Suite B Profile of Certificate Management over CMS
RFC 6403

Internet Engineering Task Force (IETF)                        L. Zieglar
Request for Comments: 6403                                           NSA
Category: Informational                                        S. Turner
ISSN: 2070-1721                                                     IECA
                                                                 M. Peck
                                                           November 2011

           Suite B Profile of Certificate Management over CMS

Abstract

   The United States government has published guidelines for "NSA
   Suite B Cryptography", which defines cryptographic algorithm policy
   for national security applications.  This document specifies a
   profile of the Certificate Management over CMS (CMC) protocol for
   managing Suite B X.509 public key certificates.  This profile is a
   refinement of RFCs 5272, 5273, and 5274.

Status of This Memo

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

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6403.

Copyright Notice

   Copyright (c) 2011 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
   (http://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 extracted from this document must

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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   This document specifies a profile for using the Certificate
   Management over CMS (CMC) protocol, defined in [RFC5272], [RFC5273],
   and [RFC5274], and updated by [RFC6402], to manage X.509 public key
   certificates compliant with the United States National Security
   Agency's Suite B Cryptography as defined in the Suite B Certificate
   and Certificate Revocation List (CRL) Profile [RFC5759].  This
   document specifically focuses on defining CMC interactions for both
   initial enrollment and rekey of Suite B 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.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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

3.  Requirements and Assumptions

   All key pairs are on either the curve P-256 or the curve P-384.  FIPS
   186-3 [DSS], Appendix B.4, provides useful guidance for elliptic
   curve key pair generation that SHOULD be followed by systems that
   conform to this document.

   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

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   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 does CMC
   (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 support 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 as defined in
   [RFC6318].  The PKIData content type complies with [RFC5272] with the
   following additional requirements:

   o  controlSequence SHOULD be present, and it SHOULD include the
      following CMC controls: Transaction ID and Sender Nonce.  Other
      CMC controls MAY be included.  If the request is being
      authenticated using a shared-secret, then the following
      requirements in this paragraph apply:  Identity Proof Version 2
      control, as defined in [RFC5272], MUST be included; hashAlgId MUST
      be id-sha256 or id-sha384 for P-256 certification requests, and
      MUST be id-sha384 for P-384 certification requests (both algorithm
      OIDs are defined in [RFC5754]); macAlgId MUST be HMAC-SHA256 when
      the hashAlgId is id-sha256, and MUST be HMAC-SHA384 when the
      hashAlgId is id-sha384 (both HMAC algorithms are defined in
      [RFC4231]).  If the subject 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 or Certificate Request Message Format (CRMF) request as
      described in Sections 4.1 and 4.2.

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   o  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.

   If the Full PKI Request contains a P-256 public key certification
   request, then the SignedData encapsulating the Full PKI Request MUST
   be generated using either SHA-256 and ECDSA on P-256 or using SHA-384
   and ECDSA on P-384.  If the Full PKI Request contains a P-384 public
   key certification request, then the SignedData MUST be generated
   using SHA-384 and ECDSA on P-384.

   A Full PKI Request MUST be signed using the private key that
   corresponds to the public key of an existing signature certificate
   unless an appropriate signature certificate does not yet exist, such
   as during initial enrollment.

   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:

   o  certificationRequestInfo:

      *  subjectPublicKeyInfo MUST be set as defined in Section 4.4 of
         [RFC5759];

      *  attributes:

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

            o  The Key Usage extension MUST be included, and it MUST be
               set as defined in [RFC5759].

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            o  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.

            o  Other extension requests MAY be included as desired.

         -  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 or SubjectAltName does not match the
            desired Subject or SubjectAltName 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 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-sha256 or id-sha384 for P-256 certification requests
            and MUST be id-sha384 for P-384 certification requests, as
            defined in [RFC5754]; macAlgorithm MUST be HMAC-SHA256 when
            the keyGenAlgorithm is id-sha256 and MUST be HMAC-SHA384
            when the keyGenAlgorithm is id-sha384, as defined in
            [RFC4231].

