path: root/doc/rfc/rfc8756.txt

Independent Submission                                        M. Jenkins
Request for Comments: 8756                                    L. Zieglar
Category: Informational                                              NSA
ISSN: 2070-1721                                               March 2020


     Commercial National Security Algorithm (CNSA) Suite Profile of
                    Certificate Management over CMS

Abstract

   This document specifies a profile of the Certificate Management over
   CMS (CMC) protocol for managing X.509 public key certificates in
   applications that use the Commercial National Security Algorithm
   (CNSA) Suite published by the United States Government.

   The profile applies to the capabilities, configuration, and operation
   of all components of US National Security Systems that manage X.509
   public key certificates over CMS.  It is also appropriate for all
   other US Government systems that process high-value information.

   The profile is made publicly available here for use by developers and
   operators of these and any other system deployments.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not candidates for any level of Internet Standard;
   see 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/rfc8756.

Copyright Notice

   Copyright (c) 2020 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.

Table of Contents

   1.  Introduction
     1.1.  Terminology
   2.  The Commercial National Security Algorithm Suite
   3.  Requirements and Assumptions
   4.  Client Requirements: Generating PKI Requests
     4.1.  Tagged Certification Request
     4.2.  Certificate Request Message
   5.  RA Requirements
     5.1.  RA Processing of Requests
     5.2.  RA-Generated PKI Requests
     5.3.  RA-Generated PKI Responses
   6.  CA Requirements
     6.1.  CA Processing of PKI Requests
     6.2.  CA-Generated PKI Responses
   7.  Client Requirements: Processing PKI Responses
   8.  Shared-Secrets
   9.  Security Considerations
   10. IANA Considerations
   11. References
     11.1.  Normative References
     11.2.  Informative References
   Appendix A.  Scenarios
     A.1.  Initial Enrollment
     A.2.  Rekey
   Authors' Addresses

1.  Introduction

   This document specifies a profile of the Certificate Management over
   CMS (CMC) protocol to comply with the United States National Security
   Agency's Commercial National Security Algorithm (CNSA) Suite [CNSA].
   The profile applies to the capabilities, configuration, and operation
   of all components of US National Security Systems [SP80059].  It is
   also appropriate for all other US Government systems that process
   high-value information.  It is made publicly available for use by
   developers and operators of these and any other system deployments.

   This document does not define any new cryptographic algorithm suites;
   instead, it defines a CNSA-compliant profile of CMC.  CMC is defined
   in [RFC5272], [RFC5273], and [RFC5274] and is updated by [RFC6402].
   This document profiles CMC to manage X.509 public key certificates in
   compliance with the CNSA Suite Certificate and Certificate Revocation
   List (CRL) profile [RFC8603].  This document specifically focuses on
   defining CMC interactions for both the initial enrollment and rekey
   of CNSA Suite public key certificates between a client and a
   Certification Authority (CA).  One or more Registration Authorities
   (RAs) may act as intermediaries between the client and the CA.  This
   profile may be further tailored by specific communities to meet their
   needs.  Specific communities will also define certificate policies
   that implementations need to comply with.

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 terminology in [RFC5272], Section 2.1 applies to this profile.

   The term "certificate request" is used to refer to a single PKCS #10
   or Certificate Request Message Format (CRMF) structure.  All PKI
   Requests are Full PKI Requests, and all PKI Responses are Full PKI
   Responses; the respective set of terms should be interpreted
   synonymously in this document.

2.  The Commercial National Security Algorithm Suite

   The National Security Agency (NSA) profiles commercial cryptographic
   algorithms and protocols as part of its mission to support secure,
   interoperable communications for US Government National Security
   Systems.  To this end, it publishes guidance both to assist with the
   US Government transition to new algorithms and to provide vendors --
   and the Internet community in general -- with information concerning
   their proper use and configuration within the scope of US Government
   National Security Systems.

   Recently, cryptographic transition plans have become overshadowed by
   the prospect of the development of a cryptographically relevant
   quantum computer.  The NSA has established the Commercial National
   Security Algorithm (CNSA) Suite to provide vendors and IT users near-
   term flexibility in meeting their cybersecurity interoperability
   requirements.  The purpose behind this flexibility is to avoid having
   vendors and customers make two major transitions in a relatively
   short timeframe, as we anticipate a need to shift to quantum-
   resistant cryptography in the near future.

