]> Coordinating the Use of Application Profiles for Ephemeral Diffie-Hellman Over COSE (EDHOC) RISE AB
Isafjordsgatan 22 Kista 16440 Stockholm Sweden marco.tiloca@ri.se
RISE AB
Isafjordsgatan 22 Kista 16440 Stockholm Sweden rikard.hoglund@ri.se
Security LAKE Working Group Internet-Draft The lightweight authenticated key exchange protocol Ephemeral Diffie-Hellman Over COSE (EDHOC) requires certain parameters to be agreed out-of-band, in order to ensure its successful completion. To this end, application profiles specify the intended use of EDHOC to allow for the relevant processing and verifications to be made. In order to ensure the applicability of such parameters and information beyond transport- or setup-specific scenarios, this document defines a canonical, CBOR-based representation that can be used to describe, distribute, and store EDHOC application profiles. Furthermore, in order to facilitate interoperability between EDHOC implementations and support EDHOC extensibility for additional integrations, this document defines a number of means to coordinate the use of EDHOC application profiles. Finally, this document defines a set of well-known EDHOC application profiles. Discussion Venues Discussion of this document takes place on the Lightweight Authenticated Key Exchange Working Group mailing list (lake@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .
Introduction Ephemeral Diffie-Hellman Over COSE (EDHOC) is a lightweight authenticated key exchange protocol, especially intended for use in constrained scenarios. A main use case for EDHOC is the establishment of a Security Context for Object Security for Constrained RESTful Environments (OSCORE) . In order to successfully run EDHOC, the two peers acting as Initiator and Responder have to agree on certain parameters. Some of those are in-band and communicated through the protocol execution, during which a few of them may even be negotiated. However, other parameters have to be known out-of-band, before running the EDHOC protocol. As discussed in , applications can use EDHOC application profiles, which specify the intended usage of EDHOC to allow for the relevant processing and verifications to be made. An EDHOC application profile may include both in-band and out-of-band parameters. In order to ensure the applicability of such parameters and information beyond transport- or setup-specific scenarios, this document defines the EDHOC_Application_Profile object, i.e., a canonical, CBOR-based representation that can be used to describe, distribute, and store EDHOC application profiles as CBOR data items (see ). The defined representation is transport- and setup-independent, and it avoids the need to reinvent an encoding for the available options to run the EDHOC protocol or the selection logic to apply on those. The EDHOC_Application_Profile object is a specialized alternative to the EDHOC_Information object defined in , building on a shared parameter namespace. In particular, an EDHOC_Information object provides a context-based description of an EDHOC application profile that is supported under a concrete circumstance to which the object applies. Conversely, an EDHOC_Application_Profile object provides a description of an EDHOC application profile as an established and immutable set of information about how EDHOC can be run, irrespective of the concrete circumstance where EDHOC is executed. An EDHOC_Application_Profile object providing the CBOR-based representation of an EDHOC application profile can be, for example: retrieved as a result of a discovery process; or retrieved/provided during the retrieval/provisioning of an EDHOC peer's public authentication credential; or obtained during the execution of a device on-boarding/registration workflow. Furthermore, in order to facilitate interoperability between EDHOC implementations and to support EDHOC extensibility for additional integrations (e.g., external security applications, or handling of authentication credentials), this document defines a number of means to coordinate the use of EDHOC application profiles, that is:
  • The new IANA registry "EDHOC Application Profiles" defined in , where to register integer identifiers of EDHOC application profiles to use as corresponding Profile IDs.
  • The new parameter "ed-prof" defined in . This parameter is employed to specify an EDHOC application profile identified by its Profile ID and can be used as target attribute in a web link to an EDHOC resource, or as filter criterion in a discovery request to discover EDHOC resources. For instance, the target attribute can be used in a CoRE link-format document describing EDHOC resources at a server, when EDHOC is transferred over the Constrained Application Protocol (CoAP) (see as well as ).
  • The new parameter "app_prof" defined in for the EDHOC_Information object specified in . When present within an instance of the EDHOC_Information object, this parameter identifies one or more EDHOC application profiles that are supported under the concrete circumstance to which the EDHOC_Information object applies. In particular, this parameter identifies each EDHOC application profile by means of the corresponding Profile ID. For instance, the parameter can be used in the EDHOC and OSCORE profile of the ACE framework for authentication and authorization in constrained environments (ACE) , in order to indicate the EDHOC application profiles supported by an ACE resource server. This parameter is also used in the EDHOC_Application_Profile object defined in of this document. That is, given an instance of the EDHOC_Application_Profile object, the parameter "app_prof" included therein specifies the Profile ID of the EDHOC application profile that is described by the instance of the object in question.
  • New parameters for web linking , which can be used to obtain relevant pieces of information from the EDHOC application profile associated with an EDHOC resource (see ). These parameters correspond to analogous elements of the EDHOC_Information object and extend the set of parameters for web linking originally defined in . In particular, they can be used as target attributes in a web link to an EDHOC resource, or as filter criteria in a discovery request to discover EDHOC resources.
  • A new EDHOC External Authorization Data (EAD) item (see ) and a new error code for the EDHOC error message (see ). When running EDHOC, a peer can use those in order to advertise the EDHOC application profiles that it supports to the other peer.
  • The use of SVCB Resource Records (RR) to advertise the support for EDHOC and for EDHOC application profiles of a given server (see ).
Finally, this document defines a set of well-known EDHOC application profiles (see ). These application profiles are meant to reflect what is most common and expected to be supported by EDHOC peers, while they are not intended as "default" application profiles or as a deviation from what is mandatory to support for EDHOC peers (see ). On the other hand, they provide implementers and users with a quick overview of the several available options to run the EDHOC protocol and of their most expected combinations.
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 when, and only when, they appear in all capitals, as shown here. The reader is expected to be familiar with terms and concepts defined in EDHOC and with the use of EDHOC with CoAP and OSCORE defined in . The reader is also expected to be familiar with the concept of EDHOC_Information parameters defined in and with their categorization as prescriptive or non-prescriptive. In particular:
  • A prescriptive parameter is used to provide an authoritative statement about how an execution of EDHOC has to be performed. An example is the parameter "message_4" indicating whether the use of EDHOC message_4 in an EDHOC session is mandatory or not. If a prescriptive parameter applies to an EDHOC session, a peer participating in the session complies with what is indicated by the parameter, and it aborts the session if it determines that the other peer has violated such indication.
  • A non-prescriptive parameter is used to provide convenient information to consider when executing EDHOC, e.g., in terms of features supported by peers. Such information is not necessarily exhaustive. An example is the parameter "methods" indicating a set of supported EDHOC methods.
Concise Binary Object Representation (CBOR) and Concise Data Definition Language (CDDL) are used in this document. CDDL predefined type names, especially bstr for CBOR byte strings and tstr for CBOR text strings, are used extensively in this document. The provided CDDL definitions can be extracted from the XML version of this document using the following XPath expression: CBOR data items are represented using the CBOR extended diagnostic notation as defined in and ("diagnostic notation"). Diagnostic notation comments are used to provide a textual representation of the parameters' keys and values. In the CBOR diagnostic notation used in this document, constructs of the form e'SOME_NAME' are replaced by the value assigned to SOME_NAME in the CDDL model shown in of . For example, {e'methods' : [0, 1, 2, 3], e'cipher_suites': 3} stands for {1 : [0, 1, 2, 3], 2 : 3}. Note to RFC Editor: Please delete the paragraph immediately preceding this note. Also, in the CBOR diagnostic notation used in this document, please replace the constructs of the form e'SOME_NAME' with the value assigned to SOME_NAME in the CDDL model shown in of . Finally, please delete this note.
EDHOC_Application_Profile This section defines the EDHOC_Application_Profile object, which can be used as a canonical representation of EDHOC application profiles for their description, distribution, and storage. An EDHOC_Application_Profile object is encoded as a CBOR map . All elements that can be included in the EDHOC_Application_Profile object are elements that can be included in the CBOR-encoded EDHOC_Information object specified in . In particular, they use the same CBOR abbreviations from the 'CBOR label' column of the IANA registry "EDHOC Information" defined in . More specifically, the EDHOC_Application_Profile object is a specialized alternative to the EDHOC_Information object. In particular, an EDHOC_Information object provides a context-based description of an EDHOC application profile that is supported under a concrete circumstance to which the object applies. Conversely, an EDHOC_Application_Profile object provides a description of an EDHOC application profile as an established and immutable set of information about how EDHOC can be run, irrespective of the concrete circumstance where EDHOC is executed. The CBOR map encoding an EDHOC_Application_Profile object MUST include the element "app_prof" defined in of this document, as well as the elements "methods" and "cred_types" defined in . Within the CBOR map, the element "app_prof" is encoded as a CBOR integer and identifies the EDHOC application profile being defined by the instance of the EDHOC_Application_Profile object in question. That is, the value of the element "app_prof" encodes the unique integer identifier of the EDHOC application profile described by the instance of the object in question. The identifier is taken from the 'Profile ID' column of the "EDHOC Application Profiles" registry defined in this document. The CBOR map MUST NOT include the following elements: "session_id", "uri_path", "initiator", "responder", and "trust_anchors". Also, the CBOR map MUST NOT include the element "exporter_out_len" defined in of this document. A consumer MUST ignore those elements if they are included in the EDHOC_Application_Profile object. The CBOR map MAY include other elements. Furthermore, consistent with Sections and of and with , the following applies:
  • If the element "cipher_suites" is not present in the CBOR map, this indicates that the EDHOC application profile uses the EDHOC cipher suites 2 and 3, and possibly other cipher suites.
  • If the element "id_cred_types" is not present in the CBOR map, this indicates that the EDHOC application profile uses "kid" as type of authentication credential identifiers for EDHOC, and possibly other types of authentication credential identifiers.
  • The absence of any other elements in the CBOR map MUST NOT result in assuming any value.
If an element is present in the CBOR map and the corresponding entry in the IANA registry "EDHOC Information" specifies "NP" (non-prescriptive) in the 'Type' column and "True or False" in the 'CBOR type' column, then the following applies. An EDHOC peer that adheres to the EDHOC application profile in question is either required to support or not required to support the property or feature of EDHOC associated with the element in the CBOR map, if that element encodes the CBOR simple value true (0xf5) or false (0xf4), respectively. For example, the presence of the parameter "comb_req" denotes whether EDHOC peers adhering to the EDHOC application profile have to support the EDHOC + OSCORE combined request defined in , or instead do not have to but might if they are willing to. If an element present in the CBOR map specifies an information that is intrinsically a set of one or more co-existing alternatives, then all the specified alternatives apply for the EDHOC application profile in question. For example, the element "cipher_suites" with value the CBOR array [0, 2] means that, in order to adhere to the EDHOC application profile in question, an EDHOC peer has to implement both the EDHOC cipher suites 0 and 2, because either of them can be used by another EDHOC peer also adhering to the same EDHOC application profile. The CDDL grammar describing the EDHOC_Application_Profile object is:
CDDL Definition of the EDHOC_Application_Profile object int / [2* int], ; methods 6 => int / [2* int], ; cred_types 23 => int, ; app_prof * (int / tstr) => any } ]]>
Identifying EDHOC Application Profiles by Profile ID This document introduces the concept of Profile IDs, i.e., integer values that uniquely identify EDHOC application profiles, for which an IANA registry is defined in . This section defines two parameters to convey such Profile IDs, i.e.:
  • The parameter "ed-prof" for web linking (see of this document).
  • The parameter "app_prof" of the EDHOC_Information object specified in (see of this document). As defined in , Profile IDs are also conveyed by the parameter "app_prof" in the EDHOC_Application_Profile object, in order to identify the EDHOC application profile described by a given instance of that object.
