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Versions: 00 01 02 03 04 05 06 07 RFC 5272

PKIX Working Group                                            M. Myers
Internet Draft                                                VeriSign
Document: draft-ietf-pkix-2797-bis-00.txt                       X. Liu
February 2001                                                    Cisco
Expires: July 2001                                           J. Schaad
                                                Soaring Hawk Consulting
                                                           J. Weinstein

                Certificate Management Messages over CMS

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
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   progress."

   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
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   Comments or suggestions for improvement may be made on the "ietf-
   pkix" mailing list, or directly to the author.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This document defines a Certificate Management protocol using CMS
   (CMC).  This protocol addresses two immediate needs within the
   Internet PKI community:

   1. The need for an interface to public key certification products
   and    services based on [CMS] and [PKCS10], and
   2. The need in [SMIMEV3] for a certificate enrollment protocol for
   DSA-signed certificates with Diffie-Hellman public keys.

   A small number of additional services are defined to supplement the
   core certificate request service.

   Throughout this specification the term CMS is used to refer to both
   [CMS] and [PKCS7].  For both signedData and envelopedData, CMS is a
   superset of the PKCS7. In general, the use of PKCS7 in this document
   is aligned to the Cryptographic Message Syntax [CMS] that provides a 


   superset of the PKCS7 syntax. The term CMC refers to this
   specification.

   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 [RFC 2119].

1.  Protocol Requirements

   -  The protocol is to be based as much as possible on the existing
   CMS, PKCS#10 and CRMF specifications.
   -  The protocol must support the current industry practice of a
   PKCS#10 request followed by a PKCS#7 response as a subset of the
   protocol.
   -  The protocol needs to easily support the multi-key enrollment
   protocols required by S/MIME and other groups.
   -  The protocol must supply a way of doing all operations in a
   single-round trip.  When this is not possible the number of round
   trips is to be minimized.
   -  The protocol will be designed such that all key generation can
   occur on the client.
   -  The mandatory algorithms must superset the required algorithms
   for S/MIME.
   -  The protocol will contain POP methods. Optional provisions for
   multiple-round trip POP will be made if necessary.
   -  The protocol will support deferred and pending responses to
   certificate request for cases where external procedures are required
   to issue a certificate.
   -  The protocol needs to support arbitrary chains of local
   registration authorities as intermediaries between certificate
   requesters and issuers.

2.  Protocol Overview

   An enrollment transaction in this specification is generally
   composed of a single round trip of messages.  In the simplest case
   an enrollment request is sent from the client to the server and an
   enrollment response is then returned from the server to the client.
   In some more complicated cases, such as delayed certificate issuance
   and polling for responses, more than one round trip is required.

   This specification supports two different request messages and two
   different response messages.

   Public key certification requests can be based on either the PKCS10
   or CRMF object.  The two different request messages are (a) the bare
   PKCS10 (in the event that no other services are needed), and (b) the
   PKCS10 or CRMF message wrapped in a CMS encapsulation as part of a
   PKIData object.

   Public key certification responses are based on the CMS signedData
   object.  The response may be either (a) a degenerate CMS signedData
   object (in the event no other services are needed), or (b) a
   ResponseBody object wrapped in a CMS signedData object.
    


   No special services are provided for doing either renewal (new
   certificates with the same key) or re-keying (new certificates on
   new keys) of clients.  Instead a renewal/re-key message looks the
   same as any enrollment message, with the identity proof being
   supplied by existing certificates from the CA.

   A provision exists for Local Registration Authorities (LRAs) to
   participate in the protocol by taking client enrollment messages,
   wrapping them in a second layer of enrollment message with
   additional requirements or statements from the LRA and then passing
   this new expanded request on to the Certification Authority.

   This specification makes no assumptions about the underlying
   transport mechanism.  The use of CMS is not meant to imply an email-
   based transport.

   Optional services available through this specification are
   transaction management, replay detection (through nonces), deferred
   certificate issuance, certificate revocation requests and
   certificate/CRL retrieval.

2.1  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.
   "LRA" or "RA" refers to a (Local) Registration Authority.  A
   registration authority acts as an intermediary between an End-Entity
   and a Certification Authority.  Multiple RAs can exist between the
   End-Entity and the Certification Authority.
   "CA" refers to a Certification Authority.  A Certification Authority
   is the entity that performs the actual issuance of a certificate.
   "Client" refers to an entity that creates a PKI request.  In this
   document both RAs and End-Entities can be clients.
   "Server" refers to the entities that process PKI requests and create
   PKI responses.  CAs and RAs can be servers in this document.
   "PKCS#10" refers the Public Key Cryptography Standard #10.  This is
   one of a set of standards defined by RSA Laboratories in the 1980s.
   PKCS#10 defines a Certificate Request Message syntax.
   "CRMF" refers to the Certificate Request Message Format RFC [CRMF].
   We are using certificate request message format defined in this
   document as part of our management protocol.
   "CMS" refers to the Cryptographic Message Syntax RFC [CMS].  This
   document provides for basic cryptographic services including
   encryption and signing with and without key management.
   "POP" is an acronym for "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 end-
   entity.
   "Transport wrapper" refers to the outermost CMS wrapping layer.

2.2  Protocol Flow Charts
    


   Figure 1 shows the Simple Enrollment Request and Response messages.
   The contents of these messages are detailed in Sections 4.1 and 4.3
   below.

   Simple PKI Request                      Simple PKI Response
   -------------------------               --------------------------

    +----------+                            +------------------+
    | PKCS #10 |                            | CMS "certs-only" |
    +----------+--------------+             |     message      |
    |                         |             +------------------+------+
    | Certificate Request     |             |                         |
    |                         |             | CMS Signed Data,        |
    | Subject Name            |             |   no signerInfo         |
    | Subject Public Key Info |             |                         |
    |   (K_PUB)               |             | signedData contains one |
    | Attributes              |             | or more certificates in |
    |                         |             | the "certificates"      |
    +-----------+-------------+             | portion of the          |
                | signed with |             | signedData.             |
                | matching    |             |                         |
                | K_PRIV      |             | encapsulatedContentInfo |
                +-------------+             | is empty.               |
                                            |                         |
                                            +--------------+----------+
                                                           | unsigned |
                                                           +----------+

                Figure 1: Simple PKI Request and Response Messages


    Full PKI Request                        Full PKI Response
    -----------------------                 ------------------------
    +----------------+                      +----------------+
    | CMS signedData |                      | CMS signedData |
    |     object     |                      |     object     |
    +----------------+--------+             +----------------+--------+
    |                         |             |                         |
    | PKIData object          |             | ResponseBody object     |
    |                         |             |                         |
    | Sequence of:            |             | Sequence of:            |
    | <enrollment attribute>* |             | <enrollment attribute>* |
    | <certification request>*|             | <CMS object>*           |
    | <CMS objects>*          |             | <other message>*        |
    | <other message>*        |             |                         |
    |                         |             | where * == zero or more |
    | where * == zero or more |             |                         |
    |                         |             | All certificates issued |
    | Certificate requests    |             | as part of the response |
    | are CRMF or PKCS#10     |             | are included in the     |
    | objects. Attributes are |             | "certificates" portion  |
    | (OID, ANY defined by    |             | of the signedData.      |
    | OID) pairs.             |             | Relevant CA certs and   |
    |                         |             | CRLs can be included as |
    +-------+-----------------+             | well.                   |
            | signed (keypair |             |                         | 


            | used may be pre-|             +---------+---------------+
            | existing or     |                       | signed by the |
            | identified in   |                       | CA or an LRA  |
            | the request)    |                       +---------------+
            +-----------------+

               Figure 2: Full PKI Request and Response Messages

   Figure 2 shows the Full Enrollment Request and Response messages.
   The contents of these messages are detailed in Sections 4.2 and 4.4
   below.

3.  Protocol Elements

   This section covers each of the different elements that may be used
   to construct enrollment request and enrollment response messages.
   Section 4 will cover how to build the enrollment request and
   response messages.

3.1  PKIData Object

   The new content object PKIData has been defined for this protocol.
   This new object is used as the body of the full PKI request message.
   The new body is identified by:

     id-cct-PKIData ::= {id-pkix id-cct(12) 2 }

   The ASN.1 structure corresponding to this new content type is:

     PKIData ::= SEQUENCE

         controlSequence    SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
         reqSequence        SEQUENCE SIZE(0..MAX) OF TaggedRequest,
         cmsSequence        SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
         otherMsgSequence   SEQUENCE SIZE(0..MAX) OF OtherMsg
     }

   -- controlSequence consists of a sequence of control attributes.
   The control attributes defined in this document are found in section
   5. As control sequences are defined by OIDs, other parties can
   define additional control attributes. Unrecognized OIDs MUST result
   in no part of the request being successfully processed.

   -- reqSequence consists of a sequence of certificate requests.  The
   certificate requests can be either a CertificateRequest (PKCS10
   request) or a CertReqMsg.  Details on each of these request types
   are found in sections 3.3.1 and 3.3.2 respectively.

   -- cmsSequence consists of a sequence of [CMS] message objects.
   This protocol only uses EnvelopedData, SignedData and EncryptedData.
   See section 3.6 for more details.

   -- otherMsgSequence allows for other arbitrary data items to be
   placed into the enrollment protocol.  The {OID, any} pair of values
   allows for arbitrary definition of material.  Data objects are
   placed here while control objects are placed in the controlSequence
   field. See section 3.7 for more details. 



3.2  ResponseBody Object

   The new content object ResponseBody has been defined for this
   protocol.  This new object is used as the body of the full PKI
   response message.  The new body is identified by:

     id-cct-PKIResponse ::= {id-pkix id-cct(12) 3  }

   The ASN.1 structure corresponding to this body content type is:

      ResponseBody ::= SEQUENCE

          controlSequence   SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
          cmsSequence       SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
          otherMsgSequence  SEQUENCE SIZE(0..MAX) OF OtherMsg
      }

   -- controlSequence consists of a sequence of control attributes.
   The control attributes defined in this document are found in section
   3.5. Other parties can define additional control attributes.

   -- cmsSequence consists of a sequence of [CMS] message objects.
   This protocol only uses EnvelopedData, SignedData and EncryptedData.
   See section 3.6 for more details.