   The NSA is authoring a set of RFCs, including this one, to provide
   updated guidance concerning the use of certain commonly available
   commercial algorithms in IETF protocols.  These RFCs can be used in
   conjunction with other RFCs and cryptographic guidance (e.g., NIST
   Special Publications) to properly protect Internet traffic and data-
   at-rest for US Government National Security Systems.

3.  Requirements and Assumptions

   Elliptic Curve Digital Signature Algorithm (ECDSA) and Elliptic Curve
   Diffie-Hellman (ECDH) key pairs are on the P-384 curve.  FIPS 186-4
   [FIPS186], Appendix B.4 provides useful guidance for elliptic curve
   key pair generation that SHOULD be followed by systems that conform
   to this document.

   RSA key pairs (public, private) are identified by the modulus size
   expressed in bits; RSA-3072 and RSA-4096 are computed using moduli of
   3072 bits and 4096 bits, respectively.

   RSA signature key pairs used in CNSA Suite-compliant implementations
   are either RSA-3072 or RSA-4096.  The RSA exponent e MUST satisfy
   2^(16) < e < 2^(256) and be odd per [FIPS186].

   It is recognized that, while the vast majority of RSA signatures are
   currently made using the RSASSA-PKCS1-v1_5 algorithm, the preferred
   RSA signature scheme for new applications is RSASSA-PSS.  CNSA Suite-
   compliant X.509 certificates will be issued in accordance with
   [RFC8603], and while those certificates must be signed and validated
   using RSASSA-PKCS1-v1_5, the subject's private key can be used to
   generate signatures of either signing scheme.  Where use of RSASSA-
   PSS is indicated in this document, the following parameters apply:

   *  The hash algorithm MUST be id-sha384 as defined in [RFC8017];

   *  The mask generation function MUST use the algorithm identifier
      mfg1SHA384Identifier as defined in [RFC4055];

   *  The salt length MUST be 48 octets; and

   *  The trailerField MUST have value 1.

   These parameters will not appear in a certificate and MUST be
   securely communicated with the signature, as required by Section 2.2
   of [RFC4056].  Application developers are obliged to ensure that the
   chosen signature scheme is appropriate for the application and will
   be interoperable within the intended operating scope of the
   application.

   This document assumes that the required trust anchors have been
   securely provisioned to the client and, when applicable, to any RAs.

   All requirements in [RFC5272], [RFC5273], [RFC5274], and [RFC6402]
   apply, except where overridden by this profile.

   This profile was developed with the scenarios described in Appendix A
   in mind.  However, use of this profile is not limited to just those
   scenarios.

   The term "client" in this profile typically refers to an end-entity.
   However, it may instead refer to a third party acting on the end-
   entity's behalf.  The client may or may not be the entity that
   actually generates the key pair, but it does perform the CMC protocol
   interactions with the RA and/or CA.  For example, the client may be a
   token management system that communicates with a cryptographic token
   through an out-of-band secure protocol.

   This profile uses the term "rekey" in the same manner as CMC does
   (defined in Section 2 of [RFC5272]).  The profile makes no specific
   statements about the ability to do "renewal" operations; however, the
   statements applicable to "rekey" should be applied to "renewal" as
   well.

   This profile may be used to manage RA and/or CA certificates.  In
   that case, the RA and/or CA whose certificate is being managed is
   considered to be the end-entity.

   This profile does not discuss key establishment certification
   requests from cryptographic modules that cannot generate a one-time
   signature with a key establishment key for proof-of-possession
   purposes.  In that case, a separate profile would be needed to define
   the use of another proof-of-possession technique.

4.  Client Requirements: Generating PKI Requests

   This section specifies the conventions employed when a client
   requests a certificate from a Public Key Infrastructure (PKI).

   The Full PKI Request MUST be used; it MUST be encapsulated in a
   SignedData; and the SignedData MUST be constructed in accordance with
   [RFC8755].  The PKIData content type defined in [RFC5272] is used
   with the following additional requirements:

   *  controlSequence SHOULD be present.

      -  TransactionId and SenderNonce SHOULD be included.  Other CMC
         controls MAY be included.

