Certificate Management over CMS (CMC): Compliance Requirements
RFC 10004
| Document | Type | RFC - Proposed Standard (July 2026) | |
|---|---|---|---|
| Authors | J. Mandel , S. Turner | ||
| Last updated | 2026-07-17 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| IESG | Responsible AD | Deb Cooley | |
| Send notices to | (None) |
RFC 10004
Internet Engineering Task Force (IETF) J. Mandel, Ed.
Request for Comments: 10004 AKAYLA, Inc.
Obsoletes: 5274, 6402 S. Turner, Ed.
Category: Standards Track sn3rd
ISSN: 2070-1721 July 2026
Certificate Management over CMS (CMC): Compliance Requirements
Abstract
This document provides a set of compliance statements about the
Certificate Management over CMS (CMC) enrollment protocol. The ASN.1
structures and the transport mechanisms for the CMC enrollment
protocol are covered in other documents (RFCs 10002 and 10003). This
document provides the information needed to make a compliant version
of CMC.
This document obsoletes RFCs 5274 and 6402.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc10004.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
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than English.
Table of Contents
1. Introduction
2. Terminology
3. Requirements Terminology
4. Changes Since RFCs 5274 and 6402
5. Requirements for All Entities
5.1. Cryptographic Algorithm Requirements
5.2. Controls
5.3. CRMF Feature Requirements
6. Requirements for Clients
7. Requirements for Servers
8. Requirements for EEs
9. Requirements for RAs
10. Requirements for CAs
11. Security Considerations
12. IANA Considerations
13. References
13.1. Normative References
13.2. Informative References
Acknowledgements
Contributors
Authors' Addresses
1. Introduction
The Certificate Management over CMS (CMC) protocol is designed in
terms of a client/server relationship. In the simplest case, the
client is the requestor of the certificate (i.e., the End-Entity
(EE)) and the server is the issuer of the certificate (i.e., the
Certification Authority (CA)). The introduction of a Registration
Authority (RA) into the set of agents complicates the picture only
slightly. The RA becomes the server with respect to the certificate
requestor, and it becomes the client with respect to the certificate
issuer. Any number of RAs can be inserted into the picture in this
manner.
The RAs may serve specialized purposes that are not currently covered
by this document. One such purpose would be a Key Escrow agent. As
such, all certificate requests for encryption keys would be directed
through this RA, and it would take appropriate action to do the key
archival. Key recovery requests could be defined in the CMC
methodology allowing for the Key Escrow agent to perform that
operation acting as the final server in the chain of agents.
If there are multiple RAs in the system, it is considered normal that
not all RAs will see all certificate requests. The routing between
the RAs may be dependent on the content of the certificate requests
involved.
This document is divided into six sections, each section specifying
the requirements that are specific to a class of agents in the CMC
model. These are 1) all entities, 2) all servers, 3) all clients, 4)
all EEs, 5) all RAs, and 6) all CAs.
This document obsoletes RFCs 5274 [CMC-COMPv1] and 6402
[CMC-Updates].
2. Terminology
There are several different terms, abbreviations, and acronyms used
in this document that we define here for convenience and consistency
of usage:
End-Entity (EE): Refers to the entity that owns a key pair and for
whom a certificate is issued.
Registration Authority (RA) or Local RA (LRA): Refers to an entity
that acts as an intermediary between the EE and the CA. Multiple
RAs can exist between the EE and the CA. RAs may perform
additional services such as key generation or key archival. This
document uses the term RA for both RA and LRA.
Certification Authority (CA): Refers to the entity that issues
certificates.
Client: Refers to an entity that creates a Public Key Infrastructure
(PKI) Request. In this document, both RAs and EEs can be clients.
Server: Refers to the entities that process PKI Requests and create
PKI Responses. In this document, both CAs and RAs can be servers.
PKCS #10: Refers to the Public Key Cryptography Standard #10
[PKCS10], which defines a certification request syntax.
CRMF: Refers to the Certificate Request Message Format [CRMF]. CMC
uses this certification request syntax defined in this document as
part of the protocol.
CMS: Refers to the Cryptographic Message Syntax [CMS]. This
document provides for basic cryptographic services including
encryption and signing with and without key management.
PKI Request/Response: Refers to the requests/responses described in
this document. PKI Requests include certification requests,
revocation requests, etc. PKI Responses include certs-only
messages, failure messages, etc.
