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Versions: 00 01 02 03 04 05 RFC 2797

PKIX Working Group                               Michael Myers (VeriSign)
Internet Draft                                         Xiaoyi Liu (Cisco)
July 14, 1999                                      Jim Schaad (Microsoft)
expires in six months                                      Jeff Weinstein


                 Certificate Management Messages over CMS
                       <draft-ietf-pkix-cmc-05.txt>

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
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  ftp.isi.edu (US West Coast).

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", "REQUIRED", "SHOULD", "RECOMMENDED", and "MAY"
   in this document are to be interpreted as described in [RFC 2119].

1.  Protocol Requirements


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  - 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

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    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
     -------------------------               --------------------------

     +----------+                            +------------------+

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     | 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)    |                       +---------------+
             +-----------------+


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             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-ct-PKIData ::= {id-ct 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


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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-ct-PKIResponse ::= {id-ct 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.

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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 draft 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

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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-octect integer encoded
in the certReqIds field for CertReqMsg objects (in a TaggedRequest) or in

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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 draft 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
     }

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     -- 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.

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.

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 }


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    -- 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.

Many advanced services specified in this draft 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 in a Full Enrollment Request is identified by a Body Part
Identifer. 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

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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.

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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.

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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 draft.

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

5.1  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 {

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          pendToken           OCTET STRING,
          pendTime            GeneralizedTime
     }

     -- cMCStatus is described in section 5.1.1

     -- 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 5.1.2. 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.

5.1.1   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

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          -- before use of certificate
     }


5.1.2   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

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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 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.

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 identitification attribute MUST be included and MUST contain the
     hardware-generated token.
  2. The shared secret value used above is the same hardware-generated
     token.

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  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 (Section5.3.1) 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.

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       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

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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

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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-entyt).

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

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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:


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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.)

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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 }


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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:

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     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.  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.


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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 forresponse 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 request is
confirmRequired, then the client MUST return a Confirm Certificate

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

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 for a confirm certificate
acceptance control.

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:

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   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

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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)

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

7.2  File-Based Transport


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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

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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.

10. Open Issues

There are currently no open issues.

11. 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.

12. References

[CMS]    R. Housley, "Cryptographic Message Syntax",

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         draft-ietf-smime-cms-06.txt, June 1998

[CRMF]   M. Myers, C. Adams, D. Solo, 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", draft-ietf-pkix-dhpop-00.txt,
         February 1999

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

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

[PKCS7]  B. Kaliski, "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] B. Kaliski, "PKCS #10: Certification Request Syntax v1.5",
         RFC 2314, October 1997

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

[RFC 2119] "Key words for use in RFCs to Indicate Requirement
         Levels", RFC 2119

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

[SMIMEV3] B. Ramsdell, "S/MIME Version 3 Message Specification",
         draft-ietf-smime-msg-05.txt, August 1998

[X942]   E. Rescorla, "Diffie-Hellman Key Agreement Method".
         (currently draft-ietf-smime-x942-*.txt)

13. Author's Addresses

Michael Myers
VeriSign Inc.
1350 Charlston Road
Mountain View, CA, 94043
(650) 429-3402
mmyers@verisign.com

Xiaoyi Liu
Cisco Systems

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170 West Tasman Drive
San Jose, CA 95134
(480) 526-7430
xliu@cisco.com

Jim Schaad
Microsoft Corporation
One Microsoft Way
Redmond, WA  98052
(425) 936-3101
jimsch@microsoft.com

Jeff Weinstein
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)}


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     -- 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}

    -- 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-ct-PKIData OBJECT IDENTIFIER ::= { id-pkix id-ct(5) 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 ::= INETGER(0..bodyIdMax)

    TaggedAttribute ::= SEQUENCE {
        bodyPartID         BodyPartId,
        attrType           OBJECT IDENTIFIER,
        attrValues         SET OF AttributeValue
    }

    AttributeValue ::= ANY

    TaggedRequest ::= CHOICE {

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        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-ct-PKIResponse OBJECT IDENTIFIER ::= {id-pkix ct(5) 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 INTEGER,
        statusString    UTF8String OPTIONAL,
        otherInfo        CHOICE {
          failInfo         CMCFailInfo,
          pendInfo         PendInfo } OPTIONAL
    }

    PendInfo ::= SEQUENCE {

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        pendToken        INTEGER,
        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 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),
        -- 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
    }

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    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}


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   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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