Network Working Group                                        T. Freeman
Request for Comments: 5055                               Microsoft Corp
Category: Standards Track                                    R. Housley
                                                         Vigil Security
                                                             A. Malpani
                                            Malpani Consulting Services
                                                              D. Cooper
                                                                W. Polk
                                                                   NIST
                                                          December 2007

Server-Based Certificate Validation Protocol (SCVP)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Server-Based Certificate Validation Protocol (SCVP) allows a
   client to delegate certification path construction and certification
   path validation to a server.  The path construction or validation
   (e.g., making sure that none of the certificates in the path are
   revoked) is performed according to a validation policy, which
   contains one or more trust anchors.  It allows simplification of
   client implementations and use of a set of predefined validation
   policies.

   1. Introduction ....................................................4
      1.1. Terminology ................................................4
      1.2. SCVP Overview ..............................................5
      1.3. SCVP Requirements ..........................................5
      1.4. Validation Policies ........................................6
      1.5. Validation Algorithm .......................................7
      1.6. Validation Requirements ....................................8
   2. Protocol Overview ...............................................9
   3. Validation Request ..............................................9
      3.1. cvRequestVersion ..........................................12
      3.2. query .....................................................12
           3.2.1. queriedCerts .......................................13
           3.2.2. checks .............................................15

           3.2.3. wantBack ...........................................16
           3.2.4. validationPolicy ...................................19
                  3.2.4.1. validationPolRef ..........................20
                           3.2.4.1.1. Default Validation Policy ......21
                  3.2.4.2. validationAlg .............................22
                           3.2.4.2.1. Basic Validation Algorithm .....22
                           3.2.4.2.2. Basic Validation
                                      Algorithm Errors ...............23
                           3.2.4.2.3. Name Validation Algorithm ......24
                           3.2.4.2.4. Name Validation
                                      Algorithm Errors ...............25
                  3.2.4.3. userPolicySet .............................26
                  3.2.4.4. inhibitPolicyMapping ......................26
                  3.2.4.5. requireExplicitPolicy .....................27
                  3.2.4.6. inhibitAnyPolicy ..........................27
                  3.2.4.7. trustAnchors ..............................27
                  3.2.4.8. keyUsages .................................28
                  3.2.4.9. extendedKeyUsages .........................28
                  3.2.4.10. specifiedKeyUsages .......................29
           3.2.5. responseFlags ......................................30
                  3.2.5.1. fullRequestInResponse .....................30
                  3.2.5.2. responseValidationPolByRef ................30
                  3.2.5.3. protectResponse ...........................31
                  3.2.5.4. cachedResponse ............................31
           3.2.6. serverContextInfo ..................................32
           3.2.7. validationTime .....................................32
           3.2.8. intermediateCerts ..................................33
           3.2.9. revInfos ...........................................34
           3.2.10. producedAt ........................................35
           3.2.11. queryExtensions ...................................35
                  3.2.11.1. extnID ...................................35
                  3.2.11.2. critical .................................35
                  3.2.11.3. extnValue ................................36
      3.3. requestorRef ..............................................36
      3.4. requestNonce ..............................................36
      3.5. requestorName .............................................37
      3.6. responderName .............................................37
      3.7. requestExtensions .........................................38
           3.7.1. extnID .............................................38
           3.7.2. critical ...........................................38
           3.7.3. extnValue ..........................................38
      3.8. signatureAlg ..............................................38
      3.9. hashAlg ...................................................39
      3.10. requestorText ............................................39
      3.11. SCVP Request Authentication ..............................40
   4. Validation Response.............................................40
     4.1. cvResponseVersion...........................................43
     4.2. serverConfigurationID.......................................43

     4.3. producedAt..................................................44
     4.4. responseStatus..............................................44
     4.5. respValidationPolicy........................................46
     4.6. requestRef..................................................47
           4.6.1. requestHash ........................................47
           4.6.2. fullRequest ........................................48
     4.7. requestorRef................................................48
     4.8. requestorName...............................................48
     4.9. replyObjects................................................49
           4.9.1. cert................................................50
           4.9.2. replyStatus.........................................50
           4.9.3. replyValTime .......................................51
           4.9.4. replyChecks ........................................51
           4.9.5. replyWantBacks .....................................53
           4.9.6. validationErrors ...................................56
           4.9.7. nextUpdate .........................................56
           4.9.8. certReplyExtensions ................................56
     4.10. respNonce..................................................57
     4.11. serverContextInfo..........................................57
     4.12. cvResponseExtensions ......................................58
     4.13. requestorText .............................................58
     4.14. SCVP Response Validation ..................................59
           4.14.1. Simple Key Validation .............................59
           4.14.2. SCVP Server Certificate Validation ................59
   5. Server Policy Request...........................................60
      5.1. vpRequestVersion...........................................60
      5.2. requestNonce...............................................60
   6. Validation Policy Response......................................61
      6.1. vpResponseVersion..........................................62
      6.2. maxCVRequestVersion........................................62
      6.3. maxVPRequestVersion........................................62
      6.4. serverConfigurationID......................................62
      6.5. thisUpdate.................................................63
      6.6. nextUpdate and requestNonce................................63
      6.7. supportedChecks............................................63
      6.8. supportedWantBacks.........................................64
      6.9. validationPolicies.........................................64
      6.10. validationAlgs............................................64
      6.11. authPolicies..............................................64
      6.12. responseTypes.............................................64
      6.13. revocationInfoTypes.......................................64
      6.14. defaultPolicyValues.......................................65
      6.15. signatureGeneration ......................................65
      6.16. signatureVerification ....................................65
      6.17. hashAlgorithms ...........................................66
      6.18. serverPublicKeys .........................................66
      6.19. clockSkew ................................................66
   7. SCVP Server Relay...............................................67

   8. SCVP ASN.1 Module...............................................68
   9. Security Considerations.........................................76
   10.IANA Considerations.............................................78
   11. References.....................................................78
       11.1. Normative References.....................................78
       11.2. Informative References...................................79
   12. Acknowledgments................................................80
   Appendix A. MIME Media Type Registrations..........................81
        A.1. application/scvp-cv-request..............................81
        A.2. application/scvp-cv-response.............................82
        A.3. application/scvp-vp-request..............................83
        A.4. application/scvp-vp-response.............................84
   Appendix B. SCVP over HTTP.........................................85
        B.1. SCVP Request.............................................85
        B.2. SCVP Response............................................85
        B.3. SCVP Policy Request......................................86
        B.4. SCVP Policy Response.....................................86

1. Introduction

   Certificate validation is complex.  If certificate handling is to be
   widely deployed in a variety of applications and environments, the
   amount of processing an application needs to perform before it can
   accept a certificate needs to be reduced.  There are a variety of
   applications that can make use of public key certificates, but these
   applications are burdened with the overhead of constructing and
   validating the certification paths.  SCVP reduces this overhead for
   two classes of certificate-using applications.

   The first class of applications wants just two things: confirmation
   that the public key belongs to the identity named in the certificate
   and confirmation that the public key can be used for the intended
   purpose.  Such clients can completely delegate certification path
   construction and validation to the SCVP server.  This is often
   referred to as delegated path validation (DPV).

   The second class of applications can perform certification path
   validation, but they lack a reliable or efficient method of
   constructing a valid certification path.  Such clients delegate
   certification path construction to the SCVP server, but not
   validation of the returned certification path.  This is often
   referred to as delegated path discovery (DPD).

1.1. Terminology

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

1.2. SCVP Overview

   The primary goals of SCVP are to make it easier to deploy Public Key
   Infrastructure (PKI)-enabled applications by delegating path
   discovery and/or validation processing to a server, and to allow
   central administration of validation policies within an organization.
   SCVP can be used by clients that do much of the certificate
   processing themselves but simply want an untrusted server to collect
   information for them.  However, when the client has complete trust in
   the SCVP server, SCVP can be used to delegate the work of
   certification path construction and validation, and SCVP can be used
   to ensure that policies are consistently enforced throughout an
   organization.

   Untrusted SCVP servers can provide clients the certification paths.
   They can also provide clients the revocation information, such as
   Certificate Revocation Lists (CRLs) and Online Certificate Status
   Protocol (OCSP) responses, that the clients need to validate the
   certification paths constructed by the SCVP server.  These services
   can be valuable to clients that do not implement the protocols needed
   to find and download intermediate certificates, CRLs, and OCSP
   responses.

   Trusted SCVP servers can perform certification path construction and
   validation for the client.  For a client that uses these services,
   the client inherently trusts the SCVP server as much as it would its
   own certification path validation software (if it contained such
   software).  There are two main reasons that a client may want to
   trust such an SCVP server:

   1. The client does not want to incur the overhead of including
      certification path validation software and running it for each
      certificate it receives.

   2. The client is in an organization or community that wants to
      centralize management of validation policies.  These policies
      might dictate that particular trust anchors are to be used and the
      types of policy checking that are to be performed during
      certification path validation.

1.3. SCVP Requirements

SCVP meets the mandatory requirements documented in [RQMTS] for DPV
and DPD.

   Note that RFC 3379 states the following requirement:

      The DPD response MUST indicate one of the following status
      alternatives:

      1) one or more certification paths was found according to the path
         discovery policy, with all of the requested revocation
         information present.

      2) one or more certification paths was found according to the path
         discovery policy, with a subset of the requested revocation
         information present.

      3) one or more certification paths was found according to the path
         discovery policy, with none of the requested revocation
         information present.

      4) no certification path was found according to the path discovery
         policy.

      5) path construction could not be performed due to an error.

   DPD responses constructed by SCVP servers do not differentiate
   between states 2) and 3).  This property was discussed on the PKIX
   working group list and determined to be conformant with the intent of
   [RQMTS].

1.4. Validation Policies

   A validation policy (as defined in RFC 3379 [RQMTS]) specifies the
   rules and parameters to be used by the SCVP server when validating a
   certificate.  In SCVP, the validation policy to be used by the server
   either can be fully referenced in the request by the client (and thus
   no additional parameters are necessary) or can be referenced in the
   request by the client with additional parameters.

   Policy definitions can be quite long and complex, and some policies
   may allow for the setting of a few parameters.  The request can
   therefore be very simple if an object identifier (OID) is used to
   specify both the algorithm to be used and all the associated
   parameters of the validation policy.  The request can be more complex
   if the validation policy fixes many of the parameters but allows the
   client to specify some of them.  When the validation policy defines
   every parameter necessary, an SCVP request needs only to contain the
   certificate to be validated, the referenced validation policy, and
   any run-time parameters for the request.

   A server publishes the references of the validation policies it
   supports.  When these policies have parameters that may be
   overridden, the server communicates the default values for these
   parameters as well.  The client can simplify the request by omitting
   a parameter from a request if the default value published by the
   server for a given validation policy reference is acceptable.
   However, if there is a desire to demonstrate to someone else that a
   specific validation policy with all its parameters has been used, the
   client will need to ask the server for the inclusion of the full
   validation policy with all the parameters in the response.

   The inputs to the basic certification path processing algorithm used
   by SCVP are defined by [PKIX-1] in Section 6.1.1 and comprise:

      Certificate to be validated (by value or by reference);

      Validation time;

      The initial policy set;

      Initial inhibit policy mapping setting;

      Initial inhibit anyPolicy setting; and

      Initial require explicit policy setting.

   The basic certification path processing algorithm also supports
   specification of one or more trust anchors (by value or reference) as
   an input.  Where the client demands a certification path originating
   with a specific Certification Authority (CA), a single trust anchor
   is specified.  Where the client is willing to accept paths beginning
   with any of several CAs, a set of trust anchors is specified.

   The basic certification path processing algorithm also supports the
   following parameters, which are defined in [PKIX-1], Section 4:

      The usage of the key contained in the certificate (e.g., key
      encipherment, key agreement, signature); and

      Other application-specific purposes for which the certified public
      key may be used.

1.5. Validation Algorithm

   The validation algorithm is determined by agreement between the
   client and the server and is represented as an OID.  The algorithm
   defines the checking that will be performed by the server to
   determine whether the certificate is valid.  A validation algorithm

   is one of the parameters to a validation policy.  SCVP defines a
   basic validation algorithm that implements the basic path validation
   algorithm as defined in [PKIX-1], and it permits the client to
   request additional information about the certificate to be validated.
   New validation algorithms can be specified that define additional
   checks if needed.  These new validation algorithms may specify
   additional parameters.  The values for these parameters may be
   defined by any validation policy that uses the algorithm or may be
   included by the client in the request.

   Application-specific validation algorithms, in addition to those
   defined in this document, can be defined to meet specific
   requirements not covered by the basic validation algorithm.  The
   validation algorithms documented here should serve as a guide for the
   development of further application-specific validation algorithms.
   For example, a new application-specific validation algorithm might
   require the presence of a particular name form in the subject
   alternative name extension of the certificate.

1.6. Validation Requirements

   For a certification path to be considered valid under a particular
   validation policy, it MUST be a valid certification path as defined
   in [PKIX-1], and all validation policy constraints that apply to the
   certification path MUST be verified.

   Revocation checking is one aspect of certification path validation
   defined in [PKIX-1].  However, revocation checking is an optional
   feature in [PKIX-1], and revocation information is distributed in
   multiple formats.  Clients specify in requests whether revocation
   checking should be performed and whether revocation information
   should be returned in the response.

   Servers MUST be capable of indicating the sources of revocation
   information that they are capable of processing:

      1. full CRLs (or full Authority Revocation Lists);

2. OCSP responses, using [OCSP];

3. delta CRLs; and

4. indirect CRLs.

2.  Protocol Overview

   SCVP uses a simple request-response model.  That is, the SCVP client
   creates a request and sends it to the SCVP server, and then the SCVP
   server creates a single response and sends it to the client.  The
   typical use of SCVP is expected to be over HTTP [HTTP], but it can
   also be used with email or any other protocol that can transport
   digitally signed objects.  Appendices A and B provide the details
   necessary to use SCVP with HTTP.

   SCVP includes two request-response pairs.  The primary request-
   response pair handles certificate validation.  The secondary request-
   response pair is used to determine the list of validation policies
   and default parameters supported by a specific SCVP server.

   Section 3 defines the certificate validation request.

   Section 4 defines the corresponding certificate validation response.

   Section 5 defines the validation policies request.

   Section 6 defines the corresponding validation policies response.

   Appendix A registers MIME types for SCVP requests and responses, and
   Appendix B describes the use of these MIME types with HTTP.

3.  Validation Request

   An SCVP client request to the server MUST be a single CVRequest item.
   When a CVRequest is encapsulated in a MIME body part,
   application/scvp-cv-request MUST be used.  There are two forms of
   SCVP request: unprotected and protected.  A protected request is used
   to authenticate the client to the server or to provide anonymous
   client integrity over the request-response pair.  The protection is
   provided by a digital signature or message authentication code (MAC).
   In the later case, the MAC key is derived using a key agreement
   algorithm, such as Diffie-Hellman.  If the client's public key is
   contained in a certificate, then it may be used to authenticate the
   client.  More commonly, the client's key agreement public key will be
   ephemeral, supporting anonymous client integrity.

   A server MAY require all requests to be protected, and a server MAY
   discard all unprotected requests.  Alternatively, a server MAY choose
   to process unprotected requests.

   The unprotected request consists of a CVRequest encapsulated in a
   Cryptographic Message Syntax (CMS) ContentInfo [CMS].  An overview of
   this structure is provided below and is only intended as

   illustrative.  The definitive ASN.1 is found in [CMS].  Many details
   are not shown, but the way that SCVP makes use of CMS is clearly
   illustrated.

      ContentInfo {
        contentType        id-ct-scvp-certValRequest,
                                     -- (1.2.840.113549.1.9.16.1.10)
        content            CVRequest }

   The protected request consists of a CVRequest encapsulated in either
   a SignedData or AuthenticatedData, which is in turn encapsulated in a
   ContentInfo.  That is, the EncapsulatedContentInfo field of either
   SignedData or AuthenticatedData consists of an eContentType field
   with a value of id-ct-scvp-certValRequest and an eContent field that
   contains a Distinguished Encoding Rules (DER)-encoded CVRequest.
   SignedData is used when the request is digitally signed.
   AuthenticatedData is used with a message authentication code (MAC).

   All SCVP clients and servers MUST support SignedData for signed
   requests and responses.  SCVP clients and servers SHOULD support
   AuthenticatedData for MAC-protected requests and responses.

   If the client uses SignedData, it MUST have a public key that has
   been bound to a subject identity by a certificate that conforms to
   the PKIX profile [PKIX-1], and that certificate MUST be suitable for
   signing the SCVP request.  That is:

      1. If the key usage extension is present, either the digital
         signature or the non-repudiation bit MUST be asserted.

      2. If the extended key usage extension is present, it MUST contain
         either the SCVP client OID (see Section 3.11), the
         anyExtendedKeyUsage OID, or another OID acceptable to the SCVP
         server.

   The client MUST put an unambiguous reference to its certificate in
   the SignedData that encapsulates the request.  The client SHOULD
   include its certificate in the request, but MAY omit the certificate
   to reduce the size of the request.  The client MAY include other
   certificates in the request to aid the validation of its certificates
   by the SCVP server.  The signerInfos field of SignedData MUST include
   exactly one SignerInfo.  The SignedData MUST NOT include the
   unsignedAttrs field.

   The client MUST put its key agreement public key, or an unambiguous
   reference to a certificate that contains its key agreement public
   key, in the AuthenticatedData that encapsulates the request.  If an
   ephemeral key agreement key pair is used, then the ephemeral key
   agreement public key is carried in the originatorKey field of
   KeyAgreeRecipientInfo, which requires the client to obtain the
   server's key agreement public key before computing the message
   authentication code (MAC).  An SCVP server's key agreement key is
   included in its validation policy response message (see Section 6).
   The recipientInfos field of AuthenticatedData MUST include exactly
   one RecipientInfo, which contains information for the SCVP server.
   The AuthenticatedData MUST NOT include the unauthAttrs field.

   The syntax and semantics for SignedData, AuthenticatedData, and
   ContentInfo are defined in [CMS].  The syntax and semantics for
   CVRequest are defined below.  The CVRequest item contains the client
   request.  The CVRequest contains the cvRequestVersion and query
   items; the CVRequest MAY also contain the requestorRef, requestNonce,
   requestorName, responderName, requestExtensions, signatureAlg, and
   hashAlg items.

   The CVRequest MUST have the following syntax:

      CVRequest ::= SEQUENCE {
        cvRequestVersion        INTEGER DEFAULT 1,
        query                   Query,
        requestorRef        [0] GeneralNames OPTIONAL,
        requestNonce        [1] OCTET STRING OPTIONAL,
        requestorName       [2] GeneralName OPTIONAL,
        responderName       [3] GeneralName OPTIONAL,
        requestExtensions   [4] Extensions OPTIONAL,
        signatureAlg        [5] AlgorithmIdentifier OPTIONAL,
        hashAlg             [6] OBJECT IDENTIFIER OPTIONAL,
        requestorText       [7] UTF8String (SIZE (1..256)) OPTIONAL }

   Conforming clients MUST be able to construct requests with
   cvRequestVersion and query.  Conforming clients MUST DER encode the
   CVRequest in both protected and unprotected messages to facilitate
   unambiguous hash-based referencing in the corresponding response
   message.  SCVP clients that insist on creation of a fresh response
   (e.g., to protect against a replay attack or ensure information is up
   to date) MUST support requestNonce.  Support for the remaining items
   is optional in client implementations.