Proof-of-Identity: Refers to the client proving they are who they
say that they are to the server.
Proof-of-Possession (POP): Refers to a value that can be used to
prove that the private key corresponding to a public key is in the
possession and can be used by an EE. See Section 2.1 of
[CMC-STRUCT].
Transport wrapper: Refers to the outermost CMS wrapping layer.
Entity: Refers to EE, RA (or LRA), or CA.
HMAC: Refers to the Hashed Message Authentication Code. CMC uses
the ASN.1 module defined in [HMAC-ALGS].
3. Requirements 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.
4. Changes Since RFCs 5274 and 6402
Merged [CMC-Updates] text.
Updated the Introduction, changed "all agents" to "all entities" in
the overview to maintain consistency throughout the document, and
renumbered the section headers.
Added RA Identity Proof Witness and Response Body controls to
Table 1.
Updated the Cryptographic Algorithm Requirements:
* Replaced SHA-1 with SHA-256
* Replaced HMAC-SHA-1 with HMAC-SHA-256
* Added algorithms for AuthEnvelopedData
Added a paragraph to maintain backward algorithm compatibility.
5. Requirements for All Entities
All [CMC-STRUCT] and [CMC-TRANS] compliance statements MUST be
adhered to unless specifically stated otherwise in this document.
All entities MUST support Full PKI Requests, Simple PKI Responses,
and Full PKI Responses. Servers SHOULD support Simple PKI Requests.
All entities MUST support the use of the CRMF syntax for
certification requests. Support for the PKCS #10 syntax for
certification requests SHOULD be implemented by servers.
The extendedFailInfo field SHOULD NOT be populated in the
CMCStatusInfoV2 object; the failInfo field SHOULD be used to relay
this information. If the extendedFailInfo field is used, it is
suggested that an additional CMCStatusInfoV2 item exist for the same
body part with a failInfo field.
All entities MUST implement the HTTP transport mechanism as defined
in [CMC-TRANS]. Other transport mechanisms MAY be implemented.
5.1. Cryptographic Algorithm Requirements
All entities MUST verify RSA-SHA256 signatures in SignedData; (see
[CMS-ALG2]). Entities MAY verify other signature algorithms.
All entities MUST generate RSA-SHA256 signatures for SignedData; (see
[CMS-ALG2]). Other signature algorithms MAY be used for generation.
All entities MUST support Advanced Encryption Standard (AES) as the
content encryption algorithm for EnvelopedData; (see [CMS-AES]).
Other content encryption algorithms MAY be implemented.
All entities MUST support AES-GCM (Galois/Counter Mode) as the
authenticated content encryption algorithm for AuthEnvelopedData;
(see [CMS-AES-AE]). They MUST also support a 12-octet nonce size and
a 12-octet Integrity Check Value (ICV) length. Other content
encryption algorithms MAY be implemented.
All entities MUST support RSA as a key transport algorithm for
EnvelopedData and AuthEnvelopedData; see [CMS-ALG2]. Other key
transport algorithms MAY be implemented.
If an entity supports key agreement for EnvelopedData or
AuthEnvelopedData, it MUST support Diffie-Hellman (DH); (see
[CMS-DH]).
If an entity supports PasswordRecipientInfo for EnvelopedData,
AuthenticatedData, or AuthEnvelopedData, it MUST support Password-
Based Key Derivation Function 2 (PBKDF2) [PBKDF2] for key derivation
algorithms. It MUST support AES key wrap (see [AES-WRAP]) as the key
encryption algorithm.
If AuthenticatedData is supported, PasswordRecipientInfo MUST be
supported.
Algorithm requirements for the Identity Proof Version 2 control
(Section 6.2.1 of [CMC-STRUCT]) are as follows:
* SHA-256 MUST be implemented for hashAlgId.
* HMAC-SHA256 MUST be implemented for macAlgId.
Algorithm requirements for the Pop Link Witness Version 2 control
(Section 6.3.1.1 of [CMC-STRUCT]) are as follows:
* SHA-256 MUST be implemented for keyGenAlgorithm.
* PBKDF2 [PBKDF2] MAY be implemented for keyGenAlgorithm.
* HMAC-SHA256 MUST be implemented for macAlgorithm.
Algorithm requirements for the Encrypted POP and Decrypted POP
controls (Section 6.7 of [CMC-STRUCT]) are as follows:
* SHA-256 MUST be implemented for witnessAlgID.