As defined later in this document, Profile IDs can be used to identify EDHOC application profiles also:
  • Within certain EDHOC messages sent during an EDHOC session by a peer that supports such EDHOC application profiles (see ).
  • When using SVCB Resource Records (RR) to advertise the support for EDHOC and for EDHOC application profiles of a given server (see ).
In Web Linking defines a number of target attributes that can be used in a web link with resource type "core.edhoc" (see ). This is the case, e.g., when using a CoRE link-format document describing EDHOC resources at a server, when EDHOC is transferred over CoAP as defined in . This allows a client to obtain relevant information about the EDHOC application profile(s) to be used with a certain EDHOC resource. In the same spirit, this section defines the following additional parameter, which can be optionally specified as a target attribute with the same name in the link to the respective EDHOC resource, or among the filter criteria in a discovery request from a client.
  • 'ed-prof', specifying an EDHOC application profile supported by the server. This parameter MUST specify a single value, which is taken from the 'Profile ID' column of the "EDHOC Application Profiles" registry defined in of this document. This parameter MAY occur multiple times, with each occurrence specifying an EDHOC application profile.
When specifying the parameter 'ed-prof' in a link to an EDHOC resource, the target attribute rt="core.edhoc" MUST be included. If a link to an EDHOC resource includes occurrences of the target attribute 'ed-prof', then the following applies.
  • The link MUST NOT include other target attributes that provide information about an EDHOC application profile (see, e.g., and of this document), with the exception of the target attribute 'ed-ead' that MAY be included. The recipient MUST ignore other target attributes that provide information about an EDHOC application profile, with the exception of the target attribute 'ed-ead'.
  • If the link includes occurrences of the target attribute 'ed-ead', the link provides the following information: when using the target EDHOC resource as per the EDHOC application profile indicated by any occurrence of the target attribute 'ed-prof', the server supports the External Authorization Data (EAD) items that are specified in the definition of that EDHOC application profile, as well as the EAD items indicated by the occurrences of the target attribute 'ed-ead'.
The example in shows how a CoAP client discovers two EDHOC resources at a CoAP server and obtains information about the application profile corresponding to each of those resources. The CoRE Link Format notation from is used. The example assumes the existence of an EDHOC application profile identified by the integer Profile ID 500, which is supported by the EDHOC resource at /edhoc-alt and whose definition includes the support for the EAD items with EAD label 111 and 222. Therefore, the link to the EDHOC resource at /edhoc-alt indicates that, when using that EDHOC resource as per the EDHOC application profile with Profile ID 500, the server supports the EAD items with EAD label 111, 222, and 333.
The Web Link. ;osc, ;if=sensor, ;rt=core.edhoc;ed-csuite=0;ed-csuite=2; ed-method=0;ed-cred-t=0;ed-cred-t=1;ed-idcred-t=4; ed-i;ed-r;ed-comb-req, ;rt=core.edhoc;ed-prof=500;ed-ead=333 ]]>
In the EDHOC_Information Object defines the EDHOC_Information object and an initial set of its parameters. The object can be used to convey information that guides two peers about executing the EDHOC protocol. This document defines the new parameter "app_prof" of the EDHOC_Information object. The parameter is of type non-prescriptive (NP) and is summarized in . The parameter is specified further below. EDHOC_Information Parameter "app_prof"
Name CBOR label CBOR type Registry Description Type
app_prof 23 int or array EDHOC Application Profiles registry Set of supported EDHOC application profiles NP
  • app_prof: This parameter specifies a set of supported EDHOC application profiles, identified by their Profile ID. If the set is composed of a single EDHOC application profile, its Profile ID is encoded as an integer. Otherwise, the set is encoded as an array of integers, where each array element encodes one Profile ID. In JSON, the "app_prof" value is an integer or an array of integers. In CBOR, "app_prof" is an integer or an array of integers, and it has label 23. The integer values are taken from the 'Profile ID' column of the "EDHOC Application Profiles" registry defined in of this document.
When present within an instance of the EDHOC_Information object, the parameter "app_prof" identifies one or more EDHOC application profiles that are supported under the concrete circumstance to which the object applies. describes the use of the parameter "app_prof" within an instance of the EDHOC_Information object, when using the EDHOC and OSCORE profile of the ACE Framework . The CDDL grammar describing the parameter "app_prof" when included in the CBOR-encoded EDHOC_Information object is:
CDDL Definition of the Parameter "app_prof" when Included in the CBOR-encoded EDHOC_Information Object. int / [2* int] ; app_prof ) ]]>
Use in the EDHOC and OSCORE Profile of the ACE Framework defines how the EDHOC_Information object can be used within the workflow of the EDHOC and OSCORE transport profile of the ACE framework for authentication and authorization in constrained environments (ACE) . In particular, the AS-to-C Access Token Response includes the parameter "edhoc_info", with value an EDHOC_Information object. This allows the ACE authorization server (AS) to provide the ACE client (C) with information about how to run the EDHOC protocol with the ACE resource server (RS) for which the access token is issued. Similarly, the access token includes the corresponding claim "edhoc_info", with value an EDHOC_Information object. This allows the AS to provide the ACE RS with information about how to run the EDHOC protocol with the ACE client, according to the issued access token. In turn, the EDHOC_Information object can include the parameter "app_prof" defined in this document. This parameter indicates a set of EDHOC application profiles associated with the EDHOC resource to use at the RS, which is either implied or specified by the parameter "uri_path" within the same EDHOC_Information object. If the EDHOC_Information object specified as the value of the parameter/claim "edhoc_info" includes the parameter "app_prof", then the following applies.
  • In addition to the parameter "app_prof", the object MUST NOT include other parameters, with the exception of the following parameters that MAY be included:
    • The parameter "eads".
    • Any parameter that is not allowed in the EDHOC_Application_Profile object defined in , unless its inclusion in the EDHOC_Information object is explicitly forbidden by the parameter's definition. For example, the parameter "session_id" is not allowed in the EDHOC_Application_Profile object (see ) and thus can be included in the EDHOC_Information object, where in fact it has to be present (see Sections and of ).
    C and RS MUST ignore other parameters that are not admitted, in the case that they are present in the EDHOC_Information object.
  • The object might provide an information that corresponds to an EDHOC_Information prescriptive parameter (see ), e.g., "message_4". The type of a parameter is indicated in the 'Type' column of the corresponding entry in the IANA registry "EDHOC Information" (see ). If the object specifies such an information multiple times, then each occurrence of that information MUST convey exactly the same content. This MUST take into account prescriptive parameters that are included: i) as elements of the EDHOC_Information object; or ii) as elements of an EDHOC_Application_Profile object (see ) encoding an EDHOC application profile, which is identified by its Profile ID specified in the parameter "app_prof" of the EDHOC_Information object. A consumer MUST treat as malformed an EDHOC_Information object that does not comply with the restriction above.
  • If the EDHOC_Information object specified in the parameter "edhoc_info" of the AS-to-C Access Token Response includes the parameter "eads", then the following applies. When using the target EDHOC resource as per any EDHOC application profile indicated by the parameter "app_prof", the ACE RS for which the access token is issued supports the EAD items that are specified in the definition of that EDHOC application profile, as well as the EAD items indicated by the parameter "eads".
  • If the EDHOC_Information object specified in the claim "edhoc_info" of the access token includes the parameter "eads", then the following applies. When using the target EDHOC resource as per any EDHOC application profile indicated by the parameter "app_prof", the ACE client to which the access token is issued supports the EAD items that are specified in the definition of that EDHOC application profile, as well as the EAD items indicated by the parameter "eads".
Additional Parameters for Web Linking Building on what is defined and prescribed in , this section defines additional parameters for web linking , which can be used to obtain relevant pieces of information from the EDHOC application profile associated with an EDHOC resource. These parameters can be optionally specified as target attributes with the same name in a link with resource type "core.edhoc" (see ) targeting an EDHOC resource, or as filter criteria in a discovery request from a client. When specifying any of the parameters defined below in a link to an EDHOC resource, the target attribute rt="core.edhoc" MUST be included.
  • 'ed-ta-edcred-uuid': Specifies the identifier of a trust anchor supported by the server for verifying authentication credentials of other EDHOC peers, as a UUID . This parameter MUST specify a single value, which is the UUID in its string format (see Section 4 of ). This parameter MAY occur multiple times, with each occurrence specifying one trust anchor identifier.
  • 'ed-ta-edcred-kid': Specifies the identifier of a trust anchor supported by the server for verifying authentication credentials of other EDHOC peers, as a binary key identifier. This parameter MUST specify a single value, which is the base64url-encoded text string of the binary representation of the key identifier. This parameter MAY occur multiple times, with each occurrence specifying one trust anchor identifier.
  • 'ed-ta-edcred-c5t': Specifies the identifier of a trust anchor supported by the server for verifying authentication credentials of other EDHOC peers, as a hash of a C509 certificate . This parameter MUST specify a single value, which is the base64url-encoded text string of the binary representation of the certificate hash encoded as a COSE_CertHash . This parameter MAY occur multiple times, with each occurrence specifying one trust anchor identifier.
  • 'ed-ta-edcred-c5u': Specifies the identifier of a trust anchor supported by the server for verifying authentication credentials of other EDHOC peers, as a URI pointing to a C509 certificate . This parameter MUST specify a single value, which is the URI pointing to the certificate. This parameter MAY occur multiple times, with each occurrence specifying one trust anchor identifier.
  • 'ed-ta-edcred-x5t': Specifies the identifier of a trust anchor supported by the server for verifying authentication credentials of other EDHOC peers, as a hash of an X.509 certificate . This parameter MUST specify a single value, which is the base64url-encoded text string of the binary representation of the certificate hash encoded as a COSE_CertHash . This parameter MAY occur multiple times, with each occurrence specifying one trust anchor identifier.
  • 'ed-ta-edcred-x5u': Specifies the identifier of a trust anchor supported by the server for verifying authentication credentials of other EDHOC peers, as a URI pointing to an X.509 certificate . This parameter MUST specify a single value, which is the URI pointing to the certificate. This parameter MAY occur multiple times, with each occurrence specifying one trust anchor identifier.
  • 'ed-psk-resumption': If present, specifies that the server supports EDHOC session resumption with EDHOC-PSK . A value MUST NOT be given to this parameter and any present value MUST be ignored by the recipient. Future documents may update the definition of this parameter by expanding its semantics and specifying what it can take as value.
The example in extends the earlier example in , by additionally showing the use of the target attributes 'ed-ta-edcred-kid' and 'ed-ta-edcred-x5t'. Compared to the example in , the following also applies.
  • The link to the EDHOC resource at /.well-known/edhoc includes the target attribute 'ed-ta-edcred-kid'. The target attribute has value "AKw", i.e., the base64url-encoded text string of 0x00ac. The latter is the binary key identifier of a trust anchor supported by the server when running EDHOC through that resource.
  • The link to the EDHOC resource at /edhoc-alt includes the target attribute 'ed-ta-edcred-kid'. The target attribute has value "_wH_", i.e., the base64url-encoded text string of 0xff01ff. The latter is the binary key identifier of a trust anchor supported by the server when running EDHOC through that resource.
  • The link to the EDHOC resource at /edhoc-alt includes the target attribute 'ed-ta-edcred-x5t'. The target attribute has value "gi5IefKkG1EMH5s", i.e., the base64url-encoded text string of 0x822e4879f2a41b510c1f9b. The latter is the binary representation of the COSE_CertHash corresponding to an X.509 certificate that the server supports as a trust anchor when running EDHOC through that resource. In CBOR diagnostic notation, the considered COSE_CertHash is as follows: [-15, h'79f2a41b510c1f9b'].
