1.  Introduction

   The Constrained Application Protocol (CoAP) [RFC7252] can be used in
   group communication environments where messages are also exchanged
   over IP multicast [I-D.ietf-core-groupcomm-bis].  Applications
   relying on CoAP can achieve end-to-end security at the application
   layer by using Object Security for Constrained RESTful Environments
   (OSCORE) [RFC8613], and especially Group OSCORE
   [I-D.ietf-core-oscore-groupcomm] in group communication scenarios.

   When group communication for CoAP is protected with Group OSCORE,
   nodes are required to explicitly join the correct OSCORE group.  To
   this end, a joining node interacts with a Group Manager (GM) entity
   responsible for that group, and retrieves the required keying
   material to securely communicate with other group members using Group
   OSCORE.

   The method in [I-D.ietf-ace-key-groupcomm-oscore] specifies how nodes
   can join an OSCORE group through the respective Group Manager.  Such
   a method builds on the ACE framework for Authentication and
   Authorization [I-D.ietf-ace-oauth-authz], so ensuring a secure
   joining process as well as authentication and authorization of
   joining nodes (clients) at the Group Manager (resource server).

   In some deployments, the application running on the Group Manager may
   know when a new OSCORE group has to be created, as well as how it
   should be configured and later on updated or deleted, e.g., based on

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   the current application state or on pre-installed policies.  In this
   case, the Group Manager application can create and configure OSCORE
   groups when needed, by using a local application interface.  However,
   this requires the Group Manager to be application-specific, which in
   turn leads to error prone deployments and is poorly flexible.

   In other deployments, a separate Administrator entity, such as a
   Commissioning Tool, is directly responsible for creating and
   configuring the OSCORE groups at a Group Manager, as well as for
   maintaining them during their whole lifetime until their deletion.
   This allows the Group Manager to be agnostic of the specific
   applications using secure group communication.

   This document specifies a RESTful admin interface at the Group
   Manager, intended for an Administrator as a separate entity external
   to the Group Manager and its application.  The interface allows the
   Administrator to create and delete OSCORE groups, as well as to
   configure and update their configuration.

   Interaction examples are provided, in Link Format [RFC6690] and CBOR
   [RFC8949], as well as in CoRAL [I-D.ietf-core-coral].  While all the
   CoRAL examples show the CoRAL textual serialization format, its
   binary serialization format is used on the wire.

   The ACE framework is used to ensure authentication and authorization
   of the Administrator (client) at the Group Manager (resource server).
   In order to achieve communication security, proof-of-possession and
   server authentication, the Administrator and the Group Manager
   leverage protocol-specific transport profiles of ACE, such as
   [I-D.ietf-ace-oscore-profile][I-D.ietf-ace-dtls-authorize].  These
   include also possible forthcoming transport profiles that comply with
   the requirements in Appendix C of [I-D.ietf-ace-oauth-authz].

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "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.

   Readers are expected to be familiar with the terms and concepts from
   the following specifications:

   *  CBOR [RFC8949] and COSE
      [I-D.ietf-cose-rfc8152bis-struct][I-D.ietf-cose-rfc8152bis-algs].

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   *  The CoAP protocol [RFC7252], also in group communication scenarios
      [I-D.ietf-core-groupcomm-bis].  These include the concepts of:

      -  "application group", as a set of CoAP nodes that share a common
         set of resources; and of

      -  "security group", as a set of CoAP nodes that share the same
         security material, and use it to protect and verify exchanged
         messages.

   *  The OSCORE [RFC8613] and Group OSCORE
      [I-D.ietf-core-oscore-groupcomm] security protocols.  These
      include the concept of Group Manager, as the entity responsible
      for a set of OSCORE groups where communications among members are
      secured using Group OSCORE.  An OSCORE group is used as security
      group for one or many application groups.

   *  The ACE framework for authentication and authorization
      [I-D.ietf-ace-oauth-authz].  The terminology for entities in the
      considered architecture is defined in OAuth 2.0 [RFC6749].  In
      particular, this includes Client (C), Resource Server (RS), and
      Authorization Server (AS).

   *  The management of keying material for groups in ACE
      [I-D.ietf-ace-key-groupcomm] and specifically for OSCORE groups
      [I-D.ietf-ace-key-groupcomm-oscore].  These include the concept of
      group-membership resource hosted by the Group Manager, that new
      members access to join the OSCORE group, while current members can
      access to retrieve updated keying material.

   Note that, unless otherwise indicated, the term "endpoint" is used
   here following its OAuth definition, aimed at denoting resources such
   as /token and /introspect at the AS, and /authz-info at the RS.  This
   document does not use the CoAP definition of "endpoint", which is "An
   entity participating in the CoAP protocol".

   This document also refers to the following terminology.

   *  Administrator: entity responsible to create, configure and delete
      OSCORE groups at a Group Manager.

   *  Group name: stable and invariant name of an OSCORE group.  The
      group name MUST be unique under the same Group Manager, and MUST
      include only characters that are valid for a URI path segment.

   *  Group-collection resource: a single-instance resource hosted by
      the Group Manager.  An Administrator accesses a group-collection
      resource to create a new OSCORE group, or to retrieve the list of

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      existing OSCORE groups, under that Group Manager.  As an example,
      this document uses /manage as the url-path of the group-collection
      resource; implementations are not required to use this name, and
      can define their own instead.

   *  Group-configuration resource: a resource hosted by the Group
      Manager, associated to an OSCORE group under that Group Manager.
      A group-configuration resource is identifiable with the invariant
      group name of the respective OSCORE group.  An Administrator
      accesses a group-configuration resource to retrieve or update the
      configuration of the respective OSCORE group, or to delete that
      group.  The url-path to a group-configuration resource has
      GROUPNAME as last segment, with GROUPNAME the invariant group name
      assigned upon its creation.  Building on the considered url-path
      of the group-collection resource, this document uses /manage/
      GROUPNAME as the url-path of a group-configuration resource;
      implementations are not required to use this name, and can define
      their own instead.

   *  Admin endpoint: an endpoint at the Group Manager associated to the
      group-collection resource or to a group-configuration resource
      hosted by that Group Manager.

2.  Group Administration

   With reference to the ACE framework and the terminology defined in
   OAuth 2.0 [RFC6749]:

   *  The Group Manager acts as Resource Server (RS).  It provides one
      single group-collection resource, and one group-configuration
      resource per existing OSCORE group.  Each of those is exported by
      a distinct admin endpoint.

   *  The Administrator acts as Client (C), and requests to access the
      group-collection resource and group-configuration resources, by
      accessing the respective admin endpoint at the Group Manager.

   *  The Authorization Server (AS) authorizes the Administrator to
      access the group-collection resource and group-configuration
      resources at a Group Manager.  Multiple Group Managers can be
      associated to the same AS.

      The authorized access for an Administrator can be limited to
      performing only a subset of operations.  The AS can authorize
      multiple Administrators to access the collection resource and the
      (same) group-configuration resources at the Group Manager.

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      [ NOTE: This will be enabled by defining the format to use for the
      'scope' claim in the Access Token, as encoding permitted actions
      on groups whose name matches with a name pattern. ]

      The AS MAY release Access Tokens to the Administrator for other
      purposes than accessing admin endpoints of registered Group
      Managers.

2.1.  Getting Access to the Group Manager

   All communications between the involved entities rely on the CoAP
   protocol and MUST be secured.

   In particular, communications between the Administrator and the Group
   Manager leverage protocol-specific transport profiles of ACE to
   achieve communication security, proof-of-possession and server
   authentication.  To this end, the AS may explicitly signal the
   specific transport profile to use, consistently with requirements and
   assumptions defined in the ACE framework [I-D.ietf-ace-oauth-authz].

   With reference to the AS, communications between the Administrator
   and the AS (/token endpoint) as well as between the Group Manager and
   the AS (/introspect endpoint) can be secured by different means, for
   instance using DTLS [RFC6347][I-D.ietf-tls-dtls13] or OSCORE
   [RFC8613].  Further details on how the AS secures communications
   (with the Administrator and the Group Manager) depend on the
   specifically used transport profile of ACE, and are out of the scope
   of this document.

   In order to get access to the Group Manager for managing OSCORE
   groups, an Administrator performs the following steps.

   The format and encoding of scope defined in Section 2.1.1 of this
   document MUST be used, for both the 'scope' claim in the Access
   Token, as well as for the 'scope' parameter in the Authorization
   Request and Authorization Response exchanged with the AS (see
   Sections 5.8.1 and 5.8.2 of [I-D.ietf-ace-oauth-authz]).

   1.  The Administrator requests an Access Token from the AS, in order
       to access the group-collection and group-configuration resources
       on the Group Manager.  The Administrator will start or continue
       using secure communications with the Group Manager, according to
       the response from the AS.

   2.  The Administrator transfers authentication and authorization
       information to the Group Manager by posting the obtained Access
       Token, according to the used profile of ACE, such as
       [I-D.ietf-ace-dtls-authorize] and [I-D.ietf-ace-oscore-profile].

