3. Data Structures

   This section contains descriptions of the data structures required
   for PKI management messages. Section 4 describes constraints on their
   values and the sequence of events for each of the various PKI
   management operations. Section 5 describes how these may be
   encapsulated in various transport mechanisms.

3.1 Overall PKI Message

   All of the messages used in this specification for the purposes of
   PKI management use the following structure:

     PKIMessage ::= SEQUENCE {
         header           PKIHeader,
         body             PKIBody,
         protection   [0] PKIProtection OPTIONAL,
         extraCerts   [1] SEQUENCE SIZE (1..MAX) OF Certificate OPTIONAL
     }

   The PKIHeader contains information which is common to many PKI
   messages.

   The PKIBody contains message-specific information.

   The PKIProtection, when used, contains bits that protect the PKI
   message.

   The extraCerts field can contain certificates that may be useful to
   the recipient. For example, this can be used by a CA or RA to present
   an end entity with certificates that it needs to verify its own new
   certificate (if, for example, the CA that issued the end entity's
   certificate is not a root CA for the end entity).  Note that this
   field does not necessarily contain a certification path - the
   recipient may have to sort, select from, or otherwise process the
   extra certificates in order to use them.

3.1.1 PKI Message Header

   All PKI messages require some header information for addressing and
   transaction identification. Some of this information will also be
   present in a transport-specific envelope; however, if the PKI message
   is protected then this information is also protected (i.e., we make
   no assumption about secure transport).

   The following data structure is used to contain this information:

     PKIHeader ::= SEQUENCE {
         pvno                INTEGER     { ietf-version2 (1) },
         sender              GeneralName,
         -- identifies the sender
         recipient           GeneralName,
         -- identifies the intended recipient
         messageTime     [0] GeneralizedTime         OPTIONAL,
         -- time of production of this message (used when sender
         -- believes that the transport will be "suitable"; i.e.,
         -- that the time will still be meaningful upon receipt)
         protectionAlg   [1] AlgorithmIdentifier     OPTIONAL,
         -- algorithm used for calculation of protection bits
         senderKID       [2] KeyIdentifier           OPTIONAL,
         recipKID        [3] KeyIdentifier           OPTIONAL,
         -- to identify specific keys used for protection
         transactionID   [4] OCTET STRING            OPTIONAL,
         -- identifies the transaction; i.e., this will be the same in
         -- corresponding request, response and confirmation messages
         senderNonce     [5] OCTET STRING            OPTIONAL,
         recipNonce      [6] OCTET STRING            OPTIONAL,
         -- nonces used to provide replay protection, senderNonce

         -- is inserted by the creator of this message; recipNonce
         -- is a nonce previously inserted in a related message by
         -- the intended recipient of this message
         freeText        [7] PKIFreeText             OPTIONAL,
         -- this may be used to indicate context-specific instructions
         -- (this field is intended for human consumption)
         generalInfo     [8] SEQUENCE SIZE (1..MAX) OF
                                InfoTypeAndValue     OPTIONAL
         -- this may be used to convey context-specific information
         -- (this field not primarily intended for human consumption)
     }

     PKIFreeText ::= SEQUENCE SIZE (1..MAX) OF UTF8String
         -- text encoded as UTF-8 String (note:  each UTF8String SHOULD
         -- include an RFC 1766 language tag to indicate the language
         -- of the contained text)

   The pvno field is fixed (at one) for this version of this
   specification.

   The sender field contains the name of the sender of the PKIMessage.
   This name (in conjunction with senderKID, if supplied) should be
   usable to verify the protection on the message.  If nothing about the
   sender is known to the sending entity (e.g., in the init. req.
   message, where the end entity may not know its own Distinguished Name
   (DN), e-mail name, IP address, etc.), then the "sender" field MUST
   contain a "NULL" value; that is, the SEQUENCE OF relative
   distinguished names is of zero length. In such a case the senderKID
   field MUST hold an identifier (i.e., a reference number) which
   indicates to the receiver the appropriate shared secret information
   to use to verify the message.

   The recipient field contains the name of the recipient of the
   PKIMessage. This name (in conjunction with recipKID, if supplied)
   should be usable to verify the protection on the message.