   -- otherMsgSequence allows for other arbitrary items to be placed
   into the enrollment protocol.  The {OID, any} pair of values allows
   for arbitrary definition of material.  Data objects are placed here
   while control objects are placed in the controlSequence field. See
   section 3.7 for more details.

3.3  Certification Requests (PKCS10/CRMF)

   Certification Requests are based on either PKCS10 or CRMF messages.
   Section 3.3.1 specifies mandatory and optional requirements for
   clients and servers dealing with PKCS10 request messages.  Section
   3.3.2 specifies mandatory and optional requirements for clients and
   servers dealing with CRMF request messages.

3.3.1  PKCS10 Request Body

   Servers MUST be able to understand and process PKCS10 request
   bodies. Clients MUST produce a PKCS10 request body when using the
   Simple Enrollment Request message. Clients MAY produce a PKCS10
   request body when using the Full Enrollment Request message.

   When producing a PKCS10 request body, clients MUST produce a PKCS10
   message body containing a subject name and public key.  Some
   certification products are operated using a central repository of
   information to assign subject names upon receipt of a public key for
   certification.  To accommodate this mode of operation, the subject
   name in a CertificationRequest MAY be NULL, but MUST be present.
   CAs that receive a CertificationRequest with a NULL subject name MAY
   reject such requests.  If rejected and a response is returned, the
   CA MUST respond with the failInfo attribute of badRequest.
    


   The client MAY incorporate one or more standard X.509 v3 extensions
   in any PKCS10 request as an ExtensionReq attribute. An ExtensionReq
   attribute is defined as

         ExtensionReq ::= SEQUENCE OF Extension

   where Extension is imported from [PKIXCERT] and ExtensionReq is
   identified by {pkcs-9 14}.

   Servers MUST be able to process all extensions defined in
   [PKIXCERT]. Servers are not required to be able to process other V3
   X.509 extensions transmitted using this protocol, nor are they
   required to be able to process other, private extensions. Servers
   are not required to put all client-requested extensions into a
   certificate. Servers are permitted to modify client-requested
   extensions. Servers MUST NOT alter an extension so as to invalidate
   the original intent of a client-requested extension.  (For example
   changing key usage from key exchange to signing.) If a certification
   request is denied due to the inability to handle a requested
   extension and a response is returned, the server MUST respond with
   the failInfo attribute of unsupportedExt.

3.3.2  CRMF Request Body

   Servers MUST be able to understand and process CRMF request body.
   Clients MAY produce a CRMF message body when using the Full
   Enrollment Request message.

   This memo imposes the following additional changes on the
   construction and processing of CRMF messages:

   -  When CRMF message bodies are used in the Full Enrollment Request
   message, each CRMF message MUST include both the subject and
   publicKey fields in the CertTemplate.  As in the case of PKCS10
   requests, the subject may be encoded as NULL, but MUST be present.
   -  In general, when both CRMF and CMC controls exist with equivalent
   functionality, the CMC control SHOULD be used.  The CMC control MUST
   override any CRMF control.
   -  The regInfo field MUST NOT be used on a CRMF message.  Equivalent
   functionality is provided in the regInfo control attribute (section
   5.12).
   -  The indirect method of proving POP is not supported in this
   protocol.  One of the other methods (including the direct method
   described in this document) MUST be used instead if POP is desired.
   The value of encrCert in SubsequentMessage MUST NOT be used.
   -  Since the subject and publicKeyValues are always present, the
   POPOSigningKeyInput MUST NOT be used when computing the value for
   POPSigningKey.

   A server is not required to use all of the values suggested by the
   client in the certificate template.  Servers MUST be able to process
   all extensions defined in [PXIXCERT].  Servers are not required to
   be able to process other V3 X.509 extension transmitted using this
   protocol, nor are they required to be able to process other, private
   extensions. Servers are permitted to modify client-requested
   extensions.  Servers MUST NOT alter an extension so as to invalidate 


   the original intent of a client-requested extension. (For example
   change key usage from key exchange to signing.)  If a certificate
   request is denied due to the inability to handle a requested
   extension, the server MUST respond with a failInfo attribute of
   unsupportedExt.

3.3.3  Production of Diffie-Hellman Public Key Certification Requests

   Part of a certification request is a signature over the request;
   Diffie-Hellman is a key agreement algorithm and cannot be used to
   directly produce the required signature object.  [DH-POP] provides
   two ways to produce the necessary signature value.  This document
   also defines a signature algorithm that does not provide a POP
   value, but can be used to produce the necessary signature value.

3.3.3.1   No-Signature Signature Mechanism

   Key management (encryption/decryption) private keys cannot always be
   used to produce some type of signature value as they can be in a
   decrypt only device.  Certification requests require that the
   signature field be populated.  This section provides a signature
   algorithm specifically for that purposes.  The following object
   identifier and signature value are used to identify this signature
   type:

      id-alg-noSignature OBJECT IDENTIFIER ::= {id-pkix id-alg(6) 2}

      NoSignatureValue ::= OCTET STRING

   The parameters for id-alg-noSignature MUST be present and MUST be
   encoded as NULL.  NoSignatureValue contains the hash of the
   certification request.  It is important to realize that there is no
   security associated with this signature type.  If this signature
   type is on a certification request and the Certification Authority
   policy requires proof-of-possession of the private key, the POP
   mechanism defined in section 5.7 MUST be used.

3.3.3.2   Diffie-Hellman POP Signature

   CMC compliant implementations MUST support section 5 of [DH-POP].

3.3.3.3   Diffie-Hellman MAC signature

   CMC compliant implementations MAY support section 4 of [DH-POP].

3.4  Body Part Identifiers

   Each element of a PKIData or PKIResponse message has an associated
   body part identifier.  The Body Part Identifier is a 4-octet integer
   encoded in the certReqIds field for CertReqMsg objects (in a
   TaggedRequest) or in the bodyPartId field of the other objects.  The
   Body Part Identifier MUST be unique within a single PKIData or
   PKIResponse object.  Body Part Identifiers can be duplicated in
   different layers (for example a CMC message embedded within
   another). The Body Part Id of zero is reserved to designate the
   current PKIData object.  This value is used in control attributes 


   such as the Add Extensions Control in the pkiDataReference field to
   refer to a request in the current PKIData object.

   Some control attribute, such as the CMC Status Info attribute, will
   also use Body Part Identifiers to refer to elements in the previous
   message.  This allows an error to be explicit about the attribute or
   request to which the error applies.

3.5  Control Attributes

   The overall control flow of how a message is processed in this
   document is based on the control attributes.  Each control attribute
   consists of an object identifier and a value based on the object
   identifier.

   Servers MUST fail the processing of an entire PKIData message if any
   included control attribute is not recognized.  The response MUST be
   the error badRequest and bodyList MUST contain the bodyPartID of the
   invalid or unrecognized control attribute.

   The syntax of a control attribute is

      TaggedAttribute ::= SEQUENCE

          bodyPartID         BodyPartId,
          attrType           OBJECT IDENTIFIER,
          attrValues         SET OF AttributeValue
      }

      -- bodyPartId is a unique integer that is used to reference this
   control attribute. The id of 0 is reserved for use as the reference
   to the current PKIData object.

      -- attrType is the OID defining the associated data in attrValues

      -- attrValues contains the set of data values used in processing
   the control attribute.

   The set of control attributes that are defined by this memo are
   found in section 5.

3.6  Content Info objects

   The cmsSequence field of the PKIRequest and PKIResponse messages
   contains zero or more tagged content info objects.  The syntax for
   this structure is

     TaggedContentInfo ::= SEQUENCE

         bodyPartID              BodyPartId,
         contentInfo             ContentInfo
     }

      -- bodyPartId is a unique integer that is used to reference this
   content info object. The id of 0 is reserved for use as the
   reference to the current PKIData object.
    


      -- contentInfo contains a ContentInfo object (defined in [CMS]).
   The three contents used in this location are SignedData,
   EnvelopedData and Data.

   EnvelopedData provides for shrouding of data.  Data allows for
   general transport of unstructured data.

   The SignedData object from [CMS] is also used in this specification
   to provide for authentication as well as serving as the general
   transport wrapper of requests and responses.

3.6.1  Signed Data

   The signedData object is used in two different locations when
   constructing enrollment messages.  The signedData object is used as
   a wrapper for a PKIData as part of the enrollment request message.
   The signedData object is also used as the outer part of an
   enrollment response message.  If the signature on a signedData
   object fails to verify, the response should be a CMCFailInfo with a
   value of badMessageCheck and a bodyPart of 0.

   For the enrollment response the signedData wrapper allows the server
   to sign the returning data, if any exists, and to carry the
   certificates and CRLs for the enrollment request.  If no data is
   being returned beyond the certificates, no signerInfo objects are
   placed in the signedData object.

3.6.2  Enveloped Data

   EnvelopedData is the primary method of providing confidentiality for
   sensitive information in this protocol.  The protocol currently uses
   EnvelopedData to provide encryption of an entire request (see
   section 4.5).  The envelopedData object would also be used to wrap
   private key material for key archival.  If the decryption on an
   envelopedData failes, the response is a CMCFailInfo with a value of
   badMessageCheck and a bodyPart of 0.

   Servers MUST implement envelopedData according to [CMS].  There is
   an ambiguity (about encrypting content types other than id-data) in
   the PKCS7 specification that has lead to non-interoperability.

3.7  Other Message Bodies

   The other message body portion of the message allows for arbitrary
   data objects to be carried as part of a message.  This is intended
   to contain data that is not already wrapped in a CMS contentInfo
   object. The data is ignored unless a control attribute references
   the data by bodyPartId.

     OtherMsg ::= SEQUENCE

         bodyPartID        BodyPartID,
         otherMsgType      OBJECT IDENTIFIER,
         otherMsgValue     ANY DEFINED BY otherMsgType }

   -- bodyPartID contains the unique id of this object
    


   -- otherMsgType contains the OID defining both the usage of this
   body part and the syntax of the value associated with this body part

   -- otherMsgValue contains the data associated with the message body
   part.

4.  PKI Messages

   This section discusses the details of putting together the different
   enrollment request and response messages.