   Conforming servers MUST be able to parse CVRequests that contain any
   or all of the optional items.

Each of the items within the CVRequest is described in the following
sections.

3.1. cvRequestVersion

   The cvRequestVersion item defines the version of the SCVP CVRequest
   used in a request.  The subsequent response MUST use the same version
   number.  The value of the cvRequestVersion item MUST be one (1) for a
   client implementing this specification.  Future updates to this
   specification must specify other values if there are any changes to
   syntax or semantics.  However, new extensions may be defined without
   changing the version number.

   SCVP clients MUST support asserting this value and SCVP servers MUST
   be capable of processing this value.

3.2. query

   The query item specifies one or more certificates that are the
   subject of the request; the certificates can be either public key
   certificates [PKIX-1] or attribute certificates [PKIX-AC].  A query
   MUST contain a queriedCerts item as well as one checks item, and one
   validationPolicy item; a query MAY also contain wantBack,
   responseFlags, serverContextInfo, validationTime, intermediateCerts,
   revInfos, producedAt, and queryExtensions items.

   A Query MUST have the following syntax:

      Query ::= SEQUENCE {
        queriedCerts            CertReferences,
        checks                  CertChecks,
         -- Note: tag [0] not used --
        wantBack            [1] WantBack OPTIONAL,
        validationPolicy        ValidationPolicy,
        responseFlags           ResponseFlags OPTIONAL,
        serverContextInfo   [2] OCTET STRING OPTIONAL,
        validationTime      [3] GeneralizedTime OPTIONAL,
        intermediateCerts   [4] CertBundle OPTIONAL,
        revInfos            [5] RevocationInfos OPTIONAL,
        producedAt          [6] GeneralizedTime OPTIONAL,
        queryExtensions     [7] Extensions OPTIONAL }

   The list of certificate references in the queriedCerts item tells the
   server the certificate(s) for which the client wants information.
   The checks item specifies the checking that the client wants
   performed.  The wantBack item specifies the objects that the client
   wants the server to return in the response.  The validationPolicy
   item specifies the validation policy that the client wants the server

   to employ.  The responseFlags item allows the client to request
   optional features for the response.  The serverContextInfo item tells
   the server that additional information from a previous request-
   response is desired.  The validationTime item tells the date and time
   relative to which the client wants the server to perform the checks.
   The intermediateCerts and revInfos items provide context for the
   client request.  The queryExtensions item provides for future
   expansion of the query syntax.  The syntax and semantics of each of
   these items are discussed in the following sections.

   Conforming clients MUST be able to construct a Query with a
   queriedCerts item that specifies at least one certificate, checks,
   and validationPolicy.  Conforming SCVP clients MAY support
   specification of multiple certificates and MAY support the optional
   items in the Query structure.

   SCVP clients that support delegated path discovery (DPD) as defined
   in [RQMTS] MUST support wantBack and responseFlags.  SCVP clients
   that insist on creation of a fresh response (e.g., to protect against
   a replay attack or ensure information is up to date) MUST support
   responseFlags.

   Conforming servers MUST be able to process a Query that contains any
   of the optional items, and MUST be able to process a Query that
   specifies multiple certificates.

3.2.1. queriedCerts

   The queriedCerts item is a SEQUENCE of one or more certificates, each
   of which is a subject of the request.  The specified certificates are
   either public key certificates or attribute certificates; if more
   than one certificate is specified, all must be of the same type.
   Each certificate is either directly included, or it is referenced.
   When referenced, a hash value of the referenced item is included to
   ensure that the SCVP client and the SCVP server both obtain the same
   certificate when the referenced certificate is fetched.  Certificate
   references use the SCVPCertID type, which is described below.  A
   single request MAY contain both directly included and referenced
   certificates.

   CertReferences has the following syntax:

   CertReferences ::= CHOICE {
     pkcRefs     [0] SEQUENCE SIZE (1..MAX) OF PKCReference,
     acRefs      [1] SEQUENCE SIZE (1..MAX) OF ACReference }

   PKCReference ::= CHOICE {
     cert        [0] Certificate,
     pkcRef      [1] SCVPCertID }

   ACReference ::= CHOICE {
     attrCert    [2] AttributeCertificate,
     acRef       [3] SCVPCertID }

   SCVPCertID ::= SEQUENCE {
     certHash        OCTET STRING,
     issuerSerial    SCVPIssuerSerial,
     hashAlgorithm   AlgorithmIdentifier DEFAULT { algorithm sha-1 } }

   The ASN.1 definition of Certificate is imported from [PKIX-1] and the
   definition of AttributeCertificate is imported from [PKIX-AC].

   When creating a SCVPCertID, the certHash is computed over the entire
   DER-encoded certificate including the signature.  The hash algorithm
   used to compute certHash is specified in hashAlgorithm.  The hash
   algorithm used to compute certHash SHOULD be one of the hash
   algorithms specified in the hashAlgorithms item of the server's
   validation policy response message.

   When encoding SCVPIssuerSerial, serialNumber is the serial number
   that uniquely identifies the certificate.  For public key
   certificates, the issuer MUST contain only the issuer name from the
   certificate encoded in the directoryName choice of GeneralNames.  For
   attribute certificates, the issuer MUST contain the issuer name field
   from the attribute certificate.

   Conforming clients MUST be able to reference a certificate by direct
   inclusion.  Clients SHOULD be able to specify a certificate using the
   SCVPCertID.  Conforming clients MAY be able to reference multiple
   certificates and MAY be able to reference both public key and
   attribute certificates.

   Conforming SCVP Server implementations MUST be able to process
   CertReferences with multiple certificates.  Conforming SCVP server
   implementations MUST be able to parse CertReferences that contain
   either public key or attribute certificates.  Conforming SCVP server
   implementations MUST be able to parse both the cert and pkcRef
   choices in PKCReference.  Conforming SCVP server implementations that
   process attribute certificates MUST be able to parse both the
   attrCert and acRef choices in ACReference.

3.2.2. checks

   The checks item describes the checking that the SCVP client wants the
   SCVP server to perform on the certificate(s) in the queriedCerts
   item.  The checks item contains a sequence of object identifiers
   (OIDs).  Each OID tells the SCVP server what checking the client
   expects the server to perform.  For each check specified in the
   request, the SCVP server MUST perform the requested check, or return
   an error.  A server may choose to perform additional checks (e.g., a
   server that is only asked to build a validated certification path may
   choose to also perform revocation status checks), although the server
   cannot indicate in the response that the additional checks have been
   performed, except in the case of an error response.

   The checks item uses the CertChecks type, which has the following
   syntax:

      CertChecks ::= SEQUENCE SIZE (1..MAX) OF OBJECT IDENTIFIER

   For public key certificates, the following checks are defined in this
   document:

   -  id-stc-build-pkc-path: Build a prospective certification path to a
      trust anchor (as defined in Section 6.1 of [PKIX-1]);

   -  id-stc-build-valid-pkc-path: Build a validated certification path
      to a trust anchor (revocation checking not required);

   -  id-stc-build-status-checked-pkc-path: Build a validated
      certification path to a trust anchor and perform revocation status
      checks on the certification path.

   Conforming SCVP server implementations that support delegated path
   discovery (DPD) as defined in [RQMTS] MUST support the id-stc-build-
   pkc-path check.  Conforming SCVP server implementations that support
   delegated path validation (DPV) as defined in [RQMTS] MUST support
   the id-stc-build-valid-pkc-path and id-stc-build-status-checked-pkc-
   path checks.

   For attribute certificates, the following checks are defined in this
   document:

   -  id-stc-build-aa-path: Build a prospective certification path to a
      trust anchor for the Attribute Certificate (AC) issuer;

   -  id-stc-build-valid-aa-path: Build a validated certification path
      to a trust anchor for the AC issuer;

   -  id-stc-build-status-checked-aa-path: Build a validated
      certification path to a trust anchor for the AC issuer and perform
      revocation status checks on the certification path for the AC
      issuer;

   -  id-stc-status-check-ac-and-build-status-checked-aa-path: Build a
      validated certification path to a trust anchor for the AC issuer
      and perform revocation status checks on the AC as well as the
      certification path for the AC issuer.

   Conforming SCVP server implementations MAY support the attribute
   certificates checks.

   For these purposes, the following OIDs are defined:

      id-stc OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
              dod(6) internet(1) security(5) mechanisms(5) pkix(7) 17 }

      id-stc-build-pkc-path         OBJECT IDENTIFIER ::= { id-stc 1 }
      id-stc-build-valid-pkc-path   OBJECT IDENTIFIER ::= { id-stc 2 }
      id-stc-build-status-checked-pkc-path
                                    OBJECT IDENTIFIER ::= { id-stc 3 }
      id-stc-build-aa-path          OBJECT IDENTIFIER ::= { id-stc 4 }
      id-stc-build-valid-aa-path    OBJECT IDENTIFIER ::= { id-stc 5 }
      id-stc-build-status-checked-aa-path
                                    OBJECT IDENTIFIER ::= { id-stc 6 }
      id-stc-status-check-ac-and-build-status-checked-aa-path
                                    OBJECT IDENTIFIER ::= { id-stc 7 }

   Other specifications may define additional checks.

   Conforming client implementations MUST support assertion of at least
   one of the standard checks.  Conforming clients MAY support assertion
   of multiple checks.  Conforming clients need not support all of the
   checks defined in this section.

3.2.3. wantBack

   The optional wantBack item describes any information the SCVP client
   wants from the SCVP server for the certificate(s) in the queriedCerts
   item in addition to the results of the checks specified in the checks
   item.  If present, the wantBack item MUST contain a sequence of
   object identifiers (OIDs).  Each OID tells the SCVP server what the
   client wants to know about the queriedCerts item.  For each type of
   information specified in the request, the server MUST return
   information regarding its finding (in a successful response).

   For example, a request might include a checks item that only
   specifies certification path building and include a wantBack item
   that requests the return of the certification path built by the
   server.  In this case, the response would not include a status for
   the validation of the certification path, but it would include a
   prospective certification path.  A client that wants to perform its
   own certification path validation might use a request of this form.

   Alternatively, a request might include a checks item that requests
   the server to build a certification path and validate it, including
   revocation checking, and not include a wantBack item.  In this case,
   the response would include only a status for the validation of the
   certification path.  A client that completely delegates certification
   path validation might use a request of this form.

   The wantBack item uses the WantBack type, which has the following
   syntax:

      WantBack ::= SEQUENCE SIZE (1..MAX) OF OBJECT IDENTIFIER

   For public key certificates, the following wantBacks are defined in
   this document:

   -  id-swb-pkc-cert: The certificate that was the subject of the
      request;

   -  id-swb-pkc-best-cert-path: The certification path built for the
      certificate including the certificate that was validated;

   -  id-swb-pkc-revocation-info: Proof of revocation status for each
      certificate in the certification path;

   -  id-swb-pkc-public-key-info: The public key from the certificate
      that was the subject of the request;

   -  id-swb-pkc-all-cert-paths: A set of certification paths for the
      certificate that was the subject of the request;

   -  id-swb-pkc-ee-revocation-info: Proof of revocation status for the
      end entity certificate in the certification path; and

   -  id-swb-pkc-CAs-revocation-info: Proof of revocation status for
      each CA certificate in the certification path.

   All conforming SCVP server implementations MUST support the id-swb-
   pkc-cert and id-swb-pkc-public-key-info wantBacks.  Conforming SCVP
   server implementations that support delegated path discovery (DPD) as
   defined in [RQMTS] MUST support the id-swb-pkc-best-cert-path and id-
   swb-pkc-revocation-info wantBacks.

   SCVP provides two methods for a client to obtain multiple
   certification paths for a certificate.  The client could use
   serverContextInfo to request one path at a time (see Section 3.2.6).
   After obtaining each path, the client could submit the
   serverContextInfo from the previous request to obtain another path
   until either the client found a suitable path or the server indicated
   (by not returning a serverContextInfo) that no more paths were
   available.  Alternatively, the client could send a single request
   with an id-swb-pkc-all-cert-paths wantBack, in which case the server
   would return all of the available paths in a single response.

   The server may, at its discretion, limit the number of paths that it
   returns in response to the id-swb-pkc-all-cert-paths.  When the
   request includes an id-swb-pkc-all-cert-paths wantBack, the response
   SHOULD NOT include a serverContextInfo.

   For attribute certificates, the following wantBacks are defined in
   this document:

   -  id-swb-ac-cert: The attribute certificate that was the subject of
      the request;

   -  id-swb-aa-cert-path: The certification path built for the AC
      issuer certificate;

   -  id-swb-ac-revocation-info: Proof of revocation status for each
      certificate in the AC issuer certification path; and

   -  id-swb-aa-revocation-info: Proof of revocation status for the
      attribute certificate.

   Conforming SCVP server implementations MAY support the attribute
   certificate wantBacks.

   The following wantBack can be used for either public key or attribute
   certificates:

   -  id-swb-relayed-responses: Any SCVP responses received by the
      server that were used to generate the response to this query.

   Conforming SCVP servers MAY support the id-swb-relayed-responses
   wantBack.

   For these purposes, the following OIDs are defined:

      id-swb OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
              dod(6) internet(1) security(5) mechanisms(5) pkix(7) 18 }

      id-swb-pkc-best-cert-path      OBJECT IDENTIFIER ::= { id-swb 1 }
      id-swb-pkc-revocation-info     OBJECT IDENTIFIER ::= { id-swb 2 }
      id-swb-pkc-public-key-info     OBJECT IDENTIFIER ::= { id-swb 4 }
      id-swb-aa-cert-path            OBJECT IDENTIFIER ::= { id-swb 5 }
      id-swb-aa-revocation-info      OBJECT IDENTIFIER ::= { id-swb 6 }
      id-swb-ac-revocation-info      OBJECT IDENTIFIER ::= { id-swb 7 }
      id-swb-relayed-responses       OBJECT IDENTIFIER ::= { id-swb 9 }
      id-swb-pkc-cert                OBJECT IDENTIFIER ::= { id-swb 10}
      id-swb-ac-cert                 OBJECT IDENTIFIER ::= { id-swb 11}
      id-swb-pkc-all-cert-paths      OBJECT IDENTIFIER ::= { id-swb 12}
      id-swb-pkc-ee-revocation-info  OBJECT IDENTIFIER ::= { id-swb 13}
      id-swb-pkc-CAs-revocation-info OBJECT IDENTIFIER ::= { id-swb 14}

   Other specifications may define additional wantBacks.

   Conforming client implementations that support delegated path
   validation (DPV) as defined in [RQMTS] SHOULD support assertion of at
   least one wantBack.  Conforming client implementations that support
   delegated path discovery (DPD) as defined in [RQMTS] MUST support
   assertion of at least one wantBack.  Conforming clients MAY support
   assertion of multiple wantBacks.  Conforming clients need not support
   all of the wantBacks defined in this section.

3.2.4. validationPolicy

   The validationPolicy item defines the validation policy that the
   client wants the SCVP server to use during certificate validation.
   If this policy cannot be used for any reason, then the server MUST
   return an error response.

   A validation policy MUST define default values for all parameters
   necessary for processing an SCVP request.  For each parameter, a
   validation policy may either allow the client to specify a non-
   default value or forbid the use of a non-default value.  If the
   client wishes to use the default values for all of the parameters,
   then the client need only supply a reference to the policy in this
   item.  If the client wishes to use non-default values for one or more
   parameters, then the client supplies a reference to the policy plus
   whatever parameters are necessary to complete the request in this
   item.  If there are any conflicts between the policy referenced in
   the request and any supplied parameter values in the request, then
   the server MUST return an error response.

   The syntax of the validationPolicy item is:

      ValidationPolicy ::= SEQUENCE {
        validationPolRef          ValidationPolRef,
        validationAlg         [0] ValidationAlg OPTIONAL,
        userPolicySet         [1] SEQUENCE SIZE (1..MAX) OF OBJECT
                                    IDENTIFIER OPTIONAL,
        inhibitPolicyMapping  [2] BOOLEAN OPTIONAL,
        requireExplicitPolicy [3] BOOLEAN OPTIONAL,
        inhibitAnyPolicy      [4] BOOLEAN OPTIONAL,
        trustAnchors          [5] TrustAnchors OPTIONAL,
        keyUsages             [6] SEQUENCE OF KeyUsage OPTIONAL,
        extendedKeyUsages     [7] SEQUENCE OF KeyPurposeId OPTIONAL,
        specifiedKeyUsages    [8] SEQUENCE OF KeyPurposeId OPTIONAL }

   The validationPolRef item is required, but the remaining items are
   optional.  The optional items are used to provide validation policy
   parameters.  When the client uses the validation policy's default
   values for all parameters, all of the optional items are absent.

   At a minimum, conforming SCVP client implementations MUST support the
   validationPolRef item.  Conforming client implementations MAY support
   any or all of the optional items in ValidationPolicy.

   Conforming SCVP servers MUST support processing of a ValidationPolicy
   that contains any or all of the optional items.

   The validationAlg item specifies the validation algorithm.  The
   userPolicySet item provides an acceptable set of certificate
   policies.  The inhibitPolicyMapping item inhibits certificate policy
   mapping during certification path validation.  The
   requireExplicitPolicy item requires at least one valid certificate
   policy in the certificate policies extension.  The inhibitAnyPolicy
   item indicates whether the anyPolicy certificate policy OID is
   processed or ignored when evaluating certificate policy.  The
   trustAnchors item indicates the trust anchors that are acceptable to
   the client.  The keyUsages item indicates the technical usage of the
   public key that is to be confirmed by the server as acceptable.  The
   extendedKeyUsages item indicates the application-specific usage of
   the public key that is to be confirmed by the server as acceptable.
   The syntax and semantics of each of these items are discussed in the
   following sections.

3.2.4.1. validationPolRef

The reference to the validation policy is an OID that the client and
server have agreed represents a particular validation policy.

   The syntax of the validationPolRef item is:

      ValidationPolRef::= SEQUENCE {
        valPolId              OBJECT IDENTIFIER,
        valPolParams          ANY DEFINED BY valPolId OPTIONAL }

   Where a validation policy supports additional policy-specific
   parameter settings, these values are specified using the valPolParams
   item.  The syntax and semantics of the parameters structure are
   defined by the object identifier encoded as the valPolId.  Where a
   validation policy has no parameters, such as the default validation
   policy (see Section 3.2.4.1.1), this item MUST be omitted.

   Parameters specified in this item are independent of the validation
   algorithm and the validation algorithm's parameters (see Section
   3.2.4.2).  For example, a server may support a validation policy
   where it validates a certificate using the name validation algorithm
   and also makes a determination regarding the creditworthiness of the
   subject.  In this case, the validation policy parameters could be
   used to specify the value of the transaction.  The validation
   algorithm parameters are used to specify the application identifier
   and name for the name validation algorithm.

   Conforming SCVP client implementations MUST support specification of
   a validation policy.  Conforming SCVP client implementations MAY be
   able to specify parameters for a validation policy.  Conforming SCVP
   server implementations MUST be able to process valPolId and MAY be
   able to process valPolParams.

3.2.4.1.1. Default Validation Policy

   The client can request the SCVP server's default validation policy or
   another validation policy.  The default validation policy corresponds
   to standard certification path processing as defined in [PKIX-1] with
   server-chosen default values (e.g., with a server-determined policy
   set and trust anchors).  The default values can be distributed out of
   band or using the policy request mechanism (see Section 5).  This
   mechanism permits the deployment of an SCVP server without obtaining
   a new object identifier.