   The protectionAlg field specifies the algorithm used to protect the
   message. If no protection bits are supplied (note that PKIProtection
   is OPTIONAL) then this field MUST be omitted; if protection bits are
   supplied then this field MUST be supplied.

   senderKID and recipKID are usable to indicate which keys have been
   used to protect the message (recipKID will normally only be required
   where protection of the message uses Diffie-Hellman (DH) keys).

   The transactionID field within the message header MAY be used to
   allow the recipient of a response message to correlate this with a
   previously issued request. For example, in the case of an RA there
   may be many requests "outstanding" at a given moment.

   The senderNonce and recipNonce fields protect the PKIMessage against
   replay attacks.

   The messageTime field contains the time at which the sender created
   the message. This may be useful to allow end entities to correct
   their local time to be consistent with the time on a central system.

   The freeText field may be used to send a human-readable message to
   the recipient (in any number of languages).  The first language used
   in this sequence indicates the desired language for replies.

   The generalInfo field may be used to send machine-processable
   additional data to the recipient.

3.1.2 PKI Message Body

     PKIBody ::= CHOICE {       -- message-specific body elements
         ir      [0]  CertReqMessages,        --Initialization Request
         ip      [1]  CertRepMessage,         --Initialization Response
         cr      [2]  CertReqMessages,        --Certification Request
         cp      [3]  CertRepMessage,         --Certification Response
         p10cr   [4]  CertificationRequest,   --PKCS #10 Cert. Req.
           -- the PKCS #10 certification request (see [PKCS10])
         popdecc [5]  POPODecKeyChallContent, --pop Challenge
         popdecr [6]  POPODecKeyRespContent,  --pop Response
         kur     [7]  CertReqMessages,        --Key Update Request
         kup     [8]  CertRepMessage,         --Key Update Response
         krr     [9]  CertReqMessages,        --Key Recovery Request
         krp     [10] KeyRecRepContent,       --Key Recovery Response
         rr      [11] RevReqContent,          --Revocation Request
         rp      [12] RevRepContent,          --Revocation Response
         ccr     [13] CertReqMessages,        --Cross-Cert. Request
         ccp     [14] CertRepMessage,         --Cross-Cert. Response
         ckuann  [15] CAKeyUpdAnnContent,     --CA Key Update Ann.
         cann    [16] CertAnnContent,         --Certificate Ann.
         rann    [17] RevAnnContent,          --Revocation Ann.
         crlann  [18] CRLAnnContent,          --CRL Announcement
         conf    [19] PKIConfirmContent,      --Confirmation
         nested  [20] NestedMessageContent,   --Nested Message
         genm    [21] GenMsgContent,          --General Message
         genp    [22] GenRepContent,          --General Response
         error   [23] ErrorMsgContent         --Error Message
     }

   The specific types are described in Section 3.3 below.

3.1.3 PKI Message Protection

   Some PKI messages will be protected for integrity. (Note that if an
   asymmetric algorithm is used to protect a message and the relevant
   public component has been certified already, then the origin of
   message can also be authenticated.  On the other hand, if the public
   component is uncertified then the message origin cannot be
   automatically authenticated, but may be authenticated via out-of-band
   means.)

   When protection is applied the following structure is used:

     PKIProtection ::= BIT STRING

   The input to the calculation of PKIProtection is the DER encoding of
   the following data structure:

     ProtectedPart ::= SEQUENCE {
         header    PKIHeader,
         body      PKIBody
     }

   There MAY be cases in which the PKIProtection BIT STRING is
   deliberately not used to protect a message (i.e., this OPTIONAL field
   is omitted) because other protection, external to PKIX, will instead
   be applied. Such a choice is explicitly allowed in this
   specification.  Examples of such external protection include PKCS #7
   [PKCS7] and Security Multiparts [RFC1847] encapsulation of the
   PKIMessage (or simply the PKIBody (omitting the CHOICE tag), if the
   relevant PKIHeader information is securely carried in the external
   mechanism); specification of external protection using PKCS #7 will
   be provided in a separate document.  It is noted, however, that many
   such external mechanisms require that the end entity already
   possesses a public-key certificate, and/or a unique Distinguished
   Name, and/or other such infrastructure-related information. Thus,
   they may not be appropriate for initial registration, key-recovery,
   or any other process with "boot-strapping" characteristics.  For
   those cases it may be necessary that the PKIProtection parameter be
   used.  In the future, if/when external mechanisms are modified to
   accommodate boot-strapping scenarios, the use of PKIProtection may
   become rare or non-existent.

