Using EDHOC with CoAP and OSCORE
draft-ietf-core-oscore-edhoc-08
The information below is for an old version of the document.
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|---|---|---|---|
| Authors | Francesca Palombini , Marco Tiloca , Rikard Höglund , Stefan Hristozov , Göran Selander | ||
| Last updated | 2023-10-06 (Latest revision 2023-08-08) | ||
| Replaces | draft-palombini-core-oscore-edhoc | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-core-oscore-edhoc-08
CoRE Working Group F. Palombini
Internet-Draft Ericsson
Intended status: Standards Track M. Tiloca
Expires: 9 February 2024 R. Höglund
RISE AB
S. Hristozov
Fraunhofer AISEC
G. Selander
Ericsson
8 August 2023
Using EDHOC with CoAP and OSCORE
draft-ietf-core-oscore-edhoc-08
Abstract
The lightweight authenticated key exchange protocol EDHOC can be run
over CoAP and used by two peers to establish an OSCORE Security
Context. This document details this use of the EDHOC protocol, by
specifying a number of additional and optional mechanisms. These
especially include 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.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the Constrained RESTful
Environments Working Group mailing list (core@ietf.org), which is
archived at https://mailarchive.ietf.org/arch/browse/core/.
Source for this draft and an issue tracker can be found at
https://github.com/core-wg/oscore-edhoc.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 9 February 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. EDHOC Overview . . . . . . . . . . . . . . . . . . . . . . . 4
3. EDHOC Combined with OSCORE . . . . . . . . . . . . . . . . . 7
3.1. EDHOC Option . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Client Processing . . . . . . . . . . . . . . . . . . . . 10
3.2.1. Supporting Block-wise . . . . . . . . . . . . . . . . 11
3.3. Server Processing . . . . . . . . . . . . . . . . . . . . 12
3.3.1. Supporting Block-wise . . . . . . . . . . . . . . . . 14
3.4. Example of EDHOC + OSCORE Request . . . . . . . . . . . . 14
4. Use of EDHOC Connection Identifiers with OSCORE . . . . . . . 15
4.1. Additional Processing of EDHOC Messages . . . . . . . . . 15
4.1.1. Initiator Processing of Message 1 . . . . . . . . . . 16
4.1.2. Responder Processing of Message 2 . . . . . . . . . . 16
4.1.3. Initiator Processing of Message 2 . . . . . . . . . . 16
5. Extension and Consistency of Application Profiles . . . . . . 17
6. Web Linking . . . . . . . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
8.1. CoAP Option Numbers Registry . . . . . . . . . . . . . . 21
8.2. Target Attributes Registry . . . . . . . . . . . . . . . 22
8.3. EDHOC Authentication Credential Types Registry . . . . . 22
8.4. Expert Review Instructions . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . 24
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9.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Document Updates . . . . . . . . . . . . . . . . . . 26
A.1. Version -07 to -08 . . . . . . . . . . . . . . . . . . . 26
A.2. Version -06 to -07 . . . . . . . . . . . . . . . . . . . 27
A.3. Version -05 to -06 . . . . . . . . . . . . . . . . . . . 27
A.4. Version -04 to -05 . . . . . . . . . . . . . . . . . . . 28
A.5. Version -03 to -04 . . . . . . . . . . . . . . . . . . . 28
A.6. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 28
A.7. Version -01 to -02 . . . . . . . . . . . . . . . . . . . 29
A.8. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 29
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
Ephemeral Diffie-Hellman Over COSE (EDHOC) [I-D.ietf-lake-edhoc] is a
lightweight authenticated key exchange protocol, especially intended
for use in constrained scenarios. In particular, EDHOC messages can
be transported over the Constrained Application Protocol (CoAP)
[RFC7252] and used for establishing a Security Context for Object
Security for Constrained RESTful Environments (OSCORE) [RFC8613].
This document details this use of the EDHOC protocol, and specifies a
number of additional and optional mechanisms. These especially
include an optimization approach that combines the EDHOC execution
with the first OSCORE transaction (see Section 3). This allows for a
minimum number of round trips necessary to setup the OSCORE Security
Context and complete an OSCORE transaction, e.g., when an IoT device
gets configured in a network for the first time.
This optimization is desirable, since the number of protocol round
trips influences the minimum number of flights, which in turn can
have a substantial impact on the latency of conveying the first
OSCORE request, when using certain radio technologies.
Without this optimization, it is not possible, not even in theory, to
achieve the minimum number of flights. This optimization makes it
possible also in practice, since the last message of the EDHOC
protocol can be made relatively small (see Section 1.2 of
[I-D.ietf-lake-edhoc]), thus allowing additional OSCORE-protected
CoAP data within target MTU sizes.
Furthermore, this document defines a number of parameters
corresponding to different information elements of an EDHOC
application profile (see Section 6). These can be specified as
target attributes in the link to an EDHOC resource associated with
that application profile, thus enabling an enhanced discovery of such
a resource for CoAP clients.
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1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The reader is expected to be familiar with terms and concepts defined
in CoAP [RFC7252], CBOR [RFC8949], OSCORE [RFC8613], and EDHOC
[I-D.ietf-lake-edhoc].
2. EDHOC Overview
This section is not normative and summarizes what is specified in
[I-D.ietf-lake-edhoc], in particular its Appendix A.2. Thus, it
provides a baseline for the enhancements in the subsequent sections.
The EDHOC protocol specified in [I-D.ietf-lake-edhoc] allows two
peers to agree on a cryptographic secret, in a mutually-authenticated
way and by using Diffie-Hellman ephemeral keys to achieve forward
secrecy. The two peers are denoted as Initiator and Responder, as
the one sending or receiving the initial EDHOC message_1,
respectively.
After successful processing of EDHOC message_3, both peers agree on a
cryptographic secret that can be used to derive further security
material, and especially to establish an OSCORE Security Context
[RFC8613]. The Responder can also send an optional EDHOC message_4
to achieve key confirmation, e.g., in deployments where no protected
application message is sent from the Responder to the Initiator.
