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ACE Working Group                                              M. Tiloca
Internet-Draft                                              RISE SICS AB
Intended status: Standards Track                                 J. Park
Expires: May 2, 2018                         Universitaet Duisburg-Essen
                                                        October 29, 2017


               Joining of OSCORE multicast groups in ACE
                   draft-tiloca-ace-oscoap-joining-02

Abstract

   This document describes a method to join a multicast group where
   communications are based on CoAP and secured with Object Security for
   Constrained RESTful Environments (OSCORE).  The proposed method
   delegates the authentication and authorization of client nodes that
   join an OSCORE multicast group through a Group Manager server.  This
   approach builds on the ACE framework for Authentication and
   Authorization, and leverages protocol-specific profiles of ACE to
   achieve communication security, proof-of-possession and server
   authentication.

Status of This Memo

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

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 2, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Joining Node to Authorization Server  . . . . . . . . . . . .   6
   4.  Joining Node to Group Manager . . . . . . . . . . . . . . . .   7
   5.  Public Keys of Joining Nodes  . . . . . . . . . . . . . . . .   8
   6.  Updating Authorization Information  . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   Object Security for Constrained RESTful Environments (OSCORE)
   [I-D.ietf-core-object-security] is a method for application layer
   protection of CoAP messages, using the CBOR Object Signing and
   Encryption (COSE) [RFC8152], and enabling end-to-end security of CoAP
   payload and options.

   OSCORE may also be used to protect group communication for CoAP over
   IP multicast, as described in [I-D.tiloca-core-multicast-oscoap].
   This relies on a Group Manager entity, which is responsible for
   managing a multicast group where members exchange CoAP messages
   secured with OSCORE.  In particular, the Group Manager coordinates
   the join process of new group members and can be responsible for
   multiple groups.

   This document builds on the ACE framework for Authentication and
   Authorization [I-D.ietf-ace-oauth-authz] and specifies how a client
   joins an OSCORE multicast group through a resource server acting as
   Group Manager.  The client acting as joining node relies on an Access
   Token, which is bound to a proof-of-possession key and authorizes the
   access to a specific join resource at the Group Manager.

   In order to achieve communication security, proof-of-possession and
   server authentication, the client and the Group Manager leverage



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   protocol-specific profiles of ACE such as the CoAP-DTLS profile
   [I-D.ietf-ace-dtls-authorize], the OSCORE profile
   [I-D.seitz-ace-oscoap-profile], or the IPsec profile
   [I-D.aragon-ace-ipsec-profile].

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
   described in the ACE framework for authentication and authorization
   [I-D.ietf-ace-oauth-authz].  Message exchanges are presented as
   RESTful protocol interactions, for which HTTP [RFC7231] provides
   useful terminology.

   The terminology for entities in the considered architecture is
   defined in OAuth 2.0 [RFC6749] and [I-D.ietf-ace-actors].  In
   particular, this includes Client (C), Resource Server (RS), and
   Authorization Server (AS).  Terminology for constrained environments,
   such as "constrained device" and "constrained-node network", is
   defined in [RFC7228].

   Readers are expected to be familiar with the terms and concepts
   related to the CoAP protocol described in [RFC7252][RFC7390].  Note
   that 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".

   Readers are expected to be familiar with the terms and concepts
   related to the DTLS protocol [RFC6347] and with the CoAP-DTLS profile
   of ACE [I-D.ietf-ace-dtls-authorize].

   Readers are expected to be familiar with the terms and concepts for
   protection and processing of CoAP messages through OSCORE
   [I-D.ietf-core-object-security] also in group communication contexts
   [I-D.tiloca-core-multicast-oscoap]; and with the OSCORE profile of
   ACE [I-D.seitz-ace-oscoap-profile].

   Readers are expected to be familiar with the terms and concepts
   related to the IPsec protocol suite [RFC4301]; and with the IPsec
   profile of ACE [I-D.aragon-ace-ipsec-profile].




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   This document refers also to the following terminology.

   o  Joining node: a network node intending to join an OSCORE multicast
      group, where communication is based on CoAP [RFC7390] and secured
      with OSCORE as described in [I-D.tiloca-core-multicast-oscoap].

   o  Join process: the process through which a joining node becomes a
      member of an OSCORE multicast group.  The join process is enforced
      and assisted by the Group Manager responsible for that group.

   o  Join resource: a resource hosted by the Group Manager, associated
      to an OSCORE multicast group under that Group Manager.  A joining
      node accesses the join resource in order to start the join process
      and become a member of that group.

   o  Join endpoint: an endpoint at the Group Manager associated to a
      join resource.