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       After that, the Administrator must have secure communication
       established with the Group Manager, before performing any admin
       operation on that Group Manager.  Possible ways to provide secure
       communication are DTLS [RFC6347][I-D.ietf-tls-dtls13] and OSCORE
       [RFC8613].  The Administrator and the Group Manager maintain the
       secure association, to support possible future communications.

   3.  Consistently with what allowed by the authorization information
       in the Access Token, the Administrator performs admin operations
       at the Group Manager, as described in the following sections.
       These include the retrieval of the existing OSCORE groups, the
       creation of new OSCORE groups, the update and retrieval of OSCORE
       group configurations, and the removal of OSCORE groups.  Messages
       exchanged among the Administrator and the Group Manager are
       specified in Section 4.

2.1.1.  Format of Scope

   This section defines the exact format and encoding of scope to use,
   in order to express authorization information for the Administrator
   (see Section 2.1).

   TODO

   [

   DESIGN CONSIDERATIONS

   *  Define a new AIF specific data model, as loosely aligned with the
      data model AIF-OSCORE-GROUPCOMM defined in Section 3 of
      [I-D.ietf-ace-key-groupcomm-oscore].

      -  The overall scope is an array of scope entries, each as a pair
         (Toid, Tperm).

      -  Toid is a text string, i.e., a wildcard pattern against which
         group names can be matched.

      -  Tperm is a set of specific permissions encoded as a bitmap,
         applied to groups whose name matches with the wildcard pattern.

   *  A valid Access Token should always allow to at least retrieve the
      list of existing group configurations.

   *  An Administrator authorized to create a group, should later be
      able to perform any possible operation on it.

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   *  An Administrator can be authorized to perform selected operations
      on a group earlier created by a different Administrator, still
      barring the group name matching with the wildcard pattern.

   ]

2.2.  Managing OSCORE Groups

   Figure 1 shows the resources of a Group Manager available to an
   Administrator.

                    ___
          Group    /   \
       Collection  \___/
                        \
                         \____________________
                          \___    \___        \___
                          /   \   /   \  ...  /   \        Group
                          \___/   \___/       \___/   Configurations

                   Figure 1: Resources of a Group Manager

   The Group Manager exports a single group-collection resource, with
   resource type "core.osc.gcoll" defined in Section 7.3 of this
   document.  The interface for the group-collection resource defined in
   Section 4 allows the Administrator to:

   *  Retrieve the complete list of existing OSCORE groups.

   *  Retrieve a partial list of existing OSCORE groups, by applying
      filter criteria.

   *  Create a new OSCORE group, specifying its invariant group name
      and, optionally, its configuration.

   The Group Manager exports one group-configuration resource for each
   of its OSCORE groups.  Each group-configuration resource has resource
   type "core.osc.gconf" defined in Section 7.3 of this document, and is
   identified by the group name specified upon creating the OSCORE
   group.  The interface for a group-configuration resource defined in
   Section 4 allows the Administrator to:

   *  Retrieve the complete current configuration of the OSCORE group.

   *  Retrieve part of the current configuration of the OSCORE group, by
      applying filter criteria.

   *  Overwrite the current configuration of the OSCORE group.

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   *  Selectively update only part of the current configuration of the
      OSCORE group.

   *  Delete the OSCORE group.

2.3.  Collection Representation

   A list of group configurations is represented as a document
   containing the corresponding group-configuration resources in the
   list.  Each group-configuration is represented as a link, where the
   link target is the URI of the group-configuration resource.

   The list can be represented as a Link Format document [RFC6690] or a
   CoRAL document [I-D.ietf-core-coral].

   In the former case, the link to each group-configuration resource
   specifies the link target attribute 'rt' (Resource Type), with value
   "core.osc.gconf" defined in Section 7.3 of this document.

   In the latter case, the CoRAL document specifies the group-
   configuration resources in the list as top-level elements.  In
   particular, the link to each group-configuration resource has
   http://coreapps.org/core.osc.gcoll#item as relation type.

2.4.  Discovery

   The Administrator can discover the group-collection resource from a
   Resource Directory, for instance [I-D.ietf-core-resource-directory]
   and [I-D.hartke-t2trg-coral-reef], or from .well-known/core, by using
   the resource type "core.osc.gcoll" defined in Section 7.3 of this
   document.

   The Administrator can discover group-configuration resources for the
   group-collection resource as specified in Section 4.1 and
   Section 4.2.

3.  Group Configurations

   A group configuration consists of a set of parameters.

3.1.  Group Configuration Representation

   The group configuration representation is a CBOR map which MUST
   include configuration properties and status properties.

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3.1.1.  Configuration Properties

   The CBOR map MUST include the following configuration parameters,
   whose CBOR abbreviations are defined in Section 7.1 of this document.

   *  'hkdf', which specifies the HKDF Algorithm used in the OSCORE
      group, encoded as a CBOR text string or a CBOR integer.  Possible
      values are the same ones admitted for the 'hkdf' parameter of the
      Group_OSCORE_Input_Material object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  'pub_key_enc', which specifies the encoding of public keys used in
      the OSCORE group, encoded as a CBOR integer.  Possible values are
      the same ones admitted for the 'pub_key_enc' parameter of the
      Group_OSCORE_Input_Material object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  'group_mode', encoded as a CBOR simple value.  Its value is True
      if the OSCORE group uses the group mode of Group OSCORE
      [I-D.ietf-core-oscore-groupcomm], or False otherwise.

   *  'sign_enc_alg', which is formatted as follows.  If the
      configuration parameter 'group_mode' has value False, this
      parameter has as value the CBOR simple value Null.  Otherwise,
      this parameter specifies the Signature Encryption Algorithm used
      in the OSCORE group to encrypt messages protected with the group
      mode, encoded as a CBOR text string or a CBOR integer.  Possible
      values are the same ones admitted for the 'sign_enc_alg' parameter
      of the Group_OSCORE_Input_Material object, defined in Section 6.4
      of [I-D.ietf-ace-key-groupcomm-oscore].

   *  'sign_alg', which is formatted as follows.  If the configuration
      parameter 'group_mode' has value False, this parameter has as
      value the CBOR simple value Null.  Otherwise, this parameter
      specifies the Signature Algorithm used in the OSCORE group,
      encoded as a CBOR text string or a CBOR integer.  Possible values
      are the same ones admitted for the 'sign_alg' parameter of the
      Group_OSCORE_Input_Material object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

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   *  'sign_params', which is formatted as follows.  If the
      configuration parameter 'group_mode' has value False, this
      parameter has as value the CBOR simple value Null.  Otherwise,
      this parameter specifies the additional parameters for the
      Signature Algorithm used in the OSCORE group, encoded as a CBOR
      array.  Possible formats and values are the same ones admitted for
      the 'sign_params' parameter of the Group_OSCORE_Input_Material
      object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  'pairwise_mode', encoded as a CBOR simple value.  Its value is
      True if the OSCORE group uses the pairwise mode of Group OSCORE
      [I-D.ietf-core-oscore-groupcomm], or False otherwise.

   *  'alg', which is formatted as follows.  If the configuration
      parameter 'pairwise_mode' has value False, this parameter has as
      value the CBOR simple value Null.  Otherwise, this parameter
      specifies the AEAD Algorithm used in the OSCORE group to encrypt
      messages protected with the pairwise mode, encoded as a CBOR text
      string or a CBOR integer.  Possible values are the same ones
      admitted for the 'alg' parameter of the
      Group_OSCORE_Input_Material object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  'ecdh_alg', which is formatted as follows.  If the configuration
      parameter 'pairwise_mode' has value False, this parameter has as
      value the CBOR simple value Null.  Otherwise, this parameter
      specifies the Pairwise Key Agreement Algorithm used in the OSCORE
      group, encoded as a CBOR text string or a CBOR integer.  Possible
      values are the same ones admitted for the 'ecdh_alg' parameter of
      the Group_OSCORE_Input_Material object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  'ecdh_params', which is formatted as follows.  If the
      configuration parameter 'pairwise_mode' has value False, this
      parameter has as value the CBOR simple value Null.  Otherwise,
      this parameter specifies the parameters for the Pairwise Key
      Agreement Algorithm used in the OSCORE group, encoded as a CBOR
      array.  Possible formats and values are the same ones admitted for
      the 'ecdh_params' parameter of the Group_OSCORE_Input_Material
      object, defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   The CBOR map MAY include the following configuration parameters,
   whose CBOR abbreviations are defined in Section 7.1 of this document.

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   *  'det_req', encoded as a CBOR simple value.  Its value is True if
      the OSCORE group uses deterministic requests as defined in
      [I-D.amsuess-core-cachable-oscore], or False otherwise.  This
      parameter MUST NOT be present if the configuration parameter
      'group_mode' has value False.