   Depending on the circumstances the PKIProtection bits may contain a
   Message Authentication Code (MAC) or signature. Only the following
   cases can occur:

   - shared secret information

   In this case the sender and recipient share secret information
   (established via out-of-band means or from a previous PKI management
   operation).  PKIProtection will contain a MAC value and the
   protectionAlg will be the following:

     PasswordBasedMac ::= OBJECT IDENTIFIER --{1 2 840 113533 7 66 13}
     PBMParameter ::= SEQUENCE {
         salt                OCTET STRING,
         owf                 AlgorithmIdentifier,
         -- AlgId for a One-Way Function (SHA-1 recommended)
         iterationCount      INTEGER,
         -- number of times the OWF is applied
         mac                 AlgorithmIdentifier
         -- the MAC AlgId (e.g., DES-MAC, Triple-DES-MAC [PKCS11],
     }   -- or HMAC [RFC2104, RFC2202])

   In the above protectionAlg the salt value is appended to the shared
   secret input. The OWF is then applied iterationCount times, where the
   salted secret is the input to the first iteration and, for each
   successive iteration, the input is set to be the output of the
   previous iteration. The output of the final iteration (called
   "BASEKEY" for ease of reference, with a size of "H") is what is used
   to form the symmetric key. If the MAC algorithm requires a K-bit key
   and K <= H, then the most significant K bits of BASEKEY are used. If
   K > H, then all of BASEKEY is used for the most significant H bits of
   the key, OWF("1" || BASEKEY) is used for the next most significant H
   bits of the key, OWF("2" || BASEKEY) is used for the next most
   significant H bits of the key, and so on, until all K bits have been
   derived. [Here "N" is the ASCII byte encoding the number N and "||"
   represents concatenation.]

   - DH key pairs

   Where the sender and receiver possess Diffie-Hellman certificates
   with compatible DH parameters, then in order to protect the message
   the end entity must generate a symmetric key based on its private DH
   key value and the DH public key of the recipient of the PKI message.
   PKIProtection will contain a MAC value keyed with this derived
   symmetric key and the protectionAlg will be the following:

     DHBasedMac ::= OBJECT IDENTIFIER --{1 2 840 113533 7 66 30}

     DHBMParameter ::= SEQUENCE {
         owf                 AlgorithmIdentifier,
         -- AlgId for a One-Way Function (SHA-1 recommended)
         mac                 AlgorithmIdentifier
         -- the MAC AlgId (e.g., DES-MAC, Triple-DES-MAC [PKCS11],
     }   -- or HMAC [RFC2104, RFC2202])

   In the above protectionAlg OWF is applied to the result of the
   Diffie-Hellman computation. The OWF output (called "BASEKEY" for ease
   of reference, with a size of "H") is what is used to form the
   symmetric key. If the MAC algorithm requires a K-bit key and K <= H,
   then the most significant K bits of BASEKEY are used. If K > H, then
   all of BASEKEY is used for the most significant H bits of the key,
   OWF("1" || BASEKEY) is used for the next most significant H bits of
   the key, OWF("2" || BASEKEY) is used for the next most significant H
   bits of the key, and so on, until all K bits have been derived. [Here
   "N" is the ASCII byte encoding the number N and "||" represents
   concatenation.]

   - signature

   Where the sender possesses a signature key pair it may simply sign
   the PKI message. PKIProtection will contain the signature value and
   the protectionAlg will be an AlgorithmIdentifier for a digital
   signature (e.g., md5WithRSAEncryption or dsaWithSha-1).

   - multiple protection

   In cases where an end entity sends a protected PKI message to an RA,
   the RA MAY forward that message to a CA, attaching its own protection
   (which MAY be a MAC or a signature, depending on the information and
   certificates shared between the RA and the CA). This is accomplished
   by nesting the entire message sent by the end entity within a new PKI
   message. The structure used is as follows.

     NestedMessageContent ::= PKIMessage

3.2 Common Data Structures

   Before specifying the specific types that may be placed in a PKIBody
   we define some data structures that are used in more than one case.

3.2.1 Requested Certificate Contents

   Various PKI management messages require that the originator of the
   message indicate some of the fields that are required to be present
   in a certificate. The CertTemplate structure allows an end entity or
   RA to specify as much as it wishes about the certificate it requires.
   CertTemplate is identical to a Certificate but with all fields
   optional.