Appendix A.2 of [I-D.ietf-lake-edhoc] specifies how to transfer EDHOC
over CoAP. That is, the EDHOC data (referred to as "EDHOC messages")
are transported in the payload of CoAP requests and responses. The
default, forward message flow of EDHOC consists in the CoAP client
acting as Initiator and the CoAP server acting as Responder.
Alternatively, the two roles can be reversed, as per the reverse
message flow of EDHOC. In the rest of this document, EDHOC messages
are considered to be transferred over CoAP.
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Figure 1 shows a CoAP client and a CoAP server running EDHOC as
Initiator and Responder, respectively. That is, the client sends a
POST request to a reserved _EDHOC resource_ at the server, by default
at the Uri-Path "/.well-known/edhoc". The request payload consists
of the CBOR simple value "true" (0xf5) concatenated with EDHOC
message_1, which also includes the EDHOC connection identifier C_I of
the client encoded as per Section 3.3 of [I-D.ietf-lake-edhoc]. The
Content-Format of the request can be set to application/cid-
edhoc+cbor-seq.
This triggers the EDHOC execution at the server, which replies with a
2.04 (Changed) response. The response payload consists of EDHOC
message_2, which also includes the EDHOC connection identifier C_R of
the server encoded as per Section 3.3 of [I-D.ietf-lake-edhoc]. The
Content-Format of the response can be set to application/edhoc+cbor-
seq.
Finally, the client sends a POST request to the same EDHOC resource
used earlier to send EDHOC message_1. The request payload consists
of the EDHOC connection identifier C_R encoded as per Section 3.3 of
[I-D.ietf-lake-edhoc], concatenated with EDHOC message_3. The
Content-Format of the request can be set to application/cid-
edhoc+cbor-seq.
After this exchange takes place, and after successful verifications
as specified in the EDHOC protocol, the client and server can derive
an OSCORE Security Context, as defined in Appendix A.1 of
[I-D.ietf-lake-edhoc]. After that, they can use OSCORE to protect
their communications as per [RFC8613].
The client and server are required to agree in advance on certain
information and parameters describing how they should use EDHOC.
These are specified in an application profile associated with the
EDHOC resource addressed (see Section 3.9 of [I-D.ietf-lake-edhoc].
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CoAP client CoAP server
(EDHOC Initiator) (EDHOC Responder)
| |
| |
| ----------------- EDHOC Request -----------------> |
| Header: 0.02 (POST) |
| Uri-Path: "/.well-known/edhoc" |
| Content-Format: application/cid-edhoc+cbor-seq |
| Payload: true, EDHOC message_1 |
| |
| <---------------- EDHOC Response------------------ |
| Header: 2.04 (Changed) |
| Content-Format: application/edhoc+cbor-seq |
| Payload: EDHOC message_2 |
| |
EDHOC verification |
| |
| ----------------- EDHOC Request -----------------> |
| Header: 0.02 (POST) |
| Uri-Path: "/.well-known/edhoc" |
| Content-Format: application/cid-edhoc+cbor-seq |
| Payload: C_R, EDHOC message_3 |
| |
| EDHOC verification
| +
| OSCORE Sec Ctx
| Derivation
| |
| <---------------- EDHOC Response------------------ |
| Header: 2.04 (Changed) |
| Content-Format: application/edhoc+cbor-seq |
| Payload: EDHOC message_4 |
| |
OSCORE Sec Ctx |
Derivation |
| |
| ---------------- OSCORE Request -----------------> |
| Header: 0.02 (POST) |
| Payload: OSCORE-protected data |
| |
| <--------------- OSCORE Response ----------------- |
| Header: 2.04 (Changed) |
| Payload: OSCORE-protected data |
| |
Figure 1: EDHOC and OSCORE run sequentially. The optional
message_4 is included in this example, without which that message
needs no payload.
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As shown in Figure 1, this purely-sequential flow where EDHOC is run
first and then OSCORE is used takes three round trips to complete.
Section 3 defines an optimization for combining EDHOC with the first
OSCORE transaction. This reduces the number of round trips required
to set up an OSCORE Security Context and to complete an OSCORE
transaction using that Security Context.
3. EDHOC Combined with OSCORE
This section defines an optimization for combining the EDHOC message
exchange with the first OSCORE transaction, thus minimizing the
number of round trips between the two peers.
This approach can be used only if the default, forward message flow
of EDHOC is used, i.e., when the client acts as Initiator and the
server acts as Responder. That is, it cannot be used in the case
with reversed roles as per the reverse message flow of EDHOC.
When running the purely-sequential flow of Section 2, the client has
all the information to derive the OSCORE Security Context already
after receiving EDHOC message_2 and before sending EDHOC message_3.
Hence, the client can potentially send both EDHOC message_3 and the
subsequent OSCORE Request at the same time. On a semantic level,
this requires sending two REST requests at once, as in Figure 2.
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CoAP client CoAP server
(EDHOC Initiator) (EDHOC Responder)
| |
| ------------------ EDHOC Request -----------------> |
| Header: 0.02 (POST) |
| Uri-Path: "/.well-known/edhoc" |
| Content-Format: application/cid-edhoc+cbor-seq |
| Payload: true, EDHOC message_1 |
| |
| <----------------- EDHOC Response------------------ |
| Header: Changed (2.04) |
| Content-Format: application/edhoc+cbor-seq |
| Payload: EDHOC message_2 |
| |
EDHOC verification |
+ |
OSCORE Sec Ctx |
Derivation |
| |
| -------------- EDHOC + OSCORE Request ------------> |
| Header: 0.02 (POST) |
| Payload: EDHOC message_3 + OSCORE-protected data |
| |
| EDHOC verification
| +
| OSCORE Sec Ctx
| Derivation
| |
| <--------------- OSCORE Response ------------------ |
| Header: 2.04 (Changed) |
| Payload: OSCORE-protected data |
| |
Figure 2: EDHOC and OSCORE combined.