   *  'det_hash_alg', encoded as a CBOR integer or text string.  If
      present, this parameter specifies the Hash Algorithm used in the
      OSCORE group when producing deterministic requests, as defined in
      [I-D.amsuess-core-cachable-oscore].  This parameter takes values
      from the "Value" column of the "COSE Algorithms" Registry
      [COSE.Algorithms].

      This parameter MUST NOT be present if the configuration parameter
      'det_req' is not present or if it is present with value False.  If
      the configuration parameter 'det_req' is present with value True
      and 'det_hash_alg' is not present, the choice of the Hash
      Algorithm to use when producing deterministic requests is left to
      the Group Manager.

3.1.2.  Status Properties

   The CBOR map MUST include the following status parameters:

   *  'rt', with value the resource type "core.osc.gconf" associated to
      group-configuration resources, encoded as a CBOR text string.

   *  'active', encoding the CBOR simple value True if the OSCORE group
      is currently active, or the CBOR simple value False otherwise.
      This parameter is defined in Section 7.1 of this document.

   *  'group_name', with value the group name of the OSCORE group
      encoded as a CBOR text string.  This parameter is defined in
      Section 7.1 of this document.

   *  'group_title', with value either a human-readable description of
      the OSCORE group encoded as a CBOR text string, or the CBOR simple
      value Null if no description is specified.  This parameter is
      defined in Section 7.1 of this document.

   *  'ace-groupcomm-profile', defined in Section 4.3.1 of
      [I-D.ietf-ace-key-groupcomm], with value "coap_group_oscore_app"
      defined in Section 25.5 of [I-D.ietf-ace-key-groupcomm-oscore]
      encoded as a CBOR integer.

   *  'exp', defined in Section 4.3.1 of [I-D.ietf-ace-key-groupcomm].

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   *  'app_groups', with value a list of names of application groups,
      encoded as a CBOR array.  Each element of the array is a CBOR text
      string, specifying the name of an application group using the
      OSCORE group as security group (see Section 2.1 of
      [I-D.ietf-core-groupcomm-bis]).

   *  'joining_uri', with value the URI of the group-membership resource
      for joining the newly created OSCORE group as per Section 6.2 of
      [I-D.ietf-ace-key-groupcomm-oscore], encoded as a CBOR text
      string.  This parameter is defined in Section 7.1 of this
      document.

   The CBOR map MAY include the following status parameters:

   *  'group_policies', defined in Section 4.3.1 of
      [I-D.ietf-ace-key-groupcomm], and consistent with the format and
      content defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  'max_stale_sets', defined in Section 7.1 of this document and
      encoded as a CBOR unsigned integer, with value strictly greater
      than 1.  With reference to Section 2.2.1 of
      [I-D.ietf-ace-key-groupcomm-oscore], this parameter specifies N,
      i.e., the maximum number of sets of stale OSCORE Sender IDs that
      the Group Manager stores in the collection associated to the
      group.

   *  'as_uri', defined in Section 7.1 of this document, specifies the
      URI of the Authorization Server associated to the Group Manager
      for the OSCORE group, encoded as a CBOR text string.  Candidate
      group members will have to obtain an Access Token from that
      Authorization Server, before starting the joining process with the
      Group Manager to join the OSCORE group (see Sections 4 and 6 of
      [I-D.ietf-ace-key-groupcomm-oscore]).

3.2.  Default Values

   This section defines the default values that the Group Manager
   assumes for configuration and status parameters.

3.2.1.  Configuration Parameters

   For each configuration parameter, the Group Manager MUST use a pre-
   configured default value, if none is specified by the Administrator.
   In particular:

   *  For 'group_mode', the Group Manager SHOULD use the CBOR simple
      value True.

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   *  If 'group_mode' has value True, the Group Manager SHOULD use the
      same default values defined in Section 23.2 of
      [I-D.ietf-ace-key-groupcomm-oscore] for the parameters
      'sign_enc_alg', 'sign_alg' and 'sign_params'.

   *  If 'group_mode' has value True, the Group Manager SHOULD use the
      CBOR simple value False for the parameter 'det_req'.

   *  If 'det_req' has value True, the Group Manager SHOULD use SHA-256
      (COSE algorithm encoding: -16) as default value for the parameter
      'det_hash_alg'.

   *  For 'pairwise_mode', the Group Manager SHOULD use the CBOR simple
      value False.

   *  If 'pairwise_mode' has value True, the Group Manager SHOULD use
      the same default values defined in Section 23.3 of
      [I-D.ietf-ace-key-groupcomm-oscore] for the parameters 'alg',
      'ecdh_alg' and 'ecdh_params'.

   *  For any other configuration parameter, the Group Manager SHOULD
      use the same default values defined in Section 23.1 of
      [I-D.ietf-ace-key-groupcomm-oscore].

3.2.2.  Status Parameters

   For the following status parameters, the Group Manager MUST use a
   pre-configured default value, if none is specified by the
   Administrator.  In particular:

   *  For 'active', the Group Manager SHOULD use the CBOR simple value
      False.

   *  For 'group_title', the Group Manager SHOULD use the CBOR simple
      value Null.

   *  For 'app_groups', the Group Manager SHOULD use the empty CBOR
      array.

   *  For 'group_policies', the Group Manager SHOULD use the default
      values defined in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore].

4.  Interactions with the Group Manager

   This section describes the operations available on the group-
   collection resource and the group-configuration resources.

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   When custom CBOR is used, the Content-Format in messages containing a
   payload is set to application/ace-groupcomm+cbor, defined in
   Section 11.2 of [I-D.ietf-ace-key-groupcomm].  Furthermore, the entry
   labels defined in Section 7.1 of this document MUST be used, when
   specifying the corresponding configuration and status parameters.

4.1.  Retrieve the Full List of Groups Configurations

   The Administrator can send a GET request to the group-collection
   resource, in order to retrieve the complete list of the existing
   OSCORE groups at the Group Manager.  This is returned as a list of
   links to the corresponding group-configuration resources.

   Example in Link Format:

   => 0.01 GET
      Uri-Path: manage

   <= 2.05 Content
      Content-Format: 40 (application/link-format)

      <coap://[2001:db8::ab]/manage/gp1>;rt="core.osc.gconf",
      <coap://[2001:db8::ab]/manage/gp2>;rt="core.osc.gconf",
      <coap://[2001:db8::ab]/manage/gp3>;rt="core.osc.gconf"

   Example in CoRAL:

   => 0.01 GET
      Uri-Path: manage

   <= 2.05 Content
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gcoll#>
      #base </manage/>
      item <gp1>
      item <gp2>
      item <gp3>

4.2.  Retrieve a List of Group Configurations by Filters

   The Administrator can send a FETCH request to the group-collection
   resource, in order to retrieve the list of the existing OSCORE groups
   that fully match a set of specified filter criteria.  This is
   returned as a list of links to the corresponding group-configuration
   resources.

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   When custom CBOR is used, the set of filter criteria is specified in
   the request payload as a CBOR map, whose possible entries are
   specified in Section 3.1 and use the same abbreviations defined in
   Section 7.1.  Entry values are the ones admitted for the
   corresponding labels in the POST request for creating a group
   configuration (see Section 4.3).  A valid request MUST NOT include
   the same entry multiple times.

   When CoRAL is used, the filter criteria are specified in the request
   payload with top-level elements, each of which corresponds to an
   entry specified in Section 3.1, with the exception of the
   'app_groups' status parameter.  If names of application groups are
   used as filter criteria, each element of the 'app_groups' array from
   the status properties is included as a separate element with name
   'app_group'.  With the exception of the 'app_group' element, a valid
   request MUST NOT include the same element multiple times.  Element
   values are the ones admitted for the corresponding labels in the POST
   request for creating a group configuration (see Section 4.3).

   Example in custom CBOR and Link Format:

   => 0.05 FETCH
      Uri-Path: manage
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
          "group_mode" : True,
          "sign_enc_alg" : 10,
          "hkdf" : 5
      }

   <= 2.05 Content
      Content-Format: 40 (application/link-format)

      <coap://[2001:db8::ab]/manage/gp1>;rt="core.osc.gconf",
      <coap://[2001:db8::ab]/manage/gp2>;rt="core.osc.gconf",
      <coap://[2001:db8::ab]/manage/gp3>;rt="core.osc.gconf"

   Example in CoRAL:

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   => 0.05 FETCH
      Uri-Path: manage
      Content-Format: TBD1 (application/coral+cbor)

      group_mode True
      sign_enc_alg 10
      hkdf 5

   <= 2.05 Content
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gcoll#>
      #base </manage/>
      item <gp1>
      item <gp2>
      item <gp3>

4.3.  Create a New Group Configuration

   The Administrator can send a POST request to the group-collection
   resource, in order to create a new OSCORE group at the Group Manager.
   The request MAY specify the intended group name GROUPNAME and group
   title, and MAY specify pieces of information concerning the group
   configuration.

   When custom CBOR is used, the request payload is a CBOR map, whose
   possible entries are specified in Section 3.1 and use the same
   abbreviations defined in Section 7.1.