The Web Link. ;osc, ;if=sensor, ;rt=core.edhoc;ed-csuite=0;ed-csuite=2; ed-method=0;ed-cred-t=0;ed-cred-t=1;ed-idcred-t=4; ed-i;ed-r;ed-comb-req;ed-ta-edcred-kid="AKw", ;rt=core.edhoc;ed-prof=500;ed-ead=333; ed-ta-edcred-kid="_wH_";ed-ta-edcred-x5t="gi5IefKkG1EMH5s" ]]>
Advertising Supported EDHOC Application Profiles during an EDHOC Session The rest of this section defines means that an EDHOC peer can use in order to advertise the EDHOC application profiles that it supports to another EDHOC peer, when running EDHOC with that other peer. Such means are an EDHOC EAD item (see ) and an EDHOC error message with a dedicated error code (see ). Differently from the discovery mechanisms defined in and , these means display a number of benefits:
  • Since EAD fields and the EDHOC error message are a core feature of EDHOC, supporting the new EAD item and the new error code is the only prerequisite for their use.
  • They allow an EDHOC peer to advertise what it supports even if it is a client-only peer.
  • They allow an EDHOC peer to advertise what it supports and prefers in the context of a specific EDHOC session and in the light of its current status, instead of only in fixed and broad terms.
In EDHOC Message 1 and Message 2 This section defines the EDHOC EAD item "Supported EDHOC application profiles", which is registered in of this document. The EAD item MAY be included:
  • In the EAD_1 field of EDHOC message_1, in order to specify EDHOC application profiles supported by the Initiator.
  • In the EAD_2 field of EDHOC message_2, in order to specify EDHOC application profiles supported by the Responder.
When the EAD item is present, its ead_label TBD_EAD_LABEL MUST be used only with negative sign, i.e., the use of the EAD item is always critical (see ). The EAD item MUST NOT occur more than once in the EAD fields of EDHOC message_1 or message_2. The recipient peer MUST abort the EDHOC session and MUST reply with an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error", if the EAD item occurs multiple times in the EAD fields of EDHOC message_1 or message_2. The EAD item MUST NOT be included in the EAD fields of EDHOC message_3 or message_4. In the case that the recipient peer supports the EAD item, the recipient peer MUST silently ignore the EAD item if this is included in the EAD fields of EDHOC message_3 or message_4. The EAD item MUST specify an ead_value, as a CBOR byte string with value the binary representation of a CBOR sequence . In particular:
  • When the EAD item is included in the EAD_1 field, the value of the CBOR byte string is the binary representation of the CBOR sequence OUTER_SEQ. In turn, OUTER_SEQ is composed of the following elements:
    • The CBOR data item advertise_flag, which MAY be present. If present, it MUST encode the CBOR simple value true (0xf5) or false (0xf4). The semantics of this element is as follows.
      • If advertise_flag is present and encodes the CBOR simple value true (0xf5), the Initiator is asking the Responder to advertise the EDHOC application profiles that it supports, within the EDHOC message sent in reply to EDHOC message_1. If such a message is EDHOC message_2, the Responder relies on the EAD item "Supported EDHOC application profiles" included in the EAD_2 field. If such a message is an EDHOC error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" (see ), the Responder relies on ERR_INFO. If the Responder sends either of those messages in reply to such an EDHOC message_1, the Responder MUST honor the wish of the Initiator and accordingly advertise the EDHOC application profiles that it supports.
      • If advertise_flag is present and encodes the CBOR simple value false (0xf4), the Initiator is suggesting the Responder to not advertise the EDHOC application profiles that it supports, within the EDHOC message sent in reply to EDHOC message_1. This is relevant when the Initiator already knows what EDHOC application profiles are supported by the Responder, e.g., based on previous interactions with that Responder or on the outcome of a discovery process. In spite of the suggestion from the Initiator, the Responder MAY still advertise the EDHOC application profiles that it supports, when replying to EDHOC message_1 with EDHOC message_2 or with an EDHOC error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" (see ). For example, when sending EDHOC message_2, the Responder might wish to steer the rest of the EDHOC session in a specific way, by including the EAD item "Supported EDHOC application profiles" that specifies information corresponding to EDHOC_Information prescriptive parameters (see ).
    • The CBOR sequence APP_PROF_SEQ, which MUST be present and is specified further below.
  • When the EAD item is included in the EAD_2 field, the value of the CBOR byte string is the binary representation of the CBOR sequence APP_PROF_SEQ.
The CBOR sequence APP_PROF_SEQ is composed of one or more elements, whose order has no meaning. Each element of the CBOR sequence MUST be either of the following:
  • A CBOR integer, specifying the Profile ID of an EDHOC application profile. The integer value is taken from the 'Profile ID' column of the "EDHOC Application Profiles" registry defined in of this document. This element of the CBOR sequence indicates that the message sender supports the EDHOC application profile identified by the Profile ID.
  • A CBOR array including at least two elements. In particular:
    • The first element MUST be a CBOR integer, specifying the Profile ID of an EDHOC application profile. The integer value is taken from the 'Profile ID' column of the "EDHOC Application Profiles" registry.
    • Each of the elements following the first one MUST be a CBOR unsigned integer, specifying the ead_label of an EAD item.
    This element of the CBOR sequence indicates that the message sender supports:
    • The EDHOC application profile PROFILE identified by the Profile ID in the first element of the array; and
    • The EAD items identified by the ead_label in the elements following the first one, in addition to the EAD items that are specified in the definition of the EDHOC application profile PROFILE.
  • An EDHOC_Information object encoded in CBOR, i.e., as a CBOR map (see ). The EDHOC_Information object MUST NOT include the element "app_prof". Also, it MUST NOT include elements that are not allowed within the EDHOC_Application_Profile object defined in , with the exception of the following elements that MAY be included:
    • "trust_anchors".
    • "exporter_out_len" (see ).
    This element of the CBOR sequence indicates that the message sender supports an EDHOC application profile consistent with the pieces of information specified by the EDHOC_Information object.
When sending EDHOC message_1, the Initiator might want to include the EAD item "Supported EDHOC application profiles" and not advertise the EDHOC application profiles that it supports, but instead just take advantage of advertise_flag and ask the Responder to advertise what is supported on its side. In order to do that, the Initiator can compose ead_value such that, following advertise_flag, the CBOR sequence APP_PROF_SEQ only consists of a single EDHOC_Information object as an empty CBOR map. The recipient peer MUST abort the EDHOC session and MUST reply with an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error", if ead_value is malformed or does not conform with the format defined above. It is possible that ead_value provides information corresponding to EDHOC_Information prescriptive parameters (see ), e.g., "message_4". The type of such parameters is indicated in the 'Type' column of the corresponding entry in the IANA registry "EDHOC Information" (see ). If the EAD item "Supported EDHOC application profiles" is included in EDHOC message_1 and/or message_2 during an EDHOC session, the peers participating in that session MUST NOT act in violation of what is indicated by prescriptive parameters that are specified in those EAD items. Note that such indications can be provided: as elements of an EDHOC_Information object specified within APP_PROF_SEQ; or as elements of an EDHOC_Application_Profile object encoding an EDHOC application profile, which is identified by its Profile ID specified within APP_PROF_SEQ. Upon receiving an EDHOC message and throughout the session, a peer MUST check whether the other peer has violated such indications. If any violation is found, the peer MUST abort the EDHOC session and MUST reply with an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error". When composing ead_value, the sender peer MUST comply with the content restrictions specified in . The CDDL grammar describing ead_value for the EAD item "Supported EDHOC application profiles" is shown in . The parameters "psk_resumption", "exporter_out_len", and "app_prof" of the EDHOC_Information object are defined in , , and , respectively.
CDDL Definition of ead_value for the EAD Item "Supported EDHOC application profiles" any } ; psk_resumption $$EDHOC_Information_item //= ( 21: true / false ) ; exporter_out_len $$EDHOC_Information_item //= ( 22: [1* [uint, uint]] ) ; app_prof $$EDHOC_Information_item //= ( 23: profile_id / [2* profile_id] ) ]]>
Examples of ead_value are shown in .
Content Restrictions When the sender peer composes ead_value of the EDHOC EAD item "Supported EDHOC application profiles", the following applies. It is possible that ead_value provides an information corresponding to an EDHOC_Information prescriptive parameter (see ). If ead_value specifies such an information multiple times, then each occurrence of that information MUST convey exactly the same content. With reference to the CBOR sequence APP_PROF_SEQ defined in , the enforcement of these content restrictions MUST take into account prescriptive parameters that are included:
  • As elements of an EDHOC_Information object specified within APP_PROF_SEQ; or
  • As elements of an EDHOC_Application_Profile object encoding an EDHOC application profile, which is identified by its Profile ID specified within APP_PROF_SEQ.
If the Responder has received the EAD item in the EAD_1 field of EDHOC message_1 and intends to include the EAD item in the EAD_2 field of EDHOC message_2, then the Responder MUST further take into account the presence of such information in the received EAD item when composing ead_value. A consumer MUST treat as malformed an EAD item "Supported EDHOC application profiles" whose ead_value does not comply with the restrictions above.
Indicating Support for Session Resumption with EDHOC-PSK The specification defines EDHOC-PSK, an EDHOC authentication method by which two peers use a symmetric Pre-Shared Key (PSK) to mutually authenticate during an EDHOC session. In particular, defines how EDHOC-PSK is used to perform session resumption. That is, after successfully completing an EDHOC session, two peers that support session resumption with EDHOC-PSK can derive a resumption PSK and the corresponding key identifier. Later on, the two peers can run EDHOC using the authentication method EDHOC-PSK, authenticating each other by using the resumption PSK. This document defines the new parameter "psk_resumption" of the EDHOC_Information object (see ). The parameter is of type non-prescriptive (NP) and is summarized in . The parameter is specified further below. EDHOC_Information Parameter "psk_resumption"
Name CBOR label CBOR type Registry Description Type
psk_resumption 21 True or False   Support for EDHOC session resumption with EDHOC-PSK NP
  • psk_resumption: This parameter indicates whether EDHOC session resumption with the authentication method EDHOC-PSK is supported, as per . In JSON, the "psk_resumption" value is a boolean. In CBOR, "psk_resumption" is the simple value true (0xf5) or false (0xf4), and has label 21.
The CDDL grammar describing the parameter "psk_resumption" when included in the CBOR-encoded EDHOC_Information object is:
CDDL Definition of the Parameter "psk_resumption" when Included in the CBOR-encoded EDHOC_Information Object. true / false ; psk_resumption ) ]]>
Agreeing on EDHOC_Exporter Output Lengths The main output of a successfully completed EDHOC session is the shared secret session key PRK_out (see ). After having established PRK_out, the two peers can use the EDHOC_Exporter interface defined in , e.g., to derive keying material for an application protocol. Among its inputs, the EDHOC_Exporter interface includes "exporter_label" as a registered numeric identifier of the intended output and "length" as the length in bytes of the intended output. When using the EDHOC_Exporter interface, it is crucial that the two peers agree about the length in bytes of each intended output, in order to ensure the correctness of their operations. To this end, the two peers can rely on pre-defined default lengths, or agree out-of-band on alternative lengths. However, the two peers might need or prefer to explicitly agree about specific output lengths to use on a per-session basis. As described below, this can be achieved in-band, by using the EDHOC EAD item "Supported EDHOC application profiles" defined in . This document defines the new parameter "exporter_out_len" of the EDHOC_Information object (see ). The parameter is of type prescriptive (P) and is summarized in . The parameter is specified further below. EDHOC_Information Parameter "exporter_out_len"
Name CBOR label CBOR type Registry Description Type
exporter_out_len 22 array EDHOC Exporter Labels Set of output lengths to use with the EDHOC_Exporter interface P
  • exporter_out_len: This parameter specifies a set of one or more pairs (X, Y), where:
    • The first element X specifies a value to use as first argument "exporter_label" when invoking the EDHOC_Exporter interface (see ). The value of X is taken from the 'Label' column of the "EDHOC Exporter Labels" registry within the "Ephemeral Diffie-Hellman Over COSE (EDHOC)" registry group .