   The object identifier that identifies the default validation policy
   is:

      id-svp OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
             dod(6) internet(1) security(5) mechanisms(5) pkix(7) 19 }

      id-svp-defaultValPolicy OBJECT IDENTIFIER ::= { id-svp 1 }

   The default validation policy MUST use the basic validation algorithm
   as its default validation algorithm (see Section 3.2.4.2.1), and has
   no validation policy parameters (see Section 3.2.4.1).

   When using the default validation policy, the client can override any
   of the default parameter values by supplying a specific value in the
   request.  The SCVP server MUST make use of the provided parameter
   values or return an error response.

   Conforming implementations of SCVP servers MUST support the default
   policy.  However, an SCVP server may be configured to send an error
   response to all requests using the default policy to meet local
   security requirements.

3.2.4.2. validationAlg

   The optional validationAlg item defines the validation algorithm to
   be used by the SCVP server during certificate validation.  The value
   of this item can be determined by agreement between the client and
   the server.  The validation algorithm is represented by an object
   identifier.

   The syntax of the validationAlg item is:

      ValidationAlg ::= SEQUENCE {
        valAlgId              OBJECT IDENTIFIER,
        parameters            ANY DEFINED BY valAlgId OPTIONAL }

   The following section specifies the basic validation algorithm and
   the name validation algorithm.

   SCVP servers MUST recognize and support both validation algorithms
   defined in this section.  SCVP clients that support explicit
   assertion of the validation algorithm MUST support the basic
   validation algorithm and SHOULD support the name validation
   algorithm.  Other validation algorithms can be specified in other
   documents for use with specific applications.  SCVP clients and
   servers MAY support any such validation algorithms.

3.2.4.2.1. Basic Validation Algorithm

   The client can request use of the SCVP basic validation algorithm or
   another algorithm.  For identity certificates, the basic validation
   algorithm MUST implement the certification path validation algorithm
   as defined in Section 6 of [PKIX-1].  For attribute certificates, the
   basic validation algorithm MUST implement certification path
   validation as defined in Section 5 of [PKIX-AC].  Other validation
   algorithms MAY implement functions over and above those in the basic

   algorithm, but validation algorithms MUST generate results compliant
   with the basic validation algorithm.  That is, none of the validation
   requirements in the basic algorithm may be omitted from any newly
   defined validation algorithms.  However, other validation algorithms
   MAY reject paths that are valid using the basic validation algorithm.
   The object identifier to identify the basic validation algorithm is:

      id-svp-basicValAlg OBJECT IDENTIFIER ::= { id-svp 3 }

   When id-svp-basicValAlg appears in valAlgId, the parameters item MUST
   be absent.

3.2.4.2.2. Basic Validation Algorithm Errors

   The following errors are defined for the basic validation algorithm
   for inclusion in the validationErrors item in the response (see
   Section 4.9.6).  These errors can be used by any other validation
   algorithm since all validation algorithms MUST implement the
   functionality of the basic validation algorithm.

      id-bvae OBJECT IDENTIFIER ::= id-svp-basicValAlg

      id-bvae-expired              OBJECT IDENTIFIER ::= { id-bvae 1 }
      id-bvae-not-yet-valid        OBJECT IDENTIFIER ::= { id-bvae 2 }
      id-bvae-wrongTrustAnchor     OBJECT IDENTIFIER ::= { id-bvae 3 }
      id-bvae-noValidCertPath      OBJECT IDENTIFIER ::= { id-bvae 4 }
      id-bvae-revoked              OBJECT IDENTIFIER ::= { id-bvae 5 }
      id-bvae-invalidKeyPurpose    OBJECT IDENTIFIER ::= { id-bvae 9 }
      id-bvae-invalidKeyUsage      OBJECT IDENTIFIER ::= { id-bvae 10 }
      id-bvae-invalidCertPolicy    OBJECT IDENTIFIER ::= { id-bvae 11 }

   The id-bvae-expired value means that the validation time used for the
   request was later than the notAfter time in the end certificate (the
   certificate specified in the queriedCerts item).

   The id-bvae-not-yet-valid value means that the validation time used
   for the request was before the notBefore time in the end certificate.

   The id-bvae-wrongTrustAnchor value means that a certification path
   could not be constructed for the client-specified trust anchor(s),
   but a path exists for one of the trust anchors specified in the
   server's default validation policy.

   The id-bvae-noValidCertPath value means that the server could not
   construct a sequence of intermediate certificates between the trust
   anchor and the target certificate that satisfied the request.

   The id-bvae-revoked value means that the end certificate has been
   revoked.

   The id-bvae-invalidKeyPurpose value means that the extended key usage
   extension ([PKIX-1], Section 4.2.1.13) in the end certificate does
   not satisfy the validation policy.

   The id-bvae-invalidKeyUsage value means that the keyUsage extension
   ([PKIX-1], Section 4.2.1.3) in the end certificate does not satisfy
   the validation policy.  For example, the keyUsage extension in the
   certificate may assert only the keyEncipherment bit, but the
   validation policy specifies in the keyUsages item that
   digitalSignature is required.

   The id-bvae-invalidCertPolicy value means that the path is not valid
   under any of the policies specified in the user policy set and
   explicit policies are required.  That is, the valid_policy_tree is
   NULL and the explicit_policy variable is zero ([PKIX-1], Section
   6.1.5).

3.2.4.2.3. Name Validation Algorithm

   The name validation algorithm allows the client to specify one or
   more subject names that MUST appear in the end certificate in
   addition to the requirements specified for the basic validation
   algorithm.  The name validation algorithm allows the client to supply
   an application identifier and a name to the server.  The application
   identifier defines the name matching rules to use in comparing the
   name supplied in the request with the names in the certificate.

      id-svp-nameValAlg OBJECT IDENTIFIER ::= { id-svp 2 }

   When the id-svp-nameValAlg appears as a valAlgId, the parameters MUST
   use the NameValidationAlgParms syntax:

      NameValidationAlgParms ::= SEQUENCE {
        nameCompAlgId     OBJECT IDENTIFIER,
        validationNames   GeneralNames }

   GeneralNames is defined in [PKIX-1].

   If more than one name is supplied in the validationNames value, all
   names MUST be of the same type.  The certificate must contain a
   matching name for each of the names supplied in validationNames
   according to the name matching rules associated with the
   nameCompAlgId.  This specification defines three sets of name
   matching rules.

   If the nameCompAlgId supplied in the request is id-nva-dnCompAlg,
   then GeneralNames supplied in the request MUST be a directoryName,
   and the matching rules to be used are defined in [PKIX-1].  The
   certificate must contain a matching name in either the subject field
   or a directoryName in the subjectAltName extension.  This
   specification defines the OID for id-nva-dnCompAlg as follows:

      id-nva-dnCompAlg   OBJECT IDENTIFIER ::= { id-svp 4 }

   If the nameCompAlgId supplied in the request is id-kp-serverAuth
   [PKIX-1], then GeneralNames supplied in the request MUST be a
   dNSName, and the matching rules to be used are defined in [PKIX-1].

   If a subjectAltName extension is present and includes one or more
   names of type dNSName, a match in any one of the set is considered
   acceptable.  If the subjectAltName extension is omitted, or does not
   include any names of type dNSName, the (most specific) Common Name
   field in the subject field of the certificate MUST be used.

   Names may contain the wildcard character *, which is considered to
   match any single domain name component.  That is, *.a.com matches
   foo.a.com but not bar.foo.a.com.

   If the nameCompAlgId supplied in the request is id-kp-mailProtection
   [PKIX-1], then GeneralNames supplied in the request MUST be an
   rfc822Name, and the matching rules are defined in [SMIME-CERT].

   Conforming SCVP servers MUST support the name validation algorithm
   and the matching rules associated with id-nva-dnCompAlg, id-kp-
   serverAuth, and id-kp-mailProtection.  SCVP servers MAY support other
   name matching rules.

3.2.4.2.4. Name Validation Algorithm Errors

   The following errors are defined for the name validation algorithm:

      id-nvae OBJECT IDENTIFIER ::= id-svp-nameValAlg

      id-nvae-name-mismatch    OBJECT IDENTIFIER ::= { id-nvae 1 }
      id-nvae-no-name          OBJECT IDENTIFIER ::= { id-nvae 2 }
      id-nvae-unknown-alg      OBJECT IDENTIFIER ::= { id-nvae 3 }
      id-nvae-bad-name         OBJECT IDENTIFIER ::= { id-nvae 4 }
      id-nvae-bad-name-type    OBJECT IDENTIFIER ::= { id-nvae 5 }
      id-nvae-mixed-names      OBJECT IDENTIFIER ::= { id-nvae 6 }

   The id-nvae-name-mismatch value means the client supplied a name with
   the request, which the server recognized and the server found a
   corresponding name type in the certificate, but was unable to find a

   match to the name supplied.  For example, the client supplied a DNS
   name of example1.com, and the certificate contained a DNS name of
   example.com.

   The id-nvae-no-name value means the client supplied a name with the
   request, which the server recognized, but the server could not find
   the corresponding name type in the certificate.  For example, the
   client supplied a DNS name of example1.com, and the certificate only
   contained a rfc822Name of user@example.com.

   The id-nvae-unknown-alg value means the client supplied a
   nameCompAlgId that the server does not recognize.

   The id-nvae-bad-name value means the client supplied either an empty
   or malformed name in the request.

   The id-nvae-bad-name-type value means the client supplied an
   inappropriate name type for the application identifier.  For example,
   the client specified a nameCompAlgId of id-kp-serverAuth, and an
   rfc822Name of user@example.com.

   The id-nvae-mixed-names value means the client supplied multiple
   names in the request of different types.

3.2.4.3. userPolicySet

   The userPolicySet item specifies a list of certificate policy
   identifiers that the SCVP server MUST use when constructing and
   validating a certification path.  The userPolicySet item specifies
   the user-initial-policy-set as defined in Section 6 of [PKIX-1].  A
   userPolicySet containing the anyPolicy OID indicates a user-initial-
   policy-set of any-policy.

   SCVP clients SHOULD support the userPolicySet item in requests, and
   SCVP servers MUST support the userPolicySet item in requests.

3.2.4.4. inhibitPolicyMapping

   The inhibitPolicyMapping item specifies an input to the certification
   path validation algorithm, and it controls whether policy mapping is
   allowed during certification path validation (see [PKIX-1], Section
   6.1.1).  If the client wants the server to inhibit policy mapping,
   inhibitPolicyMapping is set to TRUE in the request.  SCVP clients MAY
   support inhibiting policy mapping.  SCVP servers SHOULD support
   inhibiting policy mapping.

3.2.4.5. requireExplicitPolicy

   The requireExplicitPolicy item specifies an input to the
   certification path validation algorithm, and it controls whether
   there must be at least one valid policy in the certificate policies
   extension (see [PKIX-1], Section 6.1.1).  If the client wants the
   server to require at least one policy, requireExplicitPolicy is set
   to TRUE in the request.

   SCVP clients MAY support requiring explicit policies.  SCVP servers
   SHOULD support requiring explicit policies.

3.2.4.6. inhibitAnyPolicy

   The inhibitAnyPolicy item specifies an input to the certification
   path validation algorithm (see [PKIX-1], Section 6.1.1), and it
   controls whether the anyPolicy OID is processed or ignored when
   evaluating certificate policy.  If the client wants the server to
   ignore the anyPolicy OID, inhibitAnyPolicy MUST be set to TRUE in the
   request.

   SCVP clients MAY support ignoring the anyPolicy OID.  SCVP servers
   SHOULD support ignoring the anyPolicy OID.

3.2.4.7. trustAnchors

   The trustAnchors item specifies the trust anchors at which the
   certification path must terminate if the path is to be considered
   valid by the SCVP server for the request.  If a trustAnchors item is
   present, the server MUST NOT consider any certification paths ending
   in other trust anchors as valid.

   The TrustAnchors type contains one or more trust anchor
   specifications.  A certificate reference can be used to identify the
   trust anchor by certificate hash and distinguished name with serial
   number.  Alternatively, trust anchors can be provided directly.  The
   order of trust anchor specifications within the sequence is not
   important.  Any CA certificate that meets the requirements of
   [PKIX-1] for signing certificates can be provided as a trust anchor.
   If a trust anchor is supplied that does not meet these requirements,
   the server MUST return an error response.

   The trust anchor itself, regardless of its form, MUST NOT be included
   in any certification path returned by the SCVP server.

   TrustAnchors has the following syntax:

      TrustAnchors ::= SEQUENCE SIZE (1..MAX) OF PKCReference

SCVP servers MUST support trustAnchors. SCVP clients SHOULD support
trustAnchors.

3.2.4.8. keyUsages

   The key usage extension ([PKIX-1], Section 4.2.1.3) in the
   certificate defines the technical purpose (such as encipherment,
   signature, and CRL signing) of the key contained in the certificate.
   If the client wishes to confirm the technical usage, then it can
   communicate the usage it wants to validate by the same structure
   using the same semantics as defined in [PKIX-1].  For example, if the
   client obtained the certificate in the context of a digital
   signature, it can confirm this use by including a keyUsage structure
   with the digital signature bit set.

   If the keyUsages item is present and contains an empty sequence, it
   indicates that the client does not require any particular key usage.

   If the keyUsages item contains one or more keyUsage definitions, then
   the certificate MUST satisfy at least one of the specified keyUsage
   definitions.  If the client is willing to accept multiple
   possibilities, then the client passes in a sequence of possible
   patterns.  Each keyUsage can contain a set of one or more bits set in
   the request, all bits MUST be set in the certificate to match against
   an instance of the keyUsage in the SCVP request.  The certificate key
   usage extension may contain more usages than requested.  For example,
   if a client wishes to check for either digital signature or non-
   repudiation, then the client provides two keyUsage values, one with
   digital signature set and the other with non-repudiation set.  If the
   key usage extension is absent from the certificate, the certificate
   MUST be considered good for all usages and therefore any pattern in
   the SCVP request will match.

   SCVP clients SHOULD support keyUsages, and SCVP servers MUST support
   keyUsages.

3.2.4.9. extendedKeyUsages

   The extended key usage extension ([PKIX-1], Section 4.2.1.13) defines
   more specific technical purposes, in addition to, or in place of, the
   purposes indicated in the key usage extension, for which the
   certified public key may be used.  If the client will accept
   certificates that are consistent with a particular value (or values)
   in the extended key usage extension, then it can communicate the
   appropriate usages using the same semantics as defined in [PKIX-1].

   For example, if the client obtained the certificate in the context of
   a Transport Layer Security (TLS) server, it can confirm the
   certificate is consistent with this usage by including the extended
   key usage structure with the id-kp-serverAuth object identifier.

   If the extension is absent, or is present and asserts the
   anyExtendedKeyUsage OID, then all usages specified in the request are
   a match.  If the extension is present and does not assert the
   anyExtendedKeyUsage OID, all usages in the request MUST be present in
   the certificate.  The certificate extension may contain more usages
   than requested.

   Where the client does not require any particular extended key usage,
   the client can specify an empty SEQUENCE.  This may be used to
   override extended key usage requirements imposed in the validation
   policy specified by valPolId.

   SCVP clients SHOULD support extendedKeyUsages, and SCVP servers MUST
   support extendedKeyUsages.

3.2.4.10. specifiedKeyUsages

   The extended key usage extension ([PKIX-1], Section 4.2.1.13) defines
   more specific technical purposes, in addition to or in place of the
   purposes indicated in the key usage extension, for which the
   certified public key may be used.  If the client requires that a
   particular value (or values) appear in the extended key usage
   extension, then it can specify the required usage(s) using the same
   semantics as defined in [PKIX-1].  For example, if the client
   obtained the certificate in the context of a TLS server, it might
   require that the server certificate include the extended key usage
   structure with the id-kp-serverAuth object identifier.  In this case,
   the client would include a specifiedKeyUsages item in the request and
   assert the id-kp-serverAuth object identifier.

   If one or more specified usages are included in the request, the
   certificate MUST contain the extended key usage extension, and all
   usages specified in the request MUST be present in the certificate
   extension.  The certificate extension may contain more usages than
   specified in the request.  Specified key usages are not satisfied by
   the presence of the anyExtendedKeyUsage OID.

   Where the client does not require any particular extended key usage,
   the client can specify an empty SEQUENCE.  This may be used to
   override specified key usage requirements imposed in the validation
   policy specified by valPolId.

SCVP clients SHOULD support specifiedKeyUsages, and SCVP servers MUST
support specifiedKeyUsages.

3.2.5. responseFlags

   The optional responseFlags item allows the client to indicate which
   optional features in the CVResponse it wants the server to include.
   If the default values for all of the flags are used, then the
   responseFlags item MUST NOT be included in the request.

   The syntax of the responseFlags item is:

      ResponseFlags ::= SEQUENCE {
        fullRequestInResponse      [0] BOOLEAN DEFAULT FALSE,
        responseValidationPolByRef [1] BOOLEAN DEFAULT TRUE,
        protectResponse            [2] BOOLEAN DEFAULT TRUE,
        cachedResponse             [3] BOOLEAN DEFAULT TRUE }

   Each of the response flags is described in the following sections.

3.2.5.1. fullRequestInResponse

   By default, the server includes a hash of the request in non-cached
   responses to allow the client to identify the response.  If the
   client wants the server to include the full request in the non-cached
   response, fullRequestInResponse is set to TRUE.  The main reason a
   client would request the server to include the full request in the
   response is to archive the request-response exchange in a single
   object.  That is, the client wants to archive a single object that
   includes both request and response.

   SCVP clients and servers MUST support the default behavior.  SCVP
   clients MAY support requesting and processing the full request.  SCVP
   servers SHOULD support returning the full request.

3.2.5.2. responseValidationPolByRef

   The responseValidationPolByRef item controls whether the response
   includes just a reference to the policy or a reference to the policy
   plus all the parameters by value of the policy used to process the
   request.  The response MUST contain a reference to the validation
   policy.  If the client wants the validation policy parameters to be
   included by value also, then responseValidationPolByRef is set to
   FALSE.  The main reason a client would request the server to include
   validation policy to be included by value is to archive the request-
   response exchange in a single object.  That is, the client wants to
   archive the CVResponse and have it include every aspect of the
   validation policy.

   SCVP clients MUST support requesting and processing the validation
   policy by reference, and SCVP servers MUST support returning the
   validation policy by reference.  SCVP clients MAY support requesting
   and processing the validation policy by values.  SVCP servers SHOULD
   support returning the validation policy by values.

3.2.5.3. protectResponse

   The protectResponse item indicates whether the client requires the
   server to protect the response.  If the client is performing full
   certification path validation on the response and it is not concerned
   about the source of the response, then the client does not benefit
   from a digital signature or MAC on the response.  In this case, the
   client can indicate to the server that protecting the message is
   unnecessary.  However, the server is always permitted to return a
   protected response.

   SCVP clients that support delegated path discovery (DPD) as defined
   in [RQMTS] MUST support setting this value to FALSE.

   SCVP clients that support delegated path validation (DPV) as defined
   in [RQMTS] require an authenticated response.  Unless a protected
   transport mechanism (such as TLS) is used, such clients MUST always
   set this value to TRUE or omit the responseFlags item entirely, which
   requires the server to return a protected response.

   SCVP servers MUST support returning protected responses, and SCVP
   servers SHOULD support returning unprotected responses.  Based on
   local policy, the server can be configured to return protected or
   unprotected responses if this value is set to FALSE.  If, based on
   local policy, the server is unable to return protected responses,
   then the server MUST return an error if this value is set to TRUE.