* HMAC-SHA256 MUST be implemented for thePOPAlgID.
Algorithm requirements for Publish Trust Anchors control
(Section 6.15 of [CMC-STRUCT]) are as follows:
* SHA-256 MUST be implemented for hashAlgorithm.
If an EE generates DH keys for certification, it MUST support
Section 4 of [DH-POP]. EEs MAY support Section 3 of [DH-POP]. CAs
and RAs that do POP verification MUST support Section 4 of [DH-POP]
and SHOULD support Section 3 of [DH-POP].
EEs that need to use a signature algorithm for keys that cannot
produce a signature MUST support Appendix C of [CMC-STRUCT] and MUST
support the Encrypted/Decrypted POP controls. CAs and RAs that do
POP verification MUST support this signature algorithm and MUST
support the Encrypted/Decrypted POP controls.
For backward compatibility with the previous version of CMC, servers
MAY offer the algorithms specified therein, but SHOULD use the CMC
requests to identify which certificates should be transitioned to
more secure algorithms, if possible.
5.2. Controls
The following table lists the name and level of support required for
each control.
+============================+==========+==========+==========+
| Control | EE | RA | CA |
+============================+==========+==========+==========+
| Extended CMC Status Info | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| CMC Status Info | SHOULD | SHOULD | SHOULD |
+----------------------------+----------+----------+----------+
| Identity Proof Version 2 | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Identity Proof | SHOULD | SHOULD | SHOULD |
+----------------------------+----------+----------+----------+
| Identification | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| POP Link Random | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| POP Link Witness Version 2 | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| POP Link Witness | SHOULD | MUST | MUST |
+----------------------------+----------+----------+----------+
| Data Return | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Modify Cert Request | N/A | MUST | (2) |
+----------------------------+----------+----------+----------+
| Add Extensions | N/A | MAY | (1) |
+----------------------------+----------+----------+----------+
| Transaction ID | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Sender Nonce | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Recipient Nonce | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Encrypted POP | (4) | (5) | SHOULD |
+----------------------------+----------+----------+----------+
| Decrypted POP | (4) | (5) | SHOULD |
+----------------------------+----------+----------+----------+
| RA POP Witness | N/A | SHOULD | (1) |
+----------------------------+----------+----------+----------+
| Get Certificate | OPTIONAL | OPTIONAL | OPTIONAL |
+----------------------------+----------+----------+----------+
| Get CRL | OPTIONAL | OPTIONAL | OPTIONAL |
+----------------------------+----------+----------+----------+
| Revocation Request | SHOULD | SHOULD | MUST |
+----------------------------+----------+----------+----------+
| Registration Info | SHOULD | SHOULD | SHOULD |
+----------------------------+----------+----------+----------+
| Response Information | SHOULD | SHOULD | SHOULD |
+----------------------------+----------+----------+----------+
| Query Pending | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Confirm Cert. Acceptance | MUST | MUST | MUST |
+----------------------------+----------+----------+----------+
| Publish Trust Anchors | (3) | (3) | (3) |
+----------------------------+----------+----------+----------+
| Authenticated Data | (3) | (3) | (3) |
+----------------------------+----------+----------+----------+
| Batch Request | N/A | MUST | (2) |
+----------------------------+----------+----------+----------+
| Batch Responses | N/A | MUST | (2) |
+----------------------------+----------+----------+----------+
| Publication Information | OPTIONAL | OPTIONAL | OPTIONAL |
+----------------------------+----------+----------+----------+
| Control Processed | N/A | MUST | (2) |
+----------------------------+----------+----------+----------+
| RA Identity Proof Witness | N/A | MUST | (2) |
+----------------------------+----------+----------+----------+
| Response Body | (6) | (6) | N/A |
+----------------------------+----------+----------+----------+
Table 1: CMC Control Attributes
Notes:
1. CAs SHOULD implement this control if designed to work with RAs.
2. CAs MUST implement this control if designed to work with RAs.
3. Implementation is OPTIONAL for these controls. We strongly
suggest that they be implemented in order to populate client
trust anchors.
4. EEs only need to implement this if (a) they support key agreement
algorithms or (b) they need to operate in environments where the
hardware keys cannot provide POP.