4.1  Simple Enrollment Request

   The simplest form of an enrollment request is a plain PKCS10
   message. If this form of enrollment request is used for a private
   key that is capable of generating a signature, the PKCS10 MUST be
   signed with that private key.  If this form of the enrollment
   request is used for a D-H key, then the D-H POP mechanism described
   in [DH-POP] MUST be used.

   Servers MUST support the Simple Enrollment Request message. If the
   Simple Enrollment Request message is used, servers MUST return the
   Simple Enrollment Response message (see Section 4.3) if the
   enrollment request is granted.  If the enrollment request fails, the
   Full Enrollment Response MAY be returned or no response MAY be
   returned.

   The Simple Enrollment Request message MUST NOT be used if a proof-
   of-identity needs to be included.

   Many advanced services specified in this memo are not supported by
   the Simple Enrollment Request message.

4.2  Full PKI Request

   The Full Enrollment Request provides the most functionality and
   flexibility.  Clients SHOULD use the Full Enrollment Request message
   when enrolling.  Servers MUST support the Full Enrollment Request
   message.  An enrollment response (full or simple as appropriate)
   MUST be returned to all Full Enrollment Requests.

   The Full Enrollment Request message consists of a PKIData object
   wrapped in a signedData CMS object. The objects in the PKIData are
   ordered as follows:

   1. All Control Attributes,
   2. All certification requests,
   3. All CMS objects,
   4. All other messages.

   Each element object in the PKIData sequencein a Full Enrollment
   Request is identified by a Body Part Identifier. If duplicate ids
   are found, the server MUST return the error badRequest with a
   bodyPartID of 0.
    


   The signedData object wrapping the PKIData may be signed either by
   the private key material of the signature certification request, or
   by a previously certified signature key. If the private key of a
   signature certification request is being used, then:
   a) the certification request containing the corresponding public key
   MUST include a Subject Key Identifier extension request,
   b) the subjectKeyIdentifier form of signerInfo MUST be used, and
   c) the value of the subjectKeyIdentifier form of signerInfo MUST be
   the Subject Key Identifier specified in the corresponding
   certification request.

   (The subjectKeyIdentifier form of signerInfo is used here because no
   certificates have yet been issued for the signing key.) If the
   request key is used for signing, there MUST be only one signerInfo
   object in the signedData object.

   When creating a message to renew a certificate, the following should
   be taken into consideration:

   1. The identification and identityProof control statements are not
   required.  The same information is provided by the use of an
   existing certificate from the CA when signing the enrollment
   message.
   2. CAs and LRAs may impose additional restrictions on the signing
   certificate used.  They may require that the most recently issued
   signing certificate for an entity be used.
   3. A renewal message may occur either by creating a new set of keys,
   or by re-using an existing set of keys.  Some CAs may prevent re-use
   of keys by policy.  In this case the CA MUST return NOKEYREUSE as
   the failure code.

4.3  Simple Enrollment Response

   Servers SHOULD use the simple enrollment response message whenever
   possible.  Clients MUST be able to process the simple enrollment
   response message.  The simple enrollment response message consists
   of a signedData object with no signerInfo objects on it.  The
   certificates requested are returned in the certificate bag of the
   signedData object.

   Clients MUST NOT assume the certificates are in any order. Servers
   SHOULD include all intermediate certificates needed to form complete
   chains to one or more self-signed certificates, not just the newly
   issued certificate(s). The server MAY additionally return CRLs in
   the CRL bag.  Servers MAY include the self-signed certificates.
   Clients MUST NOT implicitly trust included self-signed
   certificate(s) merely due to its presence in the certificate bag. In
   the event clients receive a new self-signed certificate from the
   server, clients SHOULD provide a mechanism to enable the user to
   explicitly trust the certificate.

4.4  Full PKI Response

   Servers MUST return full PKI response messages if a) a full PKI
   request message failed or b) additional services other than
   returning certificates are required.  Servers MAY return full PKI 


   responses with failure information for simple PKI requests.
   Following section 4.3 above, servers returning only certificates and
   a success status to the client SHOULD use the simple PKI response
   message.

   Clients MUST be able to process a full PKI response message.

   The full enrollment response message consists of a signedData object
   encapsulating a responseBody object.  In a responseBody object all
   Control Attributes MUST precede all CMS objects.  The certificates
   granted in an enrollment response are returned in the certificates
   field of the immediately encapsulating signedData object.

   Clients MUST NOT assume the certificates are in any order. Servers
   SHOULD include all intermediate certificates needed to form complete
   chains one ore more self-signed certificates, not just the newly
   issued certificate(s). The server MAY additionally return CRLs in
   the CRL bag.  Servers MAY include the self-signed certificates.
   Clients MUST NOT implicitly trust included self-signed
   certificate(s) merely due to its presence in the certificate bag. In
   the event clients receive a new self-signed certificate from the
   server, clients SHOULD provide a mechanism to enable the user to
   explicitly trust the certificate.

4.5  Application of Encryption to a PKI Message

   There are occasions where a PKI request or response message must be
   encrypted in order to prevent any information about the enrollment
   from being accessible to unauthorized entities.  This section
   describes the means used to encrypt a PKI message.  This section is
   not applicable to a simple enrollment message.

   Confidentiality is provided by wrapping the PKI message (a
   signedData object) in a CMS EnvelopedData object.  The nested
   content type in the EnvelopedData is id-signedData.  Note that this
   is different from S/MIME where there is a MIME layer placed between
   the encrypted and signed data objects.  It is recommended that if an
   enveloped data layer is applied to a PKI message, a second signing
   layer be placed outside of the enveloped data layer.  The following
   figure shows how this nesting would be done:


     Normal              Option 1                  Option 2
     ------              --------                  --------
     SignedData          EnvelopedData             SignedData
      PKIData             SignedData                EnvelopedData
                           PKIData                   SignedData
                                                      PKIData

   Options 1 and 2 provide the benefit of preventing leakage of
   sensitive data by encrypting the information.  LRAs can remove the
   enveloped data wrapping, and replace or forward without further
   processing. Section 6 contains more information about LRA
   processing.
    


   PKI Messages MAY be encrypted or transmitted in the clear.  Servers
   MUST provided support for all three versions.

   Alternatively, an authenticated, secure channel could exist between
   the parties requiring encryption.  Clients and servers MAY use such
   channels instead of the technique described above to provide secure,
   private communication of PKI request and response messages.

5.  Control Attributes

   Control attributes are carried as part of both PKI requests and
   responses. Each control attribute is encoded as a unique Object
   Identifier followed by that data for the control attribute.  The
   encoding of the data is based on the control attribute object
   identifier.  Processing systems would first detect the OID and
   process the corresponding attribute value prior to processing the
   message body.

   The following table lists the names, OID and syntactic structure for
   each of the control attributes documented in this memo.

      Control Attribute         OID            Syntax
      -----------------       ----------     --------------
      cMCStatusInfo           id-cmc 1       CMCStatusInfo
      identification          id-cmc 2       UTF8String
      identityProof           id-cmc 3       OCTET STRING
      dataReturn              id-cmc 4       OCTET STRING
      transactionId           id-cmc 5       INTEGER
      senderNonce             id-cmc 6       OCTET STRING
      recipientNonce          id-cmc 7       OCTET STRING
      addExtensions           id-cmc 8       AddExtensions
      encryptedPOP            id-cmc 9       EncryptedPOP
      decryptedPOP            id-cmc 10      DecryptedPOP
      lraPOPWitness           id-cmc 11      LraPOPWitness
      getCert                 id-cmc 15      GetCert
      getCRL                  id-cmc 16      GetCRL
      revokeRequest           id-cmc 17      RevokeRequest
      regInfo                 id-cmc 18      OCTET STRING
      responseInfo            id-cmc 19      OCTET STRING
      QueryPending            id-cmc 21      OCTET STRING
      idPOPLinkRandom         id-cmc 22      OCTET STRING
      idPOPLinkWitness        id-cmc 23      OCTET STRING
      idConfirmCertAcceptance id-cmc 24      CMCCertId
      cmcStatusInfoExt        id-cmc XX      CMCStatusInfoExt

5.1 CMC Status Info Control Attributes

   The CMC status info control is used in full PKI Response messages to
   return information about the processing of a client request.  Two
   controls are described in this section.  The first is the preferred
   control, the second is included for backwards compatibility with RFC
   2797.

   Servers MAY emit multiple CMC status info controls referring to a
   single body part.  Clients MUST be able to deal with multiple CMC
   status info controls in a response message.  Servers MUST use the 


   CMCStatusInfoExt control, but MAY additionally use the CMCStatusInfo
   attribute.  Clients MUST be able to process the CMCStatusInfoExt
   control.

5.1.1 Extended CMC Status Info Control Attribute

   This control uses the following ASN.1 definition:

      CMCStatusInfoExt ::= SEQUENCE

         CMCStatus               CMCStatus,
         BodyList                SEQUENCE SIZE (1..MAX) OF
   BodyPartReference,
         StatusString            UTF8String OPTIONAL,
         OtherInfo               CHOICE

           FailInfo                 CMCFailInfo,
           PendInfo                 PendInfo,
           ExtendedFailInfo         SEQUENCE

              FailInfoOID              OBJECT IDENTIFIER,
              FailInfoValue            AttributeValue
           }
         }
       }

         BodyPartReference ::= CHOICE

            BodyPartID           BodyPartID,
            BodyPartPath         SEQUENCE SIZE (2..MAX) OF BodyPartID
         }

         PendInfo ::= SEQUENCE

              pendToken           OCTET STRING,
              pendTime            GeneralizedTime
         }

         -- cMCStatus is described in section 5.1.3

         -- bodyList contains the list of references to body parts in
   the request message to which this status information applies.  If an
   error is being returned for a simple enrollment message, body list
   will contain a single integer of value '1'.

         -- statusString contains a string with additional description
   information.  This string is human readable.

         -- failInfo is described in section 5.1.4. It provides a
   detailed error on what the failure was.  This choice is present only
   if cMCStatus is failed.

         -- extendedFailInfo is provided for other users of the
   enrollment protocol to provided their own error codes.  This choice
   is present only if cMCStatus is failed.

         -- pendToken is the token to be used in the queryPending
   control attribute.

