CoAP Publish-Subscribe Profile for Authentication and Authorization for Constrained Environments (ACE)

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 [RFC9200]. The terminology for entities in the considered architecture is defined in OAuth 2.0 [RFC6749]. In particular, this includes Client, Resource Server (RS), and Authorization Server (AS).¶

• The Authorization Information Format (AIF) [RFC9237] used to express authorization information.¶

• The terms and concept related to the message formats and processing specified in [RFC9594], for provisioning and renewing keying material in group communication scenarios. These include the abbreviations REQx and OPTx denoting the numbered mandatory-to-address and optional-to-address requirements, respectively.¶

• The terms and concepts described in CDDL [RFC8610], CBOR [RFC8949], and COSE [RFC9052][RFC9053][RFC9338].¶

• The terms and concepts described in CoAP [RFC7252]. Note that the term "endpoint" is used here following its OAuth definition [RFC6749], aimed at denoting resources such as /token and /introspect at the AS, and /authz-info at the RS. The CoAP definition, which is "[a]n entity participating in the CoAP protocol" [RFC7252], is not used in this document.¶

• The terms and concepts of Pub-Sub group communication with CoAP, as described in [I-D.ietf-core-coap-pubsub].¶

A party interested in participating in group communication as well as already participating as a group member is interchangeably denoted as "Client", "Pub-Sub client", or "node".¶

• Group: a set of nodes that share common keying material and security parameters to protect their communications with one another. That is, the term refers to a "security group".¶

  This is not to be confused with an "application group", which has relevance at the application level and whose members are in this case the Clients acting as Publishers and/or Subscribers for a topic.¶

Examples throughout this document are expressed in CBOR diagnostic notation as defined in Section 8 of [RFC8949] and Appendix G of [RFC8610]. Diagnostic notation comments are often used to provide a textual representation of the parameters' keys and values.¶

3.1. Topic Discovery at the Broker (Optional)

The discovery of a topic at the Broker can be performed by discovering the corresponding topic resource hosted at the Broker. For example, the Client can send a lookup request to /.well-known/core at the Broker, specifying as lookup criterion the resource type "core.ps.conf" (see Section 2.3.3 of [I-D.ietf-core-coap-pubsub]).¶

Although the links to the topic resources are also specified in the representation of the collection resource at the Broker (see Section 2.4 of [I-D.ietf-core-coap-pubsub]), the Client is not supposed to access such a resource, as intended for administrative operations that are out of the scope of this document.¶

3.2. AS Discovery at the Broker (Optional)

Complementary to what is defined in Section 5.1 of [RFC9200] for AS discovery, the Broker MAY send the address of the AS to the Client in the 'AS' parameter of the AS Request Creation Hints, as a response to an Unauthorised Resource Request (see Section 5.2 of [RFC9200]). An example using the CBOR diagnostic notation and CoAP is given below.¶

    4.01 Unauthorized
    Content-Format: 19 (application/ace+cbor)
    Payload:
    {
     / AS / 1 : "coaps://as.example.com/token"
    }

3.3. KDC Discovery at the Broker (Optional)

Once a Client has obtained an access token from the AS and accordingly established a secure association with the Broker, the Client has the permission to access the topic resources at the Broker that pertain to the topics on which the Client is authorised to operate.¶

In particular the Client is authorised to retrieve the representation of a topic resource, from which the Client can retrieve information related to the topic in question, as specified in Section 2.5 of [I-D.ietf-core-coap-pubsub].¶

This profile extends the set of CoAP Pub-Sub Parameters that is possible to specify within the representation of a topic resource, as originally defined in Section 3 of [I-D.ietf-core-coap-pubsub]. In particular, this profile defines the following two parameters that the Broker can specify in a response to a request that targets a topic resource (see Section 2.5 of [I-D.ietf-core-coap-pubsub]). Note that, when these parameters are transported in their respective fields of the message payload, the Content-Format "application/core-pubsub+cbor" defined in [I-D.ietf-core-coap-pubsub] MUST be used.¶

• 'kdc_uri', with value the URI of the group-membership resource at the KDC, where Clients can send a request to join the security group associated with the topic in question. The URI is encoded as a CBOR text string. Clients will have to obtain an access token from the AS to upload to the KDC, before starting the process to join the security group at the KDC.¶

• 'sec_gp', specifying the name of the security group associated with the topic in question, as a stable and invariant identifier. The name of the security group is encoded as a CBOR text string.¶

Furthermore, the Resource Type (rt=) Link Target Attribute value "core.ps.gm" is registered in Section 9.3 (REQ10), and can be used to describe group-membership resources at the KDC, e.g., by using a CoRE link-format document [RFC6690]. As an alternative to the discovery approach defined above and provided by the Broker, applications can use this common resource type to discover links to group-membership resources at the KDC for joining security groups associated with Pub-Sub topics.¶

3.4. Authorisation Request/Response for the KDC and the Broker

A Client sends two Authorisation Requests to the AS, targeting two different audiences, i.e., the Broker and the KDC.¶

As to the former, the AS handles Authorisation Requests related to a topic for which the Client is allowed to perform topic data operations at the Broker, as corresponding to an application group.¶

As to the latter, the AS handles Authorization Requests for security groups that the Client is allowed to join, in order to obtain the group keying material for protecting end-to-end and verifying the content of exchanged messages on the associated Pub-Sub topics.¶

This section builds on Section 3 of [RFC9594] and defines only additions or modifications to that specification.¶

Both Authorisation Requests include the following fields (see Section 3.1 of [RFC9594]):¶

• 'scope': Optional. If present, it specifies the following information, depending on the specifically targeted audience.¶

  If the audience is the Broker, the scope specifies the names of the topics that the Client wishes to access, together with the corresponding requested permissions.¶

  If the audience is the KDC, the scope specifies the names of the security groups that the Client wishes to join, together with the corresponding requested permissions.¶