To this end, the specific approach defined in this section consists
of sending a single EDHOC + OSCORE request, which conveys the pair
(C_R, EDHOC message_3) within an OSCORE-protected CoAP message.
That is, the EDHOC + OSCORE request is composed of the following two
parts combined together in a single CoAP message:
* The OSCORE Request from Figure 1, which is also in this case sent
to a protected resource, with the correct CoAP method and options
intended for accessing that resource.
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* EDHOC data consisting of the pair (C_R, EDHOC message_3) required
for completing the EDHOC session. Note that, as specified in
Section 3.2, C_R is transported in the OSCORE Option of the OSCORE
Request rather than in the CoAP payload of the EDHOC + OSCORE
request.
Since EDHOC message_3 may be too large to be included in a CoAP
Option, e.g., if conveying a large public key certificate chain as
ID_CRED_I (see Section 3.5.3 of [I-D.ietf-lake-edhoc]) or if
conveying large External Authorization Data as EAD_3 (see
Section 3.8 of [I-D.ietf-lake-edhoc]), EDHOC message_3 has instead
to be transported in the CoAP payload of the EDHOC + OSCORE
request, as prepended to the payload of the OSCORE Request.
The rest of this section specifies how to transport the data in the
EDHOC + OSCORE request and their processing order. In particular,
the use of this approach is explicitly signalled by including an
EDHOC Option (see Section 3.1) in the EDHOC + OSCORE request. The
processing of the EDHOC + OSCORE request is specified in Section 3.2
for the client side and in Section 3.3 for the server side.
3.1. EDHOC Option
This section defines the EDHOC Option. The option is used in a CoAP
request, to signal that the request payload conveys both an EDHOC
message_3 and OSCORE-protected data, combined together.
The EDHOC Option has the properties summarized in Table 1, which
extends Table 4 of [RFC7252]. The option is Critical, Safe-to-
Forward, and part of the Cache-Key. The option MUST occur at most
once and MUST be empty. If any value is sent, the recipient MUST
ignore it. (Future documents may update the definition of the
option, by expanding its semantics and specifying admitted values.)
The option is intended only for CoAP requests and is of Class U for
OSCORE [RFC8613].
+=======+===+===+===+===+=======+========+========+=========+
| No. | C | U | N | R | Name | Format | Length | Default |
+=======+===+===+===+===+=======+========+========+=========+
| TBD21 | x | | | | EDHOC | Empty | 0 | (none) |
+-------+---+---+---+---+-------+--------+--------+---------+
Table 1: The EDHOC Option. C=Critical, U=Unsafe,
N=NoCacheKey, R=Repeatable
Note to RFC Editor: Following the registration of the CoAP Option
Number 21 as per Section 8.1, please replace "TBD21" with "21" in the
figure above. Then, please delete this paragraph.
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The presence of this option means that the message payload also
contains EDHOC data, which must be extracted and processed as defined
in Section 3.3, before the rest of the message can be processed.
Figure 3 shows an example of a CoAP message transported over UDP and
containing both the EDHOC data and the OSCORE ciphertext, using the
newly defined EDHOC option for signalling.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver| T | TKL | Code | Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token (if any, TKL bytes) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Observe Option| OSCORE Option ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EDHOC Option | Other Options (if any) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 1 1 1| Payload ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Example of CoAP message transported over UDP, combining
EDHOC data and OSCORE data as signalled with the EDHOC Option.
3.2. Client Processing
The client prepares an EDHOC + OSCORE request as follows.
1. Compose EDHOC message_3 as per Section 5.4.2 of
[I-D.ietf-lake-edhoc].
2. Establish the new OSCORE Security Context and use it to encrypt
the original CoAP request as per Section 8.1 of [RFC8613].
Note that the OSCORE ciphertext is not computed over EDHOC
message_3, which is not protected by OSCORE. That is, the result
of this step is the OSCORE Request as in Figure 1.
3. Build COMB_PAYLOAD as the concatenation of EDHOC_MSG_3 and
OSCORE_PAYLOAD in this order: COMB_PAYLOAD = EDHOC_MSG_3 |
OSCORE_PAYLOAD, where | denotes byte string concatenation and:
* EDHOC_MSG_3 is the binary encoding of EDHOC message_3
resulting from step 1. As per Section 5.4.1 of
[I-D.ietf-lake-edhoc], EDHOC message_3 consists of one CBOR
data item CIPHERTEXT_3, which is a CBOR byte string.
Therefore, EDHOC_MSG_3 is the binary encoding of CIPHERTEXT_3.
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* OSCORE_PAYLOAD is the OSCORE ciphertext of the OSCORE-
protected CoAP request resulting from step 2.
4. Compose the EDHOC + OSCORE request, as the OSCORE-protected CoAP
request resulting from step 2, where the payload is replaced with
COMB_PAYLOAD built at step 3.
Note that the new payload includes EDHOC message_3, but it does
not include the EDHOC connection identifier C_R. As the client
is the EDHOC Initiator, C_R is the OSCORE Sender ID of the
client, which is already specified as 'kid' in the OSCORE Option
of the request from step 2, hence of the EDHOC + OSCORE request.
5. Signal the usage of this approach, by including the new EDHOC
Option defined in Section 3.1 into the EDHOC + OSCORE request.
The application/cid-edhoc+cbor-seq media type does not apply to
this message, whose media type is unnamed.
6. Send the EDHOC + OSCORE request to the server.
With the same server, the client SHOULD NOT have multiple
simultaneous outstanding interactions (see Section 4.7 of [RFC7252])
such that: they consist of an EDHOC + OSCORE request; and their EDHOC
data pertain to the EDHOC session with the same connection identifier
C_R.