    • The second element Y specifies the value to use as third argument "length" when invoking the EDHOC_Exporter interface using the value specified by X as first argument "exporter_label" (see ). The value specified by Y MUST be a valid value to use as "length" when using the value specified by X as "exporter_label". For example, when X specifies 0 as the "exporter_label" to derive an OSCORE Master Secret , Y is required to be not less than the "length" default value defined in , i.e., the key length (in bytes) of the application AEAD Algorithm of the selected cipher suite for the EDHOC session.
    The set is encoded as a non-empty array, each element of which MUST be an array of exactly two elements, hence encoding one pair (X, Y). That is, each inner array includes X encoded as an unsigned integer and Y encoded as an unsigned integer, in this order. Within the set of pairs (X, Y), the order of the inner arrays encoding the pairs is not relevant. The set MUST NOT specify multiple pairs that have the same unsigned integer value as their first element X. In JSON, the "exporter_out_len" value is a non-empty array, each element of which is an array including two unsigned integers. In CBOR, "exporter_out_len" is a non-empty array that has label 22, each element of which is an array including two unsigned integers.
The CDDL grammar describing the parameter "exporter_out_len" when included in the CBOR-encoded EDHOC_Information object is:
CDDL Definition of the Parameter "exporter_out_len" when Included in the CBOR-encoded EDHOC_Information Object. [1* [uint, uint]] ; exporter_out_len ) ]]>
Within ead_value of the EAD item "Supported EDHOC application profiles", the parameter "exporter_out_len" can be included within instances of the EDHOC_Information object that are specified within the CBOR sequence APP_PROF_SEQ (see ). The recipient peer MUST abort the EDHOC session and MUST reply with an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error", if any of the following occurs:
  • The recipient peer does not recognize the value encoded by the first element X of a pair (X, Y) as a valid "exporter_label" to be used when invoking the EDHOC_Exporter interface.
  • In a pair (X, Y), the value encoded by the second element Y is not valid to be used as "length" when invoking the EDHOC_Exporter interface using the value encoded by the first element X as "exporter_label".
  • For a pair (X, Y), the recipient peer is not going to be able to invoke the EDHOC_Exporter interface using the values encoded by X and Y as the first argument "exporter_label" and the third argument "length", respectively.
If the Responder has received an EDHOC message_1 including the EAD item "Supported EDHOC application profiles" and specifying the parameter "exporter_out_len", then the following applies if the Responder includes the EAD item "Supported EDHOC application profiles" in EDHOC message_2, with ead_value specifying the parameter "exporter_out_len". Within ead_value of the EAD item included in EDHOC message_2, the Responder MUST NOT specify any pair (X, Y) such that the unsigned integer value encoded by X was encoded by the first element of a pair within the EAD item included in the received EDHOC message_1. If the Initiator receives an EDHOC message_2 including the EAD item "Supported EDHOC application profiles" and specifying the parameter "exporter_out_len", then the following applies if the Initiator included the EAD item "Supported EDHOC application profiles" in EDHOC message_1, with ead_value specifying the parameter "exporter_out_len". The Initiator MUST abort the EDHOC session and MUST reply with an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error", if ead_value of the EAD item included in EDHOC message_2 specifies any pair (X, Y) such that the unsigned integer value encoded by X was encoded by the first element of a pair of the EAD item included in the sent EDHOC message_1. Since the parameter "exporter_out_len" is of type prescriptive, the restrictions compiled in apply. In particular, the "information" corresponding to the prescriptive parameter "exporter_out_len" is the "length" Y to use when invoking the EDHOC_Exporter interface using the paired "exporter_label" X. That is, if ead_value provides the length of the EDHOC_Exporter output for a given "exporter_label" multiple times, then each of such occurrences MUST specify the same "length" value. Within this constraint, it remains possible for ead_value to specify multiple instances of the EDHOC_Information object within APP_PROF_SEQ and for each of such instances to include the parameter "exporter_out_len", which can overall encode a value different from that of the same parameter in another instance of the EDHOC_Information object. The recipient peer MUST abort the EDHOC session and MUST reply with an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error", if the parameter "exporter_out_len" is malformed or does not conform with the format and constraints defined above. In an EDHOC session during which the EAD item "Supported EDHOC application profiles" has been included in EDHOC message_1 and/or message_2 as specifying the parameter "exporter_out_len", the following applies.
  • The Initiator (Responder) considers the successful verification of EDHOC message_2 (message_3) as a confirmed agreement with the other peer about how to invoke the EDHOC_Exporter interface, once the session key PRK_out for the present EDHOC session is available. That is, for each pair (X, Y) specified by the exchanged EAD items, the two peers MUST use the unsigned integer values encoded by X and Y as the first argument "exporter_label" and the third argument "length", respectively.
  • If a particular "exporter_label" value is not specified by the exchanged EAD items, then a possible invocation of the EDHOC_Exporter interface using that value as its first argument takes as value for its third argument "length" a pre-defined default value, or an alternative value agreed out-of-band.
When using the EDHOC and OSCORE transport profile of the ACE framework , the parameter "exporter_out_len" MUST NOT be included within the EDHOC_Information object specified as the value of the parameter/claim "edhoc_info".
Examples of ead_value shows an example in CBOR diagnostic notation of ead_value for the EDHOC EAD item "Supported EDHOC application profiles", when used in EDHOC message_1. With reference to the CDDL grammar in , the following applies. The CBOR data item advertise_flag is present and encodes the CBOR simple value true (0xf5), hence asking the Responder to advertise the EDHOC application profiles that it supports, when replying to the present EDHOC message_1. The CBOR sequence APP_PROF_SEQ includes the following three elements:
  • An element profile_id, specifying the Profile ID of an EDHOC application profile supported by the Initiator. Specifically, that EDHOC application profile is the well-known application profile MINIMAL-CS-2 defined in .
  • An element profile_id, specifying the Profile ID of an EDHOC application profile supported by the Initiator. Specifically, that EDHOC application profile is the well-known application profile MINIMAL-CS-0 defined in .
  • An element EDHOC_Information, which in turn includes the following parameters:
    • "message_4", with value the CBOR simple value true (0xf5), hence indicating that EDHOC message_4 is expected in the current EDHOC session.
    • "eads", with value a CBOR array. The array includes two elements encoded as unsigned integers, i.e., the EAD labels 500 and 333 of the corresponding EAD items supported by the Initiator.
    • "trust_anchors", with value a CBOR map. The map includes a single element with value a CBOR array, which pertains to trust anchors whose purpose is the verification of authentication credentials of other EDHOC peers in an EDHOC session. In turn, the array includes two CBOR maps. Within the first CBOR map, its entry's value is a CBOR byte string that encodes 0x00ac. Within the second CBOR map, its entry's value is a CBOR byte string that encodes 0xff01ff. Both 0x00ac and 0xff01ff are binary key identifiers of trust anchors supported by the Initiator in the current EDHOC session.
Example of ead_value for the EAD Item "Supported EDHOC application profiles" in EDHOC message_1 > ]]>
shows an example in CBOR diagnostic notation of ead_value for the EDHOC EAD item "Supported EDHOC application profiles", when used in EDHOC message_2. With reference to the CDDL grammar in , the following applies. The CBOR sequence APP_PROF_SEQ includes the following two elements:
  • An element profile_id, specifying the Profile ID of an EDHOC application profile supported by the Responder. Specifically, that EDHOC application profile is the well-known application profile MINIMAL-CS-2 defined in .
  • An element EDHOC_Information, which in turn includes the following parameters:
    • "comb_req", with value the CBOR simple value true (0xf5), hence indicating that the Responder supports the EDHOC + OSCORE combined request defined in .
    • "eads", with value a CBOR array. The array includes two elements encoded as unsigned integers, i.e., the EAD labels 500 and 999 of the corresponding EAD items supported by the Responder.
    • "trust_anchors", with value a CBOR map. The map includes a single element with value an inner CBOR map, which pertains to trust anchors whose purpose is the verification of authentication credentials of other EDHOC peers in an EDHOC session. Within the inner map, its entry's value is a CBOR byte string that encodes 0x91ab, i.e., the binary key identifier of a trust anchor supported by the Responder in the current EDHOC session.
Example of ead_value for the EAD Item "Supported EDHOC application profiles" in EDHOC message_2 > ]]>
In the EDHOC Error Message This section defines the error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles", which is registered in of this document. The error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" MUST only be used when replying to EDHOC message_1. If an EDHOC error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" is received as reply to an EDHOC message different from EDHOC message_1, then the recipient of the error message MUST ignore what is specified in ERR_INFO. The Responder MUST NOT abort an EDHOC session exclusively due to the wish of sending an error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles". Instead, the Responder can advertise the EDHOC application profiles that it supports to the Initiator by means of the EAD item "Supported EDHOC application profiles" defined in , specifying it in the EAD_2 field of the EDHOC message_2 to send in the EDHOC session. When replying to an EDHOC message_1 with an error message, the Responder has to consider the reason for which it is aborting the EDHOC session and MUST NOT specify error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" if a different, more appropriate error code can be specified instead. For example, if the negotiation of the selected cipher suite fails (see ), the error message MUST NOT specify error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles", since the error message intended to be used in that case specifies error code (ERR_CODE) 2 "Wrong selected cipher suite" and conveys SUITES_R as ERR_INFO. When using error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles", the error information specified in ERR_INFO MUST be a CBOR byte string with value the binary representation of the CBOR sequence ERROR_OUTER_SEQ. In turn, ERROR_OUTER_SEQ is composed of the following elements, in the order specified below:
  • The CBOR text string diagnostic_info, which encodes a human-readable diagnostic message that SHOULD be written in English (for example, "Method not supported"). The diagnostic text message provides information about the error that occurred, and it is mainly intended for software engineers who during debugging need to interpret it in the context of the EDHOC specification. The diagnostic message SHOULD be provided to the calling application where it SHOULD be logged. This element conveys the same information that would be conveyed by ERR_INFO within an EDHOC error message with error code (ERR_CODE) 1 "Unspecified error" (see ).
  • The CBOR sequence APP_PROF_SEQ, which has the same format and semantics specified in , except for the following difference: for each element of the CBOR sequence that is an EDHOC_Information object, such an object MUST NOT include the element "exporter_out_len" defined in . The recipient peer MUST silently ignore elements of the CBOR sequence APP_PROF_SEQ that are malformed or do not conform with the intended format of APP_PROF_SEQ.
The CDDL grammar describing ERR_INFO is shown in .
CDDL Definition of ERR_INFO for the EDHOC Error Message with Error Code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles"
Example of ERR_INFO shows an example in CBOR diagnostic notation of ERR_INFO for the EDHOC error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles". With reference to the CDDL grammar in and , the following applies. The CBOR text string diagnostic_info encodes the text string "Method not supported". The CBOR sequence APP_PROF_SEQ includes the following two elements:
  • An element profile_id, specifying the Profile ID of an EDHOC application profile supported by the Responder. Specifically, that EDHOC application profile is the well-known application profile MINIMAL-CS-0 defined in .