      -  If the request is being authenticated using a shared-secret,
         then Identity Proof Version 2 control MUST be included with the
         following constraints:

         o  hashAlgId MUST be id-sha384 for all certification requests
            (algorithm OIDs are defined in [RFC5754]).

         o  macAlgId MUST be HMAC-SHA384 (the Hashed Message
            Authentication Code (HMAC) algorithm is defined in
            [RFC4231]).

      -  If the subject name included in the certification request is
         NULL or otherwise does not uniquely identify the end-entity,
         then the POP Link Random control MUST be included, and the POP
         Link Witness Version 2 control MUST be included in the inner
         PKCS #10 [RFC2986] or Certificate Request Message Format (CRMF)
         [RFC4211] request as described in Sections 4.1 and 4.2.

   *  reqSequence MUST be present.  It MUST include at least one tcr
      (see Section 4.1) or crm (see Section 4.2) TaggedRequest.  Support
      for the orm choice is OPTIONAL.

   The private signing key used to generate the encapsulating SignedData
   MUST correspond to the public key of an existing signature
   certificate unless an appropriate signature certificate does not yet
   exist, such as during initial enrollment.

   The encapsulating SignedData MUST be generated using SHA-384 and
   either ECDSA on P-384 or RSA using either RSASSA-PKCS1-v1_5 or
   RSASSA-PSS with an RSA-3072 or RSA-4096 key.

   If an appropriate signature certificate does not yet exist and if a
   Full PKI Request includes one or more certification requests and is
   authenticated using a shared-secret (because no appropriate
   certificate exists yet to authenticate the request), the Full PKI
   Request MUST be signed using the private key corresponding to the
   public key of one of the requested certificates.  When necessary
   (i.e., because there is no existing signature certificate and there
   is no signature certification request included), a Full PKI Request
   MAY be signed using a key pair intended for use in a key
   establishment certificate.  However, servers are not required to
   allow this behavior.

4.1.  Tagged Certification Request

   The reqSequence tcr choice conveys PKCS #10 [RFC2986] syntax.  The
   CertificateRequest MUST comply with [RFC5272], Section 3.2.1.2.1,
   with the following additional requirements:

   *  certificationRequestInfo:

      -  subjectPublicKeyInfo MUST be set as defined in Section 5.4 of
         [RFC8603].

      -  Attributes:

         o  The ExtensionReq attribute MUST be included with its
            contents as follows:

            +  The keyUsage extension MUST be included, and it MUST be
               set as defined in [RFC8603].

            +  For rekey requests, the SubjectAltName extension MUST be
               included and set equal to the SubjectAltName of the
               certificate that is being used to sign the SignedData
               encapsulating the request (i.e., not the certificate
               being rekeyed) if the subject field of the certificate
               being used to generate the signature is NULL.

            +  Other extension requests MAY be included as desired.

         o  The ChangeSubjectName attribute, as defined in [RFC6402],
            MUST be included if the Full PKI Request encapsulating this
            Tagged Certification Request is being signed by a key for
            which a certificate currently exists and the existing
            certificate's subject field or SubjectAltName extension does
            not match the desired subject name or SubjectAltName
            extension of this certification request.

         o  The POP Link Witness Version 2 attribute MUST be included if
            the request is being authenticated using a shared-secret and
            the subject name in the certification request is NULL or
            otherwise does not uniquely identify the end-entity.  In the
            POP Link Witness Version 2 attribute, keyGenAlgorithm MUST
            be id-sha384 for certification requests, as defined in
            [RFC5754]; macAlgorithm MUST be HMAC-SHA384, as defined in
            [RFC4231].

      -  signatureAlgorithm MUST be ecdsa-with-sha384 for P-384
         certification requests and sha384WithRSAEncryption or id-
         RSASSA-PSS for RSA-3072 and RSA-4096 certification requests.

      -  signature MUST be generated using the private key corresponding
         to the public key in the CertificationRequestInfo for both
         signature and key establishment certification requests.  The
         signature provides proof-of-possession of the private key to
         the CA.