(An exception might apply for clients that operate under particular
time constraints over particularly unreliable networks, thus raising
the chances to promptly complete the EDHOC execution with the server
through multiple, simultaneous EDHOC + OSCORE requests. As discussed
in Section 7, this does not have any impact in terms of security.)
3.2.1. Supporting Block-wise
If Block-wise [RFC7959] is supported, the client may fragment the
first application CoAP request before protecting it as an original
message with OSCORE, as defined in Section 4.1.3.4.1 of [RFC8613].
In such a case, the OSCORE processing in step 2 of Section 3.2 is
performed on each inner block of the first application CoAP request,
and the following also applies.
* The client takes the additional following step between steps 2 and
3 of Section 3.2.
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A. If the OSCORE-protected request from step 2 conveys a non-
first inner block of the first application CoAP request (i.e., the
Block1 Option processed at step 2 had NUM different than 0), then
the client skips the following steps and sends the OSCORE-
protected request to the server. In particular, the client MUST
NOT include the EDHOC Option in the OSCORE-protected request.
* The client takes the additional following step between steps 3 and
4 of Section 3.2.
B. If the size of COMB_PAYLOAD exceeds MAX_UNFRAGMENTED_SIZE (see
Section 4.1.3.4.2 of [RFC8613]), the client MUST stop processing
the request and MUST abandon the Block-wise transfer. Then, the
client can continue by switching to the purely sequential workflow
shown in Figure 1. That is, the client first sends EDHOC
message_3 prepended by the EDHOC Connection Identifier C_R encoded
as per Section 3.3 of [I-D.ietf-lake-edhoc], and then sends the
OSCORE-protected CoAP request once the EDHOC execution is
completed.
The performance advantage of using the EDHOC + OSCORE request can be
lost when used in combination with Block-wise transfers that rely on
specific parameter values and block sizes.
3.3. Server Processing
In order to process a request containing the EDHOC option, i.e., an
EDHOC + OSCORE request, the server MUST perform the following steps.
1. Check that the EDHOC + OSCORE request includes the OSCORE option
and that the request payload has the format defined at step 3 of
Section 3.2 for COMB_PAYLOAD. If this is not the case, the
server MUST stop processing the request and MUST reply with a
4.00 (Bad Request) error response.
2. Extract EDHOC message_3 from the payload COMB_PAYLOAD of the
EDHOC + OSCORE request, as the first element EDHOC_MSG_3 (see
step 3 of Section 3.2).
3. Take the value of 'kid' from the OSCORE option of the EDHOC +
OSCORE request (i.e., the OSCORE Sender ID of the client), and
use it as the EDHOC connection identifier C_R.
4. Retrieve the correct EDHOC session by using the connection
identifier C_R from step 3.
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If the application profile used in the EDHOC session specifies
that EDHOC message_4 shall be sent, the server MUST stop the
EDHOC processing and consider it failed, as due to a client
error.
Otherwise, perform the EDHOC processing on the EDHOC message_3
extracted at step 2 as per Section 5.4.3 of
[I-D.ietf-lake-edhoc], based on the protocol state of the
retrieved EDHOC session.
The application profile used in the EDHOC session is the same one
associated with the EDHOC resource where the server received the
request conveying EDHOC message_1 that started the session. This
is relevant in case the server provides multiple EDHOC resources,
which may generally refer to different application profiles.
5. Establish a new OSCORE Security Context associated with the
client as per Appendix A.1 of [I-D.ietf-lake-edhoc], using the
EDHOC output from step 4.
6. Extract the OSCORE ciphertext from the payload COMB_PAYLOAD of
the EDHOC + OSCORE request, as the second element OSCORE_PAYLOAD
(see step 3 of Section 3.2).
7. Rebuild the OSCORE-protected CoAP request, as the EDHOC + OSCORE
request where the payload is replaced with the OSCORE ciphertext
extracted at step 6. Then, remove the EDHOC option.
8. Decrypt and verify the OSCORE-protected CoAP request rebuilt at
step 7, as per Section 8.2 of [RFC8613], by using the OSCORE
Security Context established at step 5.
When the decrypted request is checked for any critical CoAP
options (as it is during regular CoAP processing), the presence
of an EDHOC option MUST be regarded as an unprocessed critical
option, unless it is processed by some further mechanism.
9. Deliver the CoAP request resulting from step 8 to the
application.
If steps 4 (EDHOC processing) and 8 (OSCORE processing) are both
successfully completed, the server MUST reply with an OSCORE-
protected response (see Section 5.4.3 of [I-D.ietf-lake-edhoc]). The
usage of EDHOC message_4 as defined in Section 5.5 of
[I-D.ietf-lake-edhoc] is not applicable to the approach defined in
this document.
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If step 4 (EDHOC processing) fails, the server discontinues the
protocol as per Section 5.4.3 of [I-D.ietf-lake-edhoc] and responds
with an EDHOC error message with error code 1, formatted as defined
in Section 6.2 of [I-D.ietf-lake-edhoc]. The server MUST NOT
establish a new OSCORE Security Context from the present EDHOC
session with the client, hence the CoAP response conveying the EDHOC
error message is not protected with OSCORE. As per Section 8.5 of
[I-D.ietf-lake-edhoc], the server has to make sure that the error
message does not reveal sensitive information. The CoAP response
conveying the EDHOC error message MUST have Content-Format set to
application/edhoc+cbor-seq defined in Section 9.9 of
[I-D.ietf-lake-edhoc].
If step 4 (EDHOC processing) is successfully completed but step 8
(OSCORE processing) fails, the same OSCORE error handling as defined
in Section 8.2 of [RFC8613] applies.
3.3.1. Supporting Block-wise
If Block-wise [RFC7959] is supported, the server takes the additional
following step before any other in Section 3.3.
A. If Block-wise is present in the request, then process the Outer
Block options according to [RFC7959], until all blocks of the request
have been received (see Section 4.1.3.4 of [RFC8613]).