3.2.5.4. cachedResponse

   The cachedResponse item indicates whether the client will accept a
   cached response.  To enhance performance and limit the exposure of
   signing keys, an SCVP service may be designed to cache responses
   until new revocation information is expected.  Where cachedResponse
   is set to TRUE, the client will accept a previously cached response.

   Clients may insist on creation of a fresh response to protect against
   a replay attack and ensure that information is up to date.  Where
   cachedResponse is FALSE, the client will not accept a cached
   response.  To ensure that a response is fresh, the client MUST also
   include the requestNonce as defined in Section 3.4.

   Servers MUST process the cachedResponse flag.  Where cachedResponse
   is FALSE, servers that cannot produce fresh responses MUST reply with
   an error message.  Servers MAY choose to provide fresh responses even
   where cachedResponse is set to TRUE.

3.2.6. serverContextInfo

   The optional serverContextInfo item, if present, contains context
   from a previous request-response exchange with the same SCVP server.
   It allows the server to return more than one certification path for
   the same certificate to the client.  For example, if a server
   constructs a particular certification path for a certificate, but the
   client finds it unacceptable, the client can then send the same query
   back to the server with the serverContextInfo from the first
   response, and the server will be able to provide a different
   certification path (if another one can be found).

   Contents of the serverContextInfo are opaque to the SCVP client.
   That is, the client only knows that it needs to return the value
   provided by the server with the subsequent request to get a different
   certification path.  Note that the subsequent query needs to be
   identical to the previous query with the exception of the following:

      - requestNonce,

      - serverContextInfo, and

      - the client's digital signature or MAC on the request.

   SCVP clients MAY support serverContextInfo, and SCVP servers SHOULD
   support serverContextInfo.

3.2.7. validationTime

   The optional validationTime item, if present, tells the date and time
   relative to which the SCVP client wants the server to perform the
   checks.  If the validationTime is not present, the server MUST
   perform the validation using the date and time at which the server
   processes the request.  If the validationTime is present, it MUST be
   encoded as GeneralizedTime.  The validationTime provided MUST be a
   retrospective time since the server can only perform a validity check
   using the current time (default) or previous time.  A server can
   ignore the validationTime provided in the request if the time is
   within the clock skew of the server's current time.

   The revocation status information is obtained with respect to the
   validation time.  When specifying a validation time other than the
   current time, the validation time should not necessarily be identical
   to the time when the private key was used.  The validation time
   specified by the client may be adjusted to compensate for:

   1) time for the end-entity to realize that its private key has been,
      or could possibly be, compromised, and/or

   2) time for the end-entity to report the key compromise, and/or

   3) time for the revocation authority to process the revocation
      request from the end-entity, and/or

   4) time for the revocation authority to update and distribute the
      revocation status information.

   GeneralizedTime values MUST be expressed in Universal Coordinated
   Time (UTC) (which is also known as Greenwich Mean Time and Zulu time)
   and MUST include seconds (i.e., times are YYYYMMDDHHMMSSZ), even when
   the number of seconds is zero.  GeneralizedTime values MUST NOT
   include fractional seconds.

   The information in the corresponding CertReply item in the response
   MUST be formatted as if the server created the response at the time
   indicated in the validationTime.  However, if the server does not
   have appropriate historical information, the server MUST return an
   error response.

   SCVP servers MUST apply a clock skew to the validation time to allow
   for minor time synchronization errors.  The default value is 10
   minutes.  If the server uses a value other than the default, it MUST
   include the clock skew value in the validation policy response.

   SCVP clients MAY support validationTime other than the current time.
   SCVP servers MUST support using its current time, and SHOULD support
   the client setting the validationTime in the request.

3.2.8. intermediateCerts

   The optional intermediateCerts item may help the SCVP server create
   valid certification paths.  The intermediateCerts item, when present,
   provides certificates that the server MAY use when forming a
   certification path.  When building certification paths, the server
   MAY use the certificates in the intermediateCerts item in addition to
   any other certificates that the server can access.  When present, the
   intermediateCerts item MUST contain at least one certificate, and

   the intermediateCerts item MUST be structured as a CertBundle.  The
   certificates in the intermediateCerts item MUST NOT be considered as
   valid by the server just because they are present in this item.

   The CertBundle type contains one or more certificates.  The order of
   the entries in the bundle is not important.  CertBundle has the
   following syntax:

      CertBundle ::= SEQUENCE SIZE (1..MAX) OF Certificate

   SCVP clients SHOULD support intermediateCerts, and SCVP servers MUST
   support intermediateCerts.

3.2.9. revInfos

   The optional revInfos item specifies revocation information such as
   CRLs, delta CRLs [PKIX-1], and OCSP responses [OCSP] that the SCVP
   server MAY use when validating certification paths.  The purpose of
   the revInfos item is to provide revocation information to which the
   server might not otherwise have access, such as an OCSP response that
   the client received along with the certificate.  Note that the
   information in the revInfos item might not be used by the server.
   For example, the revocation information might be associated with
   certificates that the server does not use in the certification path
   that it constructs.

   Clients SHOULD be courteous to the SCVP server by separating CRLs and
   delta CRLs.  However, since the two share a common syntax, SCVP
   servers SHOULD accept delta CRLs even if they are identified as
   regular CRLs by the SCVP client.

   CRLs, delta CRLs, and OCSP responses can be provided as revocation
   information.  If needed, additional object identifiers can be
   assigned for additional revocation information types in the future.

   The revInfos item uses the RevocationInfos type, which has the
   following syntax:

      RevocationInfos ::= SEQUENCE SIZE (1..MAX) OF RevocationInfo

      RevocationInfo ::= CHOICE {
        crl                    [0] CertificateList,
        delta-crl              [1] CertificateList,
        ocsp                   [2] OCSPResponse,
        other                  [3] OtherRevInfo }

      OtherRevInfo ::= SEQUENCE {
        riType                     OBJECT IDENTIFIER,
        riValue                    ANY DEFINED BY riType }

3.2.10. producedAt

   The client MAY allow the server to use a cached SCVP response.  When
   doing so, the client MAY use the producedAt item to express
   requirements on the freshness of the cached response.  The producedAt
   item tells the earliest date and time at which an acceptable cached
   response could have been produced.  The producedAt item represents
   the date and time in UTC, using the GeneralizedTime type.  The value
   in the producedAt item is independent of the validation time.

   GeneralizedTime value MUST be expressed in UTC, as defined in Section
   3.2.7.

   SCVP clients MAY support using producedAt values in the request.
   SCVP servers MAY support the producedAt values in the request.  SCVP
   servers that support cached responses SHOULD support the producedAt
   value in requests.

3.2.11. queryExtensions

   The optional queryExtensions item contains extensions.  If present,
   each extension in the sequence extends the query.  This specification
   does not define any extensions; the facility is provided to allow
   future specifications to extend SCVP.  The syntax for Extensions is
   imported from [PKIX-1].  The queryExtensions item, when present, MUST
   contain a sequence of Extension items, and each of the extensions
   MUST contain extnID, critical, and extnValue items.  Each of these is
   described in the following sections.

3.2.11.1. extnID

The extnID item is an identifier for the extension. It contains the
object identifier that names the extension.

3.2.11.2. critical

   The critical item is a BOOLEAN.  Each extension is designated as
   either critical (with a value of TRUE) or non-critical (with a value
   of FALSE).  By default, the extension is non-critical.  An SCVP
   server MUST reject the query if it encounters a critical extension
   that it does not recognize; however, a non-critical extension MAY be
   ignored if it is not recognized, but MUST be processed if it is
   recognized.

3.2.11.3. extnValue

   The extnValue item contains an OCTET STRING.  Within the OCTET STRING
   is the extension value.  An ASN.1 type is specified for each
   extension, identified by the associated extnID object identifier.

3.3. requestorRef

   The optional requestorRef item contains a list of names identifying
   SCVP servers, and it is intended for use in environments where SCVP
   relay is employed.  Although requestorRef is encoded as a SEQUENCE,
   no order is implied.  The requestorRef item is used to detect looping
   in some configurations.  The value and use of requestorRef are
   described in Section 7.

   Conforming SCVP clients MAY support specification of the requestorRef
   value.  Conforming SCVP server implementations MUST process the
   requestorRef value if present.  If the SCVP client includes a
   requestorRef value in the request, then the SCVP server MUST return
   the same value in a non-cached response.  The SCVP server MAY omit
   the requestorRef value from cached SCVP responses.

   The requestorRef item MUST be a sequence of GeneralName.  No
   provisions are made to ensure uniqueness of the requestorRef
   GeneralName values.

3.4. requestNonce

   The optional requestNonce item contains a request identifier
   generated by the SCVP client.  If the client includes a requestNonce
   value in the request, it is expressing a preference that the SCVP
   server SHOULD return a non-cached response.  If the server returns a
   non-cached response, it MUST include the value of requestNonce from
   the request in the response as the respNonce item; however, the
   server MAY return a cached response which MUST NOT have a respNonce.

   SCVP clients that insist on creation of a fresh response (e.g., to
   protect against a replay attack or ensure information is up to date)
   MUST support requestNonce.  Conforming SCVP server implementations
   MUST process the requestNonce value if present.

   If the client includes a requestNonce and also sets the
   cachedResponse flag to FALSE as described in Section 3.2.5.4, the
   client is indicating that the SCVP server MUST return either a non-
   cached response including the respNonce or an error response.  The
   client SHOULD include a requestNonce item in every request to prevent

   an attacker from acting as a man-in-the-middle by replaying old
   responses from the server.  The requestNonce value SHOULD change with
   every request sent by the client.

   The client MUST NOT set the cachedResponse flag to FALSE without also
   including a requestNonce.  A server receiving such a request SHOULD
   return an invalidRequest error response.

   The requestNonce item, if present, MUST be an OCTET STRING that was
   generated exclusively for this request.

3.5. requestorName

   The optional requestorName item is used by the client to include an
   identifier in the request.  The client MAY include this information
   for the DPV server to copy into the response.

   Conforming SCVP clients MAY support specification of this item in
   requests.  SCVP servers MUST be able to process requests that include
   this item.

3.6. responderName

   The optional responderName item is used by the client to indicate the
   identity of the SCVP server that the client expects to sign the SCVP
   response if the response is digitally signed.  The responderName item
   SHOULD only be included if:

   1. the request is either unprotected or digitally signed (i.e., is
      not protected using a MAC), and

   2. the responseFlags item is either absent or present with the
      protectResponse set to TRUE.

   Conforming SCVP clients MAY support specification of this item in
   requests.  SCVP servers MUST be able to process requests that include
   this item.  SCVP servers that maintain a single private key for
   signing SCVP responses or that are unable to return digitally signed
   responses MAY ignore the value in this item.  SCVP servers that
   maintain more than one private key for signing SCVP responses SHOULD
   either (a) digitally sign the response using a private key that
   corresponds to a certificate that includes the name specified in
   responderName in either subject field or subjectAltName extension or
   (b) return a error indicating that the server does not possess a
   certificate that asserts the specified name.

3.7. requestExtensions

   The OPTIONAL requestExtensions item contains extensions.  If present,
   each extension in the sequence extends the request.  This
   specification does not define any extensions; the facility is
   provided to allow future specifications to extend SCVP.  The syntax
   for Extensions is imported from [PKIX-1].  The requestExtensions
   item, when present, MUST contain a sequence of Extension items, and
   each of the extensions MUST contain extnID, critical, and extnValue
   items.  Each of these is described in the following sections.

3.7.1. extnID

The extnID item is an identifier for the extension. It contains the
object identifier that names the extension.

3.7.2. critical

   The critical item is a BOOLEAN.  Each extension is designated as
   either critical (with a value of TRUE) or non-critical (with a value
   of FALSE).  By default, the extension is non-critical.  An SCVP
   server MUST reject the query if it encounters a critical extension it
   does not recognize.  A non-critical extension MAY be ignored if it is
   not recognized, but MUST be processed if it is recognized.

3.7.3. extnValue

   The extnValue item contains an OCTET STRING.  Within the OCTET STRING
   is the extension value.  An ASN.1 type is specified for each
   extension, identified by the associated extnID object identifier.

3.8. signatureAlg

   The signatureAlg item contains an AlgorithmIdentifier indicating
   which algorithm the server should use to sign the response message.
   The signatureAlg item SHOULD only be included if:

   1. the request is either unprotected or digitally signed (i.e., is
      not protected using a MAC), and

   2. the responseFlags item is either absent or present with the
      protectResponse set to TRUE.

   If included, the signatureAlg item SHOULD specify one of the
   signature algorithms specified in the signatureGeneration item of the
   server's validation policy response message.

   SCVP servers MUST be able to process requests that include this item.
   If the server is returning a digitally signed response to this
   message, then:

   1. If the signatureAlg item is present and specifies an algorithm
      that is included in the signatureGeneration item of the server's
      validation policy response message, the server MUST sign the
      response using the signature algorithm specified in signatureAlg.

   2. Otherwise, if the signatureAlg item is absent or is present but
      specifies an algorithm that is not supported by the server, the
      server MUST sign the response using the server's default signature
      algorithm as specified in the signatureGeneration item of the
      server's validation policy response message.

3.9. hashAlg

   The hashAlg item contains an object identifier indicating which hash
   algorithm the server should use to compute the hash value for the
   requestHash item in the response.  SCVP clients SHOULD NOT include
   this item if fullRequestInResponse is set to TRUE.  If included, the
   hashAlg item SHOULD specify one of the hash algorithms specified in
   the hashAlgorithms item of the server's validation policy response
   message.

   SCVP servers MUST be able to process requests that include this item.
   If the server is returning a response to this message that includes a
   requestHash, then:

   1. If the hashAlg item is present and specifies an algorithm that is
      included in the hashAlgorithms item of the server's validation
      policy response message, the server MUST use the algorithm
      specified in hashAlg to compute the requestHash.

   2. Otherwise, if the hashAlg item is absent or is present but
      specifies an algorithm that is not supported by the server, the
      server MUST compute the requestHash using the server's default
      hash algorithm as specified in the hashAlgorithms item of the
      server's validation policy response message.

3.10. requestorText

   SCVP clients MAY use the requestorText item to provide text for
   inclusion in the corresponding response.  For example, this field may
   describe the nature or reason for the request.

   Conforming SCVP client implementations MAY support inclusion of this
   item in requests.  Conforming SCVP server implementations MUST accept
   requests that include this item.  When generating non-cached
   responses, conforming SCVP server implementations MUST copy the
   contents of this item into the requestorText item in the
   corresponding response (see Section 4.13).

3.11. SCVP Request Authentication

   It is a matter of local policy what validation policy the server uses
   when authenticating requests.  When authenticating protected SCVP
   requests, the SCVP servers SHOULD use the validation algorithm
   defined in Section 6 of [PKIX-1].

   If the certificate used to validate a SignedData validation request
   includes the key usage extension ([PKIX-1], Section 4.2.1.3), it MUST
   have either the digital signature bit set, the non-repudiation bit
   set, or both bits set.

   If the certificate used to validate an AuthenticatedData validation
   request includes the key usage extension, it MUST have the key
   agreement bit set.

   If the certificate used on a validation request contains the extended
   key usage extension ([PKIX-1], Section 4.2.1.13), the server SHALL
   verify that it contains the SCVP client OID, the anyExtendedKeyUsage
   OID, or another OID acceptable to the server.  The SCVP client OID is
   defined as follows:

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

      id-kp-scvpClient             OBJECT IDENTIFIER ::= { id-kp 16 }

   If a protected request fails to meet the validation policy of the
   server, it MUST be treated as an unauthenticated request.

4.  Validation Response

   An SCVP server response to the client MUST be a single CVResponse
   item.  When a CVResponse is encapsulated in a MIME body part,
   application/scvp-cv-response MUST be used.

   There are a number of forms of an SCVP response:

   1. A success response to a request that has protectResponse set to
      FALSE.  These responses SHOULD NOT be protected by the server.

   2. The server MUST protect all other success responses.  If the
      server is unable to return a protected success response due to
      local policy, then it MUST return an error response.

   3. An error response to a request made over a protected transport
      such as TLS.  These responses SHOULD NOT be protected by the
      server.

   4. An error response to a request that has protectResponse set to
      FALSE.  These responses SHOULD NOT be protected by the server.

5. An error response to an authenticated request. The server SHOULD
protect these responses.

6. An error response to an AuthenticatedData request where MAC is
valid. The server MUST protect these responses.

7. All other error responses MUST NOT be protected by the server.

   Successful responses are made when the server has fully complied with
   the request.  That is, the server was able to attempt to build a
   certification path using the referenced or supplied validation
   policy, and it was able to comply with all the requested parameters.
   If the server is unable to perform validations using the required
   validation policy or the request contains an unsupported option, then
   the server MUST return an error response.

   For protected requests and responses, SCVP servers MUST support
   SignedData and SHOULD support AuthenticatedData.  It is a matter of
   local policy which types are used.  Where a protected response is
   required, SCVP servers MUST use SignedData or AuthenticatedData, even
   if the transaction is performed using a protected transport (e.g.,
   TLS).

   If the server is making a protected response to a protected request,
   then the server MUST use the same protection mechanism (SignedData or
   AuthenticatedData) as in the request.

   An overview of the structure used for an unprotected response is
   provided below.  Many details are not shown, but the way that SCVP
   makes use of CMS is clearly illustrated.

      ContentInfo {
        contentType        id-ct-scvp-certValResponse,
                                    -- (1.2.840.113549.1.9.16.1.11)
        content            CVResponse }

   The protected response consists of a CVResponse encapsulated in
   either a SignedData or an AuthenticatedData, which is in turn
   encapsulated in a ContentInfo.  That is, the EncapsulatedContentInfo
   field of either SignedData or AuthenticatedData consists of an
   eContentType field with a value of id-ct-scvp-certValResponse and an
   eContent field that contains a DER-encoded CVResponse.

   The SCVP server MUST include its own certificate in the certificates
   field within SignedData.  Other certificates MAY also be included.

   The SCVP server MAY also provide one or more CRLs in the crls field
   within SignedData.  The signerInfos field of SignedData MUST include
   exactly one SignerInfo.  The SignedData MUST NOT include the
   unsignedAttrs field.

   The signedAttrs field within SignerInfo MUST include the content-type
   and message-digest attributes defined in [CMS], and it SHOULD include
   the signing-certificate attribute as defined in [ESS].  Within the
   signing-certificate attribute, the first certificate identified in
   the sequence of certificate identifiers MUST be the certificate of
   the SCVP server.  The inclusion of other certificate identifiers in
   the signing-certificate attribute is OPTIONAL.  The inclusion of
   policies in the signing-certificate is OPTIONAL.

   The recipientInfos field of AuthenticatedData MUST include exactly
   one RecipientInfo, which contains information for the client that
   sent the request.  The AuthenticatedData MUST NOT include the
   unauthAttrs field.

   The CVResponse item contains the server's response.  The CVResponse
   MUST contain the cvResponseVersion, serverConfigurationID,
   producedAt, and responseStatus items.  The CVResponse MAY also
   contain the respValidationPolicy, requestRef, requestorRef,
   requestorName, replyObjects, respNonce, serverContextInfo, and
   cvResponseExtensions items.  The replyObjects item MUST contain
   exactly one CertReply item for each certificate requested.  The
   requestorRef item MUST be included if the request included a
   requestorRef item and a non-cached response is provided.  The
   respNonce item MUST be included if the request included a
   requestNonce item and a non-cached response is provided.