4.2.  Certificate Request Message

   The reqSequence crm choice conveys Certificate Request Message Format
   (CRMF) [RFC4211] syntax.  The CertReqMsg MUST comply with [RFC5272],
   Section 3.2.1.2.2, with the following additional requirements:

   *  popo MUST be included using the signature (POPOSigningKey) proof-
      of-possession choice and be set as defined in [RFC4211],
      Section 4.1 for both signature and key establishment certification
      requests.  The POPOSigningKey poposkInput field MUST be omitted.
      The POPOSigningKey algorithmIdentifier MUST be ecdsa-with-sha384
      for P-384 certification requests and sha384WithRSAEncryption or
      id-RSASSA-PSS for RSA-3072 and RSA-4096 certification requests.
      The signature MUST be generated using the private key
      corresponding to the public key in the CertTemplate.

   The CertTemplate MUST comply with [RFC5272], Section 3.2.1.2.2, with
   the following additional requirements:

   *  If version is included, it MUST be set to 2 as defined in
      Section 5.3 of [RFC8603].

   *  publicKey MUST be set as defined in Section 5.4 of [RFC8603].

   *  Extensions:

      -  The keyUsage extension MUST be included, and it MUST be set as
         defined in [RFC8603].

      -  For rekey requests, the SubjectAltName extension MUST be
         included and set equal to the SubjectAltName of the certificate
         that is being used to sign the SignedData encapsulating the
         request (i.e., not the certificate being rekeyed) if the
         subject name of the certificate being used to generate the
         signature is NULL.

      -  Other extension requests MAY be included as desired.

   *  Controls:

      -  The ChangeSubjectName attribute, as defined in [RFC6402], MUST
         be included if the Full PKI Request encapsulating this Tagged
         Certification Request is being signed by a key for which a
         certificate currently exists and the existing certificate's
         subject name or SubjectAltName extension does not match the
         desired subject name or SubjectAltName extension of this
         certification request.

      -  The POP Link Witness Version 2 attribute MUST be included if
         the request is being authenticated using a shared-secret and
         the subject name in the certification request is NULL or
         otherwise does not uniquely identify the end-entity.  In the
         POP Link Witness Version 2 attribute, keyGenAlgorithm MUST be
         id-sha384 for certification requests; macAlgorithm MUST be
         HMAC-SHA384 when keyGenAlgorithm is id-sha384.

5.  RA Requirements

   This section addresses the optional case where one or more RAs act as
   intermediaries between clients and a CA as described in Section 7 of
   [RFC5272].  In this section, the term "client" refers to the entity
   from which the RA received the PKI Request.  This section is only
   applicable to RAs.

5.1.  RA Processing of Requests

   RAs conforming to this document MUST ensure that only the permitted
   signature, hash, and MAC algorithms described throughout this profile
   are used in requests; if they are not, the RA MUST reject those
   requests.  The RA SHOULD return a CMCFailInfo with the value of
   badAlg [RFC5272].

   When processing end-entity-generated SignedData objects, RAs MUST NOT
   perform Cryptographic Message Syntax (CMS) Content Constraints (CCC)
   certificate extension processing [RFC6010].

   Other RA processing is performed as described in [RFC5272].

5.2.  RA-Generated PKI Requests

   RAs mediate the certificate request process by collecting client
   requests in batches.  The RA MUST encapsulate client-generated PKI
   Requests in a new RA-signed PKI Request, it MUST create a Full PKI
   Request encapsulated in a SignedData, and the SignedData MUST be
   constructed in accordance with [RFC8755].  The PKIData content type
   complies with [RFC5272] with the following additional requirements:

   *  controlSequence MUST be present.  It MUST include the following
      CMC controls: Transaction ID, Sender Nonce, and Batch Requests.
      Other appropriate CMC controls MAY be included.

   *  cmsSequence MUST be present.  It contains the original, unmodified
      request(s) received from the client.

         SignedData (applied by the RA)
           PKIData
             controlSequence (Transaction ID, Sender Nonce,
                                                  Batch Requests)
             cmsSequence
               SignedData (applied by client)
                 PKIData
                   controlSequence (Transaction ID, Sender Nonce)
                   reqSequence
                     TaggedRequest
                     {TaggedRequest}
               {SignedData     (second client request)
                 PKIData...}

   Authorization to sign RA-generated Full PKI Requests SHOULD be
   indicated in the RA certificate by inclusion of the id-kp-cmcRA
   Extended Key Usage (EKU) from [RFC6402].  The RA certificate MAY also
   include the CCC certificate extension [RFC6010], or it MAY indicate
   authorization through inclusion of the CCC certificate extension
   alone.  The RA certificate may also be authorized through the local
   configuration.