3.4. Example of EDHOC + OSCORE Request
Figure 4 shows an example of EDHOC + OSCORE Request transported over
UDP. In particular, the example assumes that:
* The OSCORE Partial IV in use is 0, consistently with the first
request protected with the new OSCORE Security Context.
* The OSCORE Sender ID of the client is 0x01.
As per Section 3.3.3 of [I-D.ietf-lake-edhoc], this
straightforwardly corresponds to the EDHOC connection identifier
C_R 0x01.
As per Section 3.3.2 of [I-D.ietf-lake-edhoc], when using the
purely-sequential flow shown in Figure 1, the same C_R with value
0x01 would be encoded on the wire as the CBOR integer 1 (0x01 in
CBOR encoding), and prepended to EDHOC message_3 in the payload of
the second EDHOC request.
* The EDHOC option is registered with CoAP option number 21.
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Note to RFC Editor: Please delete the last bullet point in the
previous list, since, at the time of publication, the CoAP option
number will be in fact registered.
This results in the following components shown in Figure 4:
* OSCORE option value: 0x090001 (3 bytes)
* EDHOC option value: - (0 bytes)
* EDHOC message_3: 0x52d5535f3147e85f1cfacd9e78abf9e0a81bbf (19
bytes)
* OSCORE ciphertext: 0x612f1092f1776f1c1668b3825e (13 bytes)
Protected CoAP request (OSCORE message):
0x44025d1f ; CoAP 4-byte header
00003974 ; Token
93 090001 ; OSCORE Option
c0 ; EDHOC Option
ff 52d5535f3147e85f1cfacd9e78abf9e0a81bbf
612f1092f1776f1c1668b3825e
(46 bytes)
Figure 4: Example of CoAP message transported over UDP, combining
EDHOC data and OSCORE data as signalled with the EDHOC Option.
4. Use of EDHOC Connection Identifiers with OSCORE
Section 3.3.3 of [I-D.ietf-lake-edhoc] defines the straightforward
mapping from an EDHOC connection identifier to an OSCORE Sender/
Recipient ID. That is, an EDHOC identifier and the corresponding
OSCORE Sender/Recipient ID are both byte strings with the same value.
Therefore, the conversion from an OSCORE Sender/Recipient ID to an
EDHOC identifier is equally straightforward. In particular, at step
3 of Section 3.3, the value of 'kid' in the OSCORE Option of the
EDHOC + OSCORE request is both the server's Recipient ID (i.e., the
client's Sender ID) and the EDHOC Connection Identifier C_R of the
server.
4.1. Additional Processing of EDHOC Messages
When using EDHOC to establish an OSCORE Security Context, the client
and server MUST perform the following additional steps during an
EDHOC execution, thus extending Section 5 of [I-D.ietf-lake-edhoc].
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4.1.1. Initiator Processing of Message 1
The Initiator selects an EDHOC Connection Identifier C_I as follows.
The Initiator MUST choose a C_I that is neither used in any current
EDHOC session as this peer's EDHOC Connection Identifier, nor the
Recipient ID in a current OSCORE Security Context where the ID
Context is not present.
The chosen C_I SHOULD NOT be the Recipient ID of any current OSCORE
Security Context. Note that, unless the two peers concurrently use
alternative methods to establish OSCORE Security Contexts, this
allows the Responder to always omit the 'kid context' in the OSCORE
Option of its messages sent to the Initiator, when protecting those
with an OSCORE Security Context where C_I is the Responder's OSCORE
Sender ID (see Section 6.1 of [RFC8613]).
4.1.2. Responder Processing of Message 2
The Responder selects an EDHOC Connection Identifier C_R as follows.
The Responder MUST choose a C_R that is neither used in any current
EDHOC session as this peer's EDHOC Connection Identifier, nor is
equal to the EDHOC Connection Identifier C_I specified in the EDHOC
message_1 of the present EDHOC session (i.e., after its decoding as
per Section 3.3 of [I-D.ietf-lake-edhoc]), nor is the Recipient ID in
a current OSCORE Security Context where the ID Context is not
present.
The chosen C_R SHOULD NOT be the Recipient ID of any current OSCORE
Security Context. Note that, for a reason analogous to the one given
above with C_I, this allows the Initiator to always omit the 'kid
context' in the OSCORE Option of its messages sent to the Responder,
when protecting those with an OSCORE Security Context where C_R is
the Initiator's OSCORE Sender ID (see Section 6.1 of [RFC8613]).
4.1.3. Initiator Processing of Message 2
If the following condition holds, the Initiator MUST discontinue the
protocol and reply with an EDHOC error message with error code 1,
formatted as defined in Section 6.2 of [I-D.ietf-lake-edhoc].
* The EDHOC Connection Identifier C_I is equal to the EDHOC
Connection Identifier C_R specified in EDHOC message_2 (i.e.,
after its decoding as per Section 3.3 of [I-D.ietf-lake-edhoc]).
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5. Extension and Consistency of Application Profiles
The application profile referred by the client and server can include
the information below, according to the specified consistency rules.
If the server supports the EDHOC + OSCORE request within an EDHOC
execution started at a certain EDHOC resource, then the application
profile associated with that resource SHOULD explicitly specify
support for the EDHOC + OSCORE request.
In case the application profile indicates that the server supports
the optional EDHOC message_4 (see Section 5.5 of
[I-D.ietf-lake-edhoc]), the client has to bear in mind that the usage
of EDHOC message_4 is not applicable to the optimized workflow based
on the EDHOC + OSCORE request (see Section 3.3).
6. Web Linking
Section 9.10 of [I-D.ietf-lake-edhoc] registers the resource type
"core.edhoc", which can be used as target attribute in a web link
[RFC8288] to an EDHOC resource, e.g., using a link-format document
[RFC6690]. This enables clients to discover the presence of EDHOC
resources at a server, possibly using the resource type as filter
criterion.
