Joining of OSCOAP multicast groups in ACE
draft-tiloca-ace-oscoap-joining-00

ACE Working Group                                              M. Tiloca
Internet-Draft                                              RISE SICS AB
Intended status: Standards Track                                 J. Park
Expires: January 3, 2018                     Universitaet Duisburg-Essen
                                                           July 02, 2017

               Joining of OSCOAP multicast groups in ACE
                   draft-tiloca-ace-oscoap-joining-00

Abstract

   This document describes a method to join a multicast group where
   communications are based on CoAP and secured with Object Security of
   CoAP (OSCOAP).  The proposed method delegates the authentication and
   authorization of client nodes that join a 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 January 3, 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
   carefully, as they describe your rights and restrictions with respect

Tiloca & Park            Expires January 3, 2018                [Page 1]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   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 . . . . . . . . . . . . . . . . . . . . .  11
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   The Constrained Application Protocol (CoAP) [RFC7252] supports also
   group communication scenarios, where request messages can be
   delivered to multiple recipients using CoAP on top of IP multicast
   [RFC7390].

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

   OSCOAP 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 OSCOAP.  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 OSCOAP 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.

Tiloca & Park            Expires January 3, 2018                [Page 2]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   The client and the Group Manager leverage protocol-specific profiles
   of ACE such as [I-D.seitz-ace-oscoap-profile] and
   [I-D.ietf-ace-dtls-authorize], in order to achieve communication
   security, proof-of-possession and server authentication.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].  These
   words may also appear in this document in lowercase, absent their
   normative meanings.

   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 for
   protection and processing of CoAP messages through OSCOAP
   [I-D.ietf-core-object-security] also in group communication contexts
   [I-D.tiloca-core-multicast-oscoap]; and with the OSCOAP profile of
   ACE described in [I-D.seitz-ace-oscoap-profile].

   Readers are expected to be familiar with the terms and concepts
   related to the DTLS protocol [RFC6347]; the support for DTLS
   handshake based on Raw Public Keys (RPK) [RFC7250] and on Pre-Shared
   Keys (PSK) [RFC4279]; and the CoAP-DTLS profile of ACE
   [I-D.ietf-ace-dtls-authorize].

   This document refers also to the following terminology.

Tiloca & Park            Expires January 3, 2018                [Page 3]
Internet-Draft         OSCOAP group joining in ACE             July 2017

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

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

   o  Join resource: a protected resource hosted by the Group Manager,
      associated to a 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 hosted by 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 of CoAP (OSCOAP)
   [I-D.ietf-core-object-security] as described in
   [I-D.tiloca-core-multicast-oscoap].  A network node explicitly joins
   an OSCOAP 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 OSCOAP
   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 owns one join
      resource for each OSCOAP 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
      OSCOAP 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 authorized to join the multicast group, the joining node receives
   from the AS an Access Token bound with a proof-of-possession key.
   After that, the joining node provides the Group Manager with the
   Access Token.  This step involves the opening of a secure

Tiloca & Park            Expires January 3, 2018                [Page 4]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   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
   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.  In particular, the AS is not necessarily expected to
   release Access Tokens for accessing protected resources at members of
   multicast groups.

   The following steps are performed for joining an OSCOAP multicast
   group, by leveraging the CoAP-DTLS profile of ACE
   [I-D.ietf-ace-dtls-authorize] or the OSCOAP profile of ACE
   [I-D.seitz-ace-oscoap-profile].

   1.  The joining node retrieves an Access Token from the AS to access
       a join resource on the Group Manager (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 (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 (Section 4).
       That is, a joining node MUST establish a secure communication
       channel with a Group Manager, before joining a multicast group
       under that Group Manager for the first time.

   3.  The joining node starts the join process to become a member of
       the multicast group, by accessing the related join resource
       hosted by the Group Manager (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, e.g. with DTLS [RFC6347] or with OSCOAP (see
   Sections 3 and 4 of [I-D.seitz-ace-oscoap-profile]).