   The CVResponse MUST have the following syntax:

      CVResponse ::= SEQUENCE {
        cvResponseVersion         INTEGER,
        serverConfigurationID     INTEGER,
        producedAt                GeneralizedTime,
        responseStatus            ResponseStatus,
        respValidationPolicy  [0] RespValidationPolicy OPTIONAL,
        requestRef            [1] RequestReference OPTIONAL,
        requestorRef          [2] GeneralNames OPTIONAL,
        requestorName         [3] GeneralNames OPTIONAL,
        replyObjects          [4] ReplyObjects OPTIONAL,
        respNonce             [5] OCTET STRING OPTIONAL,
        serverContextInfo     [6] OCTET STRING OPTIONAL,
        cvResponseExtensions  [7] Extensions OPTIONAL,
        requestorText         [8] UTF8String (SIZE (1..256)) OPTIONAL }

   Conforming SCVP servers MAY be capable of constructing a CVResponse
   that includes the serverContextInfo or cvResponseExtensions items.
   Conforming SCVP servers MUST be capable of constructing a CVResponse
   with any of the remaining optional items.  Conforming SCVP clients
   MUST be capable of processing a CVResponse with the following
   optional items: respValidationPolicy, requestRef, requestorName,
   replyObjects, and respNonce.

   Conforming SCVP clients that are capable of including requestorRef in
   a request MUST be capable of processing a CVResponse that includes
   the requestorRef item.  Conforming SCVP clients MUST be capable of
   processing a CVResponse that includes the serverContextInfo or
   cvResponseExtensions items.  Conforming clients MUST be able to
   determine if critical extensions are present in the
   cvResponseExtensions item.

4.1. cvResponseVersion

   The syntax and semantics of cvResponseVersion are the same as
   cvRequestVersion as described in Section 3.1.  The cvResponseVersion
   MUST match the cvRequestVersion in the request.  If the server cannot
   generate a response with a matching version number, then the server
   MUST return an error response that indicates the highest version
   number that the server supports as the version number.

4.2. serverConfigurationID

   The server configuration ID item represents the version of the SCVP
   server configuration when it processed the request.  See Section 6.4
   for details.

4.3. producedAt

   The producedAt item tells the date and time at which the SCVP server
   generated the response.  The producedAt item MUST be expressed in
   UTC, and it MUST be interpreted as defined in Section 3.2.7.  This
   value is independent of the validation time.

4.4. responseStatus

   The responseStatus item gives status information to the SCVP client
   about its request.  The responseStatus item has a numeric status code
   and an optional string that is a sequence of characters from the
   ISO/IEC 10646-1 character set encoded with the UTF-8 transformation
   format defined in [UTF8].

   The string MAY be used to transmit status information.  The client
   MAY choose to display the string to a human user.  However, because
   there is often no way to know the languages understood by a human
   user, the string may be of little or no assistance.

   The responseStatus item uses the ResponseStatus type, which has the
   following syntax:

      ResponseStatus ::= SEQUENCE {
        statusCode            CVStatusCode DEFAULT  okay,
        errorMessage          UTF8String OPTIONAL }

      CVStatusCode ::= ENUMERATED {
        okay                               (0),
        skipUnrecognizedItems              (1),
        tooBusy                           (10),
        invalidRequest                    (11),
        internalError                     (12),
        badStructure                      (20),
        unsupportedVersion                (21),
        abortUnrecognizedItems            (22),
        unrecognizedSigKey                (23),
        badSignatureOrMAC                 (24),
        unableToDecode                    (25),
        notAuthorized                     (26),
        unsupportedChecks                 (27),
        unsupportedWantBacks              (28),
        unsupportedSignatureOrMAC         (29),
        invalidSignatureOrMAC             (30),
        protectedResponseUnsupported      (31),
        unrecognizedResponderName         (32),
        relayingLoop                      (40),
        unrecognizedValPol                (50),

        unrecognizedValAlg                (51),
        fullRequestInResponseUnsupported  (52),
        fullPolResponseUnsupported        (53),
        inhibitPolicyMappingUnsupported   (54),
        requireExplicitPolicyUnsupported  (55),
        inhibitAnyPolicyUnsupported       (56),
        validationTimeUnsupported         (57),
        unrecognizedCritQueryExt          (63),
        unrecognizedCritRequestExt        (64) }

   The CVStatusCode values have the following meaning:

    0 The request was fully processed.
    1 The request included some unrecognized non-critical extensions;
      however, processing was able to continue ignoring them.
   10 Too busy; try again later.
   11 The server was able to decode the request, but there was some
      other problem with the request.
   12 An internal server error occurred.
   20 The structure of the request was wrong.
   21 The version of request is not supported by this server.
   22 The request included unrecognized items, and the server was not
      able to continue processing.
   23 The server could not validate the key used to protect the
      request.
   24 The signature or message authentication code did not match the
      body of the request.
   25 The encoding was not understood.
   26 The request was not authorized.
   27 The request included unsupported checks items, and the server was
      not able to continue processing.
   28 The request included unsupported wantBack items, and the server
      was not able to continue processing.
   29 The server does not support the signature or message
      authentication code algorithm used by the client to protect the
      request.
   30 The server could not validate the client's signature or message
      authentication code on the request.
   31 The server could not generate a protected response as requested
      by the client.
   32 The server does not have a certificate matching the requested
      responder name.
   40 The request was previously relayed by the same server.
   50 The request contained an unrecognized validation policy
      reference.
   51 The request contained an unrecognized validation algorithm OID.
   52 The server does not support returning the full request in the
      response.

   53 The server does not support returning the full validation policy
      by value in the response.
   54 The server does not support the requested value for inhibit
      policy mapping.
   55 The server does not support the requested value for require
      explicit policy.
   56 The server does not support the requested value for inhibit
      anyPolicy.
   57 The server only validates requests using current time.
   63 The query item in the request contains a critical extension whose
      OID is not recognized.
   64 The request contains a critical request extension whose OID is
      not recognized.

   Status codes 0-9 are reserved for codes that indicate the request was
   processed by the server and therefore MUST be sent in a success
   response.  Status codes 10 and above indicate an error and MUST
   therefore be sent in an error response.

4.5. respValidationPolicy

   The respValidationPolicy item contains either a reference to the full
   validation policy or the full policy by value used by the server to
   validate the request.  It MUST be present in success responses and
   MUST NOT be present in error responses.  The choice between returning
   the policy by reference or by value is controlled by the
   responseValidationPolByRef item in the request.  The resultant
   validation policy is the union of the following:

   1. Values from the request.

   2. For values that are not explicitly included in the request, values
      from the validation policy specified by reference in the request.

   The RespValidationPolicy syntax is:

      RespValidationPolicy ::= ValidationPolicy

   The validationPolicy item is defined in Section 3.2.4.  When
   responseValidationPolByRef is set to FALSE in the request, all items
   in the validationPolicy item MUST be populated.  When
   responseValidationPolByRef is set to TRUE, OPTIONAL items in the
   validationPolicy item only need to be populated for items for which
   the value in the request differs from the value from the referenced
   validation policy.

   Conforming SCVP clients MUST be capable of processing the validation
   policy by reference.  SCVP clients MAY be capable of processing the
   optional items in the validation policy.

   Conforming SCVP server implementations MUST be capable of asserting
   the policy by reference, and MUST be capable of including the
   optional items.

4.6. requestRef

   The requestRef item allows the SCVP client to identify the request
   that corresponds to this response from the server.  It associates the
   response to a particular request using either a hash of the request
   or a copy of CVRequest from the request.

   The requestRef item does not provide authentication, but does allow
   the client to determine that the request was not maliciously
   modified.

   The requestRef item allows the client to associate a response with a
   request.  The requestNonce provides an alternative mechanism for
   matching requests and responses.  When the fullRequest alternative is
   used, the response provides a single data structure that is suitable
   for archive of the transaction.

   The requestRef item uses the RequestReference type, which has the
   following syntax:

      RequestReference ::= CHOICE {
        requestHash       [0] HashValue, -- hash of CVRequest
        fullRequest       [1] CVRequest }

   SCVP clients MUST support requestHash, and they MAY support
   fullRequest.  SCVP servers MUST support using requestHash, and they
   SHOULD support using fullRequest.

4.6.1. requestHash

   The requestHash item is the hash of the CVRequest.  The one-way hash
   function used to compute the hash of the CVRequest is as specified in
   Section 3.9.  The requestHash item serves two purposes.  First, it
   allows a client to determine that the request was not maliciously
   modified.  Second, it allows the client to associate a response with
   a request when using connectionless protocols.  The requestNonce
   provides an alternative mechanism for matching requests and
   responses.

   The requestHash item uses the HashValue type, which has the following
   syntax:

      HashValue ::= SEQUENCE {
        algorithm       AlgorithmIdentifier DEFAULT { algorithm sha-1 },
        value           OCTET STRING }

      sha-1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
          oiw(14) secsig(3) algorithm(2) 26 }

   The algorithm identifier for SHA-1 is imported from [PKIX-ALG].  It
   is repeated here for convenience.

4.6.2. fullRequest

   Like requestHash, the fullRequest alternative allows a client to
   determine that the request was not maliciously modified.  It also
   provides a single data structure that is suitable for archive of the
   transaction.

   The fullRequest item uses the CVRequest type.  The syntax and
   semantics of the CVRequest type are described in Section 3.

4.7. requestorRef

   The optional requestorRef item is used by the client to identify the
   original requestor in cases where SCVP relay is used.  The value is
   only of local significance to the client.  If the SCVP client
   includes a requestorRef value in the request, then the SCVP server
   MUST return the same value if the server is generating a non-cached
   response.

4.8. requestorName

   The optional requestorName item is used by the server to return one
   or more identities associated with the client in the response.

   The SCVP server MAY choose to include any or all of the following:

   (1) the identity asserted by the client in the requestorName item of
      the request,

   (2) an authenticated identity for the client from a certificate or
      other credential used to authenticate the request, or

   (3) a client identifier from an out-of-band mechanism.

   Alternatively, the SCVP server MAY omit this item.

   In the case of non-cached responses to authenticated requests, the
   SCVP server SHOULD return a requestor name.

   SCVP servers that support authenticated requests SHOULD support this
   item.

   SCVP clients MUST be able to process responses that include this
   item, although the item value might not impact the processing in any
   manner.

4.9. replyObjects

   The replyObjects item returns requested objects to the SCVP client,
   each of which tells the client about a single certificate from the
   request.  The replyObjects item MUST be present in the response,
   unless the response is reporting an error.  The CertReply item MUST
   contain cert, replyStatus, replyValTime, replyChecks, and
   replyWantBacks items, and the CertReply item MAY contain the
   validationErrors, nextUpdate, and certReplyExtensions items.

   A success response MUST contain one CertReply for each certificate
   specified in the queriedCerts item in the request.  The order is
   important.  The first CertReply in the sequence MUST correspond to
   the first certificate in the request, the second CertReply in the
   sequence MUST correspond to the second certificate in the request,
   and so on.

   The checks item in the request determines the content of the
   replyChecks item in the response.  The wantBack item in the request
   determines the content of the replyWantBacks item in the response.
   The queryExtensions items in the request controls the absence or the
   presence and content of the certReplyExtensions item in the response.

   The replyObjects item uses the ReplyObjects type, which has the
   following syntax:

      ReplyObjects ::= SEQUENCE SIZE (1..MAX) OF CertReply

      CertReply ::= SEQUENCE {
        cert                       CertReference,
        replyStatus                ReplyStatus DEFAULT success,
        replyValTime               GeneralizedTime,
        replyChecks                ReplyChecks,
        replyWantBacks             ReplyWantBacks,
        validationErrors       [0] SEQUENCE SIZE (1..MAX) OF
                                     OBJECT IDENTIFIER OPTIONAL,
        nextUpdate             [1] GeneralizedTime OPTIONAL,
        certReplyExtensions    [2] Extensions OPTIONAL }

4.9.1. cert

   The cert item contains either the certificate or a reference to the
   certificate about which the client is requesting information.  If the
   certificate was specified by reference in the request, the request
   included either the id-swb-pkc-cert or id-swb-aa-cert wantBack, and
   the server was able to obtain the referenced certificate, then this
   item MUST include the certificate.  Otherwise, this item MUST include
   the same value as was used in the queriedCerts item in the request.

   CertReference has the following syntax:

      CertReference ::= CHOICE {
        pkc                   PKCReference,
        ac                    ACReference }

4.9.2. replyStatus

   The replyStatus item gives status information to the client about the
   request for the specific certificate.  Note that the responseStatus
   item is different from the replyStatus item.  The responseStatus item
   is the status of the whole request, while the replyStatus item is the
   status for the individual query item.

   The replyStatus item uses the ReplyStatus type, which has the
   following syntax:

      ReplyStatus ::= ENUMERATED {
          success                    (0),
          malformedPKC               (1),
          malformedAC                (2),
          unavailableValidationTime  (3),
          referenceCertHashFail      (4),
          certPathConstructFail      (5),
          certPathNotValid           (6),
          certPathNotValidNow        (7),
          wantBackUnsatisfied        (8) }

   The meanings of the various ReplyStatus values are:

   0 Success: all checks were performed successfully.
   1 Failure: the public key certificate was malformed.
   2 Failure: the attribute certificate was malformed.
   3 Failure: historical data for the requested validation time is not
      available.
   4 Failure: the server could not locate the reference certificate or
      the referenced certificate did not match the hash value provided.
   5 Failure: no certification path could be constructed.

   6 Failure: the constructed certification path is not valid with
      respect to the validation policy.
   7 Failure: the constructed certification path is not valid with
      respect to the validation policy, but a query at a later time may
      be successful.
   8 Failure: all checks were performed successfully; however, one or
      more of the wantBacks could not be satisfied.

   Codes 1 and 2 are used to tell the client that the request was
   properly formed, but the certificate in question was not.  This is
   especially useful to clients that do not parse certificates.

   Code 7 is used to tell the client that a valid certification path was
   found with the exception that a certificate in the path is on hold,
   current revocation information is unavailable, or the validation time
   precedes the notBefore time in one or more certificates in the path.

   For codes 1, 2, 3, and 4, the replyChecks and replyWantBacks items
   are not populated (i.e., they MUST be an empty sequence).  For codes
   5, 6, 7, and 8, replyChecks MUST include an entry corresponding to
   each check in the request; the replyWantBacks item is not populated.

4.9.3. replyValTime

   The replyValTime item tells the time at which the information in the
   CertReply was correct.  The replyValTime item represents the date and
   time in UTC, using GeneralizedTime type.  The encoding rules for
   GeneralizedTime in Section 3.2.7 MUST be used.

   Within the request, the optional validationTime item tells the date
   and time relative to which the SCVP client wants the server to
   perform the checks.  If the validationTime is not present, the server
   MUST respond as if the client provided the date and time at which the
   server processes the request.

   The information in the CertReply item MUST be formatted as if the
   server created this portion of the response at the time indicated in
   the validationTime item of the query.  However, if the server does
   not have appropriate historical information, the server MAY either
   return an error or return information for a later time.

4.9.4. replyChecks

   The replyChecks item contains the responses to the checks item in the
   query.  The replyChecks item includes the object identifier (OID)
   from the query and an integer.  The value of the integer indicates
   whether the requested check was successful.  The OIDs in the checks
   item of the query are used to identify the corresponding replyChecks

   values.  Each OID specified in the checks item in the request MUST be
   matched by an OID in the replyChecks item of the response.  In the
   case of an error response, the server MAY include additional checks
   in the response to further explain the error.  Clients MUST ignore
   any unrecognized ReplyCheck included in the response.

   The replyChecks item uses the ReplyChecks type, which has the
   following syntax:

      ReplyChecks ::= SEQUENCE OF ReplyCheck

      ReplyCheck ::= SEQUENCE {
        check                      OBJECT IDENTIFIER,
        status                     INTEGER DEFAULT 0 }

   The status value for public key certification path building to a
   trusted root, { id-stc 1 }, can be one of the following:

0: Built a path
1: Could not build a path

   The status value for public key certification path building to a
   trusted root along with simple validation processing, { id-stc 2 },
   can be one of the following:

      0: Valid
      1: Not valid

   The status value for public key certification path building to a
   trusted root along with complete status checking, { id-stc 3 }, can
   be one of the following:

      0: Valid
      1: Not valid
      2: Revocation off-line
      3: Revocation unavailable
      4: No known source for revocation information

   Revocation off-line means that the server or distribution point for
   the revocation information was connected to successfully without a
   network error but either no data was returned or if data was returned
   it was stale.  Revocation unavailable means that a network error was
   returned when an attempt was made to reach the server or distribution
   point.  No known source for revocation information means that the
   server was able to build a valid certification path but was unable to
   locate a source for revocation information for one or more
   certificates in the path.

   The status value for AC issuer certification path building to a
   trusted root, { id-stc 4 }, can be one of the following:

      0: Built a path
      1: Could not build a path

   The status value for AC issuer certification path building to a
   trusted root along with simple validation processing, { id-stc 5 },
   can be one of the following:

      0: Valid
      1: Not valid

   The status value for AC issuer certification path building to a
   trusted root along with complete status checking, { id-stc 6 }, can
   be one of the following:

      0: Valid
      1: Not valid
      2: Revocation off-line
      3: Revocation unavailable
      4: No known source for revocation information

   The status value for revocation status checking of an AC as well as
   AC issuer certification path building to a trusted root along with
   complete status checking, { id-stc 7 }, can be one of the following:

      0: Valid
      1: Not valid
      2: Revocation off-line
      3: Revocation unavailable
      4: No known source for revocation information

4.9.5. replyWantBacks

   The replyWantBacks item contains the responses to the wantBack item
   in the request.  The replyWantBacks item includes the object
   identifier (OID) from the wantBack item in the request and an OCTET
   STRING.  Within the OCTET STRING is the requested value.  The OIDs in
   the wantBack item in the request are used to identify the
   corresponding reply value.  The OIDs in the replyWantBacks item MUST
   match the OIDs in the wantBack item in the request.  For a non-error
   response, replyWantBacks MUST include exactly one ReplyWantBack for
   each wantBack specified in the request (excluding id-swb-pkc-cert and
   id-swb-ac-cert, where the requested information is included in the
   cert item).

   The replyWantBacks item uses the ReplyWantBacks type, which has the
   following syntax:

      ReplyWantBacks ::= SEQUENCE OF ReplyWantBack

      ReplyWantBack::= SEQUENCE {
        wb                         OBJECT IDENTIFIER,
        value                      OCTET STRING }

   The OCTET STRING value for the certification path used to verify the
   certificate in the request, { id-swb 1 }, contains the CertBundle
   type.  The syntax and semantics of the CertBundle type are described
   in Section 3.2.8.  This CertBundle includes all the certificates in
   the path, starting with the end certificate and ending with the
   certificate issued by the trust anchor.

   The OCTET STRING value for the proof of revocation status,
   { id-swb 2 }, contains the RevInfoWantBack type.  The RevInfoWantBack
   type is a SEQUENCE of the RevocationInfos type and an optional
   CertBundle.  The syntax and semantics of the RevocationInfos type are
   described in Section 3.2.9.  The CertBundle MUST be included if any
   certificates required to validate the revocation information were not
   returned in the id-swb-pkc-best-cert-path or
   id-swb-pkc-all-cert-paths wantBack.  The CertBundle MUST include all
   such certificates, but there are no ordering requirements.