At the same time, the application profile associated with an EDHOC
resource provides information describing how the EDHOC protocol can
be used through that resource. While a client may become aware of
the application profile through several means, it would be convenient
to obtain its information elements upon discovering the EDHOC
resources at the server. This might aim at discovering especially
the EDHOC resources whose associated application profile denotes a
way of using EDHOC which is most suitable to the client, e.g., with
EDHOC cipher suites or authentication methods that the client also
supports or prefers.
That is, it would be convenient that a client discovering an EDHOC
resource contextually obtains relevant pieces of information from the
application profile associated with that resource. The resource
discovery can occur by means of a direct interaction with the server,
or instead by means of the CoRE Resource Directory [RFC9176], where
the server may have registered the links to its resources.
In order to enable the above, this section defines a number of
parameters, each of which can be optionally specified as a target
attribute with the same name in the link to the respective EDHOC
resource, or as filter criteria in a discovery request from the
client. When specifying these parameters in a link to an EDHOC
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resource, the target attribute rt="core.edhoc" MUST be included, and
the same consistency rules defined in Section 5 for the corresponding
information elements of an application profile MUST be followed.
The following parameters are defined.
* 'ed-i', specifying, if present, that the server supports the EDHOC
Initiator role, hence the reverse message flow of EDHOC. A value
MUST NOT be given to this parameter and any present value MUST be
ignored by the recipient.
* 'ed-r', specifying, if present, that the server supports the EDHOC
Responder role, hence the forward message flow of EDHOC. A value
MUST NOT be given to this parameter and any present value MUST be
ignored by the recipient.
* 'ed-method', specifying an authentication method supported by the
server. This parameter MUST specify a single value, which is
taken from the 'Value' column of the "EDHOC Method Type" registry
defined in Section 9.3 of [I-D.ietf-lake-edhoc]. This parameter
MAY occur multiple times, with each occurrence specifying an
authentication method.
* 'ed-csuite', specifying an EDHOC cipher suite supported by the
server. This parameter MUST specify a single value, which is
taken from the 'Value' column of the "EDHOC Cipher Suites"
registry defined in Section 9.2 of [I-D.ietf-lake-edhoc]. This
parameter MAY occur multiple times, with each occurrence
specifying a cipher suite.
* 'ed-cred-t', specifying a type of authentication credential
supported by the server. This parameter MUST specify a single
value, which is taken from the 'Value' column of the "EDHOC
Authentication Credential Types" Registry defined in Section 8.3
of this document. This parameter MAY occur multiple times, with
each occurrence specifying a type of authentication credential.
* 'ed-idcred-t', specifying a type of identifier supported by the
server for identifying authentication credentials. This parameter
MUST specify a single value, which is taken from the 'Label'
column of the "COSE Header Parameters" registry
[COSE.Header.Parameters]. This parameter MAY occur multiple
times, with each occurrence specifying a type of identifier for
authentication credentials.
Note that the values in the 'Label' column of the "COSE Header
Parameters" registry are strongly typed. On the contrary, Link
Format is weakly typed and thus does not distinguish between, for
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instance, the string value "-10" and the integer value -10. Thus,
if responses in Link Format are returned, string values which look
like an integer are not supported. Therefore, such values MUST
NOT be used in the 'ed-idcred-t' parameter.
* 'ed-ead', specifying the support of the server for an External
Authorization Data (EAD) item (see Section 3.8 of
[I-D.ietf-lake-edhoc]). This parameter MUST specify a single
value, which is taken from the 'Label' column of the "EDHOC
External Authorization Data" registry defined in Section 9.5 of
[I-D.ietf-lake-edhoc]. This parameter MAY occur multiple times,
with each occurrence specifying the ead_label of an EAD item that
the server supports.
* 'ed-comb-req', specifying, if present, that the server supports
the EDHOC + OSCORE request defined in Section 3. 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 the parameters 'ed-i',
'ed-r', and 'ed-comb-req', by expanding their semantics and
specifying admitted values.)
The example in Figure 5 shows how a client discovers one EDHOC
resource at a server, obtaining information elements from the
respective application profile. The Link Format notation from
Section 5 of [RFC6690] is used.
REQ: GET /.well-known/core
RES: 2.05 Content
</sensors/temp>;osc,
</sensors/light>;if=sensor,
</.well-known/edhoc>;rt=core.edhoc;ed-csuite=0;ed-csuite=2;
ed-method=0;ed-cred-t=1;ed-cred-t=3;ed-idcred-t=4;
ed-i;ed-r;ed-comb-req
Figure 5: The Web Link.
7. Security Considerations
The same security considerations from OSCORE [RFC8613] and EDHOC
[I-D.ietf-lake-edhoc] hold for this document. In addition, the
following considerations also apply.
Section 3.2 specifies that a client SHOULD NOT have multiple
outstanding EDHOC + OSCORE requests pertaining to the same EDHOC
session. Even if a client did not fulfill this requirement, it would
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not have any impact in terms of security. That is, the server would
still not process different instances of the same EDHOC message_3
more than once in the same EDHOC session (see Section 5.1 of
[I-D.ietf-lake-edhoc]), and would still enforce replay protection of
the OSCORE-protected request (see Sections 7.4 and 8.2 of [RFC8613]).
When using the optimized workflow in Figure 2, a minimum of 128-bit
security against online brute force attacks is achieved after the
client receives and successfully verifies the first OSCORE-protected
response (see Section 8.1 of [I-D.ietf-lake-edhoc]). As an example,
if EDHOC is used with method 3 (see Section 3.2 of
[I-D.ietf-lake-edhoc]) and cipher suite 2 (see Section 3.6 of
[I-D.ietf-lake-edhoc]), then the following holds.