  This parameter is encoded as a CBOR byte string, whose value is the binary encoding of a CBOR array. The format of the encoded scope MUST follow the data model AIF-PUBSUB-GROUPCOMM defined in Section 3.4.1.¶

  The textual format specified in Section 3.1 of [RFC9594] is not used in this application profile (OPT1).¶

• 'audience': Required identifier corresponding to either the Broker or the KDC.¶

Other additional parameters can be included if necessary, as defined in [RFC9200].¶

When using this profile, it is expected that a one-to-one mapping is enforced between the application group and the security group (see Section 2). If this is not the case, the correct access policies for both sets of scopes have to be available to the AS.¶

      AIF-Generic<Toid, Tperm> = [* [Toid, Tperm]]

  AIF-PUBSUB-GROUPCOMM = AIF-Generic<pubsub-group, pubsub-perm>
   pubsub-group = tstr ; name of Pub-Sub topic or of
                       ; the associated security group

   pubsub-perm = uint .bits pubsub-perm-details

   pubsub-perm-details = &(
    Admin: 0,
    AppGroup: 1,
    Publish: 2,
    Read: 3,
    Delete: 4
   )

   scope_entry = [pubsub-group, pubsub-perm]

3.5. Authorization response

The AS responds with an Authorization Response as defined in Section 5.8.2 of [RFC9200] and Section 3.2 of [RFC9594], with the following additions:¶

• In the Authorization Response, the AS MUST include the 'expires_in' parameter.¶

• In the Authorization Response, the AS MUST include the 'scope' parameter, when the value included in the access token differs from the one specified by the Client in the Authorization Request. In such a case, the second element of each scope entry specifies the set of operations that the Client is authorised for that scope entry, encoded as specified in Section 3.4.¶

Furthermore, the AS MAY use the extended format of scope defined in Section 7 of [RFC9594] for the 'scope' claim of the access token. In such a case, the AS MUST use the CBOR tag with tag number TAG_NUMBER, associated with the CoAP Content-Format CF_ID for the media type "application/aif+cbor" registered in Section 9.5 of this document (REQ28).¶

Note to RFC Editor: In the previous paragraph, please replace "TAG_NUMBER" with the CBOR tag number computed as TN(ct) in Section 4.3 of [RFC9277], where ct is the ID assigned to the CoAP Content-Format registered in Section 9.5 of this document. Then, please replace "CF_ID" with the ID assigned to that CoAP Content-Format. Finally, please delete this paragraph.¶

This indicates that the binary encoded scope follows the scope semantics defined for this application profile in Section 3.4.1 of this document.¶

3.6. Token Transfer to the KDC

The Client transfers its access token to the KDC using one of the methods defined in the Section 3.3 of [RFC9594]. This typically includes sending a POST request to the /authz-info endpoint. However, if the DTLS transport profile of ACE [RFC9202] is used and the Client uses a symmetric proof-of-possession (PoP) key in the DTLS handshake, the Client MAY provide the access token to the KDC in the "psk_identity" field of the DTLS ClientKeyExchange message when using DTLS 1.2 [RFC6347], or in the "identity" field of a PskIdentity within the PreSharedKeyExtension of the ClientHello message when using DTLS 1.3 [RFC9147]. In addition to that, the following applies.¶

In the Token Transfer Response to the Publishers, i.e., the Clients whose scope of the access token includes the "Publish" permission for at least one scope entry, the KDC MUST include the parameter 'kdcchallenge' in the CBOR map. 'kdcchallenge' is a nonce N_S generated by the KDC. As to the N_S value, it is RECOMMENDED to be at least 8-byte long and it is RECOMMENDED to be a random value. Later when joining the group, the Publisher can use the 'kdcchallenge' nonce as part of proving possession of its private key (see [RFC9594]). If a Publisher provides the access token to the KDC through an /authz-info endpoint, the Client MUST support the parameter 'kdcchallenge' (REQ30).¶

If 'sign_info' is included in the Token Transfer Request, the KDC SHOULD include the 'sign_info' parameter in the Token Transfer Response. Note that the joining node may have obtained such information by alternative means, e.g., the 'sign_info' may have been pre-configured (OPT3).¶

The following applies for each element 'sign_info_entry'.¶

• 'sign_alg' MUST take its value from the "Value" column of one of the recommended algorithms in the "COSE Algorithms" registry [IANA.cose_algorithms] (REQ3).¶

• 'sign_parameters' is a CBOR array. Its format and value are the same of the COSE capabilities array for the algorithm indicated in 'sign_alg' under the "Capabilities" column of the "COSE Algorithms" registry [IANA.cose_algorithms] (REQ4).¶

• 'sign_key_parameters' is a CBOR array. Its format and value are the same of the COSE capabilities array for the COSE key type of the keys used with the algorithm indicated in 'sign_alg', as specified for that key type in the "Capabilities" column of the "COSE Key Types" registry [IANA.cose_key-type] (REQ5).¶

• 'cred_fmt' takes value from the "Label" column of the "COSE Header Parameters" registry [IANA.cose_header-parameters] (REQ6). Acceptable values denote a format of authentication credential that MUST explicitly provide the public key as well as the comprehensive set of information related to the public key algorithm, including, e.g., the used elliptic curve (when applicable).¶

  Acceptable formats of authentication credentials include CBOR Web Tokens (CWTs) and CWT Claims Sets (CCSs) [RFC8392], X.509 certificates [RFC7925], and C509 certificates [I-D.ietf-cose-cbor-encoded-cert]. Future formats would be acceptable to use as long as they comply with the criteria defined above.¶

This application profile does not define additional parameters to be used in the exchange of Token Transfer Request and Response (OPT2).¶

4.1. Joining a Security Group

This section describes the interactions between a Client and the KDC to join a security group. Source authentication of a message sent within the group is ensured by means of a digital signature embedded in the message. Subscribers must be able to retrieve Publishers' authentication credentials from a trusted repository, to verify source authentication of received messages. Hence, on joining a security group, a Publisher is expected to provide its own authentication credential to the KDC.¶

