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Versions: (draft-turner-caclearanceconstraints) 00 01 02 03 RFC 5913

IETF PKIX Working Group                                     Sean Turner
Internet Draft                                                     IECA
Intended Status: Standard Track                        Santosh Chokhani
                                                     CygnaCom Solutions
Expires: April 30, 2009                                October 31, 2008



          Clearance Attribute and Authority Clearance Constraints
                           Certificate Extension
           draft-ietf-pkix-authorityclearanceconstraints-00.txt


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Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   This document defines the syntax and semantics for the Clearance
   attribute and the Authority Clearance Constraints extension in X.509
   certificates.  The Clearance attribute is used to indicate the
   clearance held by the subject.  The Clearance attribute may appear in



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   the subject directory attributes extension of a public key
   certificate or in the attributes field of an attribute certificate.
   The Authority Clearance Constraints certificate extension values in a
   Trust Anchor (TA), CA public key certificates, and an Attribute
   Authority (AA) public key certificate in a public key certification
   path constrain the effective Clearance of the subject.

Table of Contents

   1. Introduction...................................................2
      1.1. Terminology...............................................3
      1.2. ASN.1 Syntax Notation.....................................3
   2. Clearance Attribute............................................4
   3. Authority Clearance Constraints Certificate Extension..........5
   4. Clearance and Authority Clearance Constraints Processing in PKC6
      4.1. Collecting Constraints....................................7
         4.1.1. Certification Path Processing........................7
   5. Clearance and Authority Clearance Constraints Processing in AC11
      5.1. Collecting Constraints...................................12
         5.1.1. Certification Path Processing.......................12
   6. Computing Intersection of securityCategories..................13
   7. Recommended securityCategories................................14
   8. Security Considerations.......................................14
   9. IANA Considerations...........................................15
   10. References...................................................15
      10.1. Normative References....................................15
      10.2. Informative References..................................15
   Appendix A. ASN.1 Module.........................................16
   Author's Addresses...............................................18
   Full Copyright Statement.........................................19
   Intellectual Property............................................19

1. Introduction

   Organizations that have implemented a security policy can issue
   certificates that include an indication of the clearance values held
   by the subject.  The Clearance attribute indicates the security
   policy, the clearance levels held by the subject, and additional
   authorization information held by the subject.  This specification
   makes use of the ASN.1 syntax for clearance from [3281bis].

   Clearance attribute may be placed in the Subject Directory extension
   of a PKC or may be placed in a separate attribute certificate (AC).

   The placement of Clearance attribute in PKCs is desirable when the
   credentials such as PKCs need to be revoked when the clearance
   information changes or when clearance information is relatively


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   static, and clearance information can be verified as part of PKC
   issuance process (e.g., using local databases).  The placement of
   Clearance attribute in PKCs may also be made to simplify the
   infrastructure, to reduce the infrastructure design cost, or to
   reduce the infrastructure operations cost.  An example of placement
   of Clearance attribute in PKCs in operational PKI is the Defense
   Messaging Service.  An example of placement of attributes in PKCs is
   Qualified Certificates [RFC3739].

   The placement of Clearance attribute in ACs is desirable when the
   clearance information is relatively dynamic and changes in the
   clearance information does not require revocation of credentials such
   as PKCs, or the clearance information can not be verified as part of
   PKC issuance process.

   Since [RFC3281] does not permit chain of ACs, the Authority
   Clearance Constraints extension may only appear in the PKCs of CA or
   AA.  The Authority Clearance Constraints extension may also appear
   in a TA or may be associated with a TA.

   Some organizations have multiple TAs, CAs, and/or AAs and these
   organizations may wish to indicate to relying parties which clearance
   values from a particular TA, CA, or AA should be accepted.  For
   example, consider the security policies described in [RFC3114], where
   a security policy has been defined for Amoco with three security
   classification values (HIGHLY CONFIDENTIAL, CONFIDENTIAL, and
   GENERAL). To constrain a CA for just one security classification, the
   Authority Clearance Constraints certificate extension would be
   included in the CA's PKC.

   Cross-certified domains can also make use of the Authority Clearance
   Constraints certificate extension to indicate which clearance values
   should be acceptable to relying parties.

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 [RFC2119].

1.2. ASN.1 Syntax Notation

   All X.509 PKC [RFC5280] extensions are defined using ASN.1 [X.680].
   All X.509 AC [RFC3281] extensions are defined using ASN.1 [X.680].





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2. Clearance Attribute

   The Clearance attribute in a certificate indicates the clearances
   held by the subject.  It uses the clearance attribute syntax from
   Section 4.4.6 of [3281bis], which is included below for convenience,
   in the Attributes field.  A certificate MUST include either zero or
   one instance of the Clearance attribute.  If the Clearance attribute
   is present, it must contain a single value.