      *  signatureAlgorithm MUST be ecdsa-with-sha256 for P-256
         certification requests and MUST be ecdsa-with-sha384 for P-384
         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 Certification Authority.

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:

   o  popo MUST be included using the signature (POPOSigningKey) proof-
      of-possession choice and set as defined in [RFC4211], Section 4.1,
      for both signature and key establishment certification requests.

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      The POPOSigningKey poposkInput field MUST be omitted.  The
      POPOSigningKey algorithmIdentifier MUST be ecdsa-with-sha256 for
      P-256 certification requests and MUST be ecdsa-with-sha384 for
      P-384 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:

   o  version MAY be included and, if included, it MUST be set to 2 as
      defined in Section 4.3 of [RFC5759];

   o  publicKey MUST be set as defined in Section 4.4 of [RFC5759];

   o  extensions:

      *  The Key Usage extension MUST be included, and it MUST be set as
         defined in [RFC5759].

      *  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  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 or SubjectAltName does not match the desired Subject or
         SubjectAltName 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 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-sha256
         or id-sha384 for P-256 certification requests and MUST be
         id-sha384 for P-384 certification requests; macAlgorithm MUST
         be HMAC-SHA256 when keyGenAlgorithm is id-sha256 and MUST be
         HMAC-SHA384 when keyGenAlgorithm is id-sha384.

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5.  RA Requirements

   This section addresses the optional case where one or more RAs act as
   intermediaries between the client and 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 as in [RFC5272].

5.2.  RA-Generated PKI Requests

   If the RA encapsulates the client-generated PKI Request in a new RA-
   signed PKI Request, it MUST create a Full PKI Request encapsulated in
   a SignedData, and the SignedData MUST be constructed as defined in
   [RFC6318].  The PKIData content type complies with [RFC5272] with the
   following additional requirements:

   o  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.

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

   RA certificates are authorized to sign Full PKI Requests with an
   Extended Key Usage (EKU) and/or with the CCC certificate extension
   [RFC6010].  Certificates may also be authorized through local
   configuration.  Authorized certificates SHOULD include the
   id-kp-cmcRA EKU from [RFC6402].  Authorized certificates MAY also
   include the CCC certificate extension [RFC6010], or the authorized
   certificate MAY just include the CCC certificate extension.  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.

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   If the RA-signed PKI Request contains a certification request for a
   P-256 public key, then the SignedData MUST be generated using either
   SHA-256 and ECDSA on P-256 or SHA-384 and ECDSA on P-384.  If the
   request contains a certification request for a P-384 public key, then
   the SignedData MUST be generated using SHA-384 and ECDSA on P-384.
   If the RA-signed PKI Request contains requests for certificates on
   the P-256 and P-384 curve, then the SignedData MUST be generated
   using SHA-384 and ECDSA on P-384.  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 SignedData MUST be signed by
   either SHA-256 and ECDSA on P-256 or SHA-384 and ECDSA on P-384, the
   algorithm used in the response MUST match the algorithm used in the
   request.

5.3.  RA-Generated Errors

   RA certificates authorized with the CCC certificate extension
   [RFC6010] MUST include the object identifier for the PKIResponse
   content type to authorize them to generate responses.

6.  CA Requirements

   This section specifies the requirements for CAs that receive PKI
   Requests and that 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
   CMCStatus of failed and a CMCFailInfo with the value of badAlg
   [RFC5272].

   For requests involving an RA, 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 key usage 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 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 the client-generated PKI Request includes a ChangeSubjectName
   attribute either in the CertRequest controls field for a CRMF request
   or in the tcr attributes field for a PKCS#10 request, then the CA

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   MUST ensure that name change is authorized.  The mechanism for
   ensuring that the name change is authorized is out of scope.  If the
   CA performs this check, and the name change is not authorized, then
   the CA MUST reject the PKI Request.  The CA SHOULD return a
   CMCStatusInfoV2 control with CMCStatus of failed.