      RevInfoWantBack ::= SEQUENCE {
        revocationInfo             RevocationInfos,
        extraCerts                 CertBundle OPTIONAL }

   The OCTET STRING value for the public key information, { id-swb 4 },
   contains the SubjectPublicKeyInfo type.  The syntax and semantics of
   the SubjectPublicKeyInfo type are described in [PKIX-1].

   The OCTET STRING value for the AC issuer certification path used to
   verify the certificate in the request, { id-swb 5 }, contains the
   CertBundle type.  The syntax and semantics of the CertBundle type are
   described in Section 3.2.8.  This CertBundle includes all the
   certificates in the path, beginning with the AC issuer certificate
   and ending with the certificate issued by the trust anchor.

   The OCTET STRING value for the proof of revocation status of the AC
   issuer certification path, { id-swb 6 }, contains the RevInfoWantBack
   type.  The RevInfoWantBack type is a SEQUENCE of the RevocationInfos
   type and an optional CertBundle.  The syntax and semantics of the
   RevocationInfos type are described in Section 3.2.9.  The CertBundle

   MUST be included if any certificates required to validate the
   revocation information were not returned in the id-aa-cert-path
   wantBack.  The CertBundle MUST include all such certificates, but
   there are no ordering requirements.

   The OCTET STRING value for the proof of revocation status of the
   attribute certificate, { id-swb 7 }, contains the RevInfoWantBack
   type.  The RevInfoWantBack type is a SEQUENCE of the RevocationInfos
   type and an optional CertBundle.  The syntax and semantics of the
   RevocationInfos type are described in Section 3.2.9.  The CertBundle
   MUST be included if any certificates required to validate the
   revocation information were not returned in the id-swb-aa-cert-path
   wantBack.  The CertBundle MUST include all such certificates, but
   there are no ordering requirements.

   The OCTET STRING value for returning all paths, { id-swb 12 },
   contains an ASN.1 type CertBundles, as defined below.  The syntax and
   semantics of the CertBundle type are described in Section 3.2.8.
   Each CertBundle includes all the certificates in one path, starting
   with the end certificate and ending with the certificate issued by
   the trust anchor.

      CertBundles ::= SEQUENCE SIZE (1..MAX) OF CertBundle

   The OCTET STRING value for relayed responses, { id-swb 9 }, contains
   an ASN.1 type SCVPResponses, as defined below.  If the SCVP server
   used information obtained from other SCVP servers when generating
   this response, then SCVPResponses MUST include each of the SCVP
   responses received from those servers.  If the SCVP server did not
   use information obtained from other SCVP servers when generating the
   response, then SCVPResponses MUST be an empty sequence.

      SCVPResponses ::= SEQUENCE OF ContentInfo

   The OCTET STRING value for the proof of revocation status of the
   path's target certificate, { id-swb-13 }, contains the
   RevInfoWantBack type.  The RevInfoWantBack type is a SEQUENCE of the
   RevocationInfos type and an optional CertBundle.  The syntax and
   semantics of the RevocationInfos type are described in Section 3.2.9.
   The CertBundle MUST be included if any certificates required to
   validate the revocation information were not returned in the id-swb-
   pkc-best-cert-path or id-swb-pkc-all-cert-paths wantBack.  The
   CertBundle MUST include all such certificates, but there are no
   ordering requirements.

   The OCTET STRING value for the proof of revocation status of the
   intermediate certificates in the path, { id-swb 14 }, contains the
   RevInfoWantBack type.  The RevInfoWantBack type is a SEQUENCE of the

   RevocationInfos type and an optional CertBundle.  The syntax and
   semantics of the RevocationInfos type are described in Section 3.2.9.
   The CertBundle MUST be included if any certificates required to
   validate the revocation information were not returned in the id-swb-
   pkc-best-cert-path or id-swb-pkc-all-cert-paths wantBack.  The
   CertBundle MUST include all such certificates, but there are no
   ordering requirements.

4.9.6. validationErrors

   The validationErrors item MUST only be present in failure responses.
   If present, it MUST contain one or more OIDs representing the reason
   the validation failed (validation errors for the basic validation
   algorithm and name validation algorithm are defined in Sections
   3.2.4.2.2 and 3.2.4.2.4).  The validationErrors item SHOULD only be
   included when the replyStatus is 3, 5, 6, 7, or 8.  SCVP servers are
   not required to specify all of the reasons that validation failed.
   SCVP clients MUST NOT assume that the OIDs included in
   validationErrors represent all of the validation errors for the
   certification path.

4.9.7. nextUpdate

   The nextUpdate item tells the time at which the server expects a
   refresh of information regarding the validity of the certificate to
   become available.  The nextUpdate item is especially interesting if
   the certificate revocation status information is not available or the
   certificate is suspended.  The nextUpdate item represents the date
   and time in UTC, using the GeneralizedTime type.  The encoding rules
   for GeneralizedTime in Section 3.2.7 MUST be used.

4.9.8. certReplyExtensions

   The certReplyExtensions item contains the responses to the
   queryExtensions item in the request.  The certReplyExtensions item
   uses the Extensions type defined in [PKIX-1].  The object identifiers
   (OIDs) in the queryExtensions item in the request are used to
   identify the corresponding reply values.  The certReplyExtensions
   item, when present, contains a sequence of Extension items, each of
   which contains an extnID item, a critical item, and an extnValue
   item.

   The extnID item is an identifier for the extension.  It contains the
   OID that names the extension, and it MUST match one of the OIDs in
   the queryExtensions item in the request.

   The critical item is a BOOLEAN, and it MUST be set to FALSE.

   The extnValue item contains an OCTET STRING.  Within the OCTET STRING
   is the extension value.  An ASN.1 type is specified for each
   extension, identified by the associated extnID object identifier.

4.10. respNonce

   The respNonce item contains an identifier to bind the request to the
   response.

   If the client includes a requestNonce value in the request and the
   server is generating a specific non-cached response to the request
   then the server MUST return the same value in the response.

   If the server is using a cached response to the request then it MUST
   omit the respNonce item.

   If the server is returning a specific non-cached response to a
   request without a nonce, then the server MAY include a message-
   specific nonce.  For digitally signed messages, the server MAY use
   the value of the message-digest attribute in the signedAttrs within
   SignerInfo of the request as the value in the respNonce item.

   The requestNonce item uses the OCTET STRING type.

   Conforming client implementations MUST be able to process a response
   that includes this item.  Conforming servers MUST support respNonce.

4.11. serverContextInfo

   The serverContextInfo item in a response is a mechanism for the
   server to pass some opaque context information to the client.  If the
   client does not like the certification path returned, it can make a
   new query and pass along this context information.

   Section 3.2.6 contains information about the client's usage of this
   item.

   The context information is opaque to the client, but it provides
   information to the server that ensures that a different certification
   path will be returned (if another one can be found).  The context
   information could indicate the state of the server, or it could
   contain a sequence of hashes of certification paths that have already
   been returned to the client.  The protocol does not dictate any
   structure or requirements for this item.  However, implementers
   should review the Security Considerations section of this document
   before selecting a structure.

Servers that are incapable of returning additional paths MUST NOT
include the serverContextInfo item in the response.

4.12. cvResponseExtensions

   If present, the cvResponseExtensions item contains a sequence of
   extensions that extend the response.  This specification does not
   define any extensions.  The facility is provided to allow future
   specifications to extend SCVP.  The syntax for Extensions is imported
   from [PKIX-1].  The cvResponseExtensions item, when present, contains
   a sequence of Extension items, each of which contains an extnID item,
   a critical item, and an extnValue item.

   The extnID item is an identifier for the extension.  It contains the
   object identifier (OID) that names the extension.

   The critical item is a BOOLEAN.  Each extension is designated as
   either critical (with a value of TRUE) or non-critical (with a value
   of FALSE).  An SCVP client MUST reject the response if it encounters
   a critical extension it does not recognize; however, a non-critical
   extension MAY be ignored if it is not recognized.

   The extnValue item contains an OCTET STRING.  Within the OCTET STRING
   is the extension value.  An ASN.1 type is specified for each
   extension, identified by the associated extnID object identifier.

4.13. requestorText

   The requestorText item contains a text field supplied by the client.

   If the client includes a requestorText value in the request and the
   server is generating a specific non-cached response to the request,
   then the server MUST return the same value in the response.

   If the server is using a cached response to the request, then it MUST
   omit the requestorText item.

   The requestNonce item uses the UTF8 string type.

   Conforming client implementations that support the requestorText item
   in requests (see Section 3.10) MUST be able to process a response
   that includes this item.  Conforming servers MUST support
   requestorText in responses.

4.14. SCVP Response Validation

   There are two mechanisms for validation of SCVP responses, one based
   on the client's knowledge of a specific SCVP server key and the other
   based on validation of the certificate corresponding to the private
   key used to protect the SCVP response.

4.14.1. Simple Key Validation

   The simple key validation method is where the SCVP client has a local
   policy of one or more SCVP server keys that directly identify the set
   of valid SCVP servers.  Mechanisms for storage of server keys or
   identifiers are a local matter.  For example, a client could store
   cryptographic hashes of public keys used to verify SignedData
   responses.  Alternatively, a client could store shared symmetric keys
   used to verify MACs in AuthenticatedData responses.

   Simple key validation MUST be used by SCVP clients that cannot
   validate PKIX-1 certificates and are therefore making delegated path
   validation requests to the SCVP server [RQMTS].  It is a matter of
   local policy with these clients whether to use SignedData or
   AuthenticatedData.  Simple key validation MAY be used by other SCVP
   clients for other reasons.

4.14.2. SCVP Server Certificate Validation

   It is a matter of local policy what validation policy the client uses
   when validating responses.  When validating protected SCVP responses,
   SCVP clients SHOULD use the validation algorithm defined in Section 6
   of [PKIX-1].  SCVP clients may impose additional limitations on the
   algorithm, such as limiting the number of certificates in the path or
   establishing initial name constraints, as specified in Section 6.2 of
   [PKIX-1].

   If the certificate used to sign the validation policy responses and
   SignedData validation responses contains the key usage extension
   ([PKIX-1], Section 4.2.1.3), it MUST have either the digital
   signature bit set, the non-repudiation bit set, or both bits set.

   If the certificate for AuthenticatedData validation responses
   contains the key usage extension, it MUST have the key agreement bit
   set.

   If the certificate used on a validation policy response or a
   validation response contains the extended key usage extension
   ([PKIX-1], Section 4.2.1.13), it MUST contain either the
   anyExtendedKeyUsage OID or the following OID:

      id-kp-scvpServer             OBJECT IDENTIFIER ::= { id-kp 15 }

5.  Server Policy Request

   An SCVP client uses the ValPolRequest item to request information
   about an SCVP server's policies and configuration information,
   including the list of validation policies supported by the SCVP
   server.  When a ValPolRequest is encapsulated in a MIME body part, it
   MUST be carried in an application/scvp-vp-request MIME body part.

   The request consists of a ValPolRequest encapsulated in a
   ContentInfo.  The client does not sign the request.

      ContentInfo {
        contentType        id-ct-scvp-valPolRequest,
                                      -- (1.2.840.113549.1.9.16.1.12)
        content            ValPolRequest }

   The ValPolRequest type has the following syntax:

      ValPolRequest ::= SEQUENCE {
        vpRequestVersion           INTEGER DEFAULT 1,
        requestNonce               OCTET STRING }

   Conforming SCVP server implementations MUST recognize and process the
   server policy request.  Conforming clients SHOULD support the server
   policy request.

5.1. vpRequestVersion

The syntax and semantics of vpRequestVersion are the same as
cvRequestVersion as described in Section 3.1.

5.2. requestNonce

   The requestNonce item contains a request identifier generated by the
   SCVP client.  If the server returns a specific response, it MUST
   include the requestNonce from the request in the response, but the
   server MAY return a cached response, which MUST NOT include a
   requestNonce.

6.  Validation Policy Response

   In response to a ValPolRequest, the SCVP server provides a
   ValPolResponse.  The ValPolResponse may not be unique to any
   ValPolRequest, so may be reused by the server in response to multiple
   ValPolRequests.  The ValPolResponse also has an indication of how
   frequently the ValPolResponse may be reissued.  The server MUST sign
   the response using its digital signature certificate.  When a
   ValPolResponse is encapsulated in a MIME body part, it MUST be
   carried in an application/scvp-vp-response MIME body part.

   The response consists of a ValPolResponse encapsulated in a
   SignedData, which is in turn encapsulated in a ContentInfo.  That is,
   the EncapsulatedContentInfo field of SignedData consists of an
   eContentType field with a value of id-ct-scvp-valPolResponse
   (1.2.840.113549.1.9.16.1.13) and an eContent field that contains a
   DER-encoded ValPolResponse.  The SCVP server MUST include its own
   certificate in the certificates field within SignedData, and the
   signerInfos field of SignedData MUST include exactly one SignerInfo.
   The SignedData MUST NOT include the unsignedAttrs field.

   The ValPolResponse type has the following syntax:

      ValPolResponse ::= SEQUENCE {
        vpResponseVersion               INTEGER,
        maxCVRequestVersion             INTEGER,
        maxVPRequestVersion             INTEGER,
        serverConfigurationID           INTEGER,
        thisUpdate                      GeneralizedTime,
        nextUpdate                      GeneralizedTime OPTIONAL,
        supportedChecks                 CertChecks,
        supportedWantBacks              WantBack,
        validationPolicies              SEQUENCE OF OBJECT IDENTIFIER,
        validationAlgs                  SEQUENCE OF OBJECT IDENTIFIER,
        authPolicies                    SEQUENCE OF AuthPolicy,
        responseTypes                   ResponseTypes,
        defaultPolicyValues             RespValidationPolicy,
        revocationInfoTypes             RevocationInfoTypes,
        signatureGeneration             SEQUENCE OF AlgorithmIdentifier,
        signatureVerification           SEQUENCE OF AlgorithmIdentifier,
        hashAlgorithms                  SEQUENCE SIZE (1..MAX) OF
                                           OBJECT IDENTIFIER,
        serverPublicKeys                SEQUENCE OF KeyAgreePublicKey
                                           OPTIONAL,
        clockSkew                       INTEGER DEFAULT 10,
        requestNonce                    OCTET STRING OPTIONAL }

      ResponseTypes  ::= ENUMERATED {
        cached-only                (0),
        non-cached-only            (1),
        cached-and-non-cached      (2) }

      RevocationInfoTypes ::= BIT STRING {
        fullCRLs                   (0),
        deltaCRLs                  (1),
        indirectCRLs               (2),
        oCSPResponses              (3) }

   SCVP clients that support validation policy requests MUST support
   validation policy responses.  SCVP servers MUST support validation
   policy responses.

   SCVP servers MUST support cached policy responses and MAY support
   specific responses to policy requests.

6.1. vpResponseVersion

   The syntax and semantics of the vpResponseVersion item are the same
   as cvRequestVersion as described in Section 3.1.  The
   vpResponseVersion used MUST be the same as the vpRequestVersion
   unless the client has used a value greater than the values the server
   supports.  If the client submits a vpRequestVersion greater than the
   version supported by the server, the server MUST return a
   vpResponseVersion using the highest version number the server
   supports as the version number.

6.2. maxCVRequestVersion

The maxCVRequestVersion item defines the maximum version number for
CV requests that the server supports.

6.3. maxVPRequestVersion

The maxVPRequestVersion item defines the maximum version number for
VP requests that the server supports.

6.4. serverConfigurationID

   The serverConfigurationID item is an integer that uniquely represents
   the version of the server configuration as represented by the
   validationPolicies, validationAlgs, authPolicies,
   defaultPolicyValues, and clockSkew.  If any of these values change,
   the server MUST create a new ValPolResponse with a new
   serverConfigurationID.  If the configuration has not changed, then
   the server may reuse serverConfigurationID across multiple

   ValPolResponse messages.  However, if the server reverts to an
   earlier configuration, the server MUST NOT revert the configuration
   ID as well, but MUST select another unique value.

6.5. thisUpdate

   This item indicates the signing date and time of this policy
   response.

   GeneralizedTime values MUST be expressed in Greenwich Mean Time
   (Zulu) and interpreted as defined in Section 3.2.7.

6.6. nextUpdate and requestNonce

   These items are used to indicate whether policy responses are
   specific to policy requests.  Where policy responses are cached,
   these items indicate when the information will be updated.  The
   optional nextUpdate item indicates the time by which the next policy
   response will be published.  The optional requestNonce item links the
   response to a specific request by returning the nonce provided in the
   request.

   If the nextUpdate item is omitted, it indicates a non-cached response
   generated in response to a specific request (i.e., the ValPolResponse
   is bound to a specific request).  If this item is omitted, the
   requestNonce item MUST be present and MUST include the requestNonce
   value from the request.

   If the nextUpdate item is present, it indicates a cached response
   that is not bound to a specific request.  An SCVP server MUST
   periodically generate a new response as defined by the next update
   time, but MAY use the same ValPolResponse to respond to multiple
   requests.  The requestNonce is omitted if the nextUpdate item is
   present.

   It is a matter of local server policy to return a cached or non-
   cached specific response.

   GeneralizedTime values in nextUpdate MUST be expressed in Greenwich
   Mean Time (Zulu) as specified in Section 3.2.7.

6.7. supportedChecks

The supportedChecks item contains a sequence of object identifiers
representing the checks supported by the server.

6.8. supportedWantBacks

The supportedWantBacks item contains a sequence of object identifiers
representing the wantBacks supported by the server.

6.9. validationPolicies

   The validationPolicies item contains a sequence of object identifiers
   representing the validation policies supported by the server.  It is
   a matter of local policy if the server wishes to process requests
   using the default validation policy, and if it does not, then it MUST
   NOT include the id-svp-defaultValPolicy in this list.

6.10. validationAlgs

The validationAlgs item contains a sequence of OIDs. Each OID
identifies a validation algorithm supported by the server.

6.11. authPolicies

   The authPolicies item contains a sequence of policy references for
   authenticating to the SCVP server.

   The reference to the authentication policy is an OID that the client
   and server have agreed represents an authentication policy.  The list
   of policies is intended to document to the client if authentication
   is required for some requests and if so how.

      AuthPolicy ::=  OBJECT IDENTIFIER

6.12. responseTypes

   The responseTypes item allows the server to publish the range of
   response types it supports.  Cached only means the server will only
   return cached responses to requests.  Non-cached only means the
   server will return a specific response to the request, i.e.,
   containing the requestor's nonce.  Both means that the server
   supports both cached and non-cached response types and will return
   either a cached or non- cached response, depending on the request.

6.13. revocationInfoTypes

   The revocationInfoTypes item allows the server to indicate the
   sources of revocation information that it is capable of processing.
   For each bit in the RevocationInfoTypes BIT STRING, the server MUST
   set the bit to one if it is capable of processing the corresponding
   revocation information type and to zero if it cannot.

6.14. defaultPolicyValues

   This is the default validation policy used by the server.  It
   contains a RespValidationPolicy, which is defined in Section 4.5.
   All OPTIONAL items in the validationPolicy item MUST be populated.  A
   server will use these default values when the request references the
   default validation policy and the client does not override the
   default values by supplying other values in the request.

   This allows the client to optimize the request by omitting parameters
   that match the server default values.