5. RAs SHOULD implement this if they implement RA POP Witness.
6. EEs SHOULD implement this if designed to work with RAs and MUST
implement if intended to be used in environments where RAs are
used for identity validation or key generation. RAs SHOULD
implement and validate responses for consistency.
Strong consideration should be given to implementing the
Authenticated Data and Publish Trust Anchors controls as this gives a
simple method for distributing trust anchors to clients without user
intervention.
5.3. CRMF Feature Requirements
The following additional restrictions are placed on CRMF features:
* The registration control tokens id-regCtrl-regToken and id-
regCtrl-authToken MUST NOT be used. No specific CMC feature is
used to replace these items, but generally the CMC control's
identification and identityProof will perform the same service and
are more specifically defined.
* The control token id-regCtrl-pkiArchiveOptions SHOULD NOT be
supported. See Section 3.2.1.3.3 of [CMC-STRUCT] and
Section 3.2.1.3.3 of [CMC-STRUCT] for alternative methods.
* The behavior of id-regCtrl-oldCertID is not presently used. It is
replaced by issuing the new certificate and using the id-cmc-
publishCert to remove the old certificate from publication. This
operation would not normally be accompanied by an immediate
revocation of the old certificate; however, that can be
accomplished by the id-cmc-revokeRequest control.
* The id-regCtrl-protocolEncrKey is not used.
6. Requirements for Clients
There are no additional requirements.
7. Requirements for Servers
There are no additional requirements.
8. Requirements for EEs
If an EE implements Diffie-Hellman, it MUST implement either the DH
POP Proof-of-Possession as defined in Section 4 of [DH-POP] or the
challenge-response POP controls id-cmc-encryptedPOP and id-cmc-
decryptedPOP.
9. Requirements for RAs
RAs SHOULD be able to do delegated POP. RAs implementing this
feature MUST implement the id-cmc-lraPOPWitness control.
All RAs MUST implement the promotion of the id-aa-cmc-unsignedData as
covered in Section 3.2.3 of [CMC-STRUCT].
10. Requirements for CAs
Providing for CAs to work in an environment with RAs is strongly
suggested. Implementation of such support is strongly suggested as
this permits the delegation of substantial administrative interaction
onto an RA rather than at the CA.
CAs MUST perform at least minimal checks on all public keys before
issuing a certificate. At a minimum, a check for syntax would occur
with the POP operation. Additionally, CAs SHOULD perform simple
checks for known bad keys such as small subgroups for DSA-SHA1 and DH
keys [SMALL-SUB-GROUP] or known bad exponents for RSA keys.
CAs MUST enforce POP checking before issuing any certificate. CAs
MAY delegate the POP operation to an RA for those cases where:
1. a challenge/response message pair must be used,
2. an RA performs escrow of a key and checks for POP in that manner,
or
3. an unusual algorithm is used and that validation is done at the
RA.
CAs SHOULD implement both the DH-POP Proof-of-Possession as defined
in Section 4 of [DH-POP] and the challenge-response POP controls id-
cmc-encryptedPOP and id-cmc-decryptedPOP.
11. Security Considerations
This document uses [CMC-STRUCT] and [CMC-TRANS] as building blocks.
The security sections of those two documents are included by
reference.
Knowledge of how an entity is expected to operate is vital in
determining which sections of requirements are applicable to that
entity. Care needs to be taken in determining which sections apply
and fully implementing the necessary code.
Cryptographic algorithms have and will be broken or weakened.
Implementers and users need to check that the cryptographic
algorithms listed in this document make sense from a security level.
The IETF from time to time may issue documents dealing with the
current state of the art. Two examples of such documents are
[SMALL-SUB-GROUP] and [HASH-ATTACKS].
12. IANA Considerations
This document has no IANA actions.
13. References
13.1. Normative References
[AES-WRAP] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
October 2002, <https://www.rfc-editor.org/info/rfc3394>.
[CMC-STRUCT]
Mandel, J., Ed. and S. Turner, Ed., "Certificate
Management over CMS (CMC)", RFC 10002,
DOI 10.17487/RFC10002, July 2026,
<https://www.rfc-editor.org/info/rfc10002>.
[CMC-TRANS]
Mandel, J., Ed. and S. Turner, Ed., "Certificate
Management over CMS (CMC): Transport Protocols",
RFC 10003, DOI 10.17487/RFC10003, July 2026,
<https://www.rfc-editor.org/info/rfc10003>.