   Other processing of PKIRequests is as in [RFC5272].

6.2.  CA-Generated PKI Responses

   If a Full PKI Response is returned, it MUST be encapsulated in a
   SignedData, and the SignedData MUST be constructed as defined in
   [RFC6318].

   If the PKI Response is in response to an RA-encapsulated 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 as defined in [RFC6318].  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)
        PKIData
          controlSequence (Transaction ID, Sender Nonce, Recipient
                           Nonce, Batch Response)
          cmsSequence
            SignedData (applied by CA and includes returned
                        certificates)
              PKIData
                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
   authorized to sign CMC responses MUST be used.  Certificates are
   authorized to sign Full PKI Responses with an EKU and/or with the CCC
   certificate extension [RFC6010].  Certificates may also be authorized
   through local configuration.  Authorized certificates SHOULD include
   the id-kp-cmcCA EKU from [RFC6402].  Authorized certificates MAY also
   include the CCC certificate extension [RFC6010], or the authorized
   certificate MAY just include the CCC certificate extension.  If the
   CA is authorized via the CCC extension, then the CCC extension MUST
   include the object identifier for the PKIResponse content type.  CCC
   SHOULD be included if constraints are to be placed on the content
   types generated.

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   The signature on the SignedData MUST be generated using either ECDSA
   P-256 on SHA-256 or ECDSA P-384 on SHA-384.  If the Full PKI Response
   is a successful response to a P-256 public key certification request,
   then the SignedData MUST be generated using either SHA-256 and ECDSA
   on P-256 or SHA-384 and ECDSA on P-384.  If the Full PKI Response is
   a successful response to a P-384 public key certification request,
   then the SignedData MUST be generated using SHA-384 and ECDSA on
   P-384.  If the Full PKI Response is a successful response to
   certification requests on both the P-256 and P-356 curves, then the
   SignedData MUST be generated using SHA-384 and ECDSA on P-384.  If
   the Full PKI Response is an unsuccessful response to a PKI Request,
   then the SignedData MUST be signed by either SHA-256 and ECDSA on
   P-256 or SHA-384 and ECDSA on P-384, the algorithm used in the
   response MUST match the algorithm used in the request.  If the Full
   PKI Response is an unsuccessful response to certification requests on
   both the P-256 and P-356 curves, then the SignedData MUST be
   generated using SHA-384 and ECDSA on P-384.  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 SignedData MUST be signed by
   either SHA-256 and ECDSA on P-256 or SHA-384 and ECDSA on P-384, the
   algorithm used in the response MUST match the algorithm used in the
   request.

   If the PKI Response is in response to an RA-encapsulated PKI Request,
   the signature algorithm for each SignedData is selected
   independently.

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 include a CCC
   extension that includes the object identifier for the PKIResponse
   content type.  Or, 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

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   extension that includes the object identifier for the PKIResponse
   content type.  Or, the RA is determined to be authorized to sign
   responses through an implementation-specific mechanism.

   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 with CMCStatus set
   to failed to a user console, error log, or the server.

   If the Full PKI Response contains an Extended Status Info 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 128 bits of
   strength for P-256 certification requests and at least 192 bits of
   strength for P-384 certification requests.

9.  Security Considerations

   Protocol security considerations are found in [RFC2986], [RFC4211],
   [RFC6318], [RFC5272], [RFC5273], [RFC5274], [RFC5759], 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 [RFC6318].

   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 pseudo-random number
   generators (PRNGs) can result in little or no security.  The
   generation of quality random numbers is difficult.  NIST Special
   Publication 800-90 [SP80090], FIPS 186-3 [DSS], and [RFC4086] offer
   random number generation guidance.

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   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.  Acknowledgments

   Michael Peck wishes to acknowledge that he was employed at the
   National Security Agency during much of the work on this document.