2.  Protocol Overview

   Group communication for CoAP over IP multicast has been enabled in
   [RFC7390] and can be secured with Object Security for Constrained
   RESTful Environments (OSCORE) [I-D.ietf-core-object-security] as
   described in [I-D.tiloca-core-multicast-oscoap].  A network node
   explicitly joins an OSCORE multicast group, by interacting with the
   responsible Group Manager.  Once registered in the group, the new
   node can securely exchange (multicast) messages with other group
   members.

   This specification describes how a network node joins an OSCORE
   multicast group leveraging the ACE framework for authentication and
   authorization [I-D.ietf-ace-oauth-authz].  With reference to the ACE
   framework and the terminology defined in OAuth 2.0 [RFC6749]:

   o  The Group Manager acts as Resource Server (RS), and hosts one join
      resource for each OSCORE multicast group it manages.  Each join
      resource is exported by a distinct join endpoint.

   o  The joining node acts as Client (C), and requests to join an
      OSCORE multicast group by accessing the related join endpoint at
      the Group Manager.

   o  The Authorization Server (AS) enables and enforces the authorized
      access of joining nodes to join endpoints at the Group Manager.
      Multiple Group Managers can be associated to the same AS.

   If the joining node is authorized to join the multicast group, it
   receives from the AS an Access Token bound with a proof-of-possession



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   key.  After that, the joining node provides the Group Manager with
   the Access Token.  This step involves the opening of a secure
   communication channel between the joining node and the Group Manager,
   in case they have not already established one.

   Finally, the joining node accesses the join endpoint at the Group
   Manager, so starting the join process to become a member of the
   OSCORE multicast group.  A same Access Token can authorize the
   joining node to access multiple groups under the same Group Manager.
   In such a case, the joining node sequentially performs multiple join
   processes with the Group Manager, separately for each multicast group
   to join and by accessing the respective join endpoint.

   The AS is not necessarily expected to release Access Tokens for any
   other purpose than accessing join resources on registered Group
   Managers.  However, the AS may be configured also to release Access
   Tokens for accessing resources at members of multicast groups.

   The following steps are performed for joining an OSCORE multicast
   group, by leveraging one of the available profiles of ACE, such as
   the CoAP-DTLS profile [I-D.ietf-ace-dtls-authorize], the OSCORE
   profile [I-D.seitz-ace-oscoap-profile], or the IPsec profile
   [I-D.aragon-ace-ipsec-profile].

   1.  The joining node retrieves an Access Token from the AS to access
       a join resource on the Group Manager (see Section 3).  The
       response from the AS enables the joining node to start a secure
       channel with the Group Manager, if not already established.  The
       joining node can also contact the AS for updating a previously
       released Access Token, in order to access further groups under
       the same Group Manager (see Section 6).

   2.  Authentication and authorization information is transferred
       between the joining node and the Group Manager, which establish a
       secure channel in case one is not already set up (see Section 4).
       That is, a joining node MUST establish a secure communication
       channel with a Group Manager, before joining an OSCORE multicast
       group under that Group Manager for the first time.

   3.  The joining node starts the join process to become a member of
       the OSCORE multicast group, by accessing the related join
       resource hosted by the Group Manager (see Section 4).

   All communications between the involved entities rely on the CoAP
   protocol and MUST be secured.  In particular, communications between
   the joining node and the AS (/token endpoint) and between the Group
   Manager and the AS (/introspection endpoint) can be secured by
   different means, for instance by means of DTLS [RFC6347], OSCORE (see



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   Sections 3 and 4 of [I-D.seitz-ace-oscoap-profile]), or IPsec (see
   Sections 3.2 and 3.4 of [I-D.aragon-ace-ipsec-profile]).

   Further details on how the AS secures communications (with the
   joining node and the Group Manager) depend on the specifically used
   profile of ACE, and are out of the scope of this specification.