   Note that even if the originator completely specifies the contents of
   a certificate it requires, a CA is free to modify fields within the
   certificate actually issued.  If the modified certificate is
   unacceptable to the requester, the Confirmation message may be
   withheld, or an Error Message may be sent (with a PKIStatus of
   "rejection").

   See [CRMF] for CertTemplate syntax.

3.2.2 Encrypted Values

   Where encrypted values (restricted, in this specification, to be
   either private keys or certificates) are sent in PKI messages the
   EncryptedValue data structure is used.

   See [CRMF] for EncryptedValue syntax.

   Use of this data structure requires that the creator and intended
   recipient respectively be able to encrypt and decrypt. Typically,
   this will mean that the sender and recipient have, or are able to
   generate, a shared secret key.

   If the recipient of the PKIMessage already possesses a private key
   usable for decryption, then the encSymmKey field MAY contain a
   session key encrypted using the recipient's public key.

3.2.3 Status codes and Failure Information for PKI messages

   All response messages will include some status information. The
   following values are defined.

     PKIStatus ::= INTEGER {
         granted                (0),
         -- you got exactly what you asked for
         grantedWithMods        (1),
         -- you got something like what you asked for; the
         -- requester is responsible for ascertaining the differences
         rejection              (2),
         -- you don't get it, more information elsewhere in the message

         waiting                (3),
         -- the request body part has not yet been processed,
         -- expect to hear more later
         revocationWarning      (4),
         -- this message contains a warning that a revocation is
         -- imminent
         revocationNotification (5),
         -- notification that a revocation has occurred
         keyUpdateWarning       (6)
         -- update already done for the oldCertId specified in
         -- the key update request message
     }

   Responders may use the following syntax to provide more information
   about failure cases.

     PKIFailureInfo ::= BIT STRING {
     -- since we can fail in more than one way!
     -- More codes may be added in the future if/when required.
         badAlg           (0),
         -- unrecognized or unsupported Algorithm Identifier
         badMessageCheck  (1),
         -- integrity check failed (e.g., signature did not verify)
         badRequest       (2),
         -- transaction not permitted or supported
         badTime          (3),
         -- messageTime was not sufficiently close to the system time,
         -- as defined by local policy
         badCertId        (4),
         -- no certificate could be found matching the provided criteria
         badDataFormat    (5),
         -- the data submitted has the wrong format
         wrongAuthority   (6),
         -- the authority indicated in the request is different from the
         -- one creating the response token
         incorrectData    (7),
         -- the requester's data is incorrect (used for notary services)
         missingTimeStamp (8),
         -- when the timestamp is missing but should be there (by policy)
         badPOP           (9)
         -- the proof-of-possession failed
     }
     PKIStatusInfo ::= SEQUENCE {
         status        PKIStatus,
         statusString  PKIFreeText     OPTIONAL,
         failInfo      PKIFailureInfo  OPTIONAL
     }

3.2.4 Certificate Identification

   In order to identify particular certificates the CertId data
   structure is used.

   See [CRMF] for CertId syntax.

3.2.5 "Out-of-band" root CA public key

   Each root CA must be able to publish its current public key via some
   "out-of-band" means. While such mechanisms are beyond the scope of
   this document, we define data structures which can support such
   mechanisms.

   There are generally two methods available: either the CA directly
   publishes its self-signed certificate; or this information is
   available via the Directory (or equivalent) and the CA publishes a
   hash of this value to allow verification of its integrity before use.

     OOBCert ::= Certificate

   The fields within this certificate are restricted as follows:

   - The certificate MUST be self-signed  (i.e., the signature must be
     verifiable using the SubjectPublicKeyInfo field);
   - The subject and issuer fields MUST be identical;
   - If the subject field is NULL then both subjectAltNames and
     issuerAltNames extensions MUST be present and have exactly the same
     value;
   - The values of all other extensions must be suitable for a self-
     signed certificate (e.g., key identifiers for subject and issuer
     must be the same).

     OOBCertHash ::= SEQUENCE {
         hashAlg     [0] AlgorithmIdentifier     OPTIONAL,
         certId      [1] CertId                  OPTIONAL,
         hashVal         BIT STRING
         -- hashVal is calculated over the self-signed
         -- certificate with the identifier certID.
     }

   The intention of the hash value is that anyone who has securely
   received the hash value (via the out-of-band means) can verify a
   self- signed certificate for that CA.