* The Initiator is authenticated with 128-bit security against
online attacks. This is the sum of the 64-bit MACs in EDHOC
message_3 and of the MAC in the AEAD of the first OSCORE-protected
CoAP request, as rebuilt at step 7 of Section 3.3.
* The Responder is authenticated with 128-bit security against
online attacks. This is the sum of the 64-bit MACs in EDHOC
message_2 and of the MAC in the AEAD of the first OSCORE-protected
CoAP response.
With reference to the purely sequential workflow in Figure 1, the
OSCORE request might have to undergo access control checks at the
server, before being actually executed for accessing the target
protected resource. The same MUST hold when the optimized workflow
in Figure 2 is used, i.e., when using the EDHOC + OSCORE request.
That is, the rebuilt OSCORE-protected application request from step 7
in Section 3.3 MUST undergo the same access control checks that would
be performed on a traditional OSCORE-protected application request
sent individually as shown in Figure 1.
To this end, validated information to perform access control checks
(e.g., an access token issued by a trusted party) has to be available
at the server before starting to process the rebuilt OSCORE-protected
application request. Such information may have been provided to the
server separately before starting the EDHOC execution altogether, or
instead as External Authorization Data during the EDHOC execution
(see Section 3.8 of [I-D.ietf-lake-edhoc]).
Thus, a successful completion of the EDHOC protocol and the following
derivation of the OSCORE Security Context at the server do not play a
role in determining whether the rebuilt OSCORE-protected request is
authorized to access the target protected resource at the server.
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8. 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.
8.1. CoAP Option Numbers Registry
IANA is asked to enter the following option number to the "CoAP
Option Numbers" registry within the "CoRE Parameters" registry group.
+========+=======+============+
| Number | Name | Reference |
+========+=======+============+
| TBD21 | EDHOC | [RFC-XXXX] |
+--------+-------+------------+
Table 2: Registrations in
CoAP Option Numbers
Registry
Note to RFC Editor: Following the registration of the CoAP Option
Number 21, please replace "TBD21" with "21" in the table above.
Then, please delete this paragraph and all the following text within
the present Section 8.1.
[
The CoAP option number 21 is consistent with the properties of the
EDHOC Option defined in Section 3.1, and it allows the EDHOC Option
to always result in an overall size of 1 byte. This is because:
* The EDHOC option is always empty, i.e., with zero-length value;
and
* Since the OSCORE Option with option number 9 is always present in
the EDHOC + OSCORE request, the EDHOC Option is encoded with a
delta equal to at most 12.
Therefore, this document suggests 21 (TBD21) as option number to be
assigned to the new EDHOC Option. Although the currently unassigned
option number 13 would also work well for the same reasons in the use
case in question, different use cases or protocols may make a better
use of the option number 13. Hence the preference for the option
number 21, and why it is _not_ necessary to register additional
option numbers than 21.
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]
8.2. Target Attributes Registry
IANA is asked to register the following entries in the "Target
Attributes" registry within the "CoRE Parameters" registry group, as
per [I-D.ietf-core-target-attr]. For all entries, the Change
Controller is IESG, and the reference is [RFC-XXXX].
+=================+=============================================+
| Attribute Name: | Brief Description: |
+=================+=============================================+
| ed-i | Hint: support for the EDHOC Initiator role |
+-----------------+---------------------------------------------+
| ed-r | Hint: support for the EDHOC Responder role |
+-----------------+---------------------------------------------+
| ed-method | A supported authentication method for EDHOC |
+-----------------+---------------------------------------------+
| ed-csuite | A supported cipher suite for EDHOC |
+-----------------+---------------------------------------------+
| ed-cred-t | A supported type of authentication |
| | credential for EDHOC |
+-----------------+---------------------------------------------+
| ed-idcred-t | A supported type of authentication |
| | credential identifier for EDHOC |
+-----------------+---------------------------------------------+
| ed-ead | A supported External Authorization Data |
| | (EAD) item for EDHOC |
+-----------------+---------------------------------------------+
| ed-comb-req | Hint: support for the EDHOC+OSCORE request |
+-----------------+---------------------------------------------+
Table 3: Registrations in Target Attributes Registry
8.3. EDHOC Authentication Credential Types Registry
IANA is requested to create a new "EDHOC Authentication Credential
Types" registry within the "Ephemeral Diffie-Hellman Over COSE
(EDHOC)" registry group defined in [I-D.ietf-lake-edhoc].
The registry uses the "Expert Review" registration procedure
[RFC8126]. Expert Review guidelines are provided in Section 8.4.
The columns of this registry are:
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* Value: This field contains the value used to identify the type of
authentication credential. These values MUST be unique. The
value can be an unsigned integer or a negative integer. Different
ranges of values use different registration policies [RFC8126]:
- 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".
* Description: This field contains a short description of the type
of authentication credential.
* Reference: This field contains a pointer to the public
specification for the type of authentication credential.
Initial entries in this registry are as listed in Table 4.
+=======+=======================+===================================+
| Value | Description | Reference |
+=======+=======================+===================================+
| 0 | CBOR Web Token | [RFC8392] |
| | (CWT) containing | |
| | a COSE_Key in a | |
| | 'cnf' claim | |
+-------+-----------------------+-----------------------------------+
| 1 | CWT Claims Set | [RFC8392] |
| | (CCS) containing | |
| | a COSE_Key in a | |
| | 'cnf' claim | |
+-------+-----------------------+-----------------------------------+
| 2 | X.509 | [RFC5280] |
| | certificate | |
+-------+-----------------------+-----------------------------------+
| 3 | C509 certificate | [I-D.ietf-cose-cbor-encoded-cert] |
+-------+-----------------------+-----------------------------------+
Table 4: Initial Entries in the "EDHOC Authentication Credential
Types" Registry
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8.4. Expert Review Instructions
The IANA registry established in this document is defined as "Expert
Review". 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 registered identifiers indicate a
type of authentication credential whose format and encoding is
clearly defined in the corresponding specification. Identifiers
of types of authentication credentials that do not meet these
objective 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. The fact that there is a range for
Standards Track documents does not mean that a Standards Track
document cannot have points assigned outside of that 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.