On a successful join, the Clients receive from the KDC the symmetric COSE Key [RFC9052] that is used as the shared group key to protect the payload of a published topic data.¶

The message exchange between the joining node and the KDC follows what is defined in Section 4.3.1.1 of [RFC9594], and only additions or modifications to that specification are defined in this document.¶

4.2. Other Group Operations through the KDC

6.1. Using COSE to Protect the Published Topic Data

The Publisher uses the symmetric COSE Key received from the KDC to protect the payload of the Publish operation (see Section 3.2.1 of [I-D.ietf-core-coap-pubsub]). Specifically, the Publisher creates a COSE_Encrypt0 object [RFC9052][RFC9053] by means of the COSE Key currently used as group key (REQ23). The encryption algorithm and Base IV to use are specified by the 'alg' and 'Base IV' parameters of the COSE Key, together with its key identifier in the 'kid' parameter.¶

Also, the Publisher uses its private key corresponding to the public key sent to the KDC, in order to countersign the COSE_Encrypt0 object as specified in [RFC9338] (REQ23). The countersignature is specified in the 'Countersignature version 2' parameter, within the 'unprotected' field of the COSE_Encrypt0 object.¶

Finally, the Publisher sends the COSE_Encrypt0 object conveying the countersignature to the Broker, as payload of the PUT request sent to the topic-data of the topic targeted by the Publish operation.¶

Upon receiving a response from the topic-data resource at the Broker, the Subscriber uses the 'kid' parameter from the 'Countersignature version 2' parameter within the 'unprotected' field of the COSE_Encrypt0 object, in order to retrieve the Publisher's public key from the KDC (see Section 4.2.1) or from its local storage. Then, the Subscriber uses that public key to verify the countersignature.¶

In case of successful verification, the Subscriber uses the 'kid' parameter from the 'unprotected' field of the COSE_Encrypt0 object, in order to retrieve the COSE Key used as current group key from its local storage. Then, the Subscriber uses that group key to verify and decrypt the COSE_Encrypt0 object. In case of successful verification, the Subscriber delivers the received topic data to the application.¶

The COSE_Encrypt0 object is constructed as follows.¶

The 'protected' field MUST include:¶

• The 'alg' parameter, with value the identifier of the AEAD algorithm specified in the 'alg' parameter of the COSE Key used as current group key.¶

The 'unprotected' field MUST include:¶

• The 'kid' parameter, with the same value specified in the 'kid' parameter of the COSE Key used as current group key. This value represents the current Group ID (Gid) of the security group associated with the application group (topic).¶

• The 'Partial IV' parameter, with value set to the current Sender Sequence Number of the Publisher. All leading bytes of value zero SHALL be removed when encoding the Partial IV, except in the case of Partial IV with value 0, which is encoded to the byte string 0x00.¶

  The Publisher MUST initialize the Sender Sequence Number to 0 upon joining the security group and MUST reset it to 0 upon receiving a new group key as the result of a group rekeying (see Section 5). The Publisher MUST increment its Sender Sequence Number value by 1, after having completed an encryption operation by means of the current group key.¶

  When the Publisher exhausts its Sender Sequence Numbers, the Publisher MUST NOT protect further topic data by using the current group key while still retaining its current Sender ID, and it MUST send a Key Renewal Request message to the KDC (see Section 4.2.2). This will result in the KDC rekeying the group and distributing a new group key, or in the KDC providing the Publisher with a new Sender ID. The Publisher MUST reset its Sender Sequence Number to 0 upon receiving a new Sender ID from the KDC.¶

• The 'Countersignature version 2' parameter, specifying the countersignature of the COSE_Encrypt0 object. In particular:¶

  • The 'protected' field includes the 'alg' parameter, with value the identifier of the Signature Algorithm used in the security group.¶

  • The 'unprotected' field includes the 'kid' parameter, with value the Publisher's Sender ID that the Publisher obtained from the KDC when joining the security group, as the value of the 'group_SenderId' parameter of the Join Response (see Section 4.1.2).¶

  • The 'signature' field, with value the countersignature.¶

  The countersignature is computed as defined in [RFC9338], by using the private key of the Publisher as signing key and by means of the Signature Algorithm used in the group. The fields of the Countersign_structure are populated as follows:¶

  • 'context' takes "CounterSignature".¶

  • 'body_protected' takes the serialized parameters from the 'protected' field of the COSE_Encrypt0 object, i.e., the 'alg' parameter.¶

  • 'sign_protected' takes the serialized parameters from the 'protected' field of the 'Countersignature version 2' parameter, i.e., the 'alg' parameter.¶

  • 'external_aad is not supplied.¶

  • 'payload' is the ciphertext of the COSE_Encrypt0 object (see below).¶

The 'ciphertext' field specifies the ciphertext computed over the topic data to publish. The ciphertext is computed as defined in [RFC9052][RFC9053], by using the current group key as encryption key, the AEAD Nonce computed as defined in Section 6.2, the topic data to publish as plaintext, and the Enc_structure populated as follows:¶

• 'context' takes "Encrypt0".¶

• 'protected' takes the serialization of the protected parameter 'alg' from the 'protected' field of the COSE_Encrypt0 object.¶

• 'external_aad is not supplied.¶

6.2. AEAD Nonce

This section defines how to generate the AEAD nonce used for encrypting and decrypting the COSE_Encrypt0 object protecting the published topic data. This construction is analogous to that used to generate the AEAD nonce in the OSCORE security protocol (see Section 5.2 of [RFC8613]).¶

The AEAD nonce for producing or consuming the COSE_Encrypt0 object is constructed as defined below and also shown in Figure 10.¶