   When CoRAL is used, each element of the request payload corresponds
   to an entry specified in Section 3.1, with the exception of the
   'app_groups' status parameter (see below).

   In particular:

   *  The payload MAY include any of the configuration parameter defined
      in Section 3.1.1.

   *  The payload MAY include any of the status parameter 'group_name',
      'group_title', 'max_stale_sets', 'exp', 'app_groups,
      'group_policies', 'as_uri' and 'active' defined in Section 3.1.2.

      -  When CoRAL is used, each element of the 'app_groups' array from
         the status properties is included as a separate element with
         name 'app_group'.

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   *  The payload MUST NOT include any of the status parameter 'rt',
      'ace-groupcomm-profile' and 'joining_uri' defined in
      Section 3.1.2.

   If any of the following occurs, the Group Manager MUST respond with a
   4.00 (Bad Request) response.

   *  Any of the received parameters is specified multiple times, with
      the exception of the 'app_group' element when using CoRAL.

   *  Any of the received parameters is not recognized, or not valid, or
      not consistent with respect to other related parameters.

   *  The 'group_name' parameter specifies the group name of an already
      existing OSCORE group.

   *  The Group Manager does not trust the Authorization Server with URI
      specified in the 'as_uri' parameter, and has no alternative
      Authorization Server to consider for the OSCORE group to create.

   After a successful processing of the request above, the Group Manager
   performs the following actions.

   First, the Group Manager creates a new group-configuration resource,
   accessible to the Administrator at /manage/GROUPNAME, where GROUPNAME
   is the name of the OSCORE group as either indicated in the parameter
   'group_name' of the request or uniquely assigned by the Group
   Manager.  Note that the final decision about the name assigned to the
   OSCORE group is of the Group Manager, which may have more constraints
   than the Administrator can be aware of, possibly beyond the
   availability of suggested names.

   The value of the status parameter 'rt' is set to "core.osc.gconf".
   The values of other parameters specified in the request are used as
   group configuration information for the newly created OSCORE group.
   For each parameter not specified in the request, the Group Manager
   MUST use default values as specified in Section 3.2.

   After that, the Group Manager creates a new group-membership resource
   accessible at ace-group/GROUPNAME to nodes that want to join the
   OSCORE group, as specified in Section 6.2 of
   [I-D.ietf-ace-key-groupcomm-oscore].  Note that such group
   membership-resource comprises a number of sub-resources intended to
   current group members, as defined in Section 4.1 of
   [I-D.ietf-ace-key-groupcomm] and Section 5 of
   [I-D.ietf-ace-key-groupcomm-oscore].

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   From then on, the Group Manager will rely on the current group
   configuration to build the Joining Response message defined in
   Section 6.4 of [I-D.ietf-ace-key-groupcomm-oscore], when handling the
   joining of a new group member.  Furthermore, the Group Manager
   generates the following pieces of information, and assigns them to
   the newly created OSCORE group.

   *  The OSCORE Master Secret.

   *  The OSCORE Master Salt (optionally).

   *  The Group ID, used as OSCORE ID Context, which MUST be unique
      within the set of OSCORE groups under the Group Manager.

   Finally, the Group Manager replies to the Administrator with a 2.01
   (Created) response.  The Location-Path option MUST be included in the
   response, indicating the location of the just created group-
   configuration resource.  The response MUST NOT include a Location-
   Query option.

   The response payload specifies the parameters 'group_name',
   'joining_uri' and 'as_uri', from the status properties of the newly
   created OSCORE group (see Section 3.1), as detailed below.

   When custom CBOR is used, the response payload is a CBOR map, where
   entries use the same abbreviations defined in Section 7.1.  When
   CoRAL is used, the response payload includes one element for each
   specified parameter.

   *  'group_name', with value the group name of the OSCORE group.  This
      value can be different from the group name possibly specified by
      the Administrator in the POST request, and reflects the final
      choice of the Group Manager as 'group_name' status property for
      the OSCORE group.  This parameter MUST be included.

   *  'joining_uri', with value the URI of the group-membership resource
      for joining the newly created OSCORE group.  This parameter MUST
      be included.

   *  'as_uri', with value the URI of the Authorization Server
      associated to the Group Manager for the newly created OSCORE
      group.  This parameter MUST be included if specified in the status
      properties of the group.  This value can be different from the URI
      possibly specified by the Administrator in the POST request, and
      reflects the final choice of the Group Manager as 'as_uri' status
      property for the OSCORE group.

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   If the POST request did not specify certain parameters and the Group
   Manager used default values different than the ones recommended in
   Section 3.2, then the response payload MUST include also those
   parameters, specifying the values chosen by the Group Manager for the
   current group configuration.

   The Group Manager can register the link to the group-membership
   resource with URI specified in 'joining_uri' to a Resource Directory
   [I-D.ietf-core-resource-directory][I-D.hartke-t2trg-coral-reef], as
   defined in Section 2 of [I-D.tiloca-core-oscore-discovery].  The
   Group Manager considers the current group configuration when
   specifying additional information for the link to register.

   Alternatively, the Administrator can perform the registration in the
   Resource Directory on behalf of the Group Manager, acting as
   Commissioning Tool.  The Administrator considers the following when
   specifying additional information for the link to register.

   *  The name of the OSCORE group MUST take the value specified in
      'group_name' from the 2.01 (Created) response above.

   *  The names of the application groups using the OSCORE group MUST
      take the values possibly specified by the elements of the
      'app_groups' parameter (when custom CBOR is used) or by the
      different 'app_group' elements (when CoRAL is used) in the POST
      request above.

   *  If also registering a related link to the Authorization Server
      associated to the OSCORE group, the related link MUST have as link
      target the URI in 'as_uri' from the 2.01 (Created) response above,
      if the 'as_uri' parameter was included in the response.

   *  Every other information element describing the current group
      configuration MUST take the value that the Administrator specified
      in the POST request.  If a certain parameter was not specified in
      the POST request, the Administrator MUST use either the value
      specified in the the 2.01 (Created) response above, if the Group
      Manager specified one, or the corresponding default value
      recommended in Section 3.2.1 otherwise.

   Note that, compared to the Group Manager, the Administrator is less
   likely to remain closely aligned with possible changes and updates
   that would require a prompt update to the registration in the
   Resource Directory.  This applies especially to the address of the
   Group Manager, as well as the URI of the group-membership resource or
   of the Authorization Server associated to the Group Manager.

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   Therefore, it is RECOMMENDED that registrations of links to group-
   membership resources in the Resource Directory are made (and possibly
   updated) directly by the Group Manager, rather than by the
   Administrator.

   Example in custom CBOR:

   => 0.02 POST
      Uri-Path: manage
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "sign_enc_alg" : 10,
        "hkdf" : 5,
        "pairwise_mode" : True,
        "active" : True,
        "group_title" : "rooms 1 and 2",
        "app_groups": : ["room1", "room2"],
        "as_uri" : "coap://as.example.com/token"
      }

   <= 2.01 Created
      Location-Path: manage
      Location-Path: gp4
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "group_name" : "gp4",
        "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/",
        "as_uri" : "coap://as.example.com/token"
      }

   Example in CoRAL:

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   => 0.02 POST
      Uri-Path: manage
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      sign_enc_alg 10
      hkdf 5
      pairwise_mode True
      active True
      group_title "rooms 1 and 2"
      app_group "room1"
      app_group "room2"
      as_uri <coap://as.example.com/token>

   <= 2.01 Created
      Location-Path: manage
      Location-Path: gp4
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      group_name "gp4"
      joining_uri <coap://[2001:db8::ab]/ace-group/gp4/>
      as_uri <coap://as.example.com/token>

4.4.  Retrieve a Group Configuration

   The Administrator can send a GET request to the group-configuration
   resource manage/GROUPNAME associated to an OSCORE group with group
   name GROUPNAME, in order to retrieve the complete current
   configuration of that group.

   After a successful processing of the request above, the Group Manager
   replies to the Administrator with a 2.05 (Content) response.  The
   response has as payload the representation of the group configuration
   as specified in Section 3.1.  The exact content of the payload
   reflects the current configuration of the OSCORE group.  This
   includes both configuration properties and status properties.

   When custom CBOR is used, the response payload is a CBOR map, whose
   possible entries are specified in Section 3.1 and use the same
   abbreviations defined in Section 7.1.

   When CoRAL is used, the response payload includes one element for
   each entry specified in Section 3.1, with the exception of the
   'app_groups' status parameter.  That is, each element of the
   'app_groups' array from the status properties is included as a
   separate element with name 'app_group'.