Tiloca & Park            Expires January 3, 2018                [Page 5]
Internet-Draft         OSCOAP group joining in ACE             July 2017

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 a 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 one
   described in Section 2.2 of [I-D.ietf-ace-dtls-authorize] to discover
   the correct AS in charge of the Group Manager.

   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  OSCOAP, indicating to consider the OSCOAP profile of ACE with
      asymmetric or symmetric proof-of-possession key, as described in
      Section 2.2 of [I-D.seitz-ace-oscoap-profile].

   Consistently with the profiles of ACE specified in
   [I-D.ietf-ace-dtls-authorize] and [I-D.seitz-ace-oscoap-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, 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

Tiloca & Park            Expires January 3, 2018                [Page 6]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   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.  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 OSCOAP profile of ACE is specified, the joining node and
      the Group Manager establish an OSCOAP channel, as described in
      Section 2.2 of [I-D.seitz-ace-oscoap-profile].  In particular, if
      the EDHOC protocol [I-D.selander-ace-cose-ecdhe] is used to this
      end, the joining node MUST include the Access Token in the EDHOC
      message_1 sent to the /authz-info resource.  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].

   Once the secure channel with the Group Manager has been established,
   the joining node requests to join the OSCOAP 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 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
   multicast group.  The request payload specifies the intended role(s)
   of the joining node in the multicast group, i.e. multicaster and/or
   (pure) listener [I-D.tiloca-core-multicast-oscoap].

   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

Tiloca & Park            Expires January 3, 2018                [Page 7]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   replies to the joining node including the following pieces of
   information in the CoAP response payload:

   o  An OSCOAP endpoint ID, if the joining node is not configured
      exclusively as pure listener (see Section 3 of
      [I-D.tiloca-core-multicast-oscoap]).  The Group Manager ensures
      that each OSCOAP endpoint ID in use is unique within a same
      multicast group.

   o  The OSCOAP Security Common Context associated to the joined
      multicast group (see Section 4 of
      [I-D.tiloca-core-multicast-oscoap]).

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

5.  Public Keys of Joining Nodes

   Source authentication of OSCOAP 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 authenticity of incoming group
   messages.  As also discussed in Section 7.4 of
   [I-D.tiloca-core-multicast-oscoap], the Group Manager can be
   configured to store public keys of group members and provide them
   upon request.

   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
   available, key repository.  However, this is not required, if at
   least one of the following conditions hold.

   o  The joining node joins a group exclusively as pure listener.

   o  The joining node joins a group where only group authentication of
      messages is provided (see Appendix C of
      [I-D.tiloca-core-multicast-oscoap]).

   In case the Group Manager is not configured to store public keys of
   group members, a joining node SHOULD specify to the Group Manager the
   address of a trusted key repository where its own public key is
   available.  In particular, upon performing a join process with a
   given Group Manager for the first time, the joining node additionally
   includes this information in the payload of the POST request

Tiloca & Park            Expires January 3, 2018                [Page 8]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   targeting the join endpoint.  The Group Manager can then redirect
   group members to the correct key repository in case of need.

   Instead, in case the Group Manager is configured to store public keys
   of group members, two main 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 payload of the POST request targeting the
      join endpoint.  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.

   Furthermore, if the Group Manager is configured as key repository, it
   SHOULD provide a joining node with the public keys of the current
   members in the joined group.  In particular, when providing the
   OSCOAP Endpoint ID and the OSCOAP Security Common Context as
   described in Section 4, the Group Manager additionally includes the
   following material in the response to the joining node:

   o  The public keys of the non-pure listeners currently in the joined
      multicast group, if the joining node is configured (also) as
      multicaster.

   o  The public keys of the multicasters currently in the joined
      multicast group, if the joining node is configured (also) as non-
      pure listener.

6.  Updating Authorization Information

   At any point in time, a node might want to join further OSCOAP
   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 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
   channel.  After that, the joining node performs the joining process
   described in Section 4, separately for each multicast group to join.