   The following object identifier identifies the Clearance attribute
   (either in the subject directory attributes extension of a PKC or in
   the Attributes field of an AC):

     id-at-clearance OBJECT IDENTIFIER ::= { joint-iso-ccitt(2)
       ds(5) module(1) selected-attribute-types(5) clearance(55) }

   The ASN.1 syntax for the Clearance attribute is as follows [PKI-ASN]:

     Clearance  ::=  SEQUENCE {
       policyId            OBJECT IDENTIFIER,
       classList           ClassList DEFAULT {unclassified},
       securityCategories  SET OF SecurityCategory OPTIONAL
     }

     ClassList  ::=  BIT STRING {
       unmarked       (0),
       unclassified   (1),
       restricted     (2),
       confidential   (3),
       secret         (4),
       topSecret      (5)
     }

     SECURITY-CATEGORY ::= TYPE-IDENTIFIER

     SecurityCategory ::= SEQUENCE {
       type  [0]
           TYPE-IDENTIFIER.&id({SupportedSecurityCategories}),
       value [1]
           EXPLICIT TYPE-IDENTIFIER.&Type
                                 ({SupportedSecurityCategories}{@type})
     }

   The Clearance attribute takes its meaning from Section 4.4.6 of
   [RFC3281], which is repeated here for convenience:




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     - policyId identifies the security policy to which the clearance
      relates.  The policyId indicates the semantics of the classList
      and securityCategory fields.

     - classlist identifies the security classifications. Six basic
      values are defined in bit positions 0 through 5 and more may be
      defined by an organizational security policy.

     - securityCategories provides additional authorization information.

   If a trust anchor's public key is used directly, then the Clearance
   associated with the trust anchor, if any, should be used as the
   effective clearance (also defined as effective-clearance for a
   certification path).

3. Authority Clearance Constraints Certificate Extension

   The Authority Clearance Constraints certificate extension indicates
   to the relying party what clearances should be acceptable for the
   subject of the AC or the subject of the last certificate in a PKC
   certification path.  It is only meaningful in trust anchor, CA PKCs,
   or AA PKCs.  A trust anchor, CA PKC, or AA PKC MUST include either
   zero or one instance of the Authority Clearance Constraints
   certificate extension.  The Authority Clearance Constraints
   certificate extension MAY be critical or non-critical.

   Absence of this certificate extension in a TA, in a CA PKC, or in an
   AA PKC indicates that clearance of the subject of the AC or the
   subject of the last certificate in a PKC certification path
   containing the TA, the CA or the AA is not constrained by the
   respective TA, CA or AA.

   The following object identifier identifies the Authority Clearance
   Constraints certificate extension:

     id-ce-authorityClearanceConstraints OBJECT IDENTIFIER ::= {
       id-TBSL }

   The ASN.1 syntax for the Authority Clearance Constraints certificate
   extension is as follows:

     AuthorityClearanceConstraints ::= SEQUENCE SIZE (1..MAX) OF
                                         Clearance

   The syntax for Authority Clearance Constraints certificate extension
   contains Clearance values that the CA or the AA asserts.  The
   sequence MUST NOT include more than one entry with the same policyId.


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   This constraint is enforced during Clearance and Authority Clearance
   Constraints Processing described below.  If more than one entry with
   the same policyId is present in AuthorityClearanceConstraints
   certificate extension, the certification path is rejected.  In
   addition, each Clearance attribute in the SEQUENCE must not contain
   more than one value.

4. Clearance and Authority Clearance Constraints Processing in PKC

   This section describes the processing of certification path when
   Clearance is asserted in PKC.

   Authority Clearance Constraints certificate extension and Clearance
   attribute processing determines the effective clearance (henceforth
   called effective-clearance) for the end PKC.  Authority Clearance
   Constraints certificate extension in the TA and in each PKC up to but
   not including the end PKC in a PKC certification path impact the
   effective-clearance.  If there is more than one path to the end-
   entity PKC, each path is processed independently.  The process
   involves two steps:

     1) collecting the Authority Clearance Constraints; and

     2) using Authority Clearance Constraints in the certification path
       and the Clearance in the end PKC to determine the effective-
       clearance for the subject of the end PKC.

   Assuming a certification path consisting of n PKCs, the effective-
   clearance for the subject of the end PKC is the intersection of
   Clearance attribute in the subject PKC, Authority Clearance
   Constraints, if present, in trust anchor and all Authority Clearance
   Constraints present in intermediate PKCs.  Any effective-clearance
   calculation algorithm that performs this calculation and provides the
   same outcome as the one from the algorithm described herein is
   considered compliant with the requirements of this RFC.

   When processing a certification path, Authority Clearance Constraints
   are maintained in one state variable: permitted-clearances.  When
   processing begins, permitted-clearances is initialized to the special
   value all-clearances if Authority Clearance Constraints certificate
   extension is not present in or associated with the trust anchor,
   otherwise this value is initialized to Authority Clearance
   Constraints associated with the trust anchor.  The permitted-
   clearances state variable is updated each time an intermediate PKC
   that contains an Authority Clearance Constraints certificate
   extension in the path is processed.



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   When processing the end PKC, the value in the Clearance attribute in
   the end PKC is intersected with the permitted-clearances state
   variable.

   The output of