   If the RA is authorized via the CCC extension, then the CCC extension
   MUST include the object identifier for the PKIData content type.  CCC
   SHOULD be included if constraints are to be placed on the content
   types generated.

   The outer SignedData MUST be generated using SHA-384 and either ECDSA
   on P-384 or RSA using RSASSA-PKCS1-v1_5 or RSASSA-PSS with an
   RSA-3072 or RSA-4096 key.

   If the Full PKI Response is a successful response to a PKI Request
   that only contained a Get Certificate or Get CRL control, then the
   algorithm used in the response MUST match the algorithm used in the
   request.

5.3.  RA-Generated PKI Responses

   In order for an RA certificate using the CCC certificate extension to
   be authorized to generate responses, the object identifier for the
   PKIResponse content type must be present in the CCC certificate
   extension.

6.  CA Requirements

   This section specifies the requirements for CAs that receive PKI
   Requests and generate PKI Responses.

6.1.  CA Processing of PKI Requests

   CAs conforming to this document MUST ensure that only the permitted
   signature, hash, and MAC algorithms described throughout this profile
   are used in requests; if they are not, the CA MUST reject those
   requests.  The CA SHOULD return a CMCStatusInfoV2 control with a
   CMCStatus of failed and a CMCFailInfo with the value of badAlg
   [RFC5272].

   For requests involving an RA (i.e., batched requests), the CA MUST
   verify the RA's authorization.  The following certificate fields MUST
   NOT be modifiable using the Modify Certification Request control:
   publicKey and the keyUsage extension.  The request MUST be rejected
   if an attempt to modify those certification request fields is
   present.  The CA SHOULD return a CMCStatusInfoV2 control with a
   CMCStatus of failed and a CMCFailInfo with a value of badRequest.

   When processing end-entity-generated SignedData objects, CAs MUST NOT
   perform CCC certificate extension processing [RFC6010].

   If a client-generated PKI Request includes the ChangeSubjectName
   attribute as described in Section 4.1 or 4.2 above, the CA MUST
   ensure that name change is authorized.  The mechanism for ensuring
   that the name change is authorized is out of scope.  A CA that
   performs this check and finds that the name change is not authorized
   MUST reject the PKI Request.  The CA SHOULD return an Extended CMC
   Status Info control (CMCStatusInfoV2) with a CMCStatus of failed.

   Other processing of PKIRequests is performed as described in
   [RFC5272].

6.2.  CA-Generated PKI Responses

   CAs send PKI Responses to both client-generated requests and RA-
   generated requests.  If a Full PKI Response is returned in direct
   response to a client-generated request, it MUST be encapsulated in a
   SignedData, and the SignedData MUST be constructed in accordance with
   [RFC8755].

   If the PKI Response is in response to an RA-generated PKI Request,
   then the above PKI Response is encapsulated in another CA-generated
   PKI Response.  That PKI Response MUST be encapsulated in a
   SignedData, and the SignedData MUST be constructed in accordance with
   [RFC8755].  The above PKI Response is placed in the encapsulating PKI
   Response cmsSequence field.  The other fields are as above with the
   addition of the batch response control in controlSequence.  The
   following illustrates a successful CA response to an RA-encapsulated
   PKI Request, both of which include Transaction IDs and Nonces:

         SignedData (applied by the CA)
           PKIResponse
             controlSequence (Transaction ID, Sender Nonce, Recipient
                              Nonce, Batch Response)
             cmsSequence
               SignedData (applied by CA and includes returned
                           certificates)
                 PKIResponse
                   controlSequence (Transaction ID, Sender Nonce,
                                    Recipient Nonce)

   The same private key used to sign certificates MUST NOT be used to
   sign Full PKI Response messages.  Instead, a separate certificate
   indicating authorization to sign CMC responses MUST be used.

   Authorization to sign Full PKI Responses SHOULD be indicated in the
   CA certificate by inclusion of the id-kp-cmcCA EKU from [RFC6402].
   The CA certificate MAY also include the CCC certificate extension
   [RFC6010], or it MAY indicate authorization through inclusion of the
   CCC certificate extension alone.  The CA certificate may also be
   authorized through local configuration.