         -- pendTime contains the suggested time the server wants to be
   queried about the status of the request. 



   If the cMCStatus field is success, the CMC Status Info Control MAY
   be omitted unless it is only item in the response message.  If no
   status exists for a certificate request or other item requiring
   processing, then the value of success is to be assumed.

5.1.2  CMC Status Info Control Attribute

   The CMC status info control is used in full PKI Response messages to
   return information on a client request.  Servers MAY emit multiple
   CMC status info controls referring to a single body part. Clients
   MUST be able to deal with multiple CMC status info controls in a
   response message. This statement uses the following ASN.1
   definition:

         CMCStatusInfo ::= SEQUENCE

              cMCStatus           CMCStatus,
              bodyList            SEQUENCE SIZE (1..MAX) OF BodyPartID,
              statusString        UTF8String OPTIONAL,
              otherInfo           CHOICE

                failInfo            CMCFailInfo,
                pendInfo            PendInfo } OPTIONAL
         }

         PendInfo ::= SEQUENCE

              pendToken           OCTET STRING,
              pendTime            GeneralizedTime
         }

      -- cMCStatus is described in section 5.1.31

      -- bodyList contains the list of body parts in the request
   message to which this status information applies.  If an error is
   being returned for a simple enrollment message, body list will
   contain a single integer of value '1'.

      -- statusString contains a string with additional description
   information.  This string is human readable.

      -- failInfo is described in section 5.1.42. It provides a
   detailed error on what the failure was.  This choice is present only
   if cMCStatus is failed.

      -- pendToken is the token to be used in the queryPending control
   attribute.

      -- pendTime contains the suggested time the server wants to be
   queried about the status of the request.

   If the cMCStatus field is success, the CMC Status Info Control MAY
   be omitted unless it is only item in the response message.  If no
   status exists for a certificate request or other item requiring
   processing, then the value of success is to be assumed.

5.1.31   CMCStatus values
    


   CMCStatus is a field in the CMCStatusInfo structure.  This field
   contains a code representing the success or failure of a specific
   operation.  CMCStatus has the ASN.1 structure of:

      CMCStatus ::= INTEGER

           success                (0),
           -- request was granted
           -- reserved            (1),
           -- not used, defined where the original structure was
   defined
           failed                 (2),
           -- you don't get what you want, more information elsewhere
   in the message
           pending                (3),
           -- the request body part has not yet been processed,
           -- requester is responsible to poll back on this
           -- pending may only be return for certificate request
   operations.
           noSupport              (4),
           -- the requested operation is not supported
           confirmRequired        (5)
           -- conformation using the idConfirmCertAcceptance control is
   required
           -- before use of certificate
      }

5.1.42   CMCFailInfo

   CMCFailInfo conveys information relevant to the interpretation of a
   failure condition. The CMCFailInfo has the following ASN.1
   structure:

      CMCFailInfo ::= INTEGER

           badAlg            (0)
           -- Unrecognized or unsupported algorithm
           badMessageCheck   (1)
           -- integrity check failed
           badRequest        (2)
           -- transaction not permitted or supported
           badTime           (3)
           -- Message time field was not sufficiently close to the
   system time
           badCertId         (4)
           -- No certificate could be identified matching the provided
   criteria
           unsuportedExt     (5)
           -- A requested X.509 extension is not supported by the
   recipient CA.
           mustArchiveKeys   (6)
           -- Private key material must be supplied
           badIdentity       (7)
           -- Identification Attribute failed to verify
           popRequired       (8)
           -- Server requires a POP proof before issuing certificate
           popFailed         (9)
           -- POP processing failed 


           noKeyReuse        (10)
           -- Server policy does not allow key re-use
           internalCAError   (11)
           tryLater          (12)
      }

   Additional failure reasons MAY be defined for closed environments
   with a need.

5.2  Identification and IdentityProof Control Attributes

   Some CAs and LRAs require that a proof of identity be included in a
   certification request.  Many different ways of doing this exist with
   different degrees of security and reliability.  Most people are
   familiar with the request of a bank to provide your mother's maiden
   name as a form of identity proof.

   CMC provides one method of proving the client's identity based on a
   shared secret between the certificate requestor and the verifying
   authority.  If clients support full request messages, clients MUST
   implement this method of identity proof.  Servers MUST provide this
   method and MAY also have a bilateral method of similar strength
   available.

   The CMC method starts with an out-of-band transfer of a token (the
   shared secret).  The shared-secret should be generated in a random
   manner.  The distribution of this token is beyond the scope of this
   document.  The client then uses this token for an identity proof as
   follows:

   1. The reqSequence field of the PKIData object (encoded exactly as
   it    appears in the request message including the sequence type and
   length) is the value to be validated.
   2. A SHA1 hash of the token is computed.
   3. An HMAC-SHA1 value is then computed over the value produced in
   Step 1, as described in [HMAC], using the hash of the token from
   Step 2 as the shared secret value.
   4. The 160-bit HMAC-SHA1 result from Step 3 is then encoded as the
   value of the identityProof attribute.

   When the server verifies the identityProof attribute, it computes
   the HMAC-SHA1 value in the same way and compares it to the
   identityProof attribute contained in the enrollment request.

   If a server fails the verification of an identityProof attribute and
   the server returns a response message, the failInfo attribute MUST
   be present in the response and MUST have a value of badIdentity.
   Reuse of the shared-secret on enrollment retries makes it easier for
   the client and to prevent getting out of sync.  However, reuse of
   the shared-secret can potentially open the door for some types of
   attacks.

   Optionally, servers MAY require the inclusion of the unprotected
   identification attribute with an identification attribute.  The
   identification attribute is intended to contain either a text string
   or a numeric quantity, such as a random number, which assists the 


   server in locating the shared secret needed to validate the contents
   of the identityProof attribute.  Numeric values MUST be converted to
   text string representations prior to encoding as UTF8-STRINGs in
   this attribute.  If the identification control attribute is included
   in the message, the derivation of the shared secret in step 2 is
   altered so that the hash of the concatenation of the token and the
   identity value are hashed rather than just the token.

5.2.1  Hardware Shared Secret Token Generation

   The shared secret between the end-entity and the identity verify is
   sometimes transferred using a hardware device that generates a
   series of tokens based on some shared secret value.  The user can
   therefore prove their identity by transferring this token in plain
   text along with a name string.  The above protocol can be used with
   a hardware shared-secret token generation device by the following
   modifications:

   1. The identification attribute MUST be included and MUST contain
   the    hardware-generated token.
   2. The shared secret value used above is the same hardware-generated
   token.
   3. All certification requests MUST have a subject name and the
   subject name MUST contain the fields required to identify the holder
   of the hardware token device.

5.3  Linking Identity and POP Information

   In a PKI Full Request message identity information about the
   creator/author of the message is carried in the signature of the CMS
   SignedData object containing all of the certificate requests. Proof-
   of-possession information for key pairs requesting certification,
   however, is carried separately for each PKCS#10 or CRMF message.
   (For keys capable of generating a digital signature, the POP is
   provided by the signature on the PKCS#10 or CRMF request. For
   encryption-only keys the controls described in Section 5.7 below are
   used.)  In order to prevent substitution-style attacks we must
   guarantee that the same entity generated both the POP and proof-of-
   identity information.

   This section describes two mechanisms for linking identity and POP
   information: witness values cryptographically derived from the
   shared-secret (Section 5.3.1) and shared-secret/subject DN matching
   (Section 5.3.2).  Clients and servers MUST support the witness value
   technique.  Clients and servers MAY support shared-secret/subject DN
   matching or other bilateral techniques of similar strength.  The
   idea behind both mechanisms is to force the client to sign some data
   into each certificate request that can be directly associated with
   the shared-secret; this will defeat attempts to include certificate
   requests from different entities in a single Full PKI Request
   message.

5.3.1  Witness values derived from the shared-secret

   The first technique for doing identity-POP linking works by forcing
   the client to include a piece of information cryptographically- 


   derived from the shared-secret token as a signed extension within
   each certificate request (PKCS#10 or CRMF) message.  This technique
   is useful if null subject DNs are used (because, for example, the
   server can generate the subject DN for the certificate based only on
   the shared secret).  Processing begins when the client receives the
   shared-secret token out-of-band from the server.  The client then
   computes the following values:

   1. The client generates a random byte-string, R, which SHOULD be at
   least 512 bits in length.
   2. A SHA1 hash of the token is computed.
   3. An HMAC-SHA1 value is then computed over the random value
   produced in Step 1, as described in [HMAC], using the hash of the
   token from Step 2 as the shared secret.
   4. The random value produced in Step 1 is encoded as the value of an
   idPOPLinkRandom control attribute.  This control attribute MUST be
   included in the Full PKI Request message.
   5. The 160-bit HMAC-SHA1 result from Step 3 is encoded as the value
   of an idPOPLinkWitness extension to the certificate request.
      a. For CRMF, idPOPLinkWitness is included in the controls section
   of the CertRequest structure.
      b. For PKCS#10, idPOPLinkWitness is included in the attributes
   section of the CertificationRequest structure.

   Upon receipt, servers MUST verify that each certificate request
   contains a copy of the idPOPLinkWitness and that its value was
   derived in the specified manner from the shared secret and the
   random string included in the idPOPLinkRandom control attribute.

5.3.2  Shared-secret/subject DN matching

   The second technique for doing identity-POP linking is to link a
   particular subject distinguished name (subject DN) to the shared-
   secrets that are distributed out-of-band and to require that clients
   using the shared-secret to prove identity include that exact subject
   DN in every certificate request.  It is expected that many client-
   server connections using shared-secret based proof-of-identity will
   use this mechanism. (It is common not to omit the subject DN
   information from the certificate request messages.)

   When the shared secret is generated and transferred out-of-band to
   initiate the registration process (Section 5.2), a particular
   subject DN is also associated with the shared secret and
   communicated to the client.  (The subject DN generated MUST be
   unique per entity in accordance with CA policy; a null subject DN
   cannot be used.  A common practice could be to place the
   identification value as part of the subject DN.)  When the client
   generates the Full PKI Request message, it MUST use these two pieces
   of information as follows:

   1. The client MUST include the specific subject DN that it received
   along with the shared secret as the subject name in every
   certificate request (PKCS#10 and/or CRMF) in the Full PKI Request.
   The subject names in the requests MUST NOT be null. 