11.  References

11.1.  Normative References

   [DSS]      National Institute of Standards and Technology (NIST),
              FIPS 186-3: Digital Signature Standard (DSS), June 2009.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2986]  Nystrom, M. and B. Kaliski, "PKCS #10: Certification
              Request Syntax Specification Version 1.7", RFC 2986,
              November 2000.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              June 2005.

   [RFC4211]  Schaad, J., "Internet X.509 Public Key Infrastructure
              Certificate Request Message Format (CRMF)", RFC 4211,
              September 2005.

   [RFC4231]  Nystrom, M., "Identifiers and Test Vectors for HMAC-
              SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
              RFC 4231, December 2005.

   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC)", RFC 5272, June 2008.

   [RFC5273]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC): Transport Protocols", RFC 5273, June 2008.

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   [RFC5274]  Schaad, J. and M. Myers, "Certificate Management Messages
              over CMS (CMC): Compliance Requirements", RFC 5274, June
              2008.

   [RFC5754]  Turner, S., "Using SHA2 Algorithms with Cryptographic
              Message Syntax", RFC 5754, January 2010.

   [RFC5759]  Solinas, J. and L. Zieglar, "Suite B Certificate and
              Certificate Revocation List (CRL) Profile", RFC 5759,
              January 2010.

   [RFC6010]  Housley, R., Ashmore, S., and C. Wallace, "Cryptographic
              Message Syntax (CMS) Content Constraints Extension", RFC
              6010, September 2010.

   [RFC6318]  Housley, R. and J. Solinas, "Suite B in
              Secure/Multipurpose Internet Mail Extensions (S/MIME)",
              RFC 6318, June 2011.

   [RFC6402]  Schaad, J., "Certificate Management over CMS (CMC)
              Updates", RFC 6402, November 2011.

11.2.  Informative References

   [SP80057]  National Institute of Standards and Technology (NIST),
              Special Publication 800-57 Part 1: Recommendation for Key
              Management, March 2007.

   [SP80090]  National Institute of Standards and Technology (NIST),
              Special Publication 800-90: Recommendation for Random
              Number Generation Using Deterministic Random Number Bits
              Generators (Revised), March 2007.

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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 installed signature certificate (e.g., Manufacturer
      Installed Certificate);

   2. Shared-secret distributed securely out-of-band;

   3. RA authentication.

A.1.1.  Previously Installed Signature Certificate

   In this scenario, the end-entity has had a signature certificate
   installed by the cryptographic module manufacturer.  As the end-
   entity already has a signature certificate, it can be used to
   authenticate a request for a new certificate.  The end-entity signs
   the Full PKI Request with the private key that corresponds to the
   subject public key of a previously installed signature certificate.
   The CA will recognize the authorization of the previously installed
   certificate and issue an appropriate 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 in the end-entity's
   enclosed PKCS #10 or CRMF 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-Subject/Subject Distinguished Name (DN) linking mechanism
   as described in [RFC5272], Section 6.3.2.  The Subject in the
   enclosed PKCS #10 or CRMF certification request does not necessarily
   match the issued certificate, as it may be used just to help identify
   the request (and corresponding shared-secret) to the CA.

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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 organizational
   policy requires RA involvement.  The end-entity creates a Full PKI
   Request and sends it to an RA.  The RA verifies the authenticity of
   the request, then, if approved, encapsulates and signs the request as
   described in Section 5.2, forwarding the new request on to the CA.
   The Subject in the PKCS #10 or CRMF 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 or CRMF
   certification request message enclosed in the Full PKI Request will
   include the same Subject 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.

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Authors' Addresses

   Lydia Zieglar
   National Information Assurance Research Laboratory
   National Security Agency

   EMail: llziegl@tycho.ncsc.mil

   Sean Turner
   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, VA 22031
   USA

   EMail: turners@ieca.com

   Michael Peck

   EMail: mpeck@alumni.virginia.edu

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