   In order for a CA certificate using the CCC certificate extension to
   be authorized to generate responses, the object identifier for the
   PKIResponse content type must be present in the CCC certificate
   extension.  CCC SHOULD be included if constraints are to be placed on
   the content types generated.

   Signatures applied to individual certificates are as required in
   [RFC8603].

   The signature on the SignedData of a successful response to a client-
   generated request, or each individual inner SignedData on the
   successful response to an RA-generated request, MUST be generated
   using SHA-384 and either ECDSA on P-384 or RSA using RSASSA-
   PKCS1-v1_5 or RSASSA-PSS with an RSA-3072 or RSA-4096 key.  An
   unsuccessful response MUST be signed using the same key type and
   algorithm that signed the request.

   The outer SignedData on the Full PKI Response to any RA-generated PKI
   Request MUST be signed with the same key type and algorithm that
   signed the request.

   The SignedData on a successful Full PKI Response to a PKI Request
   that only contained a Get Certificate or Get CRL control MUST be
   signed with the same key type and algorithm that signed the request.

7.  Client Requirements: Processing PKI Responses

   Clients conforming to this document MUST ensure that only the
   permitted signature, hash, and MAC algorithms described throughout
   this profile are used in responses; if they are not, the client MUST
   reject those responses.

   Clients MUST authenticate all Full PKI Responses.  This includes
   verifying that the PKI Response is signed by an authorized CA or RA
   whose certificate validates back to a trust anchor.  The authorized
   CA certificate MUST include the id-kp-cmcCA EKU and/or a CCC
   extension that includes the object identifier for the PKIResponse
   content type.  Otherwise, the CA is determined to be authorized to
   sign responses through an implementation-specific mechanism.  The PKI
   Response can be signed by an RA if it is an error message, if it is a
   response to a Get Certificate or Get CRL request, or if the PKI
   Response contains an inner PKI Response signed by a CA.  In the last
   case, each layer of PKI Response MUST still contain an authorized,
   valid signature signed by an entity with a valid certificate that
   verifies back to an acceptable trust anchor.  The authorized RA
   certificate MUST include the id-kp-cmcRA EKU and/or include a CCC
   extension that includes the object identifier for the PKIResponse
   content type.  Otherwise, the RA is determined to be authorized to
   sign responses through local configuration.

   When a newly issued certificate is included in the PKI Response, the
   client MUST verify that the newly issued certificate's public key
   matches the public key that the client requested.  The client MUST
   also ensure that the certificate's signature is valid and that the
   signature validates back to an acceptable trust anchor.

   Clients MUST reject PKI Responses that do not pass these tests.
   Local policy will determine whether the client returns a Full PKI
   Response with an Extended CMC Status Info control (CMCStatusInfoV2)
   with the CMCStatus set to failed to a user console, error log, or the
   server.

   If the Full PKI Response contains an Extended CMC Status Info control
   with a CMCStatus set to failed, then local policy will determine
   whether the client resends a duplicate certification request back to
   the server or an error state is returned to a console or error log.

8.  Shared-Secrets

   When the Identity Proof V2 and POP Link Witness V2 controls are used,
   the shared-secret MUST be randomly generated and securely
   distributed.  The shared-secret MUST provide at least 192 bits of
   strength.

9.  Security Considerations

   Protocol security considerations are found in [RFC2986], [RFC4211],
   [RFC8755], [RFC5272], [RFC5273], [RFC5274], [RFC8603], and [RFC6402].
   When CCC is used to authorize RA and CA certificates, then the
   security considerations in [RFC6010] also apply.  Algorithm security
   considerations are found in [RFC8755].

   Compliant with NIST Special Publication 800-57 [SP80057], this
   profile defines proof-of-possession of a key establishment private
   key by performing a digital signature.  Except for one-time proof-of-
   possession, a single key pair MUST NOT be used for both signature and
   key establishment.

   This specification requires implementations to generate key pairs and
   other random values.  The use of inadequate pseudorandom number
   generators (PRNGs) can result in little or no security.  The
   generation of quality random numbers is difficult.  NIST Special
   Publication 800-90A [SP80090A], FIPS 186-3 [FIPS186], and [RFC4086]
   offer random number generation guidance.

   When RAs are used, the list of authorized RAs MUST be securely
   distributed out of band to CAs.