1. Left-pad the Partial IV (PIV) with zeroes to exactly 5 bytes.¶

2. Left-pad the Sender ID of the Publisher that generated the Partial IV (ID_PIV) with zeroes to exactly the nonce length of the AEAD algorithm minus 6 bytes.¶

3. Concatenate the size of the ID_PIV (a single byte S) with the padded ID_PIV and the padded PIV.¶

4. XOR the result from the previous step with the Base IV.¶

     <- nonce length minus 6 B -> <-- 5 bytes -->
+---+-------------------+--------+---------+-----+
| S |      padding      | ID_PIV | padding | PIV |-----+
+---+-------------------+--------+---------+-----+     |
                                                       |
 <---------------- nonce length ---------------->      |
+------------------------------------------------+     |
|                    Base IV                     |-->(XOR)
+------------------------------------------------+     |
                                                       |
 <---------------- nonce length ---------------->      |
+------------------------------------------------+     |
|                     Nonce                      |<----+
+------------------------------------------------+

The construction above only supports AEAD algorithms that use nonces with length equal or greater than 7 bytes. At the same time, it makes it easy to verify that the nonces will be unique when used with the same group key, even though this is shared and used by all the Publishers in the security group. In fact:¶

• Since Publisher's Sender IDs are unique within the security group and they are not reassigned until a group rekeying occurs (see Section 4.1.2 and Section 5), two Publisher Clients cannot share the same tuple (S, padded ID_PIV) by construction.¶

• Since a Publisher increments by 1 its Sender Sequence Number after each use that it makes of the current group key, the Publisher never reuses the same tuple (S, padded ID_PIV, padded PIV) together with the same group key.¶

• Therefore neither the same Publisher reuses the same AEAD nonce with the same group key, nor any two Publishers use the same AEAD nonce with the same group key.¶

6.3. Replay Checks

In order to protect from replay of published topic data, every Subscriber maintains a Replay Window for each different Publisher in the same group. It is RECOMMENDED that the Replay Window has a default size of 32.¶

Upon receiving a topic data published by a given Publisher P, the Subscriber retrieves the Sender ID of P conveyed as 'kid' in the 'Countersignature version 2' parameter of the COSE_Encrypt0 object (see Section 6.1) and determines the Replay Window W_P associated with P.¶

The Subscriber MUST verify that, according to W_P, the Sender Sequence Number SN_P specified by the 'Partial IV' parameter of the COSE_Encrypt0 object has not been received before from P.¶

If the verification above fails, the Subscriber MUST stop processing the COSE_Encrypt0 object conveying the topic data. If the value of SN_P is strictly smaller than the currently smallest value in W_P, then the Subscriber MUST stop processing the COSE_Encrypt0 object.¶

If the verification above succeeds, the Subscriber proceeds with processing the COSE_Encrypt0 object, by verifying the countersignature from P using P's public key as well as by decrypting and verifying the COSE_Encrypt0 object using the group key. If both operations succeed, the Subscriber updates W_P as follows:¶

• If SN_P is strictly greater than the currently largest value in W_P, then W_P is updated in order to set SN_P as its largest value.¶

• SN_P is marked to denote that it has been received.¶

The operation of validating the 'Partial IV' and updating the Replay Window MUST be atomic.¶

Upon installing a new group key (e.g., due to a group rekeying performed by the KDC, see Section 5) or upon receiving published topic data from a given Publisher for the first time, the Subscriber initializes the Replay Window corresponding to that Publisher, i.e., the smallest value of the Replay Window is set to 0.¶

7.1. Logging

When performing its normal operations, the KDC is expected to produce and store timestamped logs about the following:¶

• Any event that has resulted in the KDC sending an error response, as a reply to a request received at any of the resources exported by the interface specified in this document.¶

  The logged information contains a description of the error occurred in the context of the present application profile, together with a description of the event related to the error and relevant metadata about the Client that has sent the request. For instance, possible metadata include: addressing information of the Client; when applicable, the Sender ID that is assigned to the Client in the group; when applicable, (an identifier of) the authentication credential of the Client (i.e., that the Client uses in the group or has used to authenticate itself to the KDC when establishing their secure communication association).¶

  Note that, if the error response uses the format problem-details defined in [RFC9290], then the optional "detail" entry in the response payload is meant to convey the diagnostic description of the error, which is meant to be part of the log entry for this event. This is consistent with Section 4.1.2 of [RFC9594], which states that the diagnostic description of the error should be logged.¶

• Any event consisting in a successfully performed operation that is triggered by a request received at any of the resources exported by the interface specified in this document.¶

  Such events include:¶

  • A Client joining or re-joining a group.¶

  • The upload of a new authentication credential for use within the group.¶

  • The acquisition of a new Sender ID for use within the group.¶

  • A Client leaving a group.¶

  The logged information contains a description of the operation performed in the context of the present application profile, together with relevant metadata about the Client that has sent the request. For instance, possible metadata include: addressing information of the Client; when applicable, the Sender ID that is assigned to the Client in the group; when applicable, (an identifier of) the authentication credential of the Client (i.e., that the Client uses in the group or has used to authenticate itself to the KDC when establishing their secure communication association).¶

• The execution and successful/unsuccessful completion of a group rekeying instance.¶

  The logged information includes:¶

  • The reason for the group rekeying (e.g., scheduled/periodic occurrence, group joining of a new member, group leaving of a current member).¶

  • A description of the group rekeying operations performed (e.g., a list of steps performed throughout the rekeying process).¶

  • The outcome of the group rekeying instance.¶

  • In case of success, the version number of the newly established group keying material and the newly established Group Identifier (Gid).¶

• The addition of a group member to the group or the eviction of a group member from the group.¶

  The logged information also contains relevant metadata about the Client that has been added to or removed from the group. For instance, possible metadata include: addressing information of the Client; when applicable, the Sender ID that is currently (was latest) assigned to the Client added to (removed from) the group; when applicable, (an identifier of) the authentication credential of the Client added to (removed from) the group (i.e., that the Client uses in the group or has used to authenticate itself to the KDC when establishing their secure communication association).¶