9. References
9.1. Normative References
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[COSE.Header.Parameters]
IANA, "COSE Header Parameters",
<https://www.iana.org/assignments/cose/cose.xhtml#header-
parameters>.
[I-D.ietf-core-target-attr]
Bormann, C., "CoRE Target Attributes Registry", Work in
Progress, Internet-Draft, draft-ietf-core-target-attr-05,
23 July 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-core-target-attr-05>.
[I-D.ietf-lake-edhoc]
Selander, G., Mattsson, J. P., and F. Palombini,
"Ephemeral Diffie-Hellman Over COSE (EDHOC)", Work in
Progress, Internet-Draft, draft-ietf-lake-edhoc-20, 7 July
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
lake-edhoc-20>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/rfc/rfc6690>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/rfc/rfc7252>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/rfc/rfc7959>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
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[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/rfc/rfc8288>.
[RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
<https://www.rfc-editor.org/rfc/rfc8613>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[RFC9176] Amsüss, C., Ed., Shelby, Z., Koster, M., Bormann, C., and
P. van der Stok, "Constrained RESTful Environments (CoRE)
Resource Directory", RFC 9176, DOI 10.17487/RFC9176, April
2022, <https://www.rfc-editor.org/rfc/rfc9176>.
9.2. Informative References
[I-D.ietf-cose-cbor-encoded-cert]
Mattsson, J. P., Selander, G., Raza, S., Höglund, J., and
M. Furuhed, "CBOR Encoded X.509 Certificates (C509
Certificates)", Work in Progress, Internet-Draft, draft-
ietf-cose-cbor-encoded-cert-06, 7 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
cbor-encoded-cert-06>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.
Appendix A. Document Updates
This section is to be removed before publishing as an RFC.
A.1. Version -07 to -08
* Fixes and clarifications from the Shepherd's review.
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A.2. Version -06 to -07
* Changed document title.
* The client creates the OSCORE Security Context after creating
EDHOC message_3.
* Revised selection of EDHOC connection identifiers.
* Use of "forward message flow" and "reverse message flow".
* The payload of the combined request is not a CBOR sequence
anymore.
* EDHOC error messages from the server are not protected with
OSCORE.
* More future-proof error handling on the server side.
* Target attribute names prefixed by "ed-".
* Defined new target attributes "ed-i" and "ed-r".
* Defined single target attribute "ed-ead" signaling supported EAD
items.
* Security consideration on the minimally achieved 128-bit security.
* Defined and used the "EDHOC Authentication Credential Types"
Registry.
* High-level sentence replacing the appendix on Block-wise
performance.
* Revised examples.
* Editorial improvements.
A.3. Version -05 to -06
* Extended figure on EDHOC sequential workflow.
* Revised naming of target attributes.
* Clarified semantics of target attributes 'eadx'.
* Registration of target attributes.
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A.4. Version -04 to -05
* Clarifications on Web Linking parameters.
* Added security considerations.
* Revised IANA considerations to focus on the CoAP option number 21.
* Guidelines on using Block-wise moved to an appendix.
* Editorial improvements.
A.5. Version -03 to -04
* Renamed "applicability statement" to "application profile".
* Use the latest Content-Formats.
* Use of SHOULD NOT for multiple simultaneous outstanding
interactions.
* No more special conversion from OSCORE ID to EDHOC ID.
* Considerations on using Block-wise.
* Wed Linking signaling of multiple supported EAD labels.
* Added security considerations.
* Editorial improvements.
A.6. Version -02 to -03
* Clarifications on transporting EDHOC message_3 in the CoAP
payload.
* At most one simultaneous outstanding interaction as an EDHOC +
OSCORE request with the same server for the same session with
connection identifier C_R.
* The EDHOC option is removed from the EDHOC + OSCORE request after
processing the EDHOC data.
* Added explicit constraints when selecting a Recipient ID as C_X.
* Added processing steps for when Block-wise is used.
* Improved error handling on the server.
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* Improved section on Web Linking.
* Updated figures; editorial improvements.
A.7. Version -01 to -02
* New title, abstract and introduction.
* Restructured table of content.
* Alignment with latest format of EDHOC messages.
* Guideline on ID conversions based on application profile.
* Clarifications, extension and consistency on application profile.
* Section on web-linking.
* RFC8126 terminology in IANA considerations.
* Revised Appendix "Checking CBOR Encoding of Numeric Values".
A.8. Version -00 to -01
* Improved background overview of EDHOC.
* Added explicit rules for converting OSCORE Sender/Recipient IDs to
EDHOC connection identifiers following the removal of
bstr_identifier from EDHOC.
* Revised section organization.
* Recommended number for EDHOC option changed to 21.
* Editorial improvements.
Acknowledgments
The authors sincerely thank Christian Amsüss, Carsten Bormann, Esko
Dijk, Klaus Hartke, John Preuß Mattsson, David Navarro, Jim Schaad,
and Mališa Vučinić for their feedback and comments.
The work on this document has been partly supported by VINNOVA and
the Celtic-Next project CRITISEC; and by the H2020 project SIFIS-Home
(Grant agreement 952652).
Authors' Addresses
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Francesca Palombini
Ericsson
Email: francesca.palombini@ericsson.com
Marco Tiloca
RISE AB
Isafjordsgatan 22
SE-16440 Stockholm Kista
Sweden
Email: marco.tiloca@ri.se
Rikard Höglund
RISE AB
Isafjordsgatan 22
SE-16440 Stockholm Kista
Sweden
Email: rikard.hoglund@ri.se
Stefan Hristozov
Fraunhofer AISEC
Email: stefan.hristozov@eriptic.com
Göran Selander
Ericsson
Email: goran.selander@ericsson.com
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