3.2.6 Archive Options

   Requesters may indicate that they wish the PKI to archive a private
   key value using the PKIArchiveOptions structure

   See [CRMF] for PKIArchiveOptions syntax.

3.2.7 Publication Information

   Requesters may indicate that they wish the PKI to publish a
   certificate using the PKIPublicationInfo structure.

   See [CRMF] for PKIPublicationInfo syntax.

3.2.8  Proof-of-Possession Structures

   If the certification request is for a signing key pair (i.e., a
   request for a verification certificate), then the proof of possession
   of the private signing key is demonstrated through use of the
   POPOSigningKey structure.

   See [CRMF] for POPOSigningKey syntax, but note that
   POPOSigningKeyInput has the following semantic stipulations in this
   specification.

     POPOSigningKeyInput ::= SEQUENCE {
         authInfo            CHOICE {
             sender              [0] GeneralName,
             -- from PKIHeader (used only if an authenticated identity
             -- has been established for the sender (e.g., a DN from a
             -- previously-issued and currently-valid certificate))
             publicKeyMAC        [1] PKMACValue
             -- used if no authenticated GeneralName currently exists for
             -- the sender; publicKeyMAC contains a password-based MAC
             -- (using the protectionAlg AlgId from PKIHeader) on the
             -- DER-encoded value of publicKey
         },
         publicKey           SubjectPublicKeyInfo    -- from CertTemplate
     }

   On the other hand, if the certification request is for an encryption
   key pair (i.e., a request for an encryption certificate), then the
   proof of possession of the private decryption key may be demonstrated
   in one of three ways.

      1) By the inclusion of the private key (encrypted) in the
         CertRequest (in the PKIArchiveOptions control structure).

      2) By having the CA return not the certificate, but an encrypted
         certificate (i.e., the certificate encrypted under a randomly-
         generated symmetric key, and the symmetric key encrypted under
         the public key for which the certification request is being
         made) -- this is the "indirect" method mentioned previously in
         Section 2.3.2.  The end entity proves knowledge of the private
         decryption key to the CA by MACing the PKIConfirm message using
         a key derived from this symmetric key.  [Note that if more than
         one CertReqMsg is included in the PKIMessage, then the CA uses
         a different symmetric key for each CertReqMsg and the MAC uses
         a key derived from the concatenation of all these keys.]  The
         MACing procedure uses the PasswordBasedMac AlgId defined in
         Section 3.1.

      3) By having the end entity engage in a challenge-response
         protocol (using the messages POPODecKeyChall and
         POPODecKeyResp; see below) between CertReqMessages and
         CertRepMessage -- this is the "direct" method mentioned
         previously in Section 2.3.2.  [This method would typically be
         used in an environment in which an RA verifies POP and then
         makes a certification request to the CA on behalf of the end
         entity.  In such a scenario, the CA trusts the RA to have done
         POP correctly before the RA requests a certificate for the end
         entity.]  The complete protocol then looks as follows (note
         that req' does not necessarily encapsulate req as a nested
         message):

                        EE            RA            CA
                         ---- req ---->
                         <--- chall ---
                         ---- resp --->
                                       ---- req' --->
                                       <--- rep -----
                                       ---- conf --->
                         <--- rep -----
                         ---- conf --->

   This protocol is obviously much longer than the 3-way exchange given
   in choice (2) above, but allows a local Registration Authority to be
   involved and has the property that the certificate itself is not
   actually created until the proof of possession is complete.

   If the cert. request is for a key agreement key (KAK) pair, then the
   POP can use any of the 3 ways described above for enc. key pairs,
   with the following changes:  (1) the parenthetical text of bullet 2)
   is replaced with "(i.e., the certificate encrypted under the
   symmetric key derived from the CA's private KAK and the public key
   for which the certification request is being made)"; (2) the first

   parenthetical text of the challenge field of "Challenge" below is
   replaced with "(using PreferredSymmAlg (see Appendix B6) and a
   symmetric key derived from the CA's private KAK and the public key
   for which the certification request is being made)".  Alternatively,
   the POP can use the POPOSigningKey structure given in [CRMF] (where
   the alg field is DHBasedMAC and the signature field is the MAC) as a
   fourth alternative for demonstrating POP if the CA already has a D-H
   certificate that is known to the EE.