• The creation, (re-)configuration, or termination of a group.¶

In addition to what is compiled above, the KDC could log additional information. Further details about what the KDC logs, with what granularity, and based on what triggering events and conditions are application-specific and left to operators to define.¶

The KDC MUST NOT log any secret or confidential information pertaining to a group, such as:¶

• The group key used in the group as symmetric encryption key.¶

• The Base Initialization Vector (Base IV) to use in the security group with the group key.¶

• The private key associated with the KDC’s authentication credential used in the group, if any.¶

• Rekeying messages that are exchanged in the group.¶

• If applicable, administrative keying material used to protect the group rekeying process.¶

It is up to the application to specify for how long a log entry is retained from the time of its creation and until its deletion. Different retention policies could be enforced for different groups. For a given group, oldest log entries are expected to be those deleted first, and different retention policies could be enforced depending on whether the group currently exists or has been deleted.¶

It is out of the scope of this document what specific semantics and data model are used by the KDC for producing and processing the logs. Specific semantics and data models can be defined by applications and future specifications.¶

The KDC is expected to make the logs that it produces available for secure access by authorized external management applications and operators.¶

In particular, logged information could be retrieved in the following ways.¶

• By accessing logs at the KDC through polling. This can occur in an occasional, regular, or event-driven way.¶

• Through notifications sent by the KDC according to an operator-defined frequency.¶

• Through notifications asynchronously sent by the KDC, throttling them in order to prevent congestion and duplication and to not create attack vectors.¶

Some of the logged information can be privacy-sensitive. This especially holds for the metadata about a Client, i.e., addressing information of the Client and, when applicable, (an identifier of) the authentication credential of the Client (i.e., that the Client uses in the group or has used to authenticate itself to the KDC when establishing their secure communication association). If external management applications and operators obtain such metadata, they become able to track a given Client, as to its interactions with one or multiple KDCs and its membership in groups under such KDC(s).¶

Therefore, the logged information that is effectively provided to external management applications and operators SHOULD be redacted by the KDC, by omitting any privacy-sensitive information element that could enable or facilitate the impairment of Clients' privacy, e.g., by tracking Clients across different groups and different KDCs. Exceptions could apply, e.g., if the KDC can verify that the management application or operator in question is specifically authorized to obtain such privacy-sensitive information and appropriately entitled to obtain it according to enforced privacy policies.¶

It is out of the scope of this document to provide operational considerations about the production, storage, processing, and sharing of logs at the Broker.¶

7.2. Administration of Groups

It is out of the scope of this document how groups are created, (re-)configured, and terminated at the KDC. Specific methods, tools, and data models to perform such operations and administer groups at the KDC can be defined by applications and future specifications.¶

It is out of the scope of this document to provide operational considerations about how application groups (topics) are created, (re-)configured, and terminated at the Broker, as well as about the store-and-forward of published topic data via the Broker.¶

7.3. Access Control

Building on the ACE framework [RFC9200] and the foundation provided in [RFC9594], this application profile enforces access control for Clients that interact with the interface at the KDC specified in this document and with the interface at the Broker specified in [I-D.ietf-core-coap-pubsub].¶

In particular, the granularity of such access control takes into account the resource specifically targeted at the KDC or at the Broker, the operation requested by sending a request to that resource, and the specific role(s) that the requesting Client is authorized to have according to its corresponding access token uploaded to the KDC or to the Broker.¶

Furthermore, the interactions that a Client has with the KDC and with the Broker are secured as per the specific transport profile of ACE used (e.g., [RFC9202] and [RFC9203]).¶

9.1. ACE Groupcomm Key Types

IANA is asked to register the following entry in the "ACE Groupcomm Key Types" registry defined in Section 11.8 of [RFC9594].¶

• Name: Group_PubSub_Keying_Material¶

• Key Type Value: GROUPCOMM_KEY_TBD (suggested value: 2)¶

• Profile: coap_group_pubsub_app (Section 9.2 of [RFC-XXXX]).¶

• Description: Encoded as described in Section 4.1.2 of [RFC-XXXX].¶

• References: [RFC9052], [RFC9053], [RFC-XXXX]¶

9.2. ACE Groupcomm Profiles

IANA is asked to register the following entries in the "ACE Groupcomm Profiles" registry defined in Section 11.9 of [RFC9594].¶

• Name: coap_group_pubsub_app¶

• Description: Application profile to provision keying material for participating in group communication based on the Pub-Sub architecture [I-D.ietf-core-coap-pubsub] for CoAP [RFC7252] and protected with COSE [RFC9052][RFC9053][RFC9338].¶

• CBOR Value: TBD (suggested value: 2)¶

• Reference: [RFC-XXXX]¶

9.3. CoRE Resource Type

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

• Value: "core.ps.gm"¶

• Description: Group-membership resource for Pub-Sub communication.¶

• Reference: [RFC-XXXX]¶

Clients can use this resource type to discover a group membership resource at the KDC.¶

9.4. AIF Media-Type Sub-Parameters

For the media-types "application/aif+cbor" and "application/aif+json" defined in Section 5.1 of [RFC9237], IANA is requested to register the following entries for the two media-type parameters Toid and Tperm, in the respective sub-registry defined in Section 5.2 of [RFC9237] within the "MIME Media Type Sub-Parameter" registry group.¶

• Parameter: Toid¶

• Name: pubsub-topic¶

• Description/Specification: Name of one application group (topic) or of a corresponding security group.¶

• Reference: [RFC-XXXX]¶

• Parameter: Tperm¶

• Name: pubsub-perm¶

• Description/Specification: Permissions pertaining to application groups (topics) or to corresponding security groups.¶