Tiloca & Park            Expires January 3, 2018                [Page 9]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   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

   This document relies on the security considerations included in
   Section 7 of [I-D.tiloca-core-multicast-oscoap], as to different
   management aspects related to OSCOAP multicast groups:

   o  Management of group keying material (Section 7.2).  This includes
      the need to revoke and renew the keying material currently used in
      the 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 7.3).  This concerns
      how a listener node that has just joined a multicast group can
      synchronize with the sender sequence number of multicasters in the
      same group.  To this end, the new listener node performs a
      challenge-response with a multicaster node, leveraging the Repeat
      Option for CoAP [I-D.amsuess-core-repeat-request-tag].

   o  Provisioning of public keys (Section 7.4).  This provides
      guidelines about how to ensure the availability of group members'
      public keys, possibly relying on the Group Manager as trusted key
      repository.  Section 5 of this specification leverages and builds
      on such considerations.

   Further security considerations are (going to be) inherited from the
   ACE framework for Authentication and Authorization
   [I-D.ietf-ace-oauth-authz], as well as from the CoAP-DTLS profile
   [I-D.ietf-ace-dtls-authorize] and the OSCOAP profile
   [I-D.seitz-ace-oscoap-profile] of ACE.

Tiloca & Park            Expires January 3, 2018               [Page 10]
Internet-Draft         OSCOAP group joining in ACE             July 2017

8.  IANA Considerations

   This document has no actions for IANA.

9.  Acknowledgments

   The authors sincerely thank Goeran Selander, Santiago Aragon, Ludwig
   Seitz and Martin Gunnarsson for their comments and feedback.

10.  References

10.1.  Normative References

   [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-00 (work in progress), June 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-06 (work in progress), March 2017.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security of CoAP (OSCOAP)", draft-ietf-core-
              object-security-04 (work in progress), July 2017.

   [I-D.seitz-ace-oscoap-profile]
              Seitz, L., Gunnarsson, M., and F. Palombini, "OSCOAP
              profile of ACE", draft-seitz-ace-oscoap-profile-03 (work
              in progress), June 2017.

   [I-D.tiloca-core-multicast-oscoap]
              Tiloca, M., Selander, G., and F. Palombini, "Secure group
              communication for CoAP", draft-tiloca-core-multicast-
              oscoap-02 (work in progress), July 2017.

Tiloca & Park            Expires January 3, 2018               [Page 11]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://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,
              <http://www.rfc-editor.org/info/rfc7252>.

10.2.  Informative References

   [I-D.amsuess-core-repeat-request-tag]
              Amsuess, C., Mattsson, J., and G. Selander, "Repeat And
              Request-Tag", draft-amsuess-core-repeat-request-tag-00
              (work in progress), July 2017.

   [I-D.ietf-cose-msg]
              Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              draft-ietf-cose-msg-24 (work in progress), November 2016.

   [I-D.selander-ace-cose-ecdhe]
              Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
              Diffie-Hellman Over COSE (EDHOC)", draft-selander-ace-
              cose-ecdhe-06 (work in progress), April 2017.

   [RFC4279]  Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
              Ciphersuites for Transport Layer Security (TLS)",
              RFC 4279, DOI 10.17487/RFC4279, December 2005,
              <http://www.rfc-editor.org/info/rfc4279>.

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

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc7231>.

Tiloca & Park            Expires January 3, 2018               [Page 12]
Internet-Draft         OSCOAP group joining in ACE             July 2017

   [RFC7250]  Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
              Weiler, S., and T. Kivinen, "Using Raw Public Keys in
              Transport Layer Security (TLS) and Datagram Transport
              Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
              June 2014, <http://www.rfc-editor.org/info/rfc7250>.

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

Authors' Addresses

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

   Phone: +46 70 604 65 01
   Email: marco.tiloca@ri.se

   Jiye Park
   Universitaet Duisburg-Essen
   Schuetzenbahn 70
   Essen  45127
   Germany

   Phone: +49 201 183-7634
   Email: ji-ye.park@uni-due.de

Tiloca & Park            Expires January 3, 2018               [Page 13]