   2. The client MUST include the identityProof control attribute
   (Section 5.2), derived from the shared secret, in the Full PKI
   Request.

   The server receiving this message MUST (a) validate the
   identityProof control attribute and then, (b) check that the subject
   DN included in each certificate request matches that associated with
   the shared secret.  If either of these checks fails the certificate
   request MUST be rejected.

5.3.3  Renewal and Re-Key Messages

   In a renewal or re-key message, the subject DN in (a) the
   certificate referenced by the CMS SignerInfo object, and (b) all
   certificate requests within the request message MUST match according
   to the standard name match rules described in [PKIXCERT].

5.4  Data Return Control Attribute

   The data return control attribute allows clients to send arbitrary
   data (usually some type of internal state information) to the server
   and to have the data returned as part of the enrollment response
   message.  Data placed in a data return statement is considered to be
   opaque to the server.  The same control is used for both requests
   and responses.  If the data return statement appears in an
   enrollment message, the server MUST return it as part of the
   enrollment response message.

   In the event that the information in the data return statement needs
   to be confidential, it is expected that the client would apply some
   type of encryption to the contained data, but the details of this
   are outside the scope of this specification.

   An example of using this feature is for a client to place an
   identifier marking the exact source of the private key material.
   This might be the identifier of a hardware device containing the
   private key.

5.5  Add Extensions Control Attribute

   The Add Extensions control attribute is used by LRAs in order to
   specify additional extensions that are to be placed on certificates.
   This attribute uses the following ASN.1 definition:

     AddExtensions ::= SEQUENCE

         pkiDataReference             BodyPartID
         certReferences               SEQUENCE OF BodyPartID,
         extensions                   SEQUENCE OF Extension
     }

      -- pkiDataReference field contains the body part id of the
   embedded request message.

      -- certReferences field is a list of references to one or more of
   the payloads contained within a PKIData.  Each element of the 


   certReferences sequence MUST be equal to either the bodyPartID of a
   TaggedCertificationRequest or the certReqId of the CertRequest
   within a CertReqMsg.   By definition, the listed extensions are to
   be applied to every element referenced in the certReferences
   sequence.  If a request corresponding to bodyPartID cannot be found,
   the error badRequest is returned referencing this control attribute.

      -- extensions field contains the sequence of extensions to be
   applied to the referenced certificate requests.

   Servers MUST be able to process all extensions defined in
   [PKIXCERT]. Servers are not required to be able to process every V3
   X.509 extension transmitted using this protocol, nor are they
   required to be able to process other, private extensions.  Servers
   are not required to put all LRA-requested extensions into a
   certificate. Servers are permitted to modify LRA-requested
   extensions.  Servers MUST NOT alter an extension so as to reverse
   the meaning of a client-requested extension If a certification
   request is denied due to the inability to handle a requested
   extension and a response is returned, the server MUST return a
   failInfo attribute with the value of unsupportedExt.

   If multiple Add Extensions statements exist in an enrollment
   message, the exact behavior is left up to the certificate issuer
   policy. However it is recommended that the following policy be used.
   These rules would be applied to individual extensions within an Add
   Extensions control attribute (as opposed to an "all or nothing"
   approach).

   1. If the conflict is within a single PKIData object, the
   certificate    request would be rejected with an error of
   badRequest.

   2. If the conflict is between different PKIData objects, the
   outermost version of the extension would be used (allowing an LRA to
   override the extension requested by the end-entity).

5.6  Transaction Management Control Attributes

   Transactions are identified and tracked using a transaction
   identifier.  If used, clients generate transaction identifiers and
   retain their value until the server responds with a message that
   completes the transaction.  Servers correspondingly include received
   transaction identifiers in the response.

   The transactionId attribute identifies a given transaction.  It is
   used between client and server to manage the state of an operation.
   Clients MAY include a transactionID attribute in request messages.
   If the original request contains a transactionID attribute, all
   subsequent request and response messages MUST include the same
   transactionID attribute.  A server MUST use only transactionIds in
   the outermost PKIdata object. TransactionIds on inner PKIdata
   objects are for intermediate entities.

   Replay protection can be supported through the use of sender and
   recipient nonces. If nonces are used, in the first message of a 


   transaction, no recipientNonce is transmitted; a senderNonce is
   instantiated by the message originator and retained for later
   reference.  The recipient of a sender nonce reflects this value back
   to the originator as a recipientNonce and includes it's own
   senderNonce.  Upon receipt by the transaction originator of this
   message, the originator compares the value of recipientNonce to its
   retained value.  If the values match, the message can be accepted
   for further security processing.  The received value for senderNonce
   is also retained for inclusion in the next message associated with
   the same transaction.

   The senderNonce and recipientNonce attribute can be used to provide
   application-level replay prevention. Clients MAY include a
   senderNonce in the initial request message.  Originating messages
   include only a value for senderNonce. If a message includes a
   senderNonce, the response MUST include the transmitted value of the
   previously received senderNonce as recipientNonce and include new
   value for senderNonce. A server MUST use only nonces in the
   outermost PKIdata object. Nonces on inner PKIdata objects are for
   intermediate entities.

5.7  Proof-of-possession (POP) for encryption-only keys

   Everything described in this section is optional to implement, for
   both servers and clients. Servers MAY require this POP method be
   used only if another POP method is unavailable. Servers SHOULD
   reject all requests contained within a PKIData if any required POP
   is missing for any element within the PKIData.

   Many servers require proof that an entity requesting a certificate
   for a public key actually possesses the corresponding private
   component of the key pair.  For keys that can be used as signature
   keys, signing the certification request with the private key serves
   as a POP on that key pair.  With keys that can only be used for
   encryption operations, POP MUST be performed by forcing the client
   to decrypt a value.  See Section 5 of [CRMF] for a detailed
   discussion of POP.

   By necessity, POP for encryption-only keys cannot be done in one
   round-trip, since there are four distinct phases:

   1. Client tells the server about the public component of a new
   encryption key pair.
   2. Server sends the client a POP challenge, encrypted with the
   presented public encryption key, which the client must decrypt.
   3. Client decrypts the POP challenge and sends it back to the
   server.
   4. Server validates the decrypted POP challenge and continues
   processing the certificate request.

   CMC defines two different attributes.  The first deals with the
   encrypted challenge sent from the server to the user in step 2.  The
   second deals with the decrypted challenge sent from the client to
   the server in step 3.
    


   The encryptedPOP attribute is used to send the encrypted challenge
   from the server to the client.  As such, it is encoded as a tagged
   attribute within the controlSequence of a ResponseBody.  (Note that
   we assume that the message sent in Step 1 above is an enrollment
   request and that the response in step 2 is a Full Enrollment
   Response including a failureInfo specifying that a POP is explicitly
   required, and providing the POP challenge in the encryptedPOP
   attribute.)

      EncryptedPOP ::= SEQUENCE

           request        TaggedRequest,
           cms            contentInfo,
           thePOPAlgID    AlgorithmIdentifier,
           witnessAlgID   AlgorithmIdentifier,
           witness        OCTET STRING
      }

      DecryptedPOP ::= SEQUENCE

           bodyPartID     BodyPartID,
           thePOPAlgID    AlgorithmIdentifier,
           thePOP         OCTET STRING
      }

   The encrypted POP algorithm works as follows:

   1. The server generates a random value y and associates it with the
   request.
   2. The server returns the encrypted pop with the following fields
   set:
      a. request is the certificate request in the original request
   message (it is included here so the client need not key a copy of
   the request),
      b. cms is an EnvelopedData object, the content type being id-data
   and the content being the value y.  If the certificate request
   contains a subject key identifier (SKI) extension, then the
   recipient identifier SHOULD be the SKI.  If the
   issuerAndSerialNumber form is used, the IsserName MUST be
   encoded as NULL and the SerialNumber as the bodyPartId of the
   certificate request,
      c. thePOPAlgID contains the algorithm to be used in computing the
   return POP value,
      d. witnessAlgID contains the hash algorithm used on y to create
   the field witness,
      e. witness contains the hashed value of y.
   3. The client decrypts the cms field to obtain the value y.  The
   client computes H(y) using the witnessAlgID and compares to the
   value of witness.  If the values do not compare or the decryption is
   not successful, the client MUST abort the enrollment process. The
   client aborts the process by sending a request message containing a
   CMCStatusInfo control attribute with failInfo value of popFailed.
   4. The client creates the decryptedPOP as part of a new PKIData
   message.  The fields in the decryptedPOP are:
      a. bodyPartID refers to the certificate request in the new
   enrollment message,
      b. thePOPAlgID is copied from the encryptedPOP, 


      c. thePOP contains the possession proof.  This value is computed
   by thePOPAlgID using the value y and request referenced in (4a).
   5. The server then re-computes the value of thePOP from its cached
   value of y and the request and compares to the value of thePOP. If
   the values do not match, the server MUST NOT issue the certificate.
   The server MAY re-issue a new challenge or MAY fail the request
   altogether.

   When defining the algorithms for thePOPAlgID and witnessAlgID care
   must be taken to ensure that the result of witnessAlgID is not a
   useful value to shortcut the computation with thePOPAlgID.  Clients
   MUST implement SHA-1 for witnessAlgID.  Clients MUST implement HMAC-
   SHA1 for thePOPAlgID.  The value of y is used as the secret value in
   the HMAC algorithm and the request referenced in (4a) is used as the
   data.  If y is greater than 64 bytes, only the first 64 bytes of y
   are used as the secret.

   One potential problem with the algorithm above is the amount of
   state that a CA needs to keep in order to verify the returned POP
   value. This describes one of many possible ways of addressing the
   problem by reducing the amount of state kept on the CA to a single
   (or small set) of values.

   1. Server generates random seed x, constant across all requests.
   (The value of x would normally be altered on a regular basis and
   kept for a short time afterwards.)

   2. For certificate request R, server computes y = F(x,R).  F can be,
   for example, HMAC-SHA1(x,R).  All that's important for statelessness
   is that y be consistently computable with only known state constant
   x and function F, other inputs coming from the cert request
   structure.  y should not be predictable based on knowledge of R,
   thus the use of a OWF like HMAC-SHA1.