  • An element EDHOC_Information, which in turn includes the following parameters:
    • "comb_req", with value the CBOR simple value true (0xf5), hence indicating that the Responder supports the EDHOC + OSCORE combined request defined in .
    • "eads", with value a CBOR array. The array includes two elements encoded as unsigned integers, i.e., the EAD labels 500 and 777 of the corresponding EAD items supported by the Responder.
    • "trust_anchors", with value a CBOR map. The map includes a single element with value an inner CBOR map, which pertains to trust anchors whose purpose is the verification of authentication credentials of other EDHOC peers in an EDHOC session. Within the inner map, its entry's value is a COSE_CertHash corresponding to an X.509 certificate that the Responder supports as a trust anchor when running EDHOC.
Example of ERR_INFO for the EDHOC Error Message with Error Code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" > ]]>
Advertising Supported EDHOC Application Profiles using DNS SVCB Resource Records Given a server, its support for EDHOC and for EDHOC application profiles can be advertised using DNS SVCB Resource Records (RR) . To this end, this document specifies the SvcParamKeys "edhocpath" and "edhoc-app-prof", which are defined below and are registered in .
  • "edhocpath" - The SvcParamKey "edhocpath" is single-valued and specifies a list of one or more absolute paths to EDHOC resources at the server.
    • The wire-format value of "edhocpath" is the binary representation of the CBOR data item edhocpath-value, which MUST exactly fill the SvcParamValue. In particular, edhocpath-value MUST be a CBOR byte string PATH_BSTR or a CBOR array. In the latter case, the array MUST include at least two elements, each of which MUST be a CBOR byte string PATH_BSTR. The SVCB RR MUST be considered malformed if the SvcParamValue ends within edhocpath-value or if edhocpath-value is malformed. The value of each CBOR byte string PATH_BSTR is the binary representation of a CBOR sequence PATH_SEQ composed of zero or more CBOR text strings. In particular, each PATH_SEQ specifies the URI path of an EDHOC resource at the server, with each CBOR text string within that PATH_SEQ specifying a URI path segment. If edhocpath-value is a CBOR array, it MUST NOT include any two elements that specify the same URI path. The CDDL grammar describing the CBOR data item edhocpath-value is shown in .
    • The presentation format value of "edhocpath" SHALL be a comma-separated list (see ) of one or more absolute paths to EDHOC resources at the server. The same considerations for the "," and "\" characters in paths for zone-file implementations as for the alpn-ids in an "alpn" SvcParam apply (see ). The i-th path in the presentation format value is the textual representation of the path specified by the i-th CBOR sequence PATH_SEQ in the wire-format value (see above). The textual representation of each path follows the semantics of path-absolute shown in the ABNF definition in , which is provided by the ABNF for path-absolute in . In particular, given the path specified by a CBOR sequence PATH_SEQ, segment-nz is the value of the first CBOR text string in PATH_SEQ (if any), while each segment is the value of a CBOR text string following the first one in PATH_SEQ (if any).
  • "edhoc-app-prof" - The SvcParamKey "edhoc-app-prof" is single-valued and specifies a set of EDHOC application profiles that the server supports.
    • The wire-format value of "edhoc-app-prof" is the binary representation of the CBOR data item edhoc-app-prof-value, which MUST exactly fill the SvcParamValue. In particular, edhoc-app-prof-value MUST be a CBOR byte string. The value of the CBOR byte string is the binary representation of the CBOR sequence SVCB_EDHOC_APP_PROF, which is composed of one or two elements as specified below. The SVCB RR MUST be considered malformed if the SvcParamValue ends within edhoc-app-prof-value or if edhoc-app-prof-value is malformed.
      • The first element advertise_flag is OPTIONAL. If present, it MUST encode the CBOR simple value true (0xf5). If advertise_flag is present, a peer that runs EDHOC with the server is encouraged to advertise the EDHOC application profiles that it supports, when sending to the server its first EDHOC message in an EDHOC session. In order to do that, the peer can rely as appropriate on the EDHOC EAD item "Supported EDHOC application profiles" (see ) when sending an EDHOC message_1 or message_2, or on an EDHOC error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles" (see ). If the peer supports the EDHOC EAD item "Supported EDHOC application profiles" or the error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles", the peer MUST use those as appropriate to honor the wish of the server and accordingly advertise the EDHOC application profiles that it supports.
      • The second element server_info is REQUIRED, and it MUST be a CBOR byte string APP_BSTR or a CBOR array. In the latter case, the array MUST include at least two elements, each of which MUST be a CBOR byte string APP_BSTR. The value of each CBOR byte string APP_BSTR is the binary representation of the CBOR sequence APP_PROF_SEQ. In particular, APP_PROF_SEQ has the same format and semantics specified in , except for the following difference: for each element of the CBOR sequence that is an EDHOC_Information object, such an object MUST NOT include the element "exporter_out_len" defined in . The SVCB RR MUST be considered malformed if APP_PROF_SEQ is malformed or does not conform with the intended format.
      An SVCB RR might not be intended to advertise what EDHOC application profiles a server supports for a given EDHOC resource that it hosts. In such a case, server_info can be composed such that the CBOR sequence APP_PROF_SEQ pertaining to that resource only consists of a single EDHOC_Information object as an empty CBOR map. The CDDL grammar describing the CBOR data item edhoc-app-prof-value is shown in .
    • The presentation format value of "edhoc-app-prof" SHALL be the CBOR extended diagnostic notation (see and ) of edhoc-app-prof-value in the wire-format value (see above). When producing the presentation format value, care ought to be taken in representing Unicode with the limited ASCII character subset (e.g., by means of Punycode ) and in removing unnecessary common blank spaces within the CBOR extended diagnostic notation.
If the SvcParamKey "edhoc-app-prof" is not present in the SVCB RR, then the SvcParamKey "edhocpath", if present, still specifies the URI paths of EDHOC resources at the server. However, no information is provided about what EDHOC application profiles the server supports. If the SvcParamKey "edhoc-app-prof" is present in the SVCB RR, then the following applies to server_info therein.
  • If the SvcParamKey "edhocpath" is not present in the SVCB RR, then server_info MUST be a CBOR byte string. The information specified by the SvcParamKey "edhoc-app-prof" pertains to the EDHOC resource at the server with URI path "/.well-known/edhoc".
  • If the SvcParamKey "edhocpath" is present in the SVCB RR, then the following applies.
    • If the value of the SvcParamKey "edhocpath" is a CBOR byte string, then server_info MUST be a CBOR byte string. The information specified by the SvcParamKey "edhoc-app-prof" pertains to the EDHOC resource at the server with URI path specified by the SvcParamKey "edhocpath".
    • If the value of the SvcParamKey "edhocpath" is a CBOR array including N elements, then server_info MUST be a CBOR array including N elements. The information specified by the i-th element of server_info pertains to the EDHOC resource at the server with URI path specified by the i-th element of the CBOR array within the SvcParamKey "edhocpath".
A consumer MUST treat as malformed an SVCB RR, in the case that the SvcParamKeys "edhocpath" and "edhoc-app-prof", if present, do not comply with the format and restrictions defined above.
CDDL Definition of the Value of the SvcParamKey "edhocpath"
ABNF Definition of path-absolute
CDDL Definition of the Value of the SvcParamKey "edhoc-app-prof"
Examples of Wire-Format Values of the SvcParamKeys Using CBOR diagnostic notation, this section provides examples of wire-format values of the SvcParamKeys "edhocpath" and "edhoc-app-prof", within an SVCB RR corresponding to a given server. shows an example of the SvcParamKey "edhocpath", with reference to the CDDL grammar in . In the example, two URI paths are specified, i.e., one for the EDHOC resource at "/.well-known/edhoc" and one for the EDHOC resource at "/edhoc-alt".
Example of Wire-Format Value of the SvcParamKey "edhocpath" within an SVCB RR >, << / PATH_BSTR / "edhoc-alt" / path_segment / >> ] ]]>
Assuming an SVCB RR that includes the SvcParamKey "edhocpath" shown in , the following shows an example of the SvcParamKey "edhoc-app-prof" within the same SVCB RR, with reference to the CDDL grammar in . In particular, the following applies. The CBOR data item advertise_flag is present and encodes the CBOR simple value true (0xf5), hence indicating that a peer that runs EDHOC with the server is encouraged to advertise the EDHOC application profiles that it supports, when sending to the server its first EDHOC message in an EDHOC session. The CBOR data item server_info is a CBOR array, which includes two CBOR byte strings APP_BSTR. In particular:
  • The value of the first CBOR byte string is the binary representation of a CBOR sequence APP_PROF_SEQ, which advertises the EDHOC application profiles that the server supports when running EDHOC through the resource with URI path "/.well-known/edhoc".
  • The value of the second CBOR byte string is the binary representation of a CBOR sequence APP_PROF_SEQ, which advertises the EDHOC application profiles that the server supports when running EDHOC through the resource with URI path "/edhoc-alt".
Example of Wire-Format Value of the SvcParamKey "edhoc-app-prof" within an SVCB RR >, << / APP_BSTR / e'APP-PROF-MINIMAL-CS-2', / profile_id / { / EDHOC_Information / e'comb_req' : true, e'eads' : [500, 999], e'trust_anchors' : { e'edhoc_cred' : { e'kid_ta_type' : h'91ab' } } } >> ] >> ]]>
Well-known EDHOC Application Profiles This section defines a set of well-known EDHOC application profiles that are meant to reflect what is most common and expected to be supported by EDHOC peers. The well-known application profiles are not to be intended as "default" profiles to use, in the case that no other indication is provided to EDHOC peers. In particular, an EDHOC peer MUST NOT assume that, unless otherwise indicated, any of such profiles is used when running EDHOC through a well-known EDHOC resource, such as the resource at /.well-known/edhoc when EDHOC messages are transported as payload of CoAP messages (see ). Building on the above, the well-known application profiles are not intended to deviate from what is mandatory to support for EDHOC peers, which is defined by the compliance requirements in . The rest of this section defines the well-known application profiles, each of which is represented by means of an EDHOC_Application_Profile object (see ) using the CBOR extended diagnostic notation. An entry for each well-known application profile is also registered at the "EDHOC Application Profiles" registry defined in of this document.
Well-Known Application Profile MINIMAL-CS-2 This minimal application profile is suitable for EDHOC peers with very limited capabilities, as they benefit from efficiently using: non-signature keys for authentication with EDHOC method 3; EDHOC cipher suite 2, which is already expected to be supported; the compact credential type CBOR Web Token Claims Set (CCS) identified by reference with a compact "kid". This application profile is aligned with the example trace of EDHOC compiled in .
Well-Known Application Profile MINIMAL-CS-0 This minimal application profile is suitable for EDHOC peers with very limited capabilities, and it differs from the one in only by indicating a different EDHOC cipher suite (0) from those intended for constrained environments.
Well-Known Application Profile BASIC-CS-2-X509 This basic application profile is suitable for EDHOC peers with fairly limited capabilities, which can afford using: signature keys or non-signature keys for authentication with EDHOC method 0 or 3; EDHOC cipher suite 2; the credential type CCS identified by reference with "kid", or X.509 certificates identified by reference with "x5t". This application profile is aligned with the example trace of EDHOC compiled in .
Well-Known Application Profile BASIC-CS-0-X509 This basic application profile is suitable for EDHOC peers with fairly limited capabilities, and it differs from the one in only by indicating a different EDHOC cipher suite (0) from those intended for constrained environments. This application profile is aligned with the example trace of EDHOC compiled in .
Well-Known Application Profile BASIC-CS-2-C509 This basic application profile is suitable for EDHOC peers with fairly limited capabilities, and it differs from the one in only by indicating support for C509 certificates identified by reference with "c5t", instead of X.509 certificates identified by reference with "x5t".