3.  Joining Node to Authorization Server

   This section considers a joining node that intends to contact the
   Group Manager for the first time.  That is, the joining node has
   never attempted before to join an OSCORE multicast group under that
   Group Manager.  Also, the joining node and the Group Manager do not
   have a secure communication channel established.

   In case the specific AS associated to the Group Manager is unknown to
   the joining node, the latter can rely on mechanisms like the
   Unauthorized Resource Request message described in Section 2.1 of
   [I-D.ietf-ace-dtls-authorize] to discover the correct AS in charge of
   the Group Manager.  As an alternative, the joining node may look up
   in a Resource Directory service [I-D.ietf-core-resource-directory].

   The joining node contacts the AS, in order to request an Access Token
   for accessing the join resource(s) hosted by the Group Manager.  In
   particular, the Access Token request sent to the /token endpoint
   specifies the join endpoint(s) of interest at the Group Manager.

   The AS is responsible for authorizing the joining node, accordingly
   to group join policies enforced on behalf of the Group Manager.  In
   case of successful authorization, the AS releases an Access Token
   bound to a proof-of-possession key associated to the joining node.
   The same Access Token can authorize the joining node to access
   multiple groups under the same Group Manager.

   Then, the AS provides the joining node with the Access Token,
   together with an Access Token response.  In particular, the Access
   Token response indicates how to secure communications with the Group
   Manager, when accessing the join resource(s) for which the Access
   Token is valid.  Specifically, the Access Token response MUST specify
   one of the following alternatives:

   o  CoAP over DTLS, i.e. coaps://, indicating to consider the CoAP-
      DTLS profile of ACE, with asymmetric or symmetric proof-of-
      possession key (see Section 3 and Section 4 of
      [I-D.ietf-ace-dtls-authorize], respectively).

   o  OSCORE, indicating to consider the OSCORE profile of ACE with the
      symmetric proof-of-possession key used directly as Master Secret



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      in OSCORE [I-D.ietf-core-object-security], as described in
      Section 2 of [I-D.seitz-ace-oscoap-profile].

   o  IPsec, indicating to consider the IPsec profile of ACE, with
      symmetric or asymmetric proof-of-possession key (see Section 3.2.2
      and Section 3.2.3 of [I-D.aragon-ace-ipsec-profile],
      respectively).

   Consistently with the profiles of ACE [I-D.ietf-ace-dtls-authorize][I
   -D.seitz-ace-oscoap-profile][I-D.aragon-ace-ipsec-profile], a
   symmetric proof-of-possession key is generated by the AS, which uses
   it as proof-of-possession key bound to the Access Token, and provides
   it to the joining node in the Access Token response.

   Instead, consistently with the profiles of ACE
   [I-D.ietf-ace-dtls-authorize][I-D.aragon-ace-ipsec-profile], in case
   of asymmetric proof-of-possession key, the joining node provides its
   own public key to the AS in the Access Token request.  Then, the AS
   uses it as proof-of-possession key bound to the Access Token, and
   provides the joining node with the Group Manager's public key in the
   Access Token response.

4.  Joining Node to Group Manager

   First, the joining node establishes a secure channel with the Group
   Manager, according to what is specified in the Access Token response.
   In particular:

   o  If the CoAP-DTLS profile of ACE is specified, the joining node
      MUST upload the Access Token to the /authz-info resource, before
      starting the DTLS handshake and establishing a DTLS channel with
      the Group Manager.  Then, the Group Manager processes the Access
      Token according to [I-D.ietf-ace-oauth-authz].  If this yields to
      a positive response, the joining node and the Group Manager
      establish a DTLS session, as described in Section 3 and Section 4
      of [I-D.ietf-ace-dtls-authorize], in case of either asymmetric or
      symmetric proof-of-possession key, respectively.

   o  If the OSCORE profile of ACE is specified, the joining node and
      the Group Manager establish an OSCORE Security Context, as
      described in Section 2.2 of [I-D.seitz-ace-oscoap-profile].  The
      Group Manager processes the Access Token as specified in
      [I-D.ietf-ace-oauth-authz] and proceeds as defined in Section 2.2
      of [I-D.seitz-ace-oscoap-profile].

   o  If the IPsec profile of ACE is specified, the joining node MUST
      upload the Access Token to the /authz-info resource, before
      performing the key management protocol indicated by the AS (e.g.