6.15. signatureGeneration

   This sequence specifies the set of digital signature algorithms
   supported by an SCVP server for signing CVResponse messages.  Each
   digital signature algorithm is specified as an AlgorithmIdentifier,
   using the encoding rules associated with the signatureAlgorithm field
   in a public key certificate [PKIX-1].  Supported algorithms are
   defined in [PKIX-ALG] and [PKIX-ALG2], but other signature algorithms
   may also be supported.

   By including an algorithm (e.g., RSA with SHA-1) in this list, the
   server states that it has a private key and corresponding certified
   public key for that asymmetric algorithm, and supports the specified
   hash algorithm.  The list is ordered; the first digital signature
   algorithm is the server's default algorithm.  The default algorithm
   will be used by the server to protect signed messages unless the
   client specifies another algorithm.

   For servers that do not have an on-line private key, and cannot sign
   CVResponse messages, the signatureGeneration item is encoded as an
   empty sequence.

6.16. signatureVerification

   This sequence specifies the set of digital signature algorithms that
   can be verified by this SCVP server.  Each digital signature
   algorithm is specified as an AlgorithmIdentifier, using the encoding
   rules associated with the signatureAlgorithm field in a public key
   certificate [PKIX-1].  Supported algorithms are defined in [PKIX-ALG]
   and [PKIX-ALG2], but other signature algorithms may also be
   supported.

   For servers that do not verify signatures on CVRequest messages, the
   signatureVerification item is encoded as an empty sequence.

6.17. hashAlgorithms

   This sequence specifies the set of hash algorithms that the server
   can use to hash certificates and requests.  The list is ordered; the
   first hash algorithm is the server's default algorithm.  The default
   algorithm will be used by the server to compute hashes included in
   responses unless the client specifies another algorithm.  Each hash
   algorithm is specified as an object identifier.  [PKIX-ALG2]
   specifies object identifiers for SHA-1, SHA-224, SHA-256, SHA-384,
   and SHA-512.  Other hash algorithms may also be supported.

6.18. serverPublicKeys

   The serverPublicKeys item is a sequence of one or more key agreement
   public keys and associated parameters.  It is used by clients making
   AuthenticatedData requests to the server.  Each item in the
   serverPublicKeys sequence is of the KeyAgreePublicKey type:

      KeyAgreePublicKey ::= SEQUENCE {
        algorithm            AlgorithmIdentifier,
        publicKey            BIT STRING,
        macAlgorithm         AlgorithmIdentifier,
        kDF                  AlgorithmIdentifier OPTIONAL }

   The KeyAgreePublicKey includes the algorithm identifier and the
   server's public key.  SCVP servers that support the key agreement
   mode of AuthenticatedData for SCVP requests MUST support
   serverPublicKeys and the Diffie-Hellman key agreement algorithm as
   specified in [PKIX-ALG].  SCVP servers that support serverPublicKeys
   MUST support the 1024-bit Modular Exponential (MODP) group key (group
   2) as defined in [IKE].  SCVP servers that support serverPublicKeys
   MAY support other Diffie-Hellman groups [IKE-GROUPS], as well as
   other key agreement algorithms.

   The macAlgorithm item specifies the symmetric algorithm the server
   expects the client to use with the result of the key agreement
   algorithm.  A key derivation function (KDF), which derives symmetric
   key material from the key agreement result, may be implied by the
   macAlgorithm.  Alternatively, the KDF may be explicitly specified
   using the optional kDF item.

6.19. clockSkew

The clockSkew item is the number of minutes the server will allow for
clock skew. The default value is 10 minutes.

7.  SCVP Server Relay

   In some network environments, especially ones that include firewalls,
   an SCVP server might not be able to obtain all of the information
   that it needs to process a request.  However, the server might be
   configured to use the services of one or more other SCVP servers to
   fulfill all requests.  In such cases, the SCVP client is unaware that
   the initial SCVP server is using the services of other SCVP servers.
   The initial SCVP server acts as a client to another SCVP server.
   Unlike the original client, the SCVP server is expected to have
   moderate computing and memory resources.   This section describes
   SCVP server-to-SCVP server exchanges.  This section does not impose
   any requirements on SCVP clients that are not also SCVP servers.
   Further, this section does not impose any requirements on SCVP
   servers that do not relay requests to other SCVP servers.

   When one SCVP server relays a request to another server, in an
   incorrectly configured system of servers, it is possible that the
   same request will be relayed back again.  Any SCVP server that relays
   requests MUST implement the conventions described in this section to
   detect and break loops.

   When an SCVP server relays a request, the request MUST include the
   requestorRef item.  If the request to be relayed already contains a
   requestorRef item, then the server-generated request MUST contain a
   requestorRef item constructed from this value and an additional
   GeneralName that contains an identifier of the SCVP server.  If the
   request to be relayed does not contain a requestorRef item, then the
   server-generated request MUST contain a requestorRef item that
   includes a GeneralName that contains an identifier of the SCVP
   server.

   To prevent false loop detection, servers should use identifiers that
   are unique within their network of cooperating SCVP servers.  SCVP
   servers that support relay SHOULD populate this item with the DNS
   name of the server or the distinguished name in the server's
   certificate.  SCVP servers MAY choose other procedures for generating
   identifiers that are unique within their community.

   When an SCVP server receives a request that contains a requestorRef
   item, the server MUST check the sequence of names in the requestorRef
   item for its own identifier.  If the server discovers its own
   identifier in the requestorRef item, it MUST respond with an error,
   setting the statusCode in the responseStatus item to 40.

   When an SCVP server generates a non-cached response to a relayed
   request, the server MUST include the requestorRef item from the
   request in the response.

8. SCVP ASN.1 Module

   This section defines the syntax for SCVP request-response pairs.  The
   semantics for the messages are defined in Sections 3, 4, 5, and 6.
   The SCVP ASN.1 module follows.

   SCVP

     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0) 21 }

   DEFINITIONS IMPLICIT TAGS ::= BEGIN

   IMPORTS

   AlgorithmIdentifier, Attribute, Certificate, Extensions,
   -- Import UTF8String if required by compiler
   -- UTF8String, -- CertificateList, CertificateSerialNumber
     FROM PKIX1Explicit88 -- RFC 3280
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0) 18 }

   GeneralNames, GeneralName, KeyUsage, KeyPurposeId
     FROM PKIX1Implicit88 -- RFC 3280
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0) 19 }

   AttributeCertificate
     FROM PKIXAttributeCertificate -- RFC 3281
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0) 12 }

   OCSPResponse
     FROM OCSP -- RFC 2560
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0) 14 }

   ContentInfo
     FROM CryptographicMessageSyntax2004 -- RFC 3852
     { iso(1) member-body(2) us(840) rsadsi(113549)
       pkcs(1) pkcs-9(9) smime(16) modules(0) cms-2004(24) } ;

   -- SCVP Certificate Validation Request

   id-ct OBJECT IDENTIFIER ::= { iso(1) member-body(2)
             us(840) rsadsi(113549) pkcs(1) pkcs9(9)
             id-smime(16) 1 }

   id-ct-scvp-certValRequest OBJECT IDENTIFIER ::= { id-ct 10 }

   CVRequest ::= SEQUENCE {
     cvRequestVersion           INTEGER DEFAULT 1,
     query                      Query,
     requestorRef           [0] GeneralNames OPTIONAL,
     requestNonce           [1] OCTET STRING OPTIONAL,
     requestorName          [2] GeneralName OPTIONAL,
     responderName          [3] GeneralName OPTIONAL,
     requestExtensions      [4] Extensions OPTIONAL,
     signatureAlg           [5] AlgorithmIdentifier OPTIONAL,
     hashAlg                [6] OBJECT IDENTIFIER OPTIONAL,
     requestorText          [7] UTF8String (SIZE (1..256)) OPTIONAL }

   Query ::= SEQUENCE {
     queriedCerts             CertReferences,
     checks                   CertChecks,
     wantBack             [1] WantBack OPTIONAL,
     validationPolicy         ValidationPolicy,
     responseFlags            ResponseFlags OPTIONAL,
     serverContextInfo    [2] OCTET STRING OPTIONAL,
     validationTime       [3] GeneralizedTime OPTIONAL,
     intermediateCerts    [4] CertBundle OPTIONAL,
     revInfos             [5] RevocationInfos OPTIONAL,
     producedAt           [6] GeneralizedTime OPTIONAL,
     queryExtensions      [7] Extensions OPTIONAL }

   CertReferences ::= CHOICE {
     pkcRefs       [0] SEQUENCE SIZE (1..MAX) OF PKCReference,
     acRefs        [1] SEQUENCE SIZE (1..MAX) OF ACReference }

   CertReference::= CHOICE {
     pkc               PKCReference,
     ac                ACReference }

   PKCReference ::= CHOICE {
     cert          [0] Certificate,
     pkcRef        [1] SCVPCertID }

   ACReference ::= CHOICE {
     attrCert      [2] AttributeCertificate,
     acRef         [3] SCVPCertID }

   SCVPCertID ::= SEQUENCE {
       certHash        OCTET STRING,
       issuerSerial    SCVPIssuerSerial,
       hashAlgorithm   AlgorithmIdentifier DEFAULT { algorithm sha-1 } }

   SCVPIssuerSerial ::= SEQUENCE {
        issuer         GeneralNames,
        serialNumber   CertificateSerialNumber
   }

   ValidationPolicy ::= SEQUENCE {
     validationPolRef           ValidationPolRef,
     validationAlg          [0] ValidationAlg OPTIONAL,
     userPolicySet          [1] SEQUENCE SIZE (1..MAX) OF OBJECT
                                  IDENTIFIER OPTIONAL,
     inhibitPolicyMapping   [2] BOOLEAN OPTIONAL,
     requireExplicitPolicy  [3] BOOLEAN OPTIONAL,
     inhibitAnyPolicy       [4] BOOLEAN OPTIONAL,
     trustAnchors           [5] TrustAnchors OPTIONAL,
     keyUsages              [6] SEQUENCE OF KeyUsage OPTIONAL,
     extendedKeyUsages      [7] SEQUENCE OF KeyPurposeId OPTIONAL,
     specifiedKeyUsages     [8] SEQUENCE OF KeyPurposeId OPTIONAL }

   CertChecks ::= SEQUENCE SIZE (1..MAX) OF OBJECT IDENTIFIER

   WantBack ::= SEQUENCE SIZE (1..MAX) OF OBJECT IDENTIFIER

   ValidationPolRef ::= SEQUENCE {
       valPolId             OBJECT IDENTIFIER,
       valPolParams         ANY DEFINED BY valPolId OPTIONAL }

   ValidationAlg ::= SEQUENCE {
     valAlgId               OBJECT IDENTIFIER,
     parameters             ANY DEFINED BY valAlgId OPTIONAL }

   NameValidationAlgParms ::= SEQUENCE {
     nameCompAlgId          OBJECT IDENTIFIER,
     validationNames        GeneralNames }

   TrustAnchors ::= SEQUENCE SIZE (1..MAX) OF PKCReference

   KeyAgreePublicKey ::= SEQUENCE {
     algorithm           AlgorithmIdentifier,
     publicKey           BIT STRING,
     macAlgorithm        AlgorithmIdentifier,
     kDF                 AlgorithmIdentifier OPTIONAL }

   ResponseFlags ::= SEQUENCE {
     fullRequestInResponse      [0] BOOLEAN DEFAULT FALSE,
     responseValidationPolByRef [1] BOOLEAN DEFAULT TRUE,
     protectResponse            [2] BOOLEAN DEFAULT TRUE,
     cachedResponse             [3] BOOLEAN DEFAULT TRUE }

   CertBundle ::= SEQUENCE SIZE (1..MAX) OF Certificate

   RevocationInfos ::= SEQUENCE SIZE (1..MAX) OF RevocationInfo

   RevocationInfo ::= CHOICE {
     crl                    [0] CertificateList,
     delta-crl              [1] CertificateList,
     ocsp                   [2] OCSPResponse,
     other                  [3] OtherRevInfo }

   OtherRevInfo ::= SEQUENCE {
     riType                     OBJECT IDENTIFIER,
     riValue                    ANY DEFINED BY riType }

   -- SCVP Certificate Validation Response

   id-ct-scvp-certValResponse OBJECT IDENTIFIER ::= { id-ct 11 }

   CVResponse ::= SEQUENCE {
     cvResponseVersion          INTEGER,
     serverConfigurationID      INTEGER,
     producedAt                 GeneralizedTime,
     responseStatus             ResponseStatus,
     respValidationPolicy   [0] RespValidationPolicy OPTIONAL,
     requestRef             [1] RequestReference OPTIONAL,
     requestorRef           [2] GeneralNames OPTIONAL,
     requestorName          [3] GeneralNames OPTIONAL,
     replyObjects           [4] ReplyObjects OPTIONAL,
     respNonce              [5] OCTET STRING OPTIONAL,
     serverContextInfo      [6] OCTET STRING OPTIONAL,
     cvResponseExtensions   [7] Extensions OPTIONAL,
     requestorText          [8] UTF8String (SIZE (1..256)) OPTIONAL }

   ResponseStatus ::= SEQUENCE {
       statusCode               CVStatusCode DEFAULT  okay,
       errorMessage             UTF8String OPTIONAL }

   CVStatusCode ::= ENUMERATED {
       okay                               (0),
       skipUnrecognizedItems              (1),
       tooBusy                           (10),
       invalidRequest                    (11),
       internalError                     (12),
       badStructure                      (20),
       unsupportedVersion                (21),
       abortUnrecognizedItems            (22),
       unrecognizedSigKey                (23),
       badSignatureOrMAC                 (24),

       unableToDecode                    (25),
       notAuthorized                     (26),
       unsupportedChecks                 (27),
       unsupportedWantBacks              (28),
       unsupportedSignatureOrMAC         (29),
       invalidSignatureOrMAC             (30),
       protectedResponseUnsupported      (31),
       unrecognizedResponderName         (32),
       relayingLoop                      (40),
       unrecognizedValPol                (50),
       unrecognizedValAlg                (51),
       fullRequestInResponseUnsupported  (52),
       fullPolResponseUnsupported        (53),
       inhibitPolicyMappingUnsupported   (54),
       requireExplicitPolicyUnsupported  (55),
       inhibitAnyPolicyUnsupported       (56),
       validationTimeUnsupported         (57),
       unrecognizedCritQueryExt          (63),
       unrecognizedCritRequestExt        (64) }

   RespValidationPolicy ::= ValidationPolicy

   RequestReference ::= CHOICE {
     requestHash   [0] HashValue, -- hash of CVRequest
     fullRequest   [1] CVRequest }

   HashValue ::= SEQUENCE {
     algorithm         AlgorithmIdentifier DEFAULT { algorithm sha-1 },
     value             OCTET STRING }

   sha-1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
             oiw(14) secsig(3) algorithm(2) 26 }

   ReplyObjects ::= SEQUENCE SIZE (1..MAX) OF CertReply

   CertReply ::= SEQUENCE {
     cert                       CertReference,
     replyStatus                ReplyStatus DEFAULT success,
     replyValTime               GeneralizedTime,
     replyChecks                ReplyChecks,
     replyWantBacks             ReplyWantBacks,
     validationErrors       [0] SEQUENCE SIZE (1..MAX) OF
                                  OBJECT IDENTIFIER OPTIONAL,
     nextUpdate             [1] GeneralizedTime OPTIONAL,
     certReplyExtensions    [2] Extensions OPTIONAL }

   ReplyStatus ::= ENUMERATED {
     success                    (0),
     malformedPKC               (1),
     malformedAC                (2),
     unavailableValidationTime  (3),
     referenceCertHashFail      (4),
     certPathConstructFail      (5),
     certPathNotValid           (6),
     certPathNotValidNow        (7),
     wantBackUnsatisfied        (8) }

   ReplyChecks ::= SEQUENCE OF ReplyCheck

   ReplyCheck ::= SEQUENCE {
     check                      OBJECT IDENTIFIER,
     status                     INTEGER DEFAULT 0 }

   ReplyWantBacks ::= SEQUENCE OF ReplyWantBack

   ReplyWantBack::= SEQUENCE {
     wb                         OBJECT IDENTIFIER,
     value                      OCTET STRING }

   CertBundles ::= SEQUENCE SIZE (1..MAX) OF CertBundle

   RevInfoWantBack ::= SEQUENCE {
     revocationInfo             RevocationInfos,
     extraCerts                 CertBundle OPTIONAL }

   SCVPResponses ::= SEQUENCE OF ContentInfo

   -- SCVP Validation Policies Request

   id-ct-scvp-valPolRequest     OBJECT IDENTIFIER ::= { id-ct 12 }

   ValPolRequest ::= SEQUENCE {
     vpRequestVersion           INTEGER DEFAULT 1,
     requestNonce               OCTET STRING }

   -- SCVP Validation Policies Response

   id-ct-scvp-valPolResponse OBJECT IDENTIFIER ::= { id-ct 13 }

   ValPolResponse ::= SEQUENCE {
     vpResponseVersion                INTEGER,
     maxCVRequestVersion              INTEGER,
     maxVPRequestVersion              INTEGER,
     serverConfigurationID            INTEGER,

     thisUpdate                       GeneralizedTime,
     nextUpdate                       GeneralizedTime OPTIONAL,
     supportedChecks                  CertChecks,
     supportedWantBacks               WantBack,
     validationPolicies               SEQUENCE OF OBJECT IDENTIFIER,
     validationAlgs                   SEQUENCE OF OBJECT IDENTIFIER,
     authPolicies                     SEQUENCE OF AuthPolicy,
     responseTypes                    ResponseTypes,
     defaultPolicyValues              RespValidationPolicy,
     revocationInfoTypes              RevocationInfoTypes,
     signatureGeneration              SEQUENCE OF AlgorithmIdentifier,
     signatureVerification            SEQUENCE OF AlgorithmIdentifier,
     hashAlgorithms                   SEQUENCE SIZE (1..MAX) OF
                                        OBJECT IDENTIFIER,
     serverPublicKeys                 SEQUENCE OF KeyAgreePublicKey
                                        OPTIONAL,
     clockSkew                        INTEGER DEFAULT 10,
     requestNonce                     OCTET STRING OPTIONAL }

   ResponseTypes  ::= ENUMERATED {
     cached-only                (0),
     non-cached-only            (1),
     cached-and-non-cached      (2) }

   RevocationInfoTypes ::= BIT STRING {
     fullCRLs                   (0),
     deltaCRLs                  (1),
     indirectCRLs               (2),
     oCSPResponses              (3) }

   AuthPolicy ::= OBJECT IDENTIFIER

   -- SCVP Check Identifiers

   id-stc OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
             dod(6) internet(1) security(5) mechanisms(5) pkix(7) 17 }

   id-stc-build-pkc-path        OBJECT IDENTIFIER ::= { id-stc 1 }
   id-stc-build-valid-pkc-path  OBJECT IDENTIFIER ::= { id-stc 2 }
   id-stc-build-status-checked-pkc-path
                                OBJECT IDENTIFIER ::= { id-stc 3 }
   id-stc-build-aa-path         OBJECT IDENTIFIER ::= { id-stc 4 }
   id-stc-build-valid-aa-path   OBJECT IDENTIFIER ::= { id-stc 5 }
   id-stc-build-status-checked-aa-path
                                OBJECT IDENTIFIER ::= { id-stc 6 }
   id-stc-status-check-ac-and-build-status-checked-aa-path
                                OBJECT IDENTIFIER ::= { id-stc 7 }