Well-Known Application Profile BASIC-CS-0-C509 This basic application profile is suitable for EDHOC peers with fairly limited capabilities, and it differs from the one in only by indicating support for C509 certificates identified by reference with "c5t", instead of X.509 certificates identified by reference with "x5t".
Well-Known Application Profile INTERMEDIATE-CS-2 This intermediate application profile is suitable for EDHOC peers that, even if with somewhat limited capabilities, can afford a moderate set of options: signature keys or non-signature keys for authentication with EDHOC method 0 or 3; EDHOC cipher suite 2; the credential type CCS identified by reference with "kid" or by value with "kccs", or X.509 certificates identified by reference with "x5t" or by value with "x5chain", or C509 certificates identified by reference with "c5t" or by value with "c5c". This application profile is aligned with the example trace of EDHOC compiled in .
Well-Known Application Profile INTERMEDIATE-CS-0 This intermediate application profile is suitable for EDHOC peers that, even if with somewhat limited capabilities, can afford a moderate set of options, and it differs from the one in only by indicating a different EDHOC cipher suite (0) from those inteded for constrained environments. This application profile is aligned with the example trace of EDHOC compiled in .
Well-Known Application Profile EXTENSIVE This extensive application profile is suitable for EDHOC peers that, even if with somewhat limited capabilities, can afford an extensive set of options: all the four original EDHOC cipher suites intended for constrained environments; all the four original EDHOC authentication methods based on public key authentication; the credential type CCS identified by reference with "kid" or by value with "kccs", or CBOR Web Token (CWT) identified by reference with "kid" or by value with "kcwt", or X.509 certificates identified by reference with "x5t" or by value with "x5chain", or C509 certificates identified by reference with "c5t" or by value with "c5c". This application profile is aligned with the example traces of EDHOC compiled in Sections and of .
Identifiers of Well-known EDHOC Application Profiles This document defines the following identifiers of well-known EDHOC application profiles. Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]" with the RFC number of this specification and delete this paragraph. EDHOC Well-known Application Profiles
Profile ID Name Description Reference
0 MINIMAL-CS-2 Method 3; Cipher Suite 2; CCS; kid [RFC-XXXX, ]
1 MINIMAL-CS-0 Method 3; Cipher Suite 0; CCS; kid [RFC-XXXX, ]
2 BASIC-CS-2-X509 Methods (0, 3); Cipher Suite 2; (CCS, X.509 certificates); (kid, x5t) [RFC-XXXX, ]
3 BASIC-CS-0-X509 Methods (0, 3); Cipher Suite 0; (CCS, X.509 certificates); (kid, x5t) [RFC-XXXX, ]
4 BASIC-CS-2-C509 Methods (0, 3); Cipher Suite 2; (CCS, C509 certificates); (kid, c5t) [RFC-XXXX, ]
5 BASIC-CS-0-C509 Methods (0, 3); Cipher Suite 0; (CCS, C509 certificates); (kid, c5t) [RFC-XXXX, ]
6 INTERMEDIATE-CS-2 Methods (0, 3); Cipher Suite 2; (CCS, X.509/C509 certificates); (kid, kccs, x5t, x5chain, c5t, c5c) [RFC-XXXX, ]
7 INTERMEDIATE-CS-0 Methods (0, 3); Cipher Suite 0; (CCS, X.509/C509 certificates); (kid, kccs, x5t, x5chain, c5t, c5c) [RFC-XXXX, ]
8 EXTENSIVE Methods (0, 1, 2, 3); Cipher Suites (0, 1, 2, 3); (CCS, CWT, X.509/C509 certificates); (kid, kccs, kcwt, x5t, x5chain, c5t, c5c) [RFC-XXXX, ]
Operational Considerations This section compiles the operational considerations that hold for this document.
Relation with Network Operations The means defined in this document are largely about aiding peers in running the EDHOC protocol by achieving a common understanding of what they support, thereby facilitating interoperability between EDHOC implementations. Such coordination is expected to keep authenticated key exchange through EDHOC a smooth process in itself and with respect to network operation and management. The use of these coordinating means in itself is not expected to have a notable impact on performance and network operations, and it is embedded within other relevant network protocols and components such as: the discovery of resources through web-linking and CoRE Link Format (see and ); the execution of the EDHOC protocol itself (see ); and the discovery of server-related information via DNS SVCB RR (see ).
Source of Data for Network Operators As further discussed in , information about what EDHOC application profiles a peer supports could be advertised in plain, depending on the approach specifically used. In such a case, a network operator can passively observe the plain exchange of such information, thereby gaining (a partial) knowledge of EDHOC application profiles that are supported and used in the network. From the perspective of an individual network operator, this knowledge can be useful for (fine-)tuning the allocation of network resources. Multiple, cooperating network operators could build an aggregated knowledge that indicates broad "trends" about EDHOC application profiles and their use. This raises awareness of what appears to be most supported and preferred by EDHOC peers, which can influence priority decisions about the development and use of EDHOC implementations, as well as the operations of infrastructures for provisioning and validating public authentication credentials. As noted in , well-known EDHOC application profiles are not meant to be default profiles to use, and they are not meant to deviate from the EDHOC compliance requirements compiled in . Instead, they are meant to reflect what is most common and expected to be supported by EDHOC peers. Hence, developing aggregated knowledge on typical uses of EDHOC can help identify EDHOC application profiles that have become de facto well-known, thereby further accelerating their adoption.
Logging and Reporting When using the means defined in this document, EDHOC peers are not expected to keep any particular log of such use, or to go beyond expectations already in place as to the logging of EDHOC sessions. However, after gaining knowledge about what EDHOC application profiles are supported by a given EDHOC peer and verifying that such knowledge is reliable and authentic (see ), it is encouraged to locally persist that knowledge for a non-negligible amount of time determined by the application. Especially under the assumption that what EDHOC peers support does not (often) change, this avoids the need to repeatedly re-gain the same knowledge at least in the short term. If an EDHOC session fails due to an apparent mismatch with gained knowledge about commonly supported EDHOC application profiles, a peer can report such a failure to a network manager or infrastructure operator. This can help identify peers whose behavior deviates from what is advertised in terms of EDHOC application profiles that they allegedly support. In turn, this can be used to detect misbehaving peers, outdated information about what peers support, or ongoing tampering of such information if that is advertised in plain (see ). It is out of the scope of this document what specific semantics and data model are used for producing and processing such reports. Specific semantics and data models can be defined by applications and future specifications.
Security Considerations The security considerations compiled in hold for this document. The security considerations compiled in also apply, when EDHOC is transported over CoAP and specifically when using the EDHOC + OSCORE request defined in . Instances of the EDHOC_Application_Profile objects (see ) ought to be accepted only if provided by an identifiable, trusted party by using secure communication. When this is not the case, an EDHOC peer can be induced to: erroneously identify a given EDHOC application profile with a wrong Profile ID; erroneously believe a given EDHOC application profile to exist in the first place; develop a wrong understanding of what a given EDHOC application profile consists of. Different security guarantees can be achieved about the acquired information on the EDHOC application profiles supported by a given peer, depending on the specific approach used. The potential consequences of acquiring such information in a non secured way are discussed later in this section.
  • With respect to using web linking (see and ), the security considerations in apply. When specifically relying on CoRE Link Format , the security considerations in also apply. Clearly, the discovery of EDHOC resources at a server is intended to happen before running EDHOC with the server. At that point in time, the peer attempting to discover EDHOC resources at the server is unlikely to already have a secure communication association with the server. Therefore, the discovery process is likely to use unsecured communication. Alternatively, EDHOC resources at a server can be discovered by securely interacting with separate discovery services, e.g., by using the CoRE Resource Directory .
  • With respect to using the EDHOC EAD item "Supported EDHOC application profiles" (see ), the following applies.
    • When the EAD item is included in EDHOC message_1, the information conveyed therein is not protected. However, changing EDHOC message_1 in transit (e.g., by adding, removing, or modifying the EAD item) would result in the Initiator aborting the EDHOC session, after receiving and failing to verify EDHOC message_2.
    • When the EAD item is included in EDHOC message_2, the information conveyed therein is protected by EDHOC.
  • With respect to using an EDHOC error message with error code (ERR_CODE) TBD_ERROR_CODE "Unspecified error and supported EDHOC application profiles", the information conveyed in ERR_INFO is not protected, just like when any other error code is used.
  • With respect to using the SvcParamKeys "edhocpath" and "edhoc-app-prof" within an SVCB RR (see ), the security considerations from and apply. It is encouraged that DNS is used with secure communication. Known threats for unprotected DNS are described in and .
If information about EDHOC application profiles supported by a peer is distributed in an unprotected way (e.g., through unsecured communication), a consumer should treat such information as a hint and does not locally persist that information until verifying that it is reliable and authentic. For example, if the Responder receives an EDHOC message_1 that includes the EDHOC EAD item "Supported EDHOC application profiles", the Responder will initially treat the information conveyed therein as a hint, and it is able to verify such information as reliable and authentic after receiving and successfully processing the later EDHOC message_3 in the same EDHOC session. If the acquired information has been tampered with and does not reflect what a given peer supports and intends to advertise, this can set wrong expectations about what is effectively possible to do when running EDHOC with that peer. Although this can still result in successfully running EDHOC with a configuration that is commonly supported, such configuration would probably not have been selected, had reliable and authentic information been acquired. In the worst case, there might be the erroneous belief that there is not sufficient shared support with that peer. What is discussed above does not have an impact on the security of the EDHOC protocol in itself. That is, even when the available information about supported EDHOC application profiles is not guaranteed to be reliable and authentic, the successful completion of an EDHOC session still provides the security guarantees that are expected as per the way the session was run (e.g., based on the selected cipher suite and EDHOC method used).
IANA Considerations This document has the following actions for IANA. Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]" with the RFC number of this specification and delete this paragraph.
Media Type Registrations IANA is asked to register the media type "application/edhoc-app-profile+cbor-seq". This registration follows the procedures specified in . Type name: application Subtype name: edhoc-app-profile+cbor-seq Required parameters: N/A Optional parameters: N/A Encoding considerations: Must be encoded as a CBOR sequence of CBOR maps . Each of the CBOR maps is an EDHOC_Application_Profile object (see of [RFC-XXXX]). Each element of each CBOR map is also defined as an element of the CBOR-encoded EDHOC_Information object from . Security considerations: See of [RFC-XXXX]. Interoperability considerations: N/A Published specification: [RFC-XXXX] Applications that use this media type: Applications that need to describe, distribute, and store a representation of an EDHOC application profile (see of [RFC-XXXX] and ). Fragment identifier considerations: N/A Additional information: N/A Person & email address to contact for further information: LAKE WG mailing list (lake@ietf.org) or IETF Applications and Real-Time Area (art@ietf.org) Intended usage: COMMON Restrictions on usage: None Author/Change controller: IETF Provisional registration: No
CoAP Content-Formats Registry IANA is asked to add the following entry to the "CoAP Content-Formats" registry within the "Constrained RESTful Environments (CoRE) Parameters" registry group. Content Type: application/edhoc-app-profile+cbor-seq Content Coding: - ID: TBD (range 0-255) Reference: [RFC-XXXX]
Target Attributes Registry IANA is asked to register the following entries in the "Target Attributes" registry within the "Constrained RESTful Environments (CoRE) Parameters" registry group.