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      IKEv2 [RFC7296]) to establish an IPsec Security Association pair
      and an IPsec channel with the Group Manager.  Then, the Group
      Manager processes the Access Token according to
      [I-D.ietf-ace-oauth-authz].  If this yields to a positive
      response, the joining node and the Group Manager establish an
      IPsec Security Association pair and an IPsec channel, as described
      in Section 3.3.2 of [I-D.aragon-ace-ipsec-profile].

   Once a secure communication channel with the Group Manager has been
   established, the joining node requests to join the OSCORE multicast
   groups of interest, by accessing the related join resources at the
   Group Manager.  That is, the joining node performs multiple join
   processes with the Group Manager, separately for each multicast group
   to join and by accessing the respective join endpoint.

   In particular, for each OSCORE multicast group to join, the joining
   node sends to the Group Manager a confirmable CoAP request, using the
   method POST and targeting the join endpoint associated to that group.
   The request payload conveys the information specified in Appendix C.1
   of [I-D.tiloca-core-multicast-oscoap], which includes the intended
   role(s) of the joining node in the multicast group, i.e. multicaster
   and/or (pure) listener.

   The Group Manager processes the request according to
   [I-D.ietf-ace-oauth-authz].  If this yields to a positive response,
   the Group Manager updates the group membership by registering the
   joining node as a new member of the group.  Then, the Group Manager
   replies to the joining node providing the information specified in
   Appendix C.1 of [I-D.tiloca-core-multicast-oscoap], which includes
   the OSCORE Security Common Context associated to the joined multicast
   group.

   From then on, the joining node is registered as a member of the
   multicast group, and can exchange group messages secured with OSCORE
   as described in Section 5 of [I-D.tiloca-core-multicast-oscoap].

5.  Public Keys of Joining Nodes

   Source authentication of OSCORE messages exchanged within the
   multicast group is ensured by means of digital counter signatures
   [I-D.tiloca-core-multicast-oscoap].  Therefore, group members must be
   able to retrieve each other's public key from a trusted key
   repository, in order to verify the source authenticity of incoming
   group messages.

   Upon joining a multicast group, a joining node is expected to make
   its own public key available to the other group members, either
   through the Group Manager or through another trusted, publicly



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   available, key repository.  However, this is not required for a node
   that joins a group exclusively as pure listener.

   As also discussed in Section 3 of [I-D.tiloca-core-multicast-oscoap],
   it is recommended that the Group Manager is configured to store the
   public keys of the group members and to provide them upon request.
   If so, two cases can occur.

   o  The joining node and the Group Manager have used an asymmetric
      proof-of-possession key to establish a secure communication
      channel.  In this case, the Group Manager stores the proof-of-
      possession key conveyed in the Access Token as the public key of
      the joining node.

   o  The joining node and the Group Manager have used a symmetric
      proof-of-possession key to establish a secure communication
      channel.  In this case, upon performing a join process with that
      Group Manager for the first time, the joining node includes its
      own public key in the "Identity credentials" of the POST request
      targeting the join endpoint (see Appendix C.1 of
      [I-D.tiloca-core-multicast-oscoap]).  Then, the Group Manager MUST
      verify that the joining node actually owns the associated private
      key, for instance by performing a proof-of-possession challenge-
      response.

   Then, if the joining node has explicitly requested it, the Group
   Manager provides also the public keys of the current members in the
   joined group, when replying to the joining node during the same join
   process (see Appendix C.1 of [I-D.tiloca-core-multicast-oscoap]).

   Instead, in case the Group Manager is not configured to store public
   keys of group members, the joining node provides the Group Manager
   with its own certificate and with the identifier of the Certification
   Authority that issued that certificate (see Appendix C.2 of
   [I-D.tiloca-core-multicast-oscoap]).

6.  Updating Authorization Information

   At any point in time, a node might want to join further OSCORE
   multicast groups under the same Group Manager.  In such a case, the
   joining node requests from the AS an updated Access Token for
   accessing the new OSCORE multicast groups of interest.

   The joining node uploads the new Access Token to the /authz-info
   resource at the Group Manager, using the already established secure
   communication channel.  After that, the joining node performs the
   joining process described in Section 4, separately for each OSCORE
   multicast group to join.