5.8  LRA POP Witnesses Control Attribute

   In an enrollment scenario involving an LRAs the CA may allow (or
   require) the LRA to perform the POP protocol with the entity
   requesting certification.  In this case the LRA needs a way to
   inform the CA it has done the POP.  This control attribute has been
   created to address this issue.

   The ASN.1 structure for the LRA POP witness is as follows:

      LraPopWitness ::= SEQUENCE

          pkiDataBodyid   BodyPartID,
          bodyIds         SEQUENCE of BodyPartID
      }

   -- pkiDataBodyid field contains the body part id of the nested CMS
   body object containing the client's full request message.
   pkiDataBodyid is set to 0 if the request is in the current
   PKIRequest body.
   -- bodyIds contains a list of certificate requests for which the LRA
   has performed an out-of-band authentication.  The method of 


   authentication could be archival of private key material, challenge-
   response or other means.

   If a certificate server does not allow for an LRA to do the POP
   verification, it returns an error of POPFAILURE.  The CA MUST NOT
   start a challenge-response to re-verify the POP itself.

5.9  Get Certificate Control Attribute

   Everything described in this section is optional to implement.

   The get certificate control attribute is used to retrieve previously
   issued certificates from a repository of certificates.  A
   Certificate Authority, an LRA or an independent service may provide
   this repository.  The clients expected to use this facility are
   those operating in a resource-constrained environment.  (An example
   of a resource-constrained client would be a low-end IP router that
   does not retain its own certificate in non-volatile memory.)

   The get certificate control attribute has the following ASN.1
   structure:

      GetCert ::= SEQUENCE

          issuerName    GeneralName,
          serialNumber  INTEGER }

   The service responding to the request will place the requested
   certificate in the certificates field of a SignedData object.  If
   the get certificate attribute is the only control in a Full PKI
   Request message, the response would be a Simple Enrollment Response.

5.10 Get CRL Control Attribute

   Everything described in this section is optional to implement.

   The get CRL control attribute is used to retrieve CRLs from a
   repository of CRLs.  A Certification Authority, an LRA or an
   independent service may provide this repository.  The clients
   expected to use this facility are those where a fully deployed
   directory is either infeasible or undesirable.

   The get CRL control attribute has the following ASN.1 structure:

      GetCRL ::= SEQUENCE

          issuerName    Name,
          cRLName       GeneralName OPTIONAL,
          time          GeneralizedTime OPTIONAL,
          reasons       ReasonFlags OPTIONAL }

   The fields in a GetCRL have the following meanings:

   -- issuerName is the name of the CRL issuer.

   -- cRLName may be the value of CRLDistributionPoints in the subject
   certificate or equivalent value in the event the certificate does
   not contain such a value. 



   -- time is used by the client to specify from among potentially
   several issues of CRL that one whose thisUpdate value is less than
   but nearest to the specified time.  In the absence of a time
   component, the CA always returns with the most recent CRL.

   -- reasons is used to specify from among CRLs partitioned by
   revocation reason.  Implementers should bear in mind that while a
   specific revocation request has a single CRLReason code--and
   consequently entries in the CRL would have a single CRLReason code
   value--a single CRL can aggregate information for one or more
   reasonFlags.

   A service responding to the request will place the requested CRL in
   the crls field of a SignedData object.  If the get CRL attribute is
   the only control in a full enrollment message, the response would be
   a simple enrollment response.

5.11 Revocation Request Control Attribute

   The revocation request control attribute is used to request that a
   certificate be revoked.

   The revocation request control attribute has the following ASN.1
   syntax:

      RevRequest ::= SEQUENCE

          issuerName      Name,
          serialNumber    INTEGER,
          reason          CRLReason,
          invalidityDate  GeneralizedTime OPTIONAL,
          sharedSecret    OCTET STRING OPTIONAL,
          comment         UTF8string OPTIONAL }

   -- issuerName contains the issuerName of the certificate to be
   revoked.

   -- serialNumber contains the serial number of the certificate to be
   revoked

   -- reason contains the suggested CRLReason code for why the
   certificate is being revoked.  The CA can use this value at its
   discretion in building the CRL.

   -- invalidityDate contains the suggested value for the Invalidity
   Date CRL Extension.  The CA can use this value at its discretion in
   building the CRL.

   -- sharedSecret contains a secret value registered by the EE when
   the certificate was obtained to allow for revocation of a
   certificate in the event of key loss.

   -- comment contains a human readable comment.

   For a revocation request to become a reliable object in the event of
   a dispute, a strong proof of originator authenticity is required. 


   However, in the instance when an end-entity has lost use of its
   signature private key, it is impossible for the end-entity to
   produce a digital signature (prior to the certification of a new
   signature key pair). The RevRequest provides for the optional
   transmission from the end-entity to the CA of a shared secret that
   may be used as an alternative authenticator in the instance of loss
   of use. The acceptability of this practice is a matter of local
   security policy.

   (Note that in some situations a Registration Authority may be
   delegated authority to revoke certificates on behalf of some
   population within its scope control.  In these situations the CA
   would accept the LRA's digital signature on the request to revoke a
   certificate, independent of whether the end entity still had access
   to the private component of the key pair.)

   Clients MUST provide the capability to produce a digitally signed
   revocation request control attribute.  Clients SHOULD be capable of
   producing an unsigned revocation request containing the end-entity's
   shared secret.  (The unsigned message consisting of a CMS signedData
   object with no signatures.)  If a client provides shared secret
   based self- revocation, the client MUST be capable of producing a
   revocation request containing the shared secret. Servers MUST be
   capable of accepting both forms of revocation requests.

   The structure of an unsigned, shared secret based revocation request
   is a matter of local implementation.  The shared secret does not
   need to be encrypted when sent in a revocation request.  The shared
   secret has a one-time use, that of causing the certificate to be
   revoked, and public knowledge of the shared secret after the
   certificate has been revoked is not a problem.  Clients need to
   inform users that the same shared secret SHOULD NOT be used for
   multiple certificates.

   A full response message MUST be returned for a revocation request.

5.12 Registration and Response Information Control Attributes

   The regInfo control attribute is for clients and LRAs to pass
   additional information as part a PKI request.  The regInfo control
   attribute uses the ASN.1 structure:

      RegInfo ::= OCTET STRING

   The content of this data is based on bilateral agreement between the
   client and server.

   If a server (or LRA) needs to return information back to a requestor
   in response to data submitted in a regInfo attribute, then that data
   is returned as a responseInfo control attribute.  The content of the
   OCTET STRING for response information is based on bilateral
   agreement between the client and server.

5.13 Query Pending Control Attribute
    


   In some environments, process requirements for manual intervention
   or other identity checking can cause a delay in returning the
   certificate related to a certificate request. The query pending
   attribute allows for a client to query a server about the state of a
   pending certificate request.  The server returns a token as part of
   the CMCStatusInfo attribute (in the otherInfo field).  The client
   puts the token into the query pending attribute to identify the
   correct request to the server.  The server can also return a
   suggested time for the client to query for the state of a pending
   certificate request.

   The ASN.1 structure used by the query pending control attribute is:

      QueryPending ::= OCTET STRING

   If a server returns a pending state (the transaction is still
   pending), the otherInfo MAY be omitted.  If it is not omitted then
   the same value MUST be returned (the token MUST NOT change during
   the request).

5.14 Confirm Certificate Acceptance

   Some Certification Authorities require that clients give a positive
   conformation that the certificates issued to it are acceptable.  The
   Confirm Certificate Acceptance control attribute is used for that
   purpose.  If the CMCStatusInfo on a certificate responserequest is
   confirmRequired, then the client MUST return a Confirm Certificate
   attribute contained in a full enrollment response message.

   Acceptance prior to any usage of the certificate.  Clients SHOULD
   wait for the response from the server that the conformation has been
   received before using the certificate for any purpose..

   The confirm certificate acceptance structure is:

      CMCCertId ::= IssuerSerial

   -- CMCCertId contains the issuer and serial number of the
   certificate being accepted.

   Servers MUST return a full enrollment response request for a confirm
   certificate acceptance control.

   Note that if the Certification Authority includes this attribute,
   there will be two full round trips of messages.

   The client sends the request to the CA.
   The CA returns the certificate and this attribute.
   The client sends a response message to the CA with an
   CMCStatusInfoEx control either accepting or rejecting the
   certificate.
   The CA sends a response message to the client with a CMCStatusInfoEx
   of success.

6.  Local Registration Authorities
    


   This specification permits the use of Local Registration Authorities
   (LRAs).  An LRA sits between the end-entity and the Certification
   Authority.  From the end-entity's perspective, the LRA appears to be
   the Certification Authority and from the server the LRA appears to
   be a client.  LRAs receive the enrollment messages, perform local
   processing and then forward onto Certificate Authorities. Some of
   the types of local processing that an LRA can perform include:

   -  batching multiple enrollment messages together,
   -  challenge/response POP proofs,
   -  addition of private or standardized certificate extensions to all
   requests,
   -  archival of private key material,
   -  routing of requests to different CAs.

   When an LRA receives an enrollment message it has three options: it
   may forward the message without modification, it may add a new
   wrapping layer to the message, or it may remove one or more existing
   layers and add a new wrapping layer.

   When an LRA adds a new wrapping layer to a message it creates a new
   PKIData object.  The new layer contains any control attributes
   required (for example if the LRA does the POP proof for an
   encryption key or the addExtension control attribute to modify an
   enrollment request) and the client enrollment message.  The client
   enrollment message is placed in the cmsSequence if it is a Full
   Enrollment message and in the reqSequence if it is a Simple
   Enrollment message. If an LRA is batching multiple client messages
   together, then each client enrollment message is placed into the
   appropriate location in the LRA's PKIData object along with all
   relevant control attributes.

   (If multiple LRAs are in the path between the end-entity and the
   Certification Authority, this will lead to multiple wrapping layers
   on the message.)

   In processing an enrollment message, an LRA MUST NOT alter any
   certificate request body (PKCS #10 or CRMF) as any alteration would
   invalidate the signature on the request and thus the POP for the
   private key.