   Presence of the POP Link Witness Version 2 and POP Link Random
   attributes protects against substitution attacks.

   The certificate policy for a particular environment will specify
   whether expired certificates can be used to sign certification
   requests.

10.  IANA Considerations

   This document has no IANA actions.

11.  References

11.1.  Normative References

   [CNSA]     Committee on National Security Systems, "Use of Public
              Standards for Secure Information Sharing", CNSS Policy 15,
              October 2016,
              <https://www.cnss.gov/CNSS/issuances/Policies.cfm>.

   [FIPS186]  National Institute of Standards and Technology, "Digital
              Signature Standard (DSS)", DOI 10.6028/NIST.FIPS.186-4,
              FIPS PUB 186-4, July 2013,
              <http://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.186-4.pdf>.

   [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>.

   [RFC2986]  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>.

   [RFC4055]  Schaad, J., Kaliski, B., and R. Housley, "Additional
              Algorithms and Identifiers for RSA Cryptography for use in
              the Internet X.509 Public Key Infrastructure Certificate
              and Certificate Revocation List (CRL) Profile", RFC 4055,
              DOI 10.17487/RFC4055, June 2005,
              <https://www.rfc-editor.org/info/rfc4055>.

   [RFC4056]  Schaad, J., "Use of the RSASSA-PSS Signature Algorithm in
              Cryptographic Message Syntax (CMS)", RFC 4056,
              DOI 10.17487/RFC4056, June 2005,
              <https://www.rfc-editor.org/info/rfc4056>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <https://www.rfc-editor.org/info/rfc4086>.

   [RFC4211]  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>.

   [RFC4231]  Nystrom, M., "Identifiers and Test Vectors for HMAC-SHA-
              224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
              RFC 4231, DOI 10.17487/RFC4231, December 2005,
              <https://www.rfc-editor.org/info/rfc4231>.

   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,
              <https://www.rfc-editor.org/info/rfc5272>.

   [RFC5273]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC): Transport Protocols", RFC 5273,
              DOI 10.17487/RFC5273, June 2008,
              <https://www.rfc-editor.org/info/rfc5273>.

   [RFC5274]  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>.

   [RFC5754]  Turner, S., "Using SHA2 Algorithms with Cryptographic
              Message Syntax", RFC 5754, DOI 10.17487/RFC5754, January
              2010, <https://www.rfc-editor.org/info/rfc5754>.

   [RFC6010]  Housley, R., Ashmore, S., and C. Wallace, "Cryptographic
              Message Syntax (CMS) Content Constraints Extension",
              RFC 6010, DOI 10.17487/RFC6010, September 2010,
              <https://www.rfc-editor.org/info/rfc6010>.

   [RFC6402]  Schaad, J., "Certificate Management over CMS (CMC)
              Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
              <https://www.rfc-editor.org/info/rfc6402>.

   [RFC8017]  Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
              "PKCS #1: RSA Cryptography Specifications Version 2.2",
              RFC 8017, DOI 10.17487/RFC8017, November 2016,
              <https://www.rfc-editor.org/info/rfc8017>.

   [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>.

   [RFC8603]  Jenkins, M. and L. Zieglar, "Commercial National Security
              Algorithm (CNSA) Suite Certificate and Certificate
              Revocation List (CRL) Profile", RFC 8603,
              DOI 10.17487/RFC8603, May 2019,
              <https://www.rfc-editor.org/info/rfc8603>.

   [RFC8755]  Jenkins, M., "Using Commercial National Security Algorithm
              Suite Algorithms in Secure/Multipurpose Internet Mail
              Extensions", RFC 8755, DOI 10.17487/RFC8755, March 2020,
              <https://www.rfc-editor.org/info/rfc8755>.

11.2.  Informative References

   [SP80057]  National Institute of Standards and Technology,
              "Recommendation for Key Management, Part 1: General",
              DOI 10.6028/NIST.SP.800-57pt1r4, Special
              Publication 800-57, Part 1, Revision 4, January 2016,
              <http://doi.org/10.6028/NIST.SP.800-57pt1r4>.

   [SP80059]  National Institute of Standards and Technology, "Guideline
              for Identifying an Information System as a National
              Security System", DOI 10.6028/NIST.SP.800-59, Special
              Publication 800-59, August 2003,
              <https://csrc.nist.gov/publications/detail/sp/800-59/
              final>.