[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[CMS-AES] Schaad, J., "Use of the Advanced Encryption Standard (AES)
Encryption Algorithm in Cryptographic Message Syntax
(CMS)", RFC 3565, DOI 10.17487/RFC3565, July 2003,
<https://www.rfc-editor.org/info/rfc3565>.
[CMS-AES-AE]
Housley, R., "Using AES-CCM and AES-GCM Authenticated
Encryption in the Cryptographic Message Syntax (CMS)",
RFC 5084, DOI 10.17487/RFC5084, November 2007,
<https://www.rfc-editor.org/info/rfc5084>.
[CMS-ALG2] Turner, S., "Using SHA2 Algorithms with Cryptographic
Message Syntax", RFC 5754, DOI 10.17487/RFC5754, January
2010, <https://www.rfc-editor.org/info/rfc5754>.
[CMS-DH] Rescorla, E., "Diffie-Hellman Key Agreement Method",
RFC 2631, DOI 10.17487/RFC2631, June 1999,
<https://www.rfc-editor.org/info/rfc2631>.
[CRMF] Schaad, J., "Internet X.509 Public Key Infrastructure
Certificate Request Message Format (CRMF)", RFC 4211,
DOI 10.17487/RFC4211, September 2005,
<https://www.rfc-editor.org/info/rfc4211>.
[DH-POP] Schaad, J. and H. Prafullchandra, "Diffie-Hellman Proof-
of-Possession Algorithms", RFC 6955, DOI 10.17487/RFC6955,
May 2013, <https://www.rfc-editor.org/info/rfc6955>.
[HMAC-ALGS]
Schaad, J. and S. Turner, "Additional New ASN.1 Modules
for the Cryptographic Message Syntax (CMS) and the Public
Key Infrastructure Using X.509 (PKIX)", RFC 6268,
DOI 10.17487/RFC6268, July 2011,
<https://www.rfc-editor.org/info/rfc6268>.
[PBKDF2] Kario, A., "Use of Password-Based Message Authentication
Code 1 (PBMAC1) in PKCS #12 Syntax", RFC 9879,
DOI 10.17487/RFC9879, September 2025,
<https://www.rfc-editor.org/info/rfc9879>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
13.2. Informative References
[CMC-COMPv1]
Schaad, J. and M. Myers, "Certificate Management Messages
over CMS (CMC): Compliance Requirements", RFC 5274,
DOI 10.17487/RFC5274, June 2008,
<https://www.rfc-editor.org/info/rfc5274>.
[CMC-Updates]
Schaad, J., "Certificate Management over CMS (CMC)
Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
<https://www.rfc-editor.org/info/rfc6402>.
[HASH-ATTACKS]
Hoffman, P. and B. Schneier, "Attacks on Cryptographic
Hashes in Internet Protocols", RFC 4270,
DOI 10.17487/RFC4270, December 2005,
<https://www.rfc-editor.org/info/rfc4270>.
[PKCS10] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986,
DOI 10.17487/RFC2986, November 2000,
<https://www.rfc-editor.org/info/rfc2986>.
[SMALL-SUB-GROUP]
Zuccherato, R., "Methods for Avoiding the "Small-Subgroup"
Attacks on the Diffie-Hellman Key Agreement Method for S/
MIME", RFC 2785, DOI 10.17487/RFC2785, March 2000,
<https://www.rfc-editor.org/info/rfc2785>.
Acknowledgements
Obviously, the authors would like to thank Jim Schaad and Michael
Myers for their work on [CMC-COMPv1].
Thank you to Mike Bishop, Mohamed Boucadair, and Erik Kline for
reviewing the document and providing comments.
The Acknowledgments section from RFC 5274 follows:
| The authors and the PKIX Working Group are grateful for the
| participation of Xiaoyi Liu and Jeff Weinstein in helping to
| author the original versions of this document.
|
| The authors would like to thank Brian LaMacchia for his work in
| developing and writing up many of the concepts presented in this
| document. The authors would also like to thank Alex Deacon and
| Barb Fox for their contributions.
Contributors
Jim Schaad
August Cellars
Michael Myers
TraceRoute Security, Inc.
Authors' Addresses
Joseph Mandel (editor)
AKAYLA, Inc.
Email: joe@akayla.com
Sean Turner (editor)
sn3rd
Email: sean@sn3rd.com