   An example of how this would look is illustrated by the following
   figure:

      SignedData (by LRA)
        PKIData
          controlSequence
               LRA added control statements
          reqSequence
               Zero or more Simple CertificationRequests from clients
          cmsSequence
               Zero or more Full PKI messages from clients
                  SignedData (by client)
                      PKIData
    


   Under some circumstances an LRA is required to remove wrapping
   layers.  The following sections look at the processing required if
   encryption layers and signing layers need to be removed.

6.1  Encryption Removal

   There are two cases that require an LRA to remove or change
   encryption in an enrollment message.  In the first case the
   encryption was applied for the purposes of protecting the entire
   enrollment request from unauthorized entities.  If the CA does not
   have a recipient info entry in the encryption layer, the LRA MUST
   remove the encryption layer.  The LRA MAY add a new encryption layer
   with or without adding a new signing layer.

   The second change of encryption that may be required is to change
   the encryption inside of a signing layer.  In this case the LRA MUST
   remove all signing layers containing the encryption.  All control
   statements MUST be merged according to local policy rules as each
   signing layer is removed and the resulting merged controls MUST be
   placed in a new signing layer provided by the LRA.  If the signing
   layer provided by the end-entity needs to be removed to the LRA can
   remove the layer.

6.2  Signature Layer Removal

   Only two instances exist where an LRA should remove a signature
   layer on a Full Enrollment message.  If an encryption needs to be
   modified within the message, or if a Certificate Authority will not
   accept secondary delegation (i.e. multiple LRA signatures).  In all
   other situations LRAs SHOULD NOT remove a signing layer from a
   message.

   If an LRA removes a signing layer from a message, all control
   statements MUST be merged according to local policy rules.  The
   resulting merged control statements MUST be placed in a new signing
   layer provided by the LRA.

7.  Transport Wrapping

   Not all methods of transporting data allow for sending unlabeled raw
   binary data, in may cases standard methods of encoding can be used
   to greatly ease this issue.  These methods normally consist of
   wrapping some identification of the content around the binary data,
   possibly applying an encoding to the data and labeling the data.
   We document for use three different wrapping methods.

   -- MIME wrapping is for transports that are natively MIME based such
   as HTTP and E-mail.
   -- Binary file transport is defined since floppy disk transport is
   still very common.  File transport can be done either as MIME
   wrapped (section 7.1) or bare (section 7.2).
   -- Socket based transport uses the raw BER encoded object.

7.1  MIME Wrapping
    


   MIME wrapping is defined for those environments that are MIME
   native. These include E-Mail based protocols as well as HTTP.

   The basic mime wrapping in this section is taken from [SMIMEV2] and
   [SMIMEV3].  Simple enrollment requests are encoded using the
   application/pkcs10 content type.  A file name MUST be included
   either in a content type or content disposition statement.  The
   extension for the file MUST be ".p10".

   Simple enrollment response messages MUST be encoded as content-type
   application/pkcs7-mime.  An smime-type parameter MUST be on the
   content-type statement with a value of "certs-only." A file name
   with the ".p7c" extension MUST be specified as part of the content-
   type or content-disposition.

   Full enrollment request messages MUST be encoded as content-type
   application/pkcs7-mime.  The smime-type parameter MUST be included
   with a value of "CMC-enroll".  A file name with the ".p7m" extension
   MUST be specified as part of the content-type or content-disposition
   statement.

   Full enrollment response messages MUST be encoded as content-type
   application/pkcs7-mime.  The smime-type parameter MUST be included
   with a value of "CMC-response."  A file name with the ".p7m"
   extensions MUST be specified as part of the content-type or content-
   disposition.

   MIME TYPE                       File Extension        SMIME-TYPE

   application/pkcs10                .p10                  N/A
   (simple PKI request)

   application/pkcs7-mime            .p7m                  CMC-request
   (full PKI request)

   application/pkcs7-mime            .p7c                  certs-only
   (simple PKI response)

   application/pkcs7-mime            .p7m                  CMC-response
   (full PKI response)

7.2  File-Based Transport

   Enrollment messages and responses may also be transferred between
   clients and servers using file system-based mechanisms, such as when
   enrollment is performed for an off-line client.  When files are used
   to transport binary, BER-encoded Full Enrollment Request and
   Response messages, the following file type extensions SHOULD be
   used:

   Message Type                   File Extension

   Full PKI Request                 .crq

   Full PKI Response                .crp
    


7.3  Socket-Based Transport

   When enrollment messages and responses are sent over sockets, no
   wrapping is required.  Messages SHOULD be sent in their binary, BER-
   encoded form.

8.  Interoperability

8.1  Mandatory and Optional Algorithms

   CMC clients and servers MUST be capable of producing and processing
   message signatures using the Digital Signature Algorithm [DSA].  DSA
   signatures MUST be indicated by the DSA AlgorithmIdentifier value
   (as specified in section 7.2.2 of [PKIXCERT]).  PKI clients and
   servers SHOULD also be capable of producing and processing RSA
   signatures (as specified in section 7.2.1 of [PKIXCERT]).

   CMC clients and servers MUST be capable of protecting and accessing
   message encryption keys using the Diffie-Hellman (D-H) key exchange
   algorithm.  D-H/3DES protection MUST be indicated by the D-H
   AlgorithmIdentifier value specified in [CMS].  PKI clients and
   servers SHOULD also be capable of producing and processing RSA key
   transport.  When used for PKI messages, RSA key transport MUST be
   indicated as specified in section 7.2.1 of [PKIXCERT].

8.2  Minimum Conformance Requirements

   A minimally compliant CMC server:

   a) MUST accept a Full PKI Request message
      i) MUST accept CRMF Request Bodies within a Full PKI Request
      ii) MUST accept PKCS#10 Request Bodies within a Full PKI Request
   b) MUST accept a Simple Enrollment Request message
   c) MUST be able to return a Full PKI Response.  (A Full PKI Response
   is always a valid response, but for interoperability with downlevel
   clients a compliant server SHOULD use the Simple Enrollment Response
   whenever possible.)

   A minimally-complaint CMC client:

   a) MAY use either the Simple Enrollment Message or the Full PKI
   Request.
      i) clients MUST use PKCS#10 with the Simple Enrollment Message
      ii) clients MAY use either PKCS#10 or CRMF with the Full PKI
   Request
   b) MUST understand the Simple Enrollment Response.
   c) MUST understand the Full PKI Response.

9.  Security Considerations

   Initiation of a secure communications channel between an end-entity
   and a CA or LRA (and, similarly, between an LRA and another LRA or
   CA) necessarily requires an out-of-band trust initiation mechanism.
   For example, a secure channel may be constructed between the end-
   entity and the CA via IPSEC or TLS. Many such schemes exist and the
   choice of any particular scheme for trust initiation is outside the 


   scope of this document.  Implementers of this protocol are strongly
   encouraged to consider generally accepted principles of secure key
   management when integrating this capability within an overall
   security architecture.

   Mechanisms for thwarting replay attacks may be required in
   particular implementations of this protocol depending on the
   operational environment. In cases where the CA maintains significant
   state information, replay attacks may be detectable without the
   inclusion of the optional nonce mechanisms. Implementers of this
   protocol need to carefully consider environmental conditions before
   choosing whether or not to implement the senderNonce and
   recipientNonce attributes described in section 5.6.  Developers of
   state-constrained PKI clients are strongly encouraged to incorporate
   the use of these attributes.

   Under no circumstances should a signing key be archived.  Doing so
   allows the archiving entity to potentially use the key for forging
   signatures.

   Due care must be taken prior to archiving keys.  Once a key is given
   to an archiving entity, the archiving entity could use the keys in a
   way not conducive to the archiving entity.  Users should be made
   especially aware that proper verification is made of the certificate
   used to encrypt the private key material.

   Clients and servers need to do some checks on cryptographic
   parameters prior to issuing certificates to make sure that weak
   parameters are not used. A description of the small subgroup attack
   is provided in [X942].  CMC implementations ought to be aware of
   this attack when doing parameter validations.

   When using a shared-secret for authentication purposes, the shared-
   secret should be generated using good random number techniques.
   User selection of the secret allows for dictionary attacks to be
   mounted.

10. Acknowledgments

   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.

11. References

   [CMS]      Housley, R., "Cryptographic Message Syntax", RFC 2630,
              June 1999.

   [CRMF]     Myers, M., Adams, C., Solo, D. and D. Kemp, "Internet
              X.509 Certificate Request Message Format", RFC 2511,
   March
              1999.

   [DH]       B. Kaliski, "PKCS 3: Diffie-Hellman Key Agreement v1.4"
    


   [DH-POP]   H. Prafullchandra, J. Schaad, "Diffie-Hellman Proof-of-
              Possession Algorithms", Work in Progress.

   [HMAC]     Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104, February
              1997.

   [PKCS1]    Kaliski, B., "PKCS #1: RSA Encryption, Version 1.5", RFC
              2313, March 1998.

   [PKCS7]    Kaliski, B., "PKCS #7: Cryptographic Message Syntax
   v1.5",
              RFC 2315, October 1997.

   [PKCS8]    RSA Laboratories, "PKCS#8: Private-Key Information Syntax
              Standard, Version 1.2", November 1, 1993.

   [PKCS10]   Kaliski, B., "PKCS #10: Certification Request Syntax
              v1.5", RFC 2314, October 1997.

   [PKIXCERT] Housley, R., Ford, W., Polk, W. and D. Solo "Internet
              X.509 Public Key Infrastructure Certificate and CRL
              Profile", RFC 2459, January 1999.

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

   [SMIMEV2]  Dusse, S., Hoffman, P., Ramsdell, B., Lundblade, L. and
   L.
              Repka, "S/MIME Version 2 Message Specification", RFC
   2311,
              March 1998.

   [SMIMEV3]  Ramsdell, B., "S/MIME Version 3 Message Specification",
              RFC 2633, June 1999.

   [X942]     Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC
              2631, June 1999.