   [SP80090A] National Institute of Standards and Technology,
              "Recommendation for Random Number Generation Using
              Deterministic Random Bit Generators",
              DOI 10.6028/NIST.SP.800-90Ar1, Special Publication
              800-90A Revision 1, June 2015,
              <http://doi.org/10.6028/NIST.SP.800-90Ar1>.

Appendix A.  Scenarios

   This section illustrates several potential certificate enrollment and
   rekey scenarios supported by this profile.  This section does not
   intend to place any limits or restrictions on the use of CMC.

A.1.  Initial Enrollment

   This section describes three scenarios for authenticating initial
   enrollment requests:

   1.  Previously certified signature key-pair (e.g., Manufacturer
       Installed Certificate).

   2.  Shared-secret distributed securely out of band.

   3.  RA authentication.

A.1.1.  Previously Certified Signature Key-Pair

   In this scenario, the end-entity has a private signing key and a
   corresponding public key certificate obtained from a cryptographic
   module manufacturer recognized by the CA.  The end-entity signs a
   Full PKI Request with the private key that corresponds to the subject
   public key of the previously installed signature certificate.  The CA
   will verify the authorization of the previously installed certificate
   and issue an appropriate new certificate to the end-entity.

A.1.2.  Shared-Secret Distributed Securely Out of Band

   In this scenario, the CA distributes a shared-secret out of band to
   the end-entity that the end-entity uses to authenticate its
   certification request.  The end-entity signs the Full PKI Request
   with the private key for which the certification is being requested.
   The end-entity includes the Identity Proof Version 2 control to
   authenticate the request using the shared-secret.  The CA uses either
   the Identification control or the subject name in the end-entity's
   enclosed PKCS #10 [RFC2986] or CRMF [RFC4211] certification request
   message to identify the request.  The end-entity performs either the
   POP Link Witness Version 2 mechanism as described in [RFC5272],
   Section 6.3.1.1 or the shared-secret/subject distinguished name
   linking mechanism as described in [RFC5272], Section 6.3.2.  The
   subject name in the enclosed PKCS #10 [RFC2986] or CRMF [RFC4211]
   certification request does not necessarily match the issued
   certificate, as it may be used just to help identify the request (and
   the corresponding shared-secret) to the CA.

A.1.3.  RA Authentication

   In this scenario, the end-entity does not automatically authenticate
   its enrollment request to the CA, either because the end-entity has
   nothing to authenticate the request with or because the
   organizational policy requires an RA's involvement.  The end-entity
   creates a Full PKI Request and sends it to an RA.  The RA verifies
   the authenticity of the request.  If the request is approved, the RA
   encapsulates and signs the request as described in Section 4.2,
   forwarding the new request on to the CA.  The subject name in the
   PKCS #10 [RFC2986] or CRMF [RFC4211] certification request is not
   required to match the issued certificate; it may be used just to help
   identify the request to the RA and/or CA.

A.2.  Rekey

   There are two scenarios to support the rekey of certificates that are
   already enrolled.  One addresses the rekey of signature certificates,
   and the other addresses the rekey of key establishment certificates.
   Typically, organizational policy will require certificates to be
   currently valid to be rekeyed, and it may require initial enrollment
   to be repeated when rekey is not possible.  However, some
   organizational policies might allow a grace period during which an
   expired certificate could be used to rekey.

A.2.1.  Rekey of Signature Certificates

   When a signature certificate is rekeyed, the PKCS #10 [RFC2986] or
   CRMF [RFC4211] certification request message enclosed in the Full PKI
   Request will include the same subject name as the current signature
   certificate.  The Full PKI Request will be signed by the current
   private key corresponding to the current signature certificate.

A.2.2.  Rekey of Key Establishment Certificates

   When a key establishment certificate is rekeyed, the Full PKI Request
   will generally be signed by the current private key corresponding to
   the current signature certificate.  If there is no current signature
   certificate, one of the initial enrollment options in Appendix A.1
   may be used.

Authors' Addresses

   Michael Jenkins
   National Security Agency

   Email: mjjenki@nsa.gov


   Lydia Zieglar
   National Security Agency

   Email: llziegl@tycho.ncsc.mil