   -- SCVP WantBack Identifiers

   id-swb OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
             dod(6) internet(1) security(5) mechanisms(5) pkix(7) 18 }

   id-swb-pkc-best-cert-path       OBJECT IDENTIFIER ::= { id-swb 1 }
   id-swb-pkc-revocation-info      OBJECT IDENTIFIER ::= { id-swb 2 }
   id-swb-pkc-public-key-info      OBJECT IDENTIFIER ::= { id-swb 4 }
   id-swb-aa-cert-path             OBJECT IDENTIFIER ::= { id-swb 5 }
   id-swb-aa-revocation-info       OBJECT IDENTIFIER ::= { id-swb 6 }
   id-swb-ac-revocation-info       OBJECT IDENTIFIER ::= { id-swb 7 }
   id-swb-relayed-responses        OBJECT IDENTIFIER ::= { id-swb 9 }
   id-swb-pkc-cert                 OBJECT IDENTIFIER ::= { id-swb 10}
   id-swb-ac-cert                  OBJECT IDENTIFIER ::= { id-swb 11}
   id-swb-pkc-all-cert-paths       OBJECT IDENTIFIER ::= { id-swb 12}
   id-swb-pkc-ee-revocation-info   OBJECT IDENTIFIER ::= { id-swb 13}
   id-swb-pkc-CAs-revocation-info  OBJECT IDENTIFIER ::= { id-swb 14}

   -- SCVP Validation Policy and Algorithm Identifiers

   id-svp OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
             dod(6) internet(1) security(5) mechanisms(5) pkix(7) 19 }

   id-svp-defaultValPolicy OBJECT IDENTIFIER ::= { id-svp 1 }

   -- SCVP Basic Validation Algorithm Identifier

   id-svp-basicValAlg OBJECT IDENTIFIER ::= { id-svp 3 }

   -- SCVP Basic Validation Algorithm Errors

   id-bvae OBJECT IDENTIFIER ::= id-svp-basicValAlg

   id-bvae-expired              OBJECT IDENTIFIER ::= { id-bvae 1 }
   id-bvae-not-yet-valid        OBJECT IDENTIFIER ::= { id-bvae 2 }
   id-bvae-wrongTrustAnchor     OBJECT IDENTIFIER ::= { id-bvae 3 }
   id-bvae-noValidCertPath      OBJECT IDENTIFIER ::= { id-bvae 4 }
   id-bvae-revoked              OBJECT IDENTIFIER ::= { id-bvae 5 }
   id-bvae-invalidKeyPurpose    OBJECT IDENTIFIER ::= { id-bvae 9 }
   id-bvae-invalidKeyUsage      OBJECT IDENTIFIER ::= { id-bvae 10 }
   id-bvae-invalidCertPolicy    OBJECT IDENTIFIER ::= { id-bvae 11 }

   -- SCVP Name Validation Algorithm Identifier

   id-svp-nameValAlg OBJECT IDENTIFIER ::= { id-svp 2 }

   -- SCVP Name Validation Algorithm DN comparison algorithm

   id-nva-dnCompAlg   OBJECT IDENTIFIER ::= { id-svp 4 }

   -- SCVP Name Validation Algorithm Errors

   id-nvae OBJECT IDENTIFIER ::= id-svp-nameValAlg

   id-nvae-name-mismatch          OBJECT IDENTIFIER ::= { id-nvae 1 }
   id-nvae-no-name                OBJECT IDENTIFIER ::= { id-nvae 2 }
   id-nvae-unknown-alg            OBJECT IDENTIFIER ::= { id-nvae 3 }
   id-nvae-bad-name               OBJECT IDENTIFIER ::= { id-nvae 4 }
   id-nvae-bad-name-type          OBJECT IDENTIFIER ::= { id-nvae 5 }
   id-nvae-mixed-names            OBJECT IDENTIFIER ::= { id-nvae 6 }

   -- SCVP Extended Key Usage Key Purpose Identifiers

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

   id-kp-scvpServer               OBJECT IDENTIFIER ::= { id-kp 15 }

   id-kp-scvpClient               OBJECT IDENTIFIER ::= { id-kp 16 }

   END

9. Security Considerations

   For security considerations specific to the Cryptographic Message
   Syntax message formats, see [CMS].  For security considerations
   specific to the process of PKI certification path validation, see
   [PKIX-1].

   A client that trusts a server's response for validation of a
   certificate inherently trusts that server as much as it would trust
   its own validation software.  This means that if an attacker
   compromises a trusted SCVP server, the attacker can change the
   validation processing for every client that relies on that server.
   Thus, an SCVP server must be protected at least as well as the trust
   anchors that the SCVP server trusts.

   Clients MUST verify that the response matches their original request.
   Clients need to ensure that the server has performed the appropriate
   checks for the correct certificates under the requested validation
   policy for the specified validation time, and that the response
   includes the requested wantBacks and meets the client's freshness
   requirements.

   When the SCVP response is used to determine the validity of a
   certificate, the client MUST validate the digital signature or MAC on
   the response to ensure that the expected SCVP server generated it.
   If the client does not check the digital signature or MAC on the
   response, a man-in-the-middle attack could fool the client into
   believing modified responses from the server or responses to
   questions the client did not ask.

   If the client does not include a requestNonce item, or if the client
   does not check that the requestNonce in the response matches the
   value in the request, an attacker can replay previous responses from
   the SCVP server.

   If the server does not require some sort of authorization (such as
   signed requests), an attacker can get the server to respond to
   arbitrary requests.  Such responses may give the attacker information
   about weaknesses in the server or about the timeliness of the
   server's checking.  This information may be valuable for a future
   attack.

   If the server uses the serverContextInfo item to indicate some server
   state associated with a requestor, implementers must take appropriate
   measures against denial-of-service attacks where an attacker sends in
   a lot of requests at one time to force the server to keep a lot of
   state information.

   SCVP does not include any confidentiality mechanisms.  If
   confidentiality is needed, it can be achieved with a lower-layer
   security protocol such as TLS [TLS].

   If an SCVP client is not operating on a network with good physical
   protection, it must ensure that there is integrity over the SCVP
   request-response pair.  The client can ensure integrity by using a
   protected transport such as TLS.  It can ensure integrity by using
   MACs or digital signatures to individually protect the request and
   response messages.

   If an SCVP client populates the userPolicySet in a request with a
   value other than anyPolicy, but does not set the
   requireExplicitPolicy flag, the server may return an affirmative
   answer for paths that do not satisfy any of the specified policies.
   In general, when a client populates the userPolicySet in a request
   with a value other than anyPolicy, the requireExplicitPolicy flag
   should also be set.  This guarantees that all valid paths satisfy at
   least one of the requested policies.

   In SCVP, historical validation of a certificate returns the known
   status of the certificate at the time specified in validationTime.
   This may be used to demonstrate due diligence, but does not
   necessarily provide the most complete information.  A certificate may
   have been revoked after the time specified in validationTime, but the
   revocation notice may specify an invalidity date that precedes the
   validationTime.  The SCVP server would provide an affirmative
   response even though the most current information available indicates
   the certificate should not be trusted at that time.  SCVP clients may
   wish to specify a validationTime later than the actual time of
   interest to mitigate this risk.

10. IANA Considerations

   The details of SCVP requests and responses are communicated using
   object identifiers (OIDs).  The objects are defined in an arc
   delegated by IANA to the PKIX Working Group.  This document also
   includes four MIME type registrations in Appendix A.  No further
   action by IANA is necessary for this document or any anticipated
   updates.

11. References

11.1. Normative References

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

   [CMS]         Housley, R., "Cryptographic Message Syntax (CMS)", RFC
                 3852, July 2004.

   [OCSP]        Myers, M., Ankney, R., Malpani, A., Galperin, S., and
                 C. Adams, "X.509 Internet Public Key Infrastructure
                 Online Certificate Status Protocol - OCSP", RFC 2560,
                 June 1999.

   [PKIX-1]      Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
                 X.509 Public Key Infrastructure Certificate and
                 Certificate Revocation List (CRL) Profile", RFC 3280,
                 April 2002.

   [PKIX-AC]     Farrell, S. and R. Housley, "An Internet Attribute
                 Certificate Profile for Authorization", RFC 3281, April
                 2002.

   [PKIX-ALG]    Bassham, L., Polk, W., and R. Housley, "Algorithms and
                 Identifiers for the Internet X.509 Public Key
                 Infrastructure Certificate and Certificate Revocation
                 List (CRL) Profile", RFC 3279, April 2002.

   [PKIX-ALG2]   Schaad, J., Kaliski, B., and R. Housley, "Additional
                 Algorithms and Identifiers for RSA Cryptography for use
                 in the Internet X.509 Public Key Infrastructure
                 Certificate and Certificate Revocation List (CRL)
                 Profile", RFC 4055, June 2005.

   [UTF8]        Yergeau, F., "UTF-8, a transformation format of ISO
                 10646", STD 63, RFC 3629, November 2003.

   [ESS]         Hoffman, P., Ed., "Enhanced Security Services for
                 S/MIME", RFC 2634, June 1999.

   [SMIME-CERT]  Ramsdell, B., Ed., "Secure/Multipurpose Internet Mail
                 Extensions (S/MIME) Version 3.1 Certificate Handling",
                 RFC 3850, July 2004.

   [IKE]         Kaufman, C., Ed., "Internet Key Exchange (IKEv2)
                 Protocol", RFC 4306, December 2005.

   [HTTP]        Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
                 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
                 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

11.2. Informative References

   [IKE-GROUPS]  Kivinen, T. and M. Kojo, "More Modular Exponential
                 (MODP) Diffie-Hellman groups for Internet Key Exchange
                 (IKE)", RFC 3526, May 2003.

   [RQMTS]       Pinkas, D. and R. Housley, "Delegated Path Validation
                 and Delegated Path Discovery Protocol Requirements",
                 RFC 3379, September 2002.

   [TLS]         Dierks, T. and E. Rescorla, "The Transport Layer
                 Security (TLS) Protocol Version 1.1", RFC 4346, April
                 2006.

12. Acknowledgments

   The lively debate in the PKIX Working Group has made a significant
   impact on this protocol.  Special thanks to the following for their
   contributions to this document and diligence in greatly improving it.

   Paul Hoffman
   Phillip Hallam-Baker
   Mike Myers
   Frank Balluffi
   Ameya Talwalkar
   John Thielens
   Peter Sylvester
   Yuriy Dzambasow
   Sean P. Turner
   Wen-Cheng Wang
   Francis Dupont
   Dave Engberg
   Faisal Maqsood

   Thanks also to working group chair Steve Kent for his support and
   help.

Appendix A. MIME Media Type Registrations

Four MIME media type registrations are provided in this appendix.

A.1. application/scvp-cv-request

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/scvp-cv-request

   MIME media type name: application

   MIME subtype name: scvp-cv-request

   Required parameters: None

   Optional parameters: None

   Encoding considerations: Binary

   Security considerations: Carries a request for information.  This
   request may optionally be cryptographically protected.

   Interoperability considerations: None

   Published specification: RFC 5055

   Applications that use this media type: SCVP clients sending
   certificate validation requests

   Additional information:

      Magic number(s): None
      File extension(s): .SCQ
      Macintosh File Type Code(s): None

   Person & email address to contact for further information:
   Ambarish Malpani <ambarish@yahoo.com>

   Intended usage: COMMON

   Restrictions on usage: This media type can be used with any protocol
   that can transport digitally signed objects.

   Author: Ambarish Malpani <ambarish@yahoo.com>

   Change controller: IESG

A.2. application/scvp-cv-response

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/scvp-cv-response

   MIME media type name: application

   MIME subtype name: scvp-cv-response

   Required parameters: None

   Optional parameters: None

   Encoding considerations: Binary

   Security considerations: The client may require that this response be
   cryptographically protected, or may choose to use a secure transport
   mechanism.  DPD responses may be unprotected, but the client
   validates the information provided in the request.

   Interoperability considerations: None

   Published specification: RFC 5055

   Applications that use this media type: SCVP servers responding to
   certificate validation requests

   Additional information:

      Magic number(s): None
      File extension(s): .SCS
      Macintosh File Type Code(s): none

   Person & email address to contact for further information:
   Ambarish Malpani <ambarish@yahoo.com>

   Intended usage: COMMON
   Restrictions on usage: This media type can be used with any protocol
   that can transport digitally signed objects.

   Author: Ambarish Malpani <ambarish@yahoo.com>

   Change controller: IESG

A.3. application/scvp-vp-request

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/scvp-vp-request

   MIME media type name: application

   MIME subtype name: scvp-vp-request

   Required parameters: None

   Optional parameters: None

   Encoding considerations: Binary

   Security considerations: Carries a request for information.

   Interoperability considerations: None

   Published specification: RFC 5055

   Applications that use this media type: SCVP clients sending
   validation policy requests

   Additional information:

      Magic number(s): None
      File extension(s): .SPQ
      Macintosh File Type Code(s): none

   Person & email address to contact for further information:
   Ambarish Malpani <ambarish@yahoo.com>

   Intended usage: COMMON

   Restrictions on usage: None

   Author: Ambarish Malpani <ambarish@yahoo.com>

   Change controller: IESG

A.4. application/scvp-vp-response

   To: ietf-types@iana.org
   Subject: Registration of MIME media type application/scvp-vp-response

   MIME media type name: application

   MIME subtype name: scvp-vp-response

   Required parameters: None

   Optional parameters: None

   Encoding considerations: Binary

   Security considerations: None

   Interoperability considerations: None

   Published specification: RFC 5055

   Applications that use this media type: SCVP servers responding to
   validation policy requests

   Additional information:

      Magic number(s): None
      File extension(s): .SPP
      Macintosh File Type Code(s): none

   Person & email address to contact for further information:
   Ambarish Malpani <ambarish@yahoo.com>

   Intended usage: COMMON

   Restrictions on usage: This media type can be used with any protocol
   that can transport digitally signed objects.

   Author: Ambarish Malpani <ambarish@yahoo.com>

   Change controller: IESG

Appendix B. SCVP over HTTP

   This appendix describes the formatting and transportation conventions
   for the SCVP request and response when carried by HTTP.

   In order for SCVP clients and servers using HTTP to interoperate, the
   following rules apply.

   -  Clients MUST use the POST method to submit their requests.

   -  Servers MUST use the 200 response code for successful responses.

   -  Clients MAY attempt to send HTTPS requests using TLS 1.0 or later,
      although servers are not required to support TLS.

   -  Servers MUST NOT assume client support for any type of HTTP
      authentication such as cookies, Basic authentication, or Digest
      authentication.

   -  Clients and servers are expected to follow the other rules and
      restrictions in [HTTP].  Note that some of those rules are for
      HTTP methods other than POST; clearly, only the rules that apply
      to POST are relevant for this specification.

B.1. SCVP Request

   An SCVP request using the POST method is constructed as follows:

   The Content-Type header MUST have the value "application/scvp-cv-
   request".

   The body of the message is the binary value of the DER encoding of
   the CVRequest, wrapped in a CMS body as described in Section 3.

B.2. SCVP Response

   An HTTP-based SCVP response is composed of the appropriate HTTP
   headers, followed by the binary value of the BER encoding of the
   CVResponse, wrapped in a CMS body as described in Section 4.

   The Content-Type header MUST have the value "application/scvp-cv-
   response".

B.3. SCVP Policy Request

   An SCVP request using the POST method is constructed as follows:

      The Content-Type header MUST have the value "application/scvp-vp-
      request".

   The body of the message is the binary value of the BER encoding of
   the ValPolRequest, wrapped in a CMS body as described in Section 5.

B.4. SCVP Policy Response

   An HTTP-based SCVP policy response is composed of the appropriate
   HTTP headers, followed by the binary value of the DER encoding of the
   ValPolResponse, wrapped in a CMS body as described in Section 6.  The
   Content-Type header MUST have the value "application/scvp-vp-
   response".

Authors' Addresses

   Trevor Freeman
   Microsoft Corporation,
   One Microsoft Way
   Redmond, WA 98052
   USA.
   EMail: trevorf@microsoft.com

   Russell Housley
   Vigil Security, LLC
   918 Spring Knoll Drive
   Herndon, VA 20170
   USA
   EMail: housley@vigilsec.com

   Ambarish Malpani
   Malpani Consulting Services
   EMail: ambarish@yahoo.com

   David Cooper
   National Institute of Standards and Technology
   100 Bureau Drive, Mail Stop 8930
   Gaithersburg, MD 20899-8930
   EMail: david.cooper@nist.gov

   Tim Polk
   National Institute of Standards and Technology
   100 Bureau Drive, Mail Stop 8930
   Gaithersburg, MD 20899-8930
   EMail: wpolk@nist.gov

Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

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   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
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   Intellectual Property Rights or other rights that might be claimed to
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   this document or the extent to which any license under such rights
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   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
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   The IETF invites any interested party to bring to its attention any
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   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.

Status of This Memo

Abstract

Table of Contents

1. Introduction

1.1. Terminology

1.2. SCVP Overview

1.3. SCVP Requirements

1.4. Validation Policies

1.5. Validation Algorithm

1.6. Validation Requirements

2. OCSP responses, using [OCSP];

3. delta CRLs; and

4. indirect CRLs.

3.1. cvRequestVersion

3.2. query

3.2.1. queriedCerts

3.2.2. checks

3.2.3. wantBack

3.2.4. validationPolicy

3.2.4.1. validationPolRef

3.2.4.1.1. Default Validation Policy

3.2.4.2. validationAlg

3.2.4.2.1. Basic Validation Algorithm

3.2.4.2.2. Basic Validation Algorithm Errors

3.2.4.2.3. Name Validation Algorithm

3.2.4.2.4. Name Validation Algorithm Errors

3.2.4.3. userPolicySet

3.2.4.4. inhibitPolicyMapping

3.2.4.5. requireExplicitPolicy

3.2.4.6. inhibitAnyPolicy

3.2.4.7. trustAnchors

3.2.4.8. keyUsages

3.2.4.9. extendedKeyUsages

3.2.4.10. specifiedKeyUsages

3.2.5. responseFlags

3.2.5.1. fullRequestInResponse

3.2.5.2. responseValidationPolByRef

3.2.5.3. protectResponse

3.2.5.4. cachedResponse

3.2.6. serverContextInfo

3.2.7. validationTime

3.2.8. intermediateCerts

3.2.9. revInfos

3.2.10. producedAt

3.2.11. queryExtensions

3.2.11.1. extnID

3.2.11.2. critical

3.2.11.3. extnValue

3.3. requestorRef

3.4. requestNonce

3.5. requestorName

3.6. responderName

3.7. requestExtensions

3.7.1. extnID

3.7.2. critical

3.7.3. extnValue

3.8. signatureAlg

3.9. hashAlg

3.10. requestorText

3.11. SCVP Request Authentication

5. An error response to an authenticated request. The server SHOULD protect these responses.

6. An error response to an AuthenticatedData request where MAC is valid. The server MUST protect these responses.

7. All other error responses MUST NOT be protected by the server.

4.1. cvResponseVersion

4.2. serverConfigurationID

4.3. producedAt

4.4. responseStatus

4.5. respValidationPolicy

4.6. requestRef

4.6.1. requestHash

4.6.2. fullRequest

4.7. requestorRef

4.8. requestorName

4.9. replyObjects

4.9.1. cert

4.9.2. replyStatus

4.9.3. replyValTime

4.9.4. replyChecks

0: Built a path 1: Could not build a path

4.9.5. replyWantBacks

5. An error response to an authenticated request. The server SHOULD
protect these responses.

6. An error response to an AuthenticatedData request where MAC is
valid. The server MUST protect these responses.

0: Built a path
1: Could not build a path