• Reference: [RFC-XXXX]¶

9.5. CoAP Content-Formats

IANA is asked to register the following entries to the "CoAP Content-Formats" registry within the "Constrained RESTful Environments (CoRE) Parameters" registry group.¶

• Content Type: application/aif+cbor;toid=pubsub-topic;tperm=pubsub-perm¶

• Content Coding: -¶

• ID: 294 (suggested)¶

• Reference: [RFC-XXXX]¶

• Content Type: application/aif+json;toid=pubsub-topic;tperm=pubsub-perm¶

• Content Coding: -¶

• ID: 295 (suggested)¶

• Reference: [RFC-XXXX]¶

9.6. TLS Exporter Labels

IANA is asked to register the following entry to the "TLS Exporter Labels" registry defined in Section 6 of [RFC5705] and updated in Section 12 of [RFC8447].¶

• Value: EXPORTER-ACE-Sign-Challenge-coap-pubsub-app¶

• DTLS-OK: Y¶

• Recommended: N¶

• Reference: Section 4.1.1.2 of [RFC-XXXX]¶

10.1. Normative References

[I-D.ietf-core-coap-pubsub]

Jimenez, J., Koster, M., and A. Keränen, "A publish-subscribe architecture for the Constrained Application Protocol (CoAP)", Work in Progress, Internet-Draft, draft-ietf-core-coap-pubsub-18, 28 February 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-core-coap-pubsub-18>.

[IANA.cose_algorithms]

IANA, "COSE Algorithms", <https://www.iana.org/assignments/cose>.

[IANA.cose_header-parameters]

IANA, "COSE Header Parameters", <https://www.iana.org/assignments/cose>.

[IANA.cose_key-type]

IANA, "COSE Key Types", <https://www.iana.org/assignments/cose>.

[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/rfc/rfc2119>.

[RFC5246]

Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, <https://www.rfc-editor.org/rfc/rfc5246>.

[RFC5705]

Rescorla, E., "Keying Material Exporters for Transport Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705, March 2010, <https://www.rfc-editor.org/rfc/rfc5705>.

[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/rfc/rfc6347>.

[RFC6690]

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

[RFC6749]

Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, <https://www.rfc-editor.org/rfc/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/rfc/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/rfc/rfc7641>.

[RFC7925]

Tschofenig, H., Ed. and T. Fossati, "Transport Layer Security (TLS) / Datagram Transport Layer Security (DTLS) Profiles for the Internet of Things", RFC 7925, DOI 10.17487/RFC7925, July 2016, <https://www.rfc-editor.org/rfc/rfc7925>.

[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/rfc/rfc8174>.

[RFC8392]

Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.

[RFC8446]

Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, <https://www.rfc-editor.org/rfc/rfc8446>.

[RFC8447]

Salowey, J. and S. Turner, "IANA Registry Updates for TLS and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018, <https://www.rfc-editor.org/rfc/rfc8447>.

[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/rfc/rfc8610>.

[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/rfc/rfc8949>.

[RFC9052]

Schaad, J., "CBOR Object Signing and Encryption (COSE): Structures and Process", STD 96, RFC 9052, DOI 10.17487/RFC9052, August 2022, <https://www.rfc-editor.org/rfc/rfc9052>.

[RFC9053]

Schaad, J., "CBOR Object Signing and Encryption (COSE): Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053, August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.

[RFC9147]

Rescorla, E., Tschofenig, H., and N. Modadugu, "The Datagram Transport Layer Security (DTLS) Protocol Version 1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022, <https://www.rfc-editor.org/rfc/rfc9147>.

[RFC9200]

Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "Authentication and Authorization for Constrained Environments Using the OAuth 2.0 Framework (ACE-OAuth)", RFC 9200, DOI 10.17487/RFC9200, August 2022, <https://www.rfc-editor.org/rfc/rfc9200>.

[RFC9237]

Bormann, C., "An Authorization Information Format (AIF) for Authentication and Authorization for Constrained Environments (ACE)", RFC 9237, DOI 10.17487/RFC9237, August 2022, <https://www.rfc-editor.org/rfc/rfc9237>.

[RFC9277]

Richardson, M. and C. Bormann, "On Stable Storage for Items in Concise Binary Object Representation (CBOR)", RFC 9277, DOI 10.17487/RFC9277, August 2022, <https://www.rfc-editor.org/rfc/rfc9277>.

[RFC9290]

Fossati, T. and C. Bormann, "Concise Problem Details for Constrained Application Protocol (CoAP) APIs", RFC 9290, DOI 10.17487/RFC9290, October 2022, <https://www.rfc-editor.org/rfc/rfc9290>.

[RFC9338]

Schaad, J., "CBOR Object Signing and Encryption (COSE): Countersignatures", STD 96, RFC 9338, DOI 10.17487/RFC9338, December 2022, <https://www.rfc-editor.org/rfc/rfc9338>.

[RFC9430]

Bergmann, O., Preuß Mattsson, J., and G. Selander, "Extension of the Datagram Transport Layer Security (DTLS) Profile for Authentication and Authorization for Constrained Environments (ACE) to Transport Layer Security (TLS)", RFC 9430, DOI 10.17487/RFC9430, July 2023, <https://www.rfc-editor.org/rfc/rfc9430>.

[RFC9594]

Palombini, F. and M. Tiloca, "Key Provisioning for Group Communication Using Authentication and Authorization for Constrained Environments (ACE)", RFC 9594, DOI 10.17487/RFC9594, September 2024, <https://www.rfc-editor.org/rfc/rfc9594>.

10.2. Informative References

[I-D.ietf-ace-key-groupcomm-oscore]

Tiloca, M. and F. Palombini, "Key Management for Group Object Security for Constrained RESTful Environments (Group OSCORE) Using Authentication and Authorization for Constrained Environments (ACE)", Work in Progress, Internet-Draft, draft-ietf-ace-key-groupcomm-oscore-19, 24 January 2026, <https://datatracker.ietf.org/doc/html/draft-ietf-ace-key-groupcomm-oscore-19>.