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   Example in custom CBOR:

   => 0.01 GET
      Uri-Path: manage
      Uri-Path: gp4

   <= 2.05 Content
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "hkdf" : 5,
        "pub_key_enc" : 33,
        "group_mode" : True,
        "sign_enc_alg" : 10,
        "sign_alg" : -8,
        "sign_params" : [[1], [1, 6]],
        "pairwise_mode" : True,
        "alg" : 10,
        "ecdh_alg" : -27,
        "ecdh_params" : [[1], [1, 6]],
        "rt" : "core.osc.gconf",
        "active" : True,
        "group_name" : "gp4",
        "group_title" : "rooms 1 and 2",
        "ace-groupcomm-profile" : "coap_group_oscore_app",
        "max_stale_sets" : 3,
        "exp" : 1360289224,
        "app_groups": : ["room1", "room2"],
        "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/",
        "as_uri" : "coap://as.example.com/token"
      }

   Example in CoRAL:

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   => 0.01 GET
      Uri-Path: manage
      Uri-Path: gp4

   <= 2.05 Content
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      hkdf 5
      pub_key_enc 33
      group_mode True
      sign_enc_alg 10
      sign_alg -8
      sign_params.alg_capab.key_type 1
      sign_params.key_type_capab.key_type 1
      sign_params.key_type_capab.curve 6
      pairwise_mode True
      alg 10
      ecdh_alg -27
      ecdh_params.alg_capab.key_type 1
      ecdh_params.key_type_capab.key_type 1
      ecdh_params.key_type_capab.curve 6
      rt "core.osc.gconf",
      active True
      group_name "gp4"
      group_title "rooms 1 and 2"
      ace-groupcomm-profile "coap_group_oscore_app"
      max_stale_sets 3
      exp 1360289224
      app_group "room1"
      app_group "room2"
      joining_uri <coap://[2001:db8::ab]/ace-group/gp4/>
      as_uri <coap://as.example.com/token>

4.5.  Retrieve Part of a Group Configuration by Filters

   The Administrator can send a FETCH request to the group-configuration
   resource manage/GROUPNAME associated to an OSCORE group with group
   name GROUPNAME, in order to retrieve part of the current
   configuration of that group.

   When custom CBOR is used, the request payload is a CBOR map, which
   contains the following fields:

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   *  'conf_filter', defined in Section 7.1 of this document and encoded
      as a CBOR array.  Each element of the array specifies one
      requested configuration parameter or status parameter of the
      current group configuration (see Section 3.1), using the
      corresponding abbreviation defined in Section 7.1.

   When CoRAL is used, the request payload includes one element for each
   requested configuration parameter or status parameter of the current
   group configuration (see Section 3.1).  All the specified elements
   have no value.

   After a successful processing of the request above, the Group Manager
   replies to the Administrator with a 2.05 (Content) response.  The
   response has as payload a partial representation of the group
   configuration (see Section 3.1).  The exact content of the payload
   reflects the current configuration of the OSCORE group, and is
   limited to the configuration properties and status properties
   requested by the Administrator in the FETCH request.

   The response payload includes the requested configuration parameters
   and status parameters, and is formatted as in the response payload of
   a GET request to a group-configuration resource (see Section 4.4).

   Example in custom CBOR:

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   => 0.05 FETCH
      Uri-Path: manage
      Uri-Path: gp4
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "conf_filter" : ["sign_enc_alg",
                         "hkdf",
                         "pairwise_mode",
                         "active",
                         "group_title",
                         "app_groups"]
      }

   <= 2.05 Content
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "sign_enc_alg" : 10,
        "hkdf" : 5,
        "pairwise_mode" : True,
        "active" : True,
        "group_title" : "rooms 1 and 2",
        "app_groups": : ["room1", "room2"]
      }

   Example in CoRAL:

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   => 0.05 FETCH
      Uri-Path: manage
      Uri-Path: gp4
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      sign_enc_alg
      hkdf
      pairwise_mode
      active
      group_title
      app_groups

   <= 2.05 Content
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      sign_enc_alg 10
      hkdf 5
      pairwise_mode True
      active True
      group_title "rooms 1 and 2"
      app_group "room1"
      app_group "room2"

4.6.  Overwrite a Group Configuration

   The Administrator can send a PUT request to the group-configuration
   resource associated to an OSCORE group, in order to overwrite the
   current configuration of that group with a new one.  The payload of
   the request has the same format of the POST request defined in
   Section 4.3, with the exception that the configuration parameters
   'group_mode' and 'pairwise_mode' as well as the status parameter
   'group_name' MUST NOT be included.

   The error handling for the PUT request is the same as for the POST
   request defined in Section 4.3.  If no error occurs, the Group
   Manager performs the following actions.

   First, the Group Manager updates the group-configuration resource,
   consistently with the values indicated in the PUT request from the
   Administrator.  For each parameter not specified in the PUT request,
   the Group Manager MUST use default values as specified in
   Section 3.2.

   If a new value N' is specified for the 'max_stale_sets' status
   parameter and N' is smaller than the current value N, the Group
   Manager preserves the (up to) N' most recent sets in the collection

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   of sets of stale OSCORE Sender IDs associated to the group, and
   deletes any possible older set from the collection (see Section 2.2.1
   of [I-D.ietf-ace-key-groupcomm-oscore]).

   From then on, the Group Manager relies on the latest updated
   configuration to build the Joining Response message defined in
   Section 6.4 of [I-D.ietf-ace-key-groupcomm-oscore], when handling the
   joining of a new group member.  Similarly, the Group Manager relies
   on the new group configuration when building responses specifying
   (part of) the group configuration to a current group member.  For
   instance, this applies when a group member retrieves from the Group
   Manager the updated group keying material (see Section 8 of
   [I-D.ietf-ace-key-groupcomm-oscore]) or the current group status (see
   Section 16 of [I-D.ietf-ace-key-groupcomm-oscore]).

   Then, the Group Manager replies to the Administrator with a 2.04
   (Changed) response.  The payload of the response has the same format
   of the 2.01 (Created) response defined in Section 4.3.

   If the PUT request did not specify certain parameters and the Group
   Manager used default values different than the ones recommended in
   Section 3.2, then the response payload MUST include also those
   parameters, specifying the values chosen by the Group Manager for the
   current group configuration.

   If the link to the group-membership resource was registered in the
   Resource Directory [I-D.ietf-core-resource-directory], the GM is
   responsible to refresh the registration, as defined in Section 3 of
   [I-D.tiloca-core-oscore-discovery].

   Alternatively, the Administrator can update the registration in the
   Resource Directory on behalf of the Group Manager, acting as
   Commissioning Tool.  The Administrator considers the following when
   specifying additional information for the link to update.

   *  The name of the OSCORE group MUST take the value specified in
      'group_name' from the 2.04 (Changed) response above.

   *  The names of the application groups using the OSCORE group MUST
      take the values possibly specified by the elements of the
      'app_groups' parameter (when custom CBOR is used) or by the
      different 'app_group' elements (when CoRAL is used) in the PUT
      request above.

   *  If also registering a related link to the Authorization Server
      associated to the OSCORE group, the related link MUST have as link
      target the URI in 'as_uri' from the 2.04 (Changed) response above,
      if the 'as_uri' parameter was included in the response.

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   *  Every other information element describing the current group
      configuration MUST take the value that the Administrator specified
      in the PUT request.  If a certain parameter was not specified in
      the PUT request, the Administrator MUST use either the value
      specified in the the 2.04 (Changed) response above, if the Group
      Manager specified one, or the corresponding default value
      recommended in Section 3.2.1 otherwise.

   As discussed in Section 4.3, it is RECOMMENDED that registrations of
   links to group-membership resources in the Resource Directory are
   made (and possibly updated) directly by the Group Manager, rather
   than by the Administrator.

   Example in custom CBOR:

   => 0.03 PUT
      Uri-Path: manage
      Uri-Path: gp4
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "sign_enc_alg" : 11,
        "hkdf" : 5
      }

   <= 2.04 Changed
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "group_name" : "gp4",
        "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/",
        "as_uri" : "coap://as.example.com/token"
      }

   Example in CoRAL:

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   => 0.03 PUT
      Uri-Path: manage
      Uri-Path: gp4
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      sign_enc_alg 11
      hkdf 5

   <= 2.04 Changed
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      group_name "gp4"
      joining_uri <coap://[2001:db8::ab]/ace-group/gp4/>
      as_uri <coap://as.example.com/token>

4.6.1.  Effects on Joining Nodes

   After having overwritten a group configuration, if the value of the
   status parameter 'active' is changed from True to False, the Group
   Manager MUST stop admitting new members in the OSCORE group.  In
   particular, until the status parameter 'active' is changed back to
   True, the Group Manager MUST respond to a Joining Request with a 5.03
   (Service Unavailable) response, as defined in Section 6.3 of
   [I-D.ietf-ace-key-groupcomm-oscore].

   If the value of the status parameter 'active' is changed from False
   to True, the Group Manager resumes admitting new members in the
   OSCORE group, by processing their Joining Requests (see Section 6.3
   of [I-D.ietf-ace-key-groupcomm-oscore]).