  • Attribute Name: ed-prof
  • Brief Description: A supported EDHOC application profile
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-ta-edcred-uuid
  • Brief Description: Identifier of a supported trust anchor for verifying authentication credentials of other EDHOC peers, as a UUID
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-ta-edcred-kid
  • Brief Description: Identifier of a supported trust anchor for verifying authentication credentials of other EDHOC peers, as a binary key identifier
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-ta-edcred-c5t
  • Brief Description: Identifier of a supported trust anchor for verifying authentication credentials of other EDHOC peers, as a hash of a C509 certificate
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-ta-edcred-c5u
  • Brief Description: Identifier of a supported trust anchor for verifying authentication credentials of other EDHOC peers, as a URI pointing to a C509 certificate
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-ta-edcred-x5t
  • Brief Description: Identifier of a supported trust anchor for verifying authentication credentials of other EDHOC peers, as a hash of an X.509 certificate
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-ta-edcred-x5u
  • Brief Description: Identifier of a supported trust anchor for verifying authentication credentials of other EDHOC peers, as a URI pointing to an X.509 certificate
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Attribute Name: ed-psk-resumption
  • Brief Description: Hint: support for EDHOC session resumption with EDHOC-PSK
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]
EDHOC Information Registry IANA is asked to register the following entries in the "EDHOC Information" registry defined in within the "Ephemeral Diffie-Hellman Over COSE (EDHOC)" registry group.
  • Name: psk_resumption
  • CBOR label: 21 (suggested)
  • CBOR type: True or False
  • Registry:
  • Description: Support for EDHOC session resumption with EDHOC-PSK
  • Type: NP
  • Specification: [RFC-XXXX]

  • Name: exporter_out_len
  • CBOR label: 22 (suggested)
  • CBOR type: array
  • Registry: EDHOC Exporter Labels
  • Description: Set of output lengths to use with the EDHOC_Exporter interface
  • Type: P
  • Specification: [RFC-XXXX]

  • Name: app_prof
  • CBOR label: 23 (suggested)
  • CBOR type: int or array
  • Registry: EDHOC Application Profiles registry
  • Description: Set of supported EDHOC application profiles
  • Type: NP
  • Specification: [RFC-XXXX]
EDHOC External Authorization Data Registry IANA is asked to register the following entry in the "EDHOC External Authorization Data" registry within the "Ephemeral Diffie-Hellman Over COSE (EDHOC)" registry group.
  • Name: Supported EDHOC application profiles
  • Label: TBD_EAD_LABEL (range 0-23)
  • Description: Set of supported EDHOC application profiles
  • Reference: [RFC-XXXX, ]
EDHOC Error Codes Registry IANA is asked to register the following entry in the "EDHOC Error Codes" registry within the "Ephemeral Diffie-Hellman Over COSE (EDHOC)" registry group.
  • ERR_CODE: TBD_ERROR_CODE (range -24 to 23)
  • ERR_INFO Type: bstr
  • Description: Unspecified error and supported EDHOC application profiles
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]
DNS SVCB Service Parameter Keys (SvcParamKeys) IANA is asked to add the following entries to the "DNS SVCB Service Parameter Keys (SvcParamKeys)" registry within the "DNS Service Bindings (SVCB)" registry group.
  • Number: 12 (suggested)
  • Name: edhocpath
  • Meaning: EDHOC resource path
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]

  • Number: 13 (suggested)
  • Name: edhoc-app-prof
  • Meaning: Supported EDHOC application profiles
  • Change Controller: IETF
  • Reference: [RFC-XXXX, ]
EDHOC Application Profiles Registry IANA is requested to create a new "EDHOC Application Profiles" registry within the "Ephemeral Diffie-Hellman Over COSE (EDHOC)" registry group defined in . The registration policy is either "Private Use", "Standards Action with Expert Review", or "Specification Required" per . "Expert Review" guidelines are provided in . All assignments according to "Standards Action with Expert Review" are made on a "Standards Action" basis per , with Expert Review additionally required per . The procedure for early IANA allocation of Standards Track code points defined in also applies. When such a procedure is used, IANA will ask the designated expert(s) to approve the early allocation before registration. In addition, WG chairs are encouraged to consult the expert(s) early during the process outlined in . The columns of this registry are:
  • Profile ID: This field contains the value used to identify the EDHOC application profile. These values MUST be unique. The value can be a positive integer or a negative integer. Different ranges of values use different registration policies . Integer values from -24 to 23 are designated as "Standards Action With Expert Review". Integer values from -65536 to -25 and from 24 to 65535 are designated as "Specification Required". Integer values smaller than -65536 and greater than 65535 are marked as "Private Use".
  • Name: This field contains the name of the EDHOC application profile.
  • Description: This field contains a short description of the EDHOC application profile.
  • Reference: This field contains a pointer to the public specification for the EDHOC application profile.
This registry has been initially populated with the values in .
Expert Review Instructions "Standards Action with Expert Review" and "Specification Required" are two of the registration policies defined for the IANA registry established in this document. This section gives some general guidelines for what the experts should be looking for, but they are being designated as experts for a reason so they should be given substantial latitude. Expert reviewers should take into consideration the following points:
  • Clarity and correctness of registrations. Experts are expected to check the clarity of purpose and use of the requested entries. Experts need to make sure that the object of registration is clearly defined in the corresponding specification. Entries that do not meet these objectives of clarity and completeness must not be registered.
  • Point squatting should be discouraged. Reviewers are encouraged to get sufficient information for registration requests to ensure that the usage is not going to duplicate one that is already registered and that the point is likely to be used in deployments. The zones tagged as "Private Use" are intended for testing purposes and closed environments. Code points in other ranges should not be assigned for testing.
  • Specifications are required for the "Standards Action With Expert Review" range of point assignment. Specifications should exist for "Specification Required" ranges, but early assignment before a specification is available is considered to be permissible. When specifications are not provided, the description provided needs to have sufficient information to identify what the point is being used for.
  • Experts should take into account the expected usage of fields when approving point assignment. Documents published via Standards Action can also register points outside the Standards Action range. The length of the encoded value should be weighed against how many code points of that length are left, the size of device it will be used on, and the number of code points left that encode to that size.
References Normative References Uniform Resource Identifier (URI): Generic Syntax A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK] Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK] Constrained RESTful Environments (CoRE) Link Format This specification defines Web Linking using a link format for use by constrained web servers to describe hosted resources, their attributes, and other relationships between links. Based on the HTTP Link Header field defined in RFC 5988, the Constrained RESTful Environments (CoRE) Link Format is carried as a payload and is assigned an Internet media type. "RESTful" refers to the Representational State Transfer (REST) architecture. A well-known URI is defined as a default entry point for requesting the links hosted by a server. [STANDARDS-TRACK] Media Type Specifications and Registration Procedures This document defines procedures for the specification and registration of media types for use in HTTP, MIME, and other Internet protocols. This memo documents an Internet Best Current Practice. Early IANA Allocation of Standards Track Code Points This memo describes the process for early allocation of code points by IANA from registries for which "Specification Required", "RFC Required", "IETF Review", or "Standards Action" policies apply. This process can be used to alleviate the problem where code point allocation is needed to facilitate desired or required implementation and deployment experience prior to publication of an RFC, which would normally trigger code point allocation. The procedures in this document are intended to apply only to IETF Stream documents. The Constrained Application Protocol (CoAP) The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation. CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments. Guidelines for Writing an IANA Considerations Section in RFCs Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226. Web Linking This specification defines a model for the relationships between resources on the Web ("links") and the type of those relationships ("link relation types"). It also defines the serialisation of such links in HTTP headers with the Link header field. CBOR Web Token (CWT) CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR), and CBOR Object Signing and Encryption (COSE) is used for added application-layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/value pair consisting of a claim name and a claim value. CWT is derived from JSON Web Token (JWT) but uses CBOR rather than JSON. Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures This document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON. Object Security for Constrained RESTful Environments (OSCORE) This document defines Object Security for Constrained RESTful Environments (OSCORE), a method for application-layer protection of the Constrained Application Protocol (CoAP), using CBOR Object Signing and Encryption (COSE). OSCORE provides end-to-end protection between endpoints communicating using CoAP or CoAP-mappable HTTP. OSCORE is designed for constrained nodes and networks supporting a range of proxy operations, including translation between different transport protocols. Although an optional functionality of CoAP, OSCORE alters CoAP options processing and IANA registration. Therefore, this document updates RFC 7252. Concise Binary Object Representation (CBOR) Sequences This document describes the Concise Binary Object Representation (CBOR) Sequence format and associated media type "application/cbor-seq". A CBOR Sequence consists of any number of encoded CBOR data items, simply concatenated in sequence. Structured syntax suffixes for media types allow other media types to build on them and make it explicit that they are built on an existing media type as their foundation. This specification defines and registers "+cbor-seq" as a structured syntax suffix for CBOR Sequences. Concise Binary Object Representation (CBOR) The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack. This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format. Authentication and Authorization for Constrained Environments Using the OAuth 2.0 Framework (ACE-OAuth) This specification defines a framework for authentication and authorization in Internet of Things (IoT) environments called ACE-OAuth. The framework is based on a set of building blocks including OAuth 2.0 and the Constrained Application Protocol (CoAP), thus transforming a well-known and widely used authorization solution into a form suitable for IoT devices. Existing specifications are used where possible, but extensions are added and profiles are defined to better serve the IoT use cases. CBOR Object Signing and Encryption (COSE): Header Parameters for Carrying and Referencing X.509 Certificates The CBOR Object Signing and Encryption (COSE) message structure uses references to keys in general. For some algorithms, additional properties are defined that carry parameters relating to keys as needed. The COSE Key structure is used for transporting keys outside of COSE messages. This document extends the way that keys can be identified and transported by providing attributes that refer to or contain X.509 certificates. Service Binding and Parameter Specification via the DNS (SVCB and HTTPS Resource Records) This document specifies the "SVCB" ("Service Binding") and "HTTPS" DNS resource record (RR) types to facilitate the lookup of information needed to make connections to network services, such as for HTTP origins. SVCB records allow a service to be provided from multiple alternative endpoints, each with associated parameters (such as transport protocol configuration), and are extensible to support future uses (such as keys for encrypting the TLS ClientHello). They also enable aliasing of apex domains, which is not possible with CNAME. The HTTPS RR is a variation of SVCB for use with HTTP (see RFC 9110, "HTTP Semantics"). By providing more information to the client before it attempts to establish a connection, these records offer potential benefits to both performance and privacy. Service Binding Mapping for DNS Servers The SVCB DNS resource record type expresses a bound collection of endpoint metadata, for use when establishing a connection to a named service. DNS itself can be such a service, when the server is identified by a domain name. This document provides the SVCB mapping for named DNS servers, allowing them to indicate support for encrypted transport protocols. Ephemeral Diffie-Hellman Over COSE (EDHOC) This document specifies Ephemeral Diffie-Hellman Over COSE (EDHOC), a very compact and lightweight authenticated Diffie-Hellman key exchange with ephemeral keys. EDHOC provides mutual authentication, forward secrecy, and identity