[I-D.ietf-cose-cbor-encoded-cert]

Mattsson, J. P., Selander, G., Raza, S., Höglund, J., and M. Furuhed, "CBOR Encoded X.509 Certificates (C509 Certificates)", Work in Progress, Internet-Draft, draft-ietf-cose-cbor-encoded-cert-16, 25 January 2026, <https://datatracker.ietf.org/doc/html/draft-ietf-cose-cbor-encoded-cert-16>.

[RFC8259]

Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, <https://www.rfc-editor.org/rfc/rfc8259>.

[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/rfc/rfc8613>.

[RFC9202]

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)", RFC 9202, DOI 10.17487/RFC9202, August 2022, <https://www.rfc-editor.org/rfc/rfc9202>.

[RFC9203]

Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson, "The Object Security for Constrained RESTful Environments (OSCORE) Profile of the Authentication and Authorization for Constrained Environments (ACE) Framework", RFC 9203, DOI 10.17487/RFC9203, August 2022, <https://www.rfc-editor.org/rfc/rfc9203>.

[RFC9770]

Tiloca, M., Palombini, F., Echeverria, S., and G. Lewis, "Notification of Revoked Access Tokens in the Authentication and Authorization for Constrained Environments (ACE) Framework", RFC 9770, DOI 10.17487/RFC9770, June 2025, <https://www.rfc-editor.org/rfc/rfc9770>.

A.1. Mandatory-to-Address Requirements

• REQ1: Specify the format and encoding of scope. This includes defining the set of possible roles and their identifiers, as well as the corresponding encoding to use in the scope entries according to the used scope format: see Section 3.4.1.¶

• REQ2: If scope uses AIF, register its specific instance of "Toid" and "Tperm" as media type parameters and a corresponding Content-Format, as per the guidelines in [RFC9237]: see Section 9.4 and Section 9.5.¶

• REQ3: If used, specify the acceptable values for the 'sign_alg' parameter: values from the "Value" column of the "COSE Algorithms" registry [IANA.cose_algorithms].¶

• REQ4: If used, specify the acceptable values and structure for the 'sign_parameters' parameter: values and structure from the COSE algorithm capabilities as specified in the "COSE Algorithms" registry [IANA.cose_algorithms].¶

• REQ5: If used, specify the acceptable values and structure for the 'sign_key_parameters' parameter: values and structure from the COSE key type capabilities as specified in the "COSE Key Types" registry [IANA.cose_key-type].¶

• REQ6: Specify the acceptable formats for authentication credentials and, if applicable, the acceptable values for the 'cred_fmt' parameter: acceptable formats explicitly provide the public key as well as the comprehensive set of information related to the public key algorithm (see Section 3.6 and Section 4.1.2). Consistent acceptable values for 'cred_fmt' are taken from the "Label" column of the "COSE Header Parameters" registry [IANA.cose_header-parameters].¶

• REQ7: If the value of the GROUPNAME URI path and the group name in the access token scope ('gname') are not required to coincide, specify the mechanism to map the GROUPNAME value in the URI to the group name: not applicable, since a perfect matching is required.¶

• REQ8: Define whether the KDC has an authentication credential as required for the correct group operation and if this has to be provided through the 'kdc_cred' parameter: optional, see Section 4.1.2.¶

• REQ9: Specify if any part of the KDC interface as defined in [RFC9594] is not supported by the KDC: part of the KDC interface is optional to support, see Section 4.¶

• REQ10: Register a Resource Type for the group-membership resources, which is used to discover the correct URL for sending a Join Request to the KDC: the Resource Type (rt=) Link Target Attribute value "core.ps.gm" is registered in Section 9.3.¶

• REQ11: Define what specific actions (e.g., CoAP methods) are allowed on each resource accessible through the KDC interface, depending on: whether the Client is a current group member; the roles that a Client is authorised to take as per the obtained access token; and the roles that the Client has as a current group member: see Section 4.¶

• REQ12: Categorize possible newly defined operations for Clients into primary operations expected to be minimally supported and secondary operations, and provide accompanying considerations: no new operations are defined.¶

• REQ13: Specify the encoding of group identifiers: CBOR byte string, with value used also to identify the current group key used in the security group (see Section 4.1.2 and Section 4.2.1).¶

• REQ14: Specify the approaches used to compute and verify the PoP evidence to include in the 'client_cred_verify' parameter and which of those approaches is used in which case: see Section 4.1.1.2.¶

• REQ15: Specify how the nonce N_S is generated, if the access token is not provided to the KDC through the Token Transfer Request sent to the /authz-info endpoint (e.g., the access token is instead transferred during the establishment of a secure communication association): see Section 4.1.1.2.¶

• REQ16: Define the initial value of the version number for the group keying material: the initial value MUST be set to 0 (see Section 4.1.2).¶

• REQ17: Specify the format of the group keying material that is conveyed in the 'key' parameter: see Section 4.1.2.¶

• REQ18: Specify the acceptable values of the 'gkty' parameter. For each of them, register a corresponding entry in the "ACE Groupcomm Key Types" IANA registry if such an entry does not exist already: Group_PubSub_Keying_Material, see Section 4.1.2 and Section 9.1.¶

• REQ19: Specify and register the application profile identifier: coap_group_pubsub_app (see Section 4.1.2 and Section 9.2).¶

• REQ20: If used, specify the format and default values of the entries of the CBOR map to include in the 'group_policies' parameter: not applicable.¶

• REQ21: Specify the approaches used to compute and verify the PoP evidence to include in the 'kdc_cred_verify' parameter and which of those approaches is used in which case. If external signature verifiers are supported, specify how those provide a nonce to the KDC to be used for computing the PoP evidence: see Section 4.1.2.¶

• REQ22: Specify the communication protocol that members of the group use to communicate with each other (e.g., CoAP for group communication): CoAP [RFC7252], used for Pub-Sub communications as defined in [I-D.ietf-core-coap-pubsub].¶