4.6.2.  Effects on the Group Members

   After having overwritten a group configuration, the Group Manager
   informs the members of the OSCORE group, over the pairwise secure
   communication channels established when joining the group (see
   Section 6 of [I-D.ietf-ace-key-groupcomm-oscore]).

   To this end, the Group Manager can individually target the
   'control_uri' URI of each group member (see Section 4.3.1 of
   [I-D.ietf-ace-key-groupcomm]), if provided by the intended recipient
   upon joining the OSCORE group (see Section 6.2 of
   [I-D.ietf-ace-key-groupcomm-oscore]).  Alternatively, group members
   can subscribe for updates to the group-membership resource of the
   OSCORE group, e.g., by using CoAP Observe [RFC7641].

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   If the value of the status parameter 'active' is changed from True to
   False:

   *  The Group Manager MUST stop accepting requests for new individual
      keying material from current group members (see Section 9 of
      [I-D.ietf-ace-key-groupcomm-oscore]).  In particular, until the
      status parameter 'active' is changed back to True, the Group
      Manager MUST respond to a Key Renewal Request with a 5.03 (Service
      Unavailable) response, as defined in Section 9 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   *  The Group Manager MUST stop accepting updated public keys uploaded
      by current group members (see Section 11 of
      [I-D.ietf-ace-key-groupcomm-oscore]).  In particular, until the
      status parameter 'active' is changed back to True, the Group
      Manager MUST respond to a Public Key Update Request with a 5.03
      (Service Unavailable) response, as defined in Section 11 of
      [I-D.ietf-ace-key-groupcomm-oscore].

   Every group member, upon learning that the OSCORE group has been
   deactivated (i.e., 'active' has value False), SHOULD stop
   communicating in the group.

   Every group member, upon learning that the OSCORE group has been
   reactivated (i.e., 'active' has value True again), can resume
   communicating in the group.

   Every group member, upon receiving updated values for 'hkdf',
   'sign_enc_alg' and 'alg', MUST either:

   *  Leave the OSCORE group (see Section 18 of
      [I-D.ietf-ace-key-groupcomm-oscore]), e.g., if not supporting the
      indicated new algorithms; or

   *  Use the new parameter values, and accordingly re-derive the OSCORE
      Security Context for the OSCORE group (see Section 2 of
      [I-D.ietf-core-oscore-groupcomm]).

   Every group member, upon receiving updated values for 'pub_key_enc',
   'sign_alg', 'sign_params', 'ecdh_alg' and 'ecdh_params' MUST either:

   *  Leave the OSCORE group, e.g., if not supporting the indicated new
      algorithms, parameters and encoding; or

   *  Leave the OSCORE group and rejoin it (see Section 6 of
      [I-D.ietf-ace-key-groupcomm-oscore]), providing the Group Manager
      with a public key which is compatible with the indicated new
      algorithms, parameters and encoding; or

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   *  Use the new parameter values, and, if required, performs the
      following actions: i) provide the Group Manager with a new public
      key to use in the OSCORE group, as compatible with the indicated
      parameters (see Section 11 of
      [I-D.ietf-ace-key-groupcomm-oscore]); ii) retrieve from the Group
      Manager the new Group Manager's public key (see Section 12 of
      [I-D.ietf-ace-key-groupcomm-oscore]), as also compatible with the
      indicated new algorithms, parameters and encoding.

4.7.  Selective Update of a Group Configuration

   The Administrator can send a PATCH/iPATCH request [RFC8132] to the
   group-configuration resource associated to an OSCORE group, in order
   to update the value of only part of the group configuration.

   The request payload has the same format of the PUT request defined in
   Section 4.6, with the difference that it MAY also specify names of
   application groups to be removed from or added to the 'app_groups'
   status parameter.  The names of such application groups are provided
   as defined below.

   *  When custom CBOR is used, the CBOR map in the request payload
      includes the field 'app_groups_diff'.  This field MUST NOT be
      present multiple times, and it is encoded as a CBOR array
      including the following two elements.

      -  The first element is a CBOR array, namely 'app_groups_del'.
         Each of its elements is a CBOR text string, with value the name
         of an application group to remove from the 'app_groups' status
         parameter.

      -  The second element is a CBOR array, namely 'app_groups_add'.
         Each of its elements is a CBOR text string, with value the name
         of an application group to add to the 'app_groups' status
         parameter.

      The CDDL definition [RFC8610] of the CBOR array 'app_groups_diff'
      formatted as in the response from the Group Manager is provided
      below.

      app-group-name = tstr
      name-patch = [* app-group-name]
      app_groups_diff = [app_groups_del: name-patch,
                         app_groups_add: name-patch]

          Figure 2: CDDL definition of the 'app_groups_diff' field

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   The Group Manager MUST respond with a 4.00 (Bad Request) response, in
   case both the inner CBOR arrays 'app_groups_del' and 'app_groups_add'
   are empty, or in case the 'app_groups_diff' field occurs more than
   once.

   The Group Manager MUST respond with a 4.00 (Bad Request) response, in
   case the CBOR map in the request payload includes both the
   'app_groups' field and the 'app_groups_diff' field.

   *  When CoRAL is used, the request payload includes the following
      top-level elements.

      -  'app_group_del', with value a text string specifying the name
         of an application group to remove from the 'app_groups' status
         parameter.  This element can be included multiple times.

      -  'app_group_add', with value a text string specifying the name
         of an application group to add to the 'app_groups' status
         parameter.  This element can be included multiple times.

      The Group Manager MUST respond with a 4.00 (Bad Request) response,
      in case the request payload includes both any 'app_group' element
      as well as any 'app_group_del' and/or 'app_group_add' element.

   The error handling for the PATCH/iPATCH request is the same as for
   the PUT request defined in Section 4.6, with the following additions.

   *  The set of group configuration parameters to update MUST NOT be
      empty.  That is, the Group Manager MUST respond with a 4.00 (Bad
      Request) response, if the request payload includes an empty CBOR
      map (when custom CBOR is used) or no elements (when CoRAL is
      used).

   *  If the Request-URI does not point to an existing group-
      configuration resource, the Group Manager MUST NOT create a new
      resource, and MUST respond with a 4.04 (Not Found) response.

   *  When applying the specified updated values would yield an
      inconsistent group configuration, the Group Manager MUST respond
      with a 4.09 (Conflict) response.

      The response, MAY include the current representation of the group
      configuration resource, like when responding to a GET request as
      defined in Section 4.4.  Otherwise, the response SHOULD include a
      diagnostic payload with additional information for the
      Administrator to recognize the source of the conflict.

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   *  When the request uses specifically the iPATCH method, the Group
      Manager MUST respond with a 4.00 (Bad Request) response, in case:

      -  When custom CBOR is used, the CBOR map includes the parameter
         'app_groups_diff'; or

      -  When CoRAL is used, any element 'app_group_del' and/or
         'app_group_add' is included.

   If no error occurs, the Group Manager performs the following actions.

   First, the Group Manager updates the group-configuration resource,
   consistently with the values indicated in the PATCH/iPATCH request
   from the Administrator.

   Unlike for the PUT request defined in Section 4.6, the Group Manager
   does not alter the value of configuration parameters and status
   parameters for which updated values are not specified in the request
   payload.  In particular, the Group Manager does not assign possible
   default values to those parameters.

   Special processing occurs when updating the 'app_groups' status
   parameter by difference, as defined below.  The Administrator should
   not expect the Group Manager to add or delete names of application
   group names according to any particular order.

   *  If the name of an application group to add (delete) is specified
      multiple times, the Group Manager considers it only once for
      addition to (deletion from) the 'app_groups' status parameter.

   *  If the name of an application group to delete is not present in
      the 'app_groups' status parameter before any change is applied,
      the Group Manager ignores that name.

   *  If the name of an application group to add is already present in
      the 'app_groups' status parameter before any change is applied,
      the Group Manager ignores that name.

   *  When custom CBOR is used, the Group Manager:

      -  Deletes from the 'app_groups' status parameter the names of the
         application groups specified in the inner 'app_groups_del' CBOR
         array of the 'app_groups_diff' field.

      -  Adds to the 'app_groups' status parameter the names of the
         application groups specified in the inner 'app_groups_add' CBOR
         array of the 'app_groups_diff' field.

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   *  When CoRAL is used, the Group Manager:

      -  Deletes from the 'app_groups' status parameter the names of the
         application groups specified in the different 'app_group_del'
         elements.

      -  Adds to the 'app_groups' status parameter the names of the
         application groups specified in the different 'app_group_add'
         elements.

   After having updated the group-configuration resource, from then on
   the Group Manager relies on the new group configuration to build the
   Joining Response message defined in Section 6.4 of
   [I-D.ietf-ace-key-groupcomm-oscore], when handling the joining of a
   new group member.  Similarly, the Group Manager relies on the new
   group configuration when building responses specifying (part of) the
   group configuration to a current group member.  For instance, this
   applies when a group member retrieves from the Group Manager the
   updated group keying material (see Section 8 of
   [I-D.ietf-ace-key-groupcomm-oscore]) or the current group status (see
   Section 16 of [I-D.ietf-ace-key-groupcomm-oscore]).