protection. EDHOC is intended for usage in constrained scenarios, and a main use case is to establish an Object Security for Constrained RESTful Environments (OSCORE) security context. By reusing CBOR Object Signing and Encryption (COSE) for cryptography, Concise Binary Object Representation (CBOR) for encoding, and Constrained Application Protocol (CoAP) for transport, the additional code size can be kept very low. Universally Unique IDentifiers (UUIDs) This specification defines UUIDs (Universally Unique IDentifiers) -- also known as GUIDs (Globally Unique IDentifiers) -- and a Uniform Resource Name namespace for UUIDs. A UUID is 128 bits long and is intended to guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System (NCS), later in the Open Software Foundation's (OSF's) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms. This specification is derived from the OSF DCE specification with the kind permission of the OSF (now known as "The Open Group"). Information from earlier versions of the OSF DCE specification have been incorporated into this document. This document obsoletes RFC 4122. Using Ephemeral Diffie-Hellman Over COSE (EDHOC) with the Constrained Application Protocol (CoAP) and Object Security for Constrained RESTful Environments (OSCORE) The lightweight authenticated key exchange protocol Ephemeral Diffie-Hellman Over COSE (EDHOC) can be run over the Constrained Application Protocol (CoAP) and used by two peers to establish a Security Context for the security protocol Object Security for Constrained RESTful Environments (OSCORE). This document details this use of the EDHOC protocol by specifying a number of additional and optional mechanisms, including an optimization approach for combining the execution of EDHOC with the first OSCORE transaction. This combination reduces the number of round trips required to set up an OSCORE Security Context and to complete an OSCORE transaction using that Security Context. Ephemeral Diffie-Hellman Over COSE (EDHOC) and Object Security for Constrained Environments (OSCORE) Profile for Authentication and Authorization for Constrained Environments (ACE) Ericsson Ericsson RISE RISE This document specifies a profile for the Authentication and Authorization for Constrained Environments (ACE) framework. It utilizes Ephemeral Diffie-Hellman Over COSE (EDHOC) for achieving mutual authentication between an ACE-OAuth client and resource server, and it binds an authentication credential of the client to an ACE-OAuth access token. EDHOC also establishes an Object Security for Constrained RESTful Environments (OSCORE) Security Context, which is used to secure communications between the client and resource server when accessing protected resources according to the authorization information indicated in the access token. This profile can be used to delegate management of authorization information from a resource-constrained server to a trusted host with less severe limitations regarding processing power and memory. CBOR Encoded X.509 Certificates (C509 Certificates) Ericsson AB Ericsson AB University of Glasgow RISE AB IN Groupe NIO This document specifies a CBOR encoding of X.509 certificates. The resulting certificates are called C509 certificates. The CBOR encoding supports a large subset of RFC 5280 and common certificate profiles, and it is extensible. Two types of C509 certificates are defined. One type is an invertible CBOR re-encoding of DER-encoded X.509 certificates with the signature field copied from the DER encoding. The other type is identical except that the signature is computed over the CBOR encoding instead of the DER encoding, thereby avoiding the use of ASN.1. Both types of certificates have the same semantics as X.509 while providing comparable size reduction. This document also specifies CBOR-encoded data structures for certification requests and certification request templates, new COSE headers, as well as a TLS certificate type and a file format for C509. This document updates RFC 6698 by extending the TLSA selectors registry to include C509 certificates. EDHOC Authenticated with Pre-Shared Keys (PSK) Inria Ericsson Ericsson University of Murcia University of Murcia This document specifies a Pre-Shared Key (PSK) authentication method for the Ephemeral Diffie-Hellman Over COSE (EDHOC) Lightweight Authenticated Key Exchange (LAKE) protocol. The PSK method provides mutual authentication, ephemeral key exchange, identity protection, and quantum resistance while incurring lower computational costs than the public-key authentication methods specified for EDHOC. It is suited for systems where nodes share a PSK provided out-of-band (external PSK) and enables efficient session resumption with less computational overhead when the PSK is provided from a previous EDHOC session (resumption PSK). This document details the PSK message flow, key derivation changes, message formatting, processing, and security considerations. EDHOC Exporter Labels IANA CoAP Content-Formats IANA Target Attributes IANA EDHOC External Authorization Data IANA EDHOC Error Codes IANA DNS SVCB Service Parameter Keys (SvcParamKeys) IANA Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDNA) Punycode is a simple and efficient transfer encoding syntax designed for use with Internationalized Domain Names in Applications (IDNA). It uniquely and reversibly transforms a Unicode string into an ASCII string. ASCII characters in the Unicode string are represented literally, and non-ASCII characters are represented by ASCII characters that are allowed in host name labels (letters, digits, and hyphens). This document defines a general algorithm called Bootstring that allows a string of basic code points to uniquely represent any string of code points drawn from a larger set. Punycode is an instance of Bootstring that uses particular parameter values specified by this document, appropriate for IDNA. [STANDARDS-TRACK] Threat Analysis of the Domain Name System (DNS) Although the DNS Security Extensions (DNSSEC) have been under development for most of the last decade, the IETF has never written down the specific set of threats against which DNSSEC is designed to protect. Among other drawbacks, this cart-before-the-horse situation has made it difficult to determine whether DNSSEC meets its design goals, since its design goals are not well specified. This note attempts to document some of the known threats to the DNS, and, in doing so, attempts to measure to what extent (if any) DNSSEC is a useful tool in defending against these threats. This memo provides information for the Internet community. DNS Privacy Considerations This document describes the privacy issues associated with the use of the DNS by Internet users. It provides general observations about typical current privacy practices. It is intended to be an analysis of the present situation and does not prescribe solutions. This document obsoletes RFC 7626. Constrained RESTful Environments (CoRE) Resource Directory In many Internet of Things (IoT) applications, direct discovery of resources is not practical due to sleeping nodes or networks where multicast traffic is inefficient. These problems can be solved by employing an entity called a Resource Directory (RD), which contains information about resources held on other servers, allowing lookups to be performed for those resources. The input to an RD is composed of links, and the output is composed of links constructed from the information stored in the RD. This document specifies the web interfaces that an RD supports for web servers to discover the RD and to register, maintain, look up, and remove information on resources. Furthermore, new target attributes useful in conjunction with an RD are defined. Traces of Ephemeral Diffie-Hellman Over COSE (EDHOC) This document contains example traces of Ephemeral Diffie-Hellman Over COSE (EDHOC). Trust Anchor Hints in Ephemeral Diffie-Hellman Over COSE (EDHOC) ASSA ABLOY Ericsson This document defines a format for transport of hints about Trust Anchors of trusted third parties when using the lightweight authenticated key exchange protocol Ephemeral Diffie-Hellman Over COSE (EDHOC).
CDDL Model
CDDL model
Document Updates
Version -04 to -05
  • Fixed CDDL definitions of the EDHOC_Application_Profile object and of the ead_value for the new EAD Item.
  • Improved EDHOC error message with the new error code:
    • Extended semantics of ERR_INFO to also provide diagnostic information.
    • Updated error code description to "Unspecified error and supported EDHOC application profiles"
  • Defined the web link parameter "ed-psk-resumption" and the EDHOC_Information object parameter "psk_resumption", to indicate support for session resumption with EDHOC-PSK.
  • Clarifications:
    • Purpose of "app_prof" in the EDHOC_Application_Profile object and in the EDHOC_Information object.
    • Difference between the EDHOC_Application_Profile object and the EDHOC_Information object.
    • Purpose and applicability of parameters for web linking in the introduction.
    • Motivation and benefits of the new EAD item and error code.
    • Handling of deviations from what is specified by prescriptive EDHOC_Information parameters.
    • Extraction of CDDL definitions from the XML, using an XPath expression.
    • Short explanation of well-known profiles.
    • Full name of error codes used through the text.
    • Gained knowledge about other peers is persisted only if verified as reliable and authentic.
  • IANA considerations:
    • Added references to IANA registries.
    • More details in the media type registration.
    • Proposed codepoints picked up among unassigned ones.
  • Editorial fixes and improvements.
Version -03 to -04
  • Removed parameters that were removed from draft-ietf-ace-edhoc-oscore-profile.
  • Renamed "reply_flag" to "advertise_flag".
  • Defined use of "advertise_flag" also in SVCB Resource Records.
  • Added guidelines on using the EAD item "Supported EDHOC application profiles" only to take advantage of advertise_flag.
  • Added guidelines on having per-resource empty advertisements in an SVCB RR.
  • Clarifications:
    • Deviations from prescriptive parameters are assessed throughout the whole EDHOC session.
  • CDDL definitions:
    • Added CDDL definitions of the parameters "app_prof" and "exporter_out_len" for the CBOR-encoded EDHOC_Information object.
    • Fixed CDDL definition of ead_value of the EAD item "Supported EDHOC application profiles".
  • Added new examples:
    • Response in CoRE link-format using the target attributes 'ed-ta-edcred-*'.
    • ead_value for the EDHOC EAD item "Supported EDHOC application profiles".
    • Added examples of wire-format values of the SvcParamKeys "edhocpath" and "edhoc-app-prof".
    • ERR_INFO for the EDHOC error message with Error Code TBD_ERROR_CODE.
  • Added "Operational Considerations" section.
  • Added security considerations.
  • Editorial fixes and improvements.
Version -02 to -03
  • Removed restrictions on the scope of the EDHOC_Application_Profile object.
  • Forbidden violations of prescriptive indications in the EAD item. The EDHOC session fails if such a violation is detected.
  • Extended semantics of ead_value: optional boolean flag when the EAD item is used in EDHOC message_1.
  • Defined parameter "exporter_out_len", for in-band negotiation of EDHOC_Exporter output lengths through the EAD item "Supported EDHOC application profiles".
  • Specified wire-format and presentation format for the SvcParamKeys.
  • Fixed errors in CDDL notations.
  • Specified type of "app_prof" in the IANA registration request.
  • Clarifications and editorial improvements.
Version -01 to -02
  • Revised order of sections.
  • Use of parameters aligned with corresponding updates in draft-ietf-ace-edhoc-oscore-profile.
  • EAD item "Supported EDHOC application profiles":
    • It can be used only in a critical way.
    • Improved semantics of ead_value.
    • Content restrictions to avoid inconsistent information.
  • Use of the parameter "app_prof" in draft-ietf-ace-edhoc-oscore-profile:
    • Improved co-existence with other parameters.
    • Content restrictions to avoid inconsistent information.
  • Error handling:
    • EAD item "Supported EDHOC application profiles" occurring multiple times in EDHOC message_1 or message_2.
    • EAD item "Supported EDHOC application profiles" in EDHOC message_3 or message_4.
    • Invalid ead_value in EAD item "Supported EDHOC application profiles".
    • Invalid information in EDHOC error message with new error code.
  • Fixed encoding of ERR_INFO for the EDHOC error message with the new error code.
  • EDHOC_Application_Profile object
    • Clarified scope.
    • Clarified meaning of boolean parameters that are non-prescriptive.
    • Forbid the presence of the element "trust_anchors".
  • Advertisement of Supported EDHOC Application Profiles using SVCB Resource Records.
  • Updated integer abbreviations for the EDHOC_Information parameters.
  • Editorial improvements.
Version -00 to -01
  • Clarified motivation in the abstract and introduction.
  • Moved definition of EDHOC_Information parameters to draft-ietf-ace-edhoc-oscore-profile.
  • Renamed ed-idep-t x as ed-epid-t.
  • Content-Format abbreviated as "ct" (not "cf").
  • CBOR abbreviation of "app_prof" changed to 23.
  • Added preamble on identifying application profiles by Profile ID.
  • Defined target attributes "ed-ta-*" for specifying supported trust anchors.
  • Defined new EAD item and error code to advertise supported EDHOC application profiles.
  • Defined how to handle non admitted parameters.
  • Renamed well-known EDHOC application profiles.
  • Updated IANA considerations:
    • Suggested range 0-255 for CoAP Content-Format ID.
    • Requested registration for target attributes "ed-ta-*".
    • Removed requests for registration of removed parameters.
  • Updated references.
  • Editorial improvements.
Acknowledgments The authors sincerely thank , , , , , , , , , , and for their feedback and comments. The target attributes "ed-ta-*" for specifying supported trust anchors build on a proposal originally described in . This work was supported by the Sweden's Innovation Agency VINNOVA within the EUREKA CELTIC-NEXT project CYPRESS.