• REQ23: Specify the security protocol that members of the group use to protect the group communication (e.g., Group OSCORE). This must provide encryption, integrity, and replay protection: Publishers in a group use a symmetric group key to protect published topic data as a COSE_Encrypt0 object, per the AEAD algorithm specified by the KDC. A Publisher also produces a COSE countersignature of the COSE_Encrypt0 object by using its private key, per the signature algorithm specified by the KDC.¶

• REQ24: Specify how the communication is secured between the Client and the KDC. Optionally, specify a transport profile of ACE [RFC9200] to use between the Client and the KDC: ACE transport profile such as for DTLS [RFC9202] or OSCORE [RFC9203].¶

• REQ25: Specify the format of the node identifiers of group members: the Sender ID defined in Section 4.1.2.¶

• REQ26: Specify policies at the KDC to handle node identifiers that are included in the 'get_creds' parameter but are not associated with any current group member: see Section 4.2.1.¶

• REQ27: Specify the format of (newly generated) individual keying material for group members or of the information to derive such keying material, as well as the corresponding CBOR map key that has to be registered in the "ACE Groupcomm Parameters" registry: see Section 4.2.2.¶

• REQ28: Specify which CBOR tag is used for identifying the semantics of binary scopes, or register a new CBOR tag if a suitable one does not exist already: see Section 3.5 and Section 9.5.¶

• REQ29: Categorize newly defined parameters according to the same criteria of Section 8 of [RFC9594]: a Publisher Client MUST support 'group_SenderId' in 'key'; see Section 4.1.2.¶

• REQ30: Define whether Clients must, should, or may support the conditional parameters defined in Section 8 of [RFC9594] and under which circumstances: a Publisher Client MUST support the client_cred' and 'client_cred_verify' parameters (see Section 4.1.1). A Publisher Client that provides the access token to the KDC through the /authz-info endpoint MUST support the parameter 'kdcchallenge' (see Section 3.6).¶

A.2. Optional-to-Address Requirements

• OPT1: Optionally, if the textual format of scope is used, specify CBOR values to use for abbreviating the role identifiers in the group: not applicable.¶

• OPT2: Optionally, specify the additional parameters used in the exchange of Token Transfer Request and Response: none are defined.¶

• OPT3: Optionally, specify the negotiation of parameter values for signature algorithm and signature keys, if the 'sign_info' parameter is not used: see Section 3.6.¶

• OPT4: Optionally, specify possible or required payload formats for specific error cases: see Section 4.1.3.¶

• OPT5: Optionally, specify additional identifiers of error types as values of the 'error-id' field within the Custom Problem Detail entry 'ace-groupcomm-error': none are defined.¶

• OPT6: Optionally, specify the encoding of the 'creds_repo' parameter if the default one is not used: no encoding is defined.¶

• OPT7: Optionally, specify the functionalities implemented at the resource hosted by the Client at the URI indicated in the 'control_uri' parameter, including the encoding of exchanged messages and other details: no functionalities are defined.¶

• OPT8: Optionally, specify the behavior of the POST handler of group-membership resources, for the case when it fails to retrieve an authentication credential for the specific Client: The KDC MUST reply with a 4.00 (Bad Request) error response to the Join Request (see Section 4.1.3).¶

• OPT9: Optionally, define a default group rekeying scheme to refer to in case the 'rekeying_scheme' parameter is not included in the Join Response: the "Point-to-Point" rekeying scheme registered in Section 11.13 of [RFC9594].¶

• OPT10: Optionally, specify the functionalities implemented at the resource hosted by the Client at the URI indicated in the 'control_group_uri' parameter, including the encoding of exchanged messages and other details: no functionalities are defined.¶

• OPT11: Optionally, specify policies that instruct Clients to retain messages and for how long, if those are unsuccessfully decrypted: no such policies are specified.¶

• OPT12: Optionally, specify for the KDC to perform a group rekeying when receiving a Key Renewal Request, together with or instead of renewing individual keying material: the KDC SHOULD perform a group rekeying if one is already scheduled to occur within an acceptably short time frame, otherwise it SHOULD NOT (see Section 4.2.2).¶

• OPT13: Optionally, specify how the identifier of a group member's authentication credential is included in requests sent to other group members: no such method is defined.¶

• OPT14: Optionally, specify additional information to include in rekeying messages for the "Point-to-Point" group rekeying scheme (see Section 6 of [RFC9594]): no additional information is defined.¶

B.1. Version -02 to -03

• Updated introduction: clarified relationships between this document and related documents.¶

• Ensured consistency with RFC 9594 when using an optimized Join Request for re-joining a group (presence of the 'client_cred' parameter).¶

• Added the "Operational Considerations" section.¶

• Clarifications:¶

  • Secure communications required as per the transport profile of ACE used.¶

  • Explicitly mentioned the rationale for computing a proof-of-possession (PoP) evidence.¶

  • Reasons for and flexibility of group rekeying.¶

• Editorial fixes and improvements.¶

B.2. Version -01 to -02

• Clarified high-level description of the authorisation flow.¶

• Clarified relation between a group rekeying and a Key Renewal Request.¶

• Editorial fixes and improvements.¶

B.3. Version -00 to -01

• Clarified recommendations about randomness and size of nonces.¶

• Clarified generation of N_S if TLS is used with the KDC instead of DTLS.¶

• Added missing references to REQ and OPT requirements.¶

• Updated IANA considerations:¶

  • Suggested values for IANA registrations.¶

  • Renamed TLS Exporter Label.¶

  • Fixed content types in the CoAP Content-Formats registrations.¶

• Updated references.¶

• Editorial fixes and improvements.¶

B.4. Version -00

• Imported content from draft-ietf-ace-pubsub-profile-11.¶

• Removed content about MQTT.¶

• New document title.¶