   Finally, the Group Manager replies to the Administrator with a 2.04
   (Changed) response.  The payload of the response has the same format
   of the 2.01 (Created) response defined in Section 4.3.

   The same considerations as for the PUT request defined in Section 4.6
   hold also in this case, with respect to refreshing a possible
   registration of the link to the group-membership resource in the
   Resource Directory [I-D.ietf-core-resource-directory].

   Example in custom CBOR:

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   => 0.06 PATCH
      Uri-Path: manage
      Uri-Path: gp4
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "sign_enc_alg" : 10,
        "app_groups_diff" : [["room1"],
                             ["room3", "room4"]]
      }

   <= 2.04 Changed
      Content-Format: TBD2 (application/ace-groupcomm+cbor)

      {
        "group_name" : "gp4",
        "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/",
        "as_uri" : "coap://as.example.com/token"
      }

   Example in CoRAL:

   => 0.06 PATCH
      Uri-Path: manage
      Uri-Path: gp4
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      sign_enc_alg 10
      app_group_del "room1"
      app_group_add "room3"
      app_group_add "room4"

   <= 2.04 Changed
      Content-Format: TBD1 (application/coral+cbor)

      #using <http://coreapps.org/core.osc.gconf#>
      group_name "gp4"
      joining_uri <coap://[2001:db8::ab]/ace-group/gp4/>
      as_uri <coap://as.example.com/token>

4.7.1.  Effects on Joining Nodes

   After having selectively updated part of a group configuration, the
   effects on candidate joining nodes are the same as defined in
   Section 4.6.1 for the case of group configuration overwriting.

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4.7.2.  Effects on the Group Members

   After having selectively updated part of a group configuration, the
   effects on the current group members are the same as defined in
   Section 4.6.2 for the case of group configuration overwriting.

4.8.  Delete a Group Configuration

   The Administrator can send a DELETE request to the group-
   configuration resource, in order to delete that OSCORE group.  The
   deletion would be successful only on an inactive OSCORE group.

   That is, the DELETE request actually yields a successful deletion of
   the OSCORE group, only if the corresponding status parameter 'active'
   has current value False.  The Administrator can ensure that, by first
   performing an update of the group-configuration resource associated
   to the OSCORE group (see Section 4.6), and setting the corresponding
   status parameter 'active' to False.

   If, upon receiving the DELETE request, the current value of the
   status parameter 'active' is True, the Group Manager MUST respond
   with a 4.09 (Conflict) response.  The response MUST have Content-
   Format set to application/ace-groupcomm+cbor and is formatted as
   defined in Section 4.1.2 of [I-D.ietf-ace-key-groupcomm].  The value
   of the 'error' field MUST be set to 8 ("Group currently active").

   After a successful processing of the request above, the Group Manager
   performs the following actions.

   First, the Group Manager deletes the OSCORE group and deallocates
   both the group-configuration resource as well as the group-membership
   resource associated to that group.

   Then, the Group Manager replies to the Administrator with a 2.02
   (Deleted) response.

   Example:

   => 0.04 DELETE
      Uri-Path: manage
      Uri-Path: gp4

   <= 2.02 Deleted

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4.8.1.  Effects on the Group Members

   After having deleted an OSCORE group, the Group Manager can inform
   the group members by means of the following two methods.  When
   contacting a group member, the Group Manager uses the pairwise secure
   communication association established with that member during its
   joining process (see Section 6 of
   [I-D.ietf-ace-key-groupcomm-oscore]).

   *  The Group Manager sends an individual request message to each
      group member, targeting the respective resource used to perform
      the group rekeying process (see Section 20.1 of
      [I-D.ietf-ace-key-groupcomm-oscore]).  The Group Manager uses the
      same format of the Joining Response message in Section 6.4 of
      [I-D.ietf-ace-key-groupcomm-oscore], where only the parameters
      'gkty', 'key' and 'ace-groupcomm-profile' are present, and the
      'key' parameter is the empty CBOR map.

   *  A group member may subscribe for updates to the group-membership
      resource associated to the OSCORE group.  In particular, if this
      relies on CoAP Observe [RFC7641], a group member would receive a
      4.04 (Not Found) notification response from the Group Manager,
      since the group-configuration resource has been deallocated upon
      deleting the OSCORE group (see Section 6.1 of
      [I-D.ietf-ace-key-groupcomm]).  The response MUST have Content-
      Format set to application/ace-groupcomm+cbor and is formatted as
      defined in Section 4.1.2 of [I-D.ietf-ace-key-groupcomm].  The
      value of the 'error' field MUST be set to 5 ("Group deleted").

   When being informed about the deletion of the OSCORE group, a group
   member deletes the OSCORE Security Context that it stores as
   associated to that group, and possibly deallocates any dedicated
   control resource intended for the Group Manager that it has for that
   group.

5.  ACE Groupcomm Error Identifiers

   In addition to what is defined in Section 9 of
   [I-D.ietf-ace-key-groupcomm], this document defines a new value that
   the Group Manager can include as error identifiers, in the 'error'
   field of an error response with Content-Format application/ace-
   groupcomm+cbor.

                    +-------+------------------------+
                    | Value |      Description       |
                    +-------+------------------------+
                    |  10   | Group currently active |
                    +-------+------------------------+

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                 Figure 3: ACE Groupcomm Error Identifiers

   A Client supporting the 'error' parameter (see Sections 4.1.2 and 8
   of [I-D.ietf-ace-key-groupcomm]) and able to understand the specified
   error may use that information to determine what actions to take
   next.  If it is included in the error response and supported by the
   Client, the 'error_description' parameter may provide additional
   context.  In particular, the following guidelines apply.

   *  In case of error 10, the Client should stop sending the request in
      question to the Group Manager, until the group becomes inactive.
      As per this document, this error is relevant only for the
      Administrator, if it tries to delete a group without having set
      its status to inactive first (see Section 4.8).  In such a case,
      the Administrator should take the expected course of actions, and
      set the group status to inactive first (see Section 4.6 and
      Section 4.7), before proceeding with the group deletion.

6.  Security Considerations

   Security considerations are inherited from the ACE framework for
   Authentication and Authorization [I-D.ietf-ace-oauth-authz], and from
   the specific transport profile of ACE used between the Administrator
   and the Group Manager, such as [I-D.ietf-ace-dtls-authorize] and
   [I-D.ietf-ace-oscore-profile].

7.  IANA Considerations

   RFC Editor: Please replace "[[this document]]" with the RFC number of
   this document and delete this paragraph.

   This document has the following actions for IANA.

7.1.  ACE Groupcomm Parameters

   IANA is asked to register the following entries in the "ACE Groupcomm
   Parameters" registry defined in Section 11.7 of
   [I-D.ietf-ace-key-groupcomm].

     +-----------------+----------+--------------+-------------------+
     | Name            | CBOR Key | CBOR Type    | Reference         |
     +-----------------+----------+--------------+-------------------+
     | hkdf            | TBD      | tstr / int   | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | pub_key_enc     | TBD      | int          | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | group_mode      | TBD      | simple value | [[this document]] |
     +-----------------+----------+--------------+-------------------+

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     | sign_enc_alg    | TBD      | tstr / int / | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | sign_alg        | TBD      | tstr / int / | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | sign_params     | TBD      | array /      | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | pairwise_mode   | TBD      | simple value | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | alg             | TBD      | tstr / int / | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | ecdh_alg        | TBD      | tstr / int / | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | ecdh_params     | TBD      | array /      | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | det_req         | TBD      | simple value | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | det_hash_alg    | TBD      | tstr / int   | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | active          | TBD      | simple value | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | group_name      | TBD      | tstr         | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | group_title     | TBD      | tstr /       | [[this document]] |
     |                 |          | simple value |                   |
     +-----------------+----------+--------------+-------------------+
     | app_groups      | TBD      | array        | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | joining_uri     | TBD      | tstr         | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | max_stale_sets  | TBD      | uint         | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | as_uri          | TBD      | tstr         | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | conf_filter     | TBD      | array        | [[this document]] |
     +-----------------+----------+--------------+-------------------+
     | app_groups_diff | TBD      | array        | [[this document]] |
     +-----------------+----------+--------------+-------------------+

                     Figure 4: ACE Groupcomm Parameters

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7.2.  ACE Groupcomm Errors

   IANA is asked to register the following entry in the "ACE Groupcomm
   Errors" registry defined in Section 11.13 of
   [I-D.ietf-ace-key-groupcomm].

   *  Value: 10

   *  Description: Group currently active.

   *  Reference: [[This document]]

7.3.  Resource Types

   IANA is asked to enter the following values in the "Resource Type
   (rt=) Link Target Attribute Values" registry within the "Constrained
   Restful Environments (CoRE) Parameters" registry group.