12. Authors' Addresses

   Michael Myers
   VeriSign Inc.
   1350 Charleston Road
   Mountain View, CA, 94043

   Phone: (650) 429-3402
   EMail: mmyers@verisign.com


   Xiaoyi Liu
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA 95134

   Phone: (480) 526-7430 


   EMail: xliu@cisco.com


   Jim Schaad

   EMail:  jimsch@nwlinkexmsft.com


   Jeff Weinstein

   EMail: jsw@meer.net

Appendix A  ASN.1 Module

   EnrollmentMessageSyntax
   { iso(1) identified-organization(3) dod(4) internet(1)
   security(5) mechansims(5) pkix(7) id-mod(0) id-mod-cmc(6) }

   DEFINITIONS IMPLICIT TAGS ::=
   BEGIN

   -- EXPORTS All --
   -- The types and values defined in this module are exported for use
   -- in the other ASN.1 modules.  Other applications may use them for
   -- their own purposes.

   IMPORTS

     -- Information Directory Framework (X.501)
           Name
              FROM InformationFramework { joint-iso-itu-t ds(5)
                   modules(1) informationFramework(1) 3 }

     -- Directory Authentication Framework (X.509)
           AlgorithmIdentifier, AttributeCertificate, Certificate,
           CertificateList, CertificateSerialNumber
              FROM AuthenticationFramework { joint-iso-itu-t ds(5)
                   module(1) authenticationFramework(7) 3 }

     -- PKIX Part 1 - Implicit
        GeneralName, CRLReason, ReasonFlags
        FROM PKIX1Implicit88 {iso(1) identified-organization(3) dod(6)
                internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
                id-pkix1-implicit-88(2)}

     -- PKIX Part 1 - Explicit
        SubjectPublicKeyInfo, Extension
        FROM PKIX1Explicit88 {iso(1) identified-organization(3) dod(6)
                internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
                id-pkix1-explicit-88(1)}

     -- Cryptographic Message Syntax
        ContentInfo, Attribute
          FROM CryptographicMessageSyntax { 1 2 840 113549 1 9 16 0 1}

     -- CRMF 


        CertReqMsg
        FROM CRMF { 1 3 6 1 5 5 7 0 5 };

    id-pkix OBJECT IDENTIFIER  ::= { iso(1) identified-organization(3)
        dod(6) internet(1) security(5) mechanisms(5) pkix(7) }

        id-cmc OBJECT IDENTIFIER ::= {id-pkix 7}   -- CMC controls
        id-cct OBJECT IDENTIFIER ::= {id-pkix 12}  -- CMC content types

    -- The following controls have simple type content (usually OCTET
   STRING)

    id-cmc-identification OBJECT IDENTIFIER ::= {id-cmc 2}
    id-cmc-identityProof OBJECT IDENTIFIER ::= {id-cmc 3}
    id-cmc-dataReturn OBJECT IDENTIFIER ::= {id-cmc 4}
    id-cmc-transactionId OBJECT IDENTIFIER ::= {id-cmc 5}
    id-cmc-senderNonce OBJECT IDENTIFIER ::= {id-cmc 6}
    id-cmc-recipientNonce OBJECT IDENTIFIER ::= {id-cmc 7}
    id-cmc-regInfo OBJECT IDENTIFIER ::= {id-cmc 18}
    id-cmc-responseInfo OBJECT IDENTIFIER ::= {id-cmc 19}
    id-cmc-queryPending OBJECT IDENTIFIER ::= {id-cmc 21}
    id-cmc-popLinkRandom OBJECT IDENTIFIER ::= {id-cmc 22)
    id-cmc-popLinkWitness OBJECT IDENTIFIER ::= (id-cmc 23)

    -- This is the content type used for a request message in the
   protocol

    id-cct-PKIData OBJECT IDENTIFIER ::= { id-cct 2 }


    PKIData ::= SEQUENCE

        controlSequence    SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
        reqSequence        SEQUENCE SIZE(0..MAX) OF TaggedRequest,
        cmsSequence        SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
        otherMsgSequence   SEQUENCE SIZE(0..MAX) OF OtherMsg
    }

    bodyIdMax INTEGER ::= 4294967295

    BodyPartID ::= INTEGER(0..bodyIdMax)

    TaggedAttribute ::= SEQUENCE

        bodyPartID         BodyPartId,
        attrType           OBJECT IDENTIFIER,
        attrValues         SET OF AttributeValue
    }

    AttributeValue ::= ANY

    TaggedRequest ::= CHOICE

        tcr               [0] TaggedCertificationRequest,
        crm               [1] CertReqMsg
    }

    TaggedCertificationRequest ::= SEQUENCE

        bodyPartID            BodyPartID, 


        certificationRequest  CertificationRequest
    }

    CertificationRequest ::= SEQUENCE

      certificationRequestInfo  SEQUENCE

        version                   INTEGER,
        subject                   Name,
        subjectPublicKeyInfo      SEQUENCE

          algorithm                 AlgorithmIdentifier,
          subjectPublicKey          BIT STRING },
        attributes                [0] IMPLICIT SET OF Attribute },
      signatureAlgorithm        AlgorithmIdentifier,
      signature                 BIT STRING
    }

    TaggedContentInfo ::= SEQUENCE

        bodyPartID              BodyPartId,
        contentInfo             ContentInfo
    }

    OtherMsg ::= SEQUENCE

        bodyPartID        BodyPartID,
        otherMsgType      OBJECT IDENTIFIER,
        otherMsgValue     ANY DEFINED BY otherMsgType }

    --  This defines the response message in the protocol
    id-cct-PKIResponse OBJECT IDENTIFIER ::= { id-cct 3 }

    ResponseBody ::= SEQUENCE

        controlSequence   SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
        cmsSequence       SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
        otherMsgSequence  SEQUENCE SIZE(0..MAX) OF OtherMsg
    }

    -- Used to return status state in a response

    id-cmc-cMCStatusInfo OBJECT IDENTIFIER ::= {id-cmc 1}

    CMCStatusInfo ::= SEQUENCE

        cMCStatus       CMCStatus,
        bodyList        SEQUENCE SIZE (1..MAX) OF INTEGERBodyPartID,
        statusString    UTF8String OPTIONAL,
        otherInfo        CHOICE

          failInfo         CMCFailInfo,
          pendInfo         PendInfo } OPTIONAL
    }

    PendInfo ::= SEQUENCE

        pendToken        INTEGEROCTET STRING,
        pendTime         GENERALIZEDTIME
    }

    CMCStatus ::= INTEGER

        success         (0),
        -- you got exactly what you asked for
        failed          (2), 


        -- you don't get it, more information elsewhere in the message
        pending         (3),
        -- the request body part has not yet been processed,
        -- requester is responsible to poll back on this
        noSupport       (4)
        -- the requested operation is not supported
    }

    CMCFailInfo ::= INTEGER

        badAlg          (0),
        -- Unrecognized or unsupported algorithm
        badMessageCheck (1),
        -- integrity check failed
        badRequest      (2),
        -- transaction not permitted or supported
        badTime         (3),
        -- Message time field was not sufficiently close to the
   systemtime
        badCertId       (4),
        -- No certificate could be identified matching the provided
   criteria
        unsuportedExt   (5),
        -- A requested X.509 extension is not supported by the
   recipient CA.
        mustArchiveKeys (6),
        -- Private key material must be supplied
        badIdentity     (7),
        -- Identification Attribute failed to verify
        popRequired     (8),
        -- Server requires a POP proof before issuing certificate
        popFailed       (9),
        -- Server failed to get an acceptable POP for the request
        noKeyReuse      (10)
        -- Server policy does not allow key re-use
        internalCAError (11)
        tryLater        (12)
    }

    -- Used for LRAs to add extensions to certificate requests
    id-cmc-addExtensions OBJECT IDENTIFIER ::= {id-cmc 8}

    AddExtensions ::= SEQUENCE

        pkiDataReference    BodyPartID,
        certReferences      SEQUENCE OF BodyPartID,
        extensions          SEQUENCE OF Extension
    }


    id-cmc-encryptedPOP OBJECT IDENTIFIER ::= {id-cmc 9}
    id-cmc-decryptedPOP OBJECT IDENTIFIER ::= {id-cmc 10}

    EncryptedPOP ::= SEQUENCE

                request       TaggedRequest,
        cms             ContentInfo,
        thePOPAlgID     AlgorithmIdentifier,
        witnessAlgID    AlgorithmIdentifier, 


        witness         OCTET STRING
    }

    DecryptedPOP ::= SEQUENCE

        bodyPartID      BodyPartID,
        thePOPAlgID     AlgorithmIdentifier,
        thePOP          OCTET STRING
    }

    id-cmc-lraPOPWitness OBJECT IDENTIFIER ::= {id-cmc 11}

    LraPopWitness ::= SEQUENCE

        pkiDataBodyid   BodyPartID,
        bodyIds         SEQUENCE OF BodyPartID
    }


    --
    id-cmc-getCert OBJECT IDENTIFIER ::= {id-cmc 15}

    GetCert ::= SEQUENCE

        issuerName      GeneralName,
        serialNumber    INTEGER }


    id-cmc-getCRL OBJECT IDENTIFIER ::= {id-cmc 16}

    GetCRL ::= SEQUENCE

        issuerName    Name,
        cRLName       GeneralName OPTIONAL,
        time          GeneralizedTime OPTIONAL,
        reasons       ReasonFlags OPTIONAL }

    id-cmc-revokeRequest OBJECT IDENTIFIER ::= {id-cmc 17}

    RevRequest ::= SEQUENCE

        issuerName            Name,
        serialNumber          INTEGER,
        reason                CRLReason,
       invalidityDate         GeneralizedTime OPTIONAL,
        passphrase            OCTET STRING OPTIONAL,
        comment               UTF8String OPTIONAL }

   id-cmc-confirmCertAcceptance OBJECT IDENTIFIER ::= {pkix-cmc 24}

   CMCCertId ::= IssuerSerial

   -- The following is used to request V3 extensions be added to a
   certificate

   id-ExtensionReq OBJECT IDENTIFIER ::= {iso(1) member-body(2) us(840)
        rsadsi(113549) pkcs(1) pkcs-9(9) 14}

   ExtensionReq ::= SEQUENCE OF Extension
    


   -- The following exists to allow Diffie-Hellman Certificate Requests
   Messages to be
   -- well-formed

   id-alg-noSignature OBJECT IDENTIFIER ::= {id-pkix id-alg(6) 2}

   NoSignatureValue ::= OCTET STRING

   END

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   Funding for the RFC Editor function is currently provided by the
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