   The challenge-response messages for proof of possession of a private
   decryption key are specified as follows (see [MvOV97, p.404] for
   details).  Note that this challenge-response exchange is associated
   with the preceding cert. request message (and subsequent cert.
   response and confirmation messages) by the nonces used in the
   PKIHeader and by the protection (MACing or signing) applied to the
   PKIMessage.

     POPODecKeyChallContent ::= SEQUENCE OF Challenge
     -- One Challenge per encryption key certification request (in the
     -- same order as these requests appear in CertReqMessages).

     Challenge ::= SEQUENCE {
         owf                 AlgorithmIdentifier  OPTIONAL,
         -- MUST be present in the first Challenge; MAY be omitted in any
         -- subsequent Challenge in POPODecKeyChallContent (if omitted,
         -- then the owf used in the immediately preceding Challenge is
         -- to be used).
         witness             OCTET STRING,
         -- the result of applying the one-way function (owf) to a
         -- randomly-generated INTEGER, A.  [Note that a different
         -- INTEGER MUST be used for each Challenge.]
         challenge           OCTET STRING
         -- the encryption (under the public key for which the cert.
         -- request is being made) of Rand, where Rand is specified as
         --   Rand ::= SEQUENCE {
         --      int      INTEGER,
         --       - the randomly-generated INTEGER A (above)
         --      sender   GeneralName
         --       - the sender's name (as included in PKIHeader)
         --   }
     }

     POPODecKeyRespContent ::= SEQUENCE OF INTEGER
     -- One INTEGER per encryption key certification request (in the
     -- same order as these requests appear in CertReqMessages).  The
     -- retrieved INTEGER A (above) is returned to the sender of the
     -- corresponding Challenge.

3.3 Operation-Specific Data Structures

3.3.1 Initialization Request

   An Initialization request message contains as the PKIBody an
   CertReqMessages data structure which specifies the requested
   certificate(s).  Typically, SubjectPublicKeyInfo, KeyId, and Validity
   are the template fields which may be supplied for each certificate
   requested (see Appendix B profiles for further information).  This
   message is intended to be used for entities first initializing into
   the PKI.

   See [CRMF] for CertReqMessages syntax.

3.3.2 Initialization Response

   An Initialization response message contains as the PKIBody an
   CertRepMessage data structure which has for each certificate
   requested a PKIStatusInfo field, a subject certificate, and possibly
   a private key (normally encrypted with a session key, which is itself
   encrypted with the protocolEncKey).

   See Section 3.3.4 for CertRepMessage syntax.  Note that if the PKI
   Message Protection is "shared secret information" (see Section
   3.1.3), then any certificate transported in the caPubs field may be
   directly trusted as a root CA certificate by the initiator.

3.3.3 Registration/Certification Request

   A Registration/Certification request message contains as the PKIBody
   a CertReqMessages data structure which specifies the requested
   certificates.  This message is intended to be used for existing PKI
   entities who wish to obtain additional certificates.

   See [CRMF] for CertReqMessages syntax.

   Alternatively, the PKIBody MAY be a CertificationRequest (this
   structure is fully specified by the ASN.1 structure
   CertificationRequest given in [PKCS10]).  This structure may be
   required for certificate requests for signing key pairs when
   interoperation with legacy systems is desired, but its use is
   strongly discouraged whenever not absolutely necessary.

3.3.4 Registration/Certification Response

   A registration response message contains as the PKIBody a
   CertRepMessage data structure which has a status value for each
   certificate requested, and optionally has a CA public key, failure
   information, a subject certificate, and an encrypted private key.

  CertRepMessage ::= SEQUENCE {
      caPubs          [1] SEQUENCE SIZE (1..MAX) OF Certificate OPTIONAL,
      response            SEQUENCE OF CertResponse
  }

  CertResponse ::= SEQUENCE {
      certReqId           INTEGER,
      -- to match this response with corresponding request (a value
      -- of -1 is to be used if certReqId is not specified in the
      -- corresponding request)
      status              PKIStatusInfo,
      certifiedKeyPair    CertifiedKeyPair    OPTIONAL,
      rspInfo             OCTET STRING        OPTIONAL
      -- analogous to the id-regInfo-asciiPairs OCTET STRING defined
      -- for regInfo in CertReqMsg [CRMF]
  }

  CertifiedKeyPair ::= SEQUENCE {
      certOrEncCert       CertOrEncCert,
      privateKey      [0] EncryptedValue      OPTIONAL,
      publicationInfo [1] PKIPublicationInfo  OPTIONAL
  }

  CertOrEncCert ::= CHOICE {
      certificate     [0] Certificate,
      encryptedCert   [1] EncryptedValue
  }

   Only one of the failInfo (in PKIStatusInfo) and certificate (in
   CertifiedKeyPair) fields can be present in each CertResponse
   (depending on the status). For some status values (e.g., waiting)
   neither of the optional fields will be present.