   +----------------+------------------------------+-------------------+
   | Value          | Description                  | Reference         |
   +----------------+------------------------------+-------------------+
   | core.osc.gcoll | Group-collection resource    | [[this document]] |
   |                | of an OSCORE Group Manager   |                   |
   |                |                              |                   |
   | core.osc.gconf | Group-configuration resource | [[this document]] |
   |                | of an OSCORE Group Manager   |                   |
   +----------------+------------------------------+-------------------+

8.  References

8.1.  Normative References

   [COSE.Algorithms]
              IANA, "COSE Algorithms",
              <https://www.iana.org/assignments/cose/
              cose.xhtml#algorithms>.

   [I-D.ietf-ace-key-groupcomm]
              Palombini, F. and M. Tiloca, "Key Provisioning for Group
              Communication using ACE", Work in Progress, Internet-
              Draft, draft-ietf-ace-key-groupcomm-14, 25 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-ace-key-
              groupcomm-14.txt>.

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   [I-D.ietf-ace-key-groupcomm-oscore]
              Tiloca, M., Park, J., and F. Palombini, "Key Management
              for OSCORE Groups in ACE", Work in Progress, Internet-
              Draft, draft-ietf-ace-key-groupcomm-oscore-12, 25 October
              2021, <https://www.ietf.org/archive/id/draft-ietf-ace-key-
              groupcomm-oscore-12.txt>.

   [I-D.ietf-ace-oauth-authz]
              Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
              H. Tschofenig, "Authentication and Authorization for
              Constrained Environments (ACE) using the OAuth 2.0
              Framework (ACE-OAuth)", Work in Progress, Internet-Draft,
              draft-ietf-ace-oauth-authz-45, 29 August 2021,
              <https://www.ietf.org/archive/id/draft-ietf-ace-oauth-
              authz-45.txt>.

   [I-D.ietf-ace-oscore-profile]
              Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson,
              "OSCORE Profile of the Authentication and Authorization
              for Constrained Environments Framework", Work in Progress,
              Internet-Draft, draft-ietf-ace-oscore-profile-19, 6 May
              2021, <https://www.ietf.org/archive/id/draft-ietf-ace-
              oscore-profile-19.txt>.

   [I-D.ietf-core-coral]
              Hartke, K., "The Constrained RESTful Application Language
              (CoRAL)", Work in Progress, Internet-Draft, draft-ietf-
              core-coral-03, 9 March 2020,
              <https://www.ietf.org/archive/id/draft-ietf-core-coral-
              03.txt>.

   [I-D.ietf-core-groupcomm-bis]
              Dijk, E., Wang, C., and M. Tiloca, "Group Communication
              for the Constrained Application Protocol (CoAP)", Work in
              Progress, Internet-Draft, draft-ietf-core-groupcomm-bis-
              05, 25 October 2021, <https://www.ietf.org/archive/id/
              draft-ietf-core-groupcomm-bis-05.txt>.

   [I-D.ietf-core-oscore-groupcomm]
              Tiloca, M., Selander, G., Palombini, F., Mattsson, J. P.,
              and J. Park, "Group OSCORE - Secure Group Communication
              for CoAP", Work in Progress, Internet-Draft, draft-ietf-
              core-oscore-groupcomm-13, 25 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-core-oscore-
              groupcomm-13.txt>.

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

   [I-D.ietf-cose-rfc8152bis-struct]
              Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Structures and Process", Work in Progress, Internet-Draft,
              draft-ietf-cose-rfc8152bis-struct-15, 1 February 2021,
              <https://www.ietf.org/archive/id/draft-ietf-cose-
              rfc8152bis-struct-15.txt>.

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

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
              <https://www.rfc-editor.org/info/rfc6690>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.

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

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

   [RFC8132]  van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
              FETCH Methods for the Constrained Application Protocol
              (CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
              <https://www.rfc-editor.org/info/rfc8132>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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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, <https://www.rfc-editor.org/info/rfc8610>.

   [RFC8613]  Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
              <https://www.rfc-editor.org/info/rfc8613>.

   [RFC8949]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949,
              DOI 10.17487/RFC8949, December 2020,
              <https://www.rfc-editor.org/info/rfc8949>.

8.2.  Informative References

   [I-D.amsuess-core-cachable-oscore]
              Amsüss, C. and M. Tiloca, "Cacheable OSCORE", Work in
              Progress, Internet-Draft, draft-amsuess-core-cachable-
              oscore-02, 12 July 2021, <https://www.ietf.org/archive/id/
              draft-amsuess-core-cachable-oscore-02.txt>.

   [I-D.hartke-t2trg-coral-reef]
              Hartke, K., "Resource Discovery in Constrained RESTful
              Environments (CoRE) using the Constrained RESTful
              Application Language (CoRAL)", Work in Progress, Internet-
              Draft, draft-hartke-t2trg-coral-reef-04, 9 May 2020,
              <https://www.ietf.org/archive/id/draft-hartke-t2trg-coral-
              reef-04.txt>.

   [I-D.ietf-ace-dtls-authorize]
              Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and
              L. Seitz, "Datagram Transport Layer Security (DTLS)
              Profile for Authentication and Authorization for
              Constrained Environments (ACE)", Work in Progress,
              Internet-Draft, draft-ietf-ace-dtls-authorize-18, 4 June
              2021, <https://www.ietf.org/archive/id/draft-ietf-ace-
              dtls-authorize-18.txt>.

   [I-D.ietf-core-resource-directory]
              Amsüss, C., Shelby, Z., Koster, M., Bormann, C., and P. V.
              D. Stok, "CoRE Resource Directory", Work in Progress,
              Internet-Draft, draft-ietf-core-resource-directory-28, 7
              March 2021, <https://www.ietf.org/archive/id/draft-ietf-
              core-resource-directory-28.txt>.

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   [I-D.ietf-tls-dtls13]
              Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
              dtls13-43, 30 April 2021, <https://www.ietf.org/internet-
              drafts/draft-ietf-tls-dtls13-43.txt>.

   [I-D.tiloca-core-oscore-discovery]
              Tiloca, M., Amsuess, C., and P. V. D. Stok, "Discovery of
              OSCORE Groups with the CoRE Resource Directory", Work in
              Progress, Internet-Draft, draft-tiloca-core-oscore-
              discovery-10, 25 October 2021,
              <https://www.ietf.org/archive/id/draft-tiloca-core-oscore-
              discovery-10.txt>.

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

Appendix A.  Document Updates

   RFC EDITOR: PLEASE REMOVE THIS SECTION.

A.1.  Version -03 to -04

   *  Clarifications on what to do in case of enhanced error responses.

   *  Clarifications on handling default values for group parameters.

   *  New configuration parameters to support OSCORE deterministic
      requests.

   *  IANA considerations - Use RFC8126 terminology.

   *  Author's change of address.

   *  Editorial improvements.

A.2.  Version -02 to -03

   *  Aligned new and old parameters to core-groupcomm-oscore and ace-
      key-groupcomm-oscore.

   *  Removed 'cs_key_params' and 'ecdh_key_params' to avoid redundant
      COSE capabilities of key types, consistently with draft-ietf-ace-
      key-groupcomm-oscore.

   *  Revised examples and side effects due to parameter changes.

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   *  New error type "Group currently active".

A.3.  Version -01 to -02

   *  Admit multiple Administrators and limited access to admin
      resources.

   *  Early design considerations for defining the format of scope.

   *  Additional error handling, using also error types.

   *  Selective update of group-configuration resources with PATCH/
      iPATCH.

   *  Editorial improvements.

A.4.  Version -00 to -01

   *  Names of application groups as status parameter.

   *  Parameters related to the pairwise mode of Group OSCORE.

   *  Defined FETCH for group-configuration resources.

   *  Policies on registration of links to the Resource Directory.

   *  Added resource type for group-configuration resources.

   *  Fixes, clarifications and editorial improvements.

Acknowledgments

   Klaus Hartke provided substantial contribution in defining the
   resource model based on group collection and group configurations, as
   well as the interactions with the Group Manager using CoRAL.

   The authors sincerely thank Christian Amsuess, Carsten Bormann and
   Jim Schaad for their comments and feedback.

   The work on this document has been partly supported by VINNOVA and
   the Celtic-Next project CRITISEC; and by the H2020 project SIFIS-Home
   (Grant agreement 952652).

Authors' Addresses

   Marco Tiloca
   RISE AB
   Isafjordsgatan 22

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   SE-16440 Stockholm Kista
   Sweden

   Email: marco.tiloca@ri.se

   Rikard Höglund
   RISE AB
   Isafjordsgatan 22
   SE-16440 Stockholm Kista
   Sweden

   Email: rikard.hoglund@ri.se

   Peter van der Stok
   Consultant

   Phone: +31-492474673 (Netherlands), +33-966015248 (France)
   Email: stokcons@bbhmail.nl

   Francesca Palombini
   Ericsson AB
   Torshamnsgatan 23
   SE-16440 Stockholm Kista
   Sweden

   Email: francesca.palombini@ericsson.com

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