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   Since the joining node and the Group Manager already share a secure
   communication channel, they are not required to establish a new one.
   However, according to the specific profile of ACE in use, the joining
   node and the Group Manager may leverage the new Access Token to
   establish a new secure communication channel or update the currently
   existing one.  For instance, Section 4.2 of
   [I-D.ietf-ace-dtls-authorize] describes how the new Access Token can
   be used to renegotiate an existing DTLS session or to establish a new
   one by performing a new DTLS handshake.

7.  Security Considerations

   The method described in this document leverages the following
   management aspects related to OSCORE multicast groups and discussed
   in the sections of [I-D.tiloca-core-multicast-oscoap] indicated
   below.

   o  Management of group keying material (Section 3.1).  This includes
      the need to revoke and renew the keying material currently used in
      the OSCORE multicast group, upon changes in the group membership.
      In particular, renewing the keying material is required upon a new
      node joining the multicast group, in order to preserve backward
      security.  The Group Manager is responsible to enforce rekeying
      policies and accordingly update the keying material within the
      multicast groups of its competence.

   o  Synchronization of sequence numbers (Section 6).  This concerns
      how a listener node that has just joined an OSCORE multicast group
      can synchronize with the sequence number of multicasters in the
      same group.

   o  Provisioning and retrieval of public keys (Appendix C.2).  This
      provides guidelines about how to ensure the availability of group
      members' public keys, possibly relying on the Group Manager as
      trusted key repository.

   Further security considerations are inherited from the ACE framework
   for Authentication and Authorization [I-D.ietf-ace-oauth-authz], as
   well as from the profiles of ACE [I-D.ietf-ace-dtls-authorize][I-D.se
   itz-ace-oscoap-profile][I-D.aragon-ace-ipsec-profile].

8.  IANA Considerations

   This document has no actions for IANA.







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9.  Acknowledgments

   The authors sincerely thank Santiago Aragon, Stefan Beck, Martin
   Gunnarsson, Francesca Palombini, Jim Schaad, Ludwig Seitz and Goeran
   Selander for their comments and feedback.

10.  References

10.1.  Normative References

   [I-D.aragon-ace-ipsec-profile]
              Aragon, S., Tiloca, M., and S. Raza, "IPsec profile of
              ACE", draft-aragon-ace-ipsec-profile-01 (work in
              progress), October 2017.

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

   [I-D.ietf-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)", draft-ietf-ace-dtls-
              authorize-01 (work in progress), July 2017.

   [I-D.ietf-ace-oauth-authz]
              Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
              H. Tschofenig, "Authentication and Authorization for
              Constrained Environments (ACE)", draft-ietf-ace-oauth-
              authz-08 (work in progress), October 2017.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", draft-ietf-core-object-security-06 (work in
              progress), October 2017.

   [I-D.seitz-ace-oscoap-profile]
              Seitz, L., Palombini, F., and M. Gunnarsson, "OSCORE
              profile of the Authentication and Authorization for
              Constrained Environments Framework", draft-seitz-ace-
              oscoap-profile-06 (work in progress), October 2017.






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   [I-D.tiloca-core-multicast-oscoap]
              Tiloca, M., Selander, G., Palombini, F., and J. Park,
              "Secure group communication for CoAP", draft-tiloca-core-
              multicast-oscoap-04 (work in progress), October 2017.

   [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>.

   [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>.

   [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>.

10.2.  Informative References

   [I-D.ietf-core-resource-directory]
              Shelby, Z., Koster, M., Bormann, C., Stok, P., and C.
              Amsuess, "CoRE Resource Directory", draft-ietf-core-
              resource-directory-11 (work in progress), July 2017.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [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>.

   [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>.

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

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014, <https://www.rfc-
              editor.org/info/rfc7231>.




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Internet-Draft         OSCORE group joining in ACE          October 2017


   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/info/rfc7296>.

   [RFC7390]  Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
              the Constrained Application Protocol (CoAP)", RFC 7390,
              DOI 10.17487/RFC7390, October 2014, <https://www.rfc-
              editor.org/info/rfc7390>.

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

Authors' Addresses

   Marco Tiloca
   RISE SICS AB
   Isafjordsgatan 22
   Kista  SE-164 29 Stockholm
   Sweden

   Email: marco.tiloca@ri.se


   Jiye Park
   Universitaet Duisburg-Essen
   Schuetzenbahn 70
   Essen  45127
   Germany

   Email: ji-ye.park@uni-due.de



















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