   Given an EncryptedCert and the relevant decryption key the
   certificate may be obtained. The purpose of this is to allow a CA to
   return the value of a certificate, but with the constraint that only
   the intended recipient can obtain the actual certificate. The benefit
   of this approach is that a CA may reply with a certificate even in
   the absence of a proof that the requester is the end entity which can
   use the relevant private key (note that the proof is not obtained

   until the PKIConfirm message is received by the CA). Thus the CA will
   not have to revoke that certificate in the event that something goes
   wrong with the proof of possession.

3.3.5 Key update request content

   For key update requests the CertReqMessages syntax is used.
   Typically, SubjectPublicKeyInfo, KeyId, and Validity are the template
   fields which may be supplied for each key to be updated.  This
   message is intended to be used to request updates to existing (non-
   revoked and non-expired) certificates.

   See [CRMF] for CertReqMessages syntax.

3.3.6 Key Update response content

   For key update responses the CertRepMessage syntax is used.  The
   response is identical to the initialization response.

   See Section 3.3.4 for CertRepMessage syntax.

3.3.7 Key Recovery Request content

   For key recovery requests the syntax used is identical to the
   initialization request CertReqMessages.  Typically,
   SubjectPublicKeyInfo and KeyId are the template fields which may be
   used to supply a signature public key for which a certificate is
   required (see Appendix B profiles for further information).

   See [CRMF] for CertReqMessages syntax.  Note that if a key history is
   required, the requester must supply a Protocol Encryption Key control
   in the request message.

3.3.8 Key recovery response content

   For key recovery responses the following syntax is used.  For some
   status values (e.g., waiting) none of the optional fields will be
   present.

     KeyRecRepContent ::= SEQUENCE {
         status          PKIStatusInfo,
         newSigCert  [0] Certificate                   OPTIONAL,
         caCerts     [1] SEQUENCE SIZE (1..MAX) OF
                                      Certificate      OPTIONAL,
         keyPairHist [2] SEQUENCE SIZE (1..MAX) OF
                                      CertifiedKeyPair OPTIONAL
     }

3.3.9 Revocation Request Content

   When requesting revocation of a certificate (or several certificates)
   the following data structure is used. The name of the requester is
   present in the PKIHeader structure.

     RevReqContent ::= SEQUENCE OF RevDetails

     RevDetails ::= SEQUENCE {
         certDetails         CertTemplate,
         -- allows requester to specify as much as they can about
         -- the cert. for which revocation is requested
         -- (e.g., for cases in which serialNumber is not available)
         revocationReason    ReasonFlags      OPTIONAL,
         -- the reason that revocation is requested
         badSinceDate        GeneralizedTime  OPTIONAL,
         -- indicates best knowledge of sender
         crlEntryDetails     Extensions       OPTIONAL
         -- requested crlEntryExtensions
     }

3.3.10 Revocation Response Content

   The response to the above message. If produced, this is sent to the
   requester of the revocation. (A separate revocation announcement
   message MAY be sent to the subject of the certificate for which
   revocation was requested.)

  RevRepContent ::= SEQUENCE {
      status        SEQUENCE SIZE (1..MAX) OF PKIStatusInfo,
      -- in same order as was sent in RevReqContent
      revCerts  [0] SEQUENCE SIZE (1..MAX) OF CertId OPTIONAL,
      -- IDs for which revocation was requested (same order as status)
      crls      [1] SEQUENCE SIZE (1..MAX) OF CertificateList  OPTIONAL
      -- the resulting CRLs (there may be more than one)
  }

3.3.11 Cross certification request content

   Cross certification requests use the same syntax (CertReqMessages) as
   for normal certification requests with the restriction that the key
   pair MUST have been generated by the requesting CA and the private
   key MUST NOT be sent to the responding CA.

   See [CRMF] for CertReqMessages syntax.

3.3.12 Cross certification response content

   Cross certification responses use the same syntax (CertRepMessage) as
   for normal certification responses with the restriction that no
   encrypted private key can be sent.

   See Section 3.3.4 for CertRepMessage syntax.

3.3.13 CA Key Update Announcement content

   When a CA updates its own key pair the following data structure MAY
   be used to announce this event.

  CAKeyUpdAnnContent ::= SEQUENCE {
      oldWithNew          Certificate, -- old pub signed with new priv
      newWithOld          Certificate, -- new pub signed with old priv
      newWithNew          Certificate  -- new pub signed with new priv
  }

3.3.14 Certificate Announcement

   This structure MAY be used to announce the existence of certificates.

   Note that this message is intended to be used for those cases (if
   any) where there is no pre-existing method for publication of
   certificates; it is not intended to be used where, for example, X.500
   is the method for publication of certificates.

     CertAnnContent ::= Certificate

3.3.15 Revocation Announcement

   When a CA has revoked, or is about to revoke, a particular
   certificate it MAY issue an announcement of this (possibly upcoming)
   event.

     RevAnnContent ::= SEQUENCE {
         status              PKIStatus,
         certId              CertId,
         willBeRevokedAt     GeneralizedTime,
         badSinceDate        GeneralizedTime,
         crlDetails          Extensions  OPTIONAL
         -- extra CRL details(e.g., crl number, reason, location, etc.)
     }

   A CA MAY use such an announcement to warn (or notify) a subject that
   its certificate is about to be (or has been) revoked. This would
   typically be used where the request for revocation did not come from
   the subject concerned.

   The willBeRevokedAt field contains the time at which a new entry will
   be added to the relevant CRLs.

3.3.16 CRL Announcement

   When a CA issues a new CRL (or set of CRLs) the following data
   structure MAY be used to announce this event.

     CRLAnnContent ::= SEQUENCE OF CertificateList

3.3.17 PKI Confirmation content

   This data structure is used in three-way protocols as the final
   PKIMessage. Its content is the same in all cases - actually there is
   no content since the PKIHeader carries all the required information.

     PKIConfirmContent ::= NULL

3.3.18 PKI General Message content

  InfoTypeAndValue ::= SEQUENCE {
      infoType               OBJECT IDENTIFIER,
      infoValue              ANY DEFINED BY infoType  OPTIONAL
  }
  -- Example InfoTypeAndValue contents include, but are not limited to:
  --  { CAProtEncCert    = {id-it 1}, Certificate                     }
  --  { SignKeyPairTypes = {id-it 2}, SEQUENCE OF AlgorithmIdentifier }
  --  { EncKeyPairTypes  = {id-it 3}, SEQUENCE OF AlgorithmIdentifier }
  --  { PreferredSymmAlg = {id-it 4}, AlgorithmIdentifier             }
  --  { CAKeyUpdateInfo  = {id-it 5}, CAKeyUpdAnnContent              }
  --  { CurrentCRL       = {id-it 6}, CertificateList                 }
  -- where {id-it} = {id-pkix 4} = {1 3 6 1 5 5 7 4}
  -- This construct MAY also be used to define new PKIX Certificate
  -- Management Protocol request and response messages, or general-
  -- purpose (e.g., announcement) messages for future needs or for
  -- specific environments.

  GenMsgContent ::= SEQUENCE OF InfoTypeAndValue
  -- May be sent by EE, RA, or CA (depending on message content).
  -- The OPTIONAL infoValue parameter of InfoTypeAndValue will typically
  -- be omitted for some of the examples given above.  The receiver is

  -- free to ignore any contained OBJ. IDs that it does not recognize.
  -- If sent from EE to CA, the empty set indicates that the CA may send
  -- any/all information that it wishes.

3.3.19 PKI General Response content

  GenRepContent ::= SEQUENCE OF InfoTypeAndValue
  -- The receiver is free to ignore any contained OBJ. IDs that it does
  -- not recognize.

3.3.20 Error Message content

     ErrorMsgContent ::= SEQUENCE {
         pKIStatusInfo          PKIStatusInfo,
         errorCode              INTEGER           OPTIONAL,
         -- implementation-specific error codes
         errorDetails           PKIFreeText       OPTIONAL
         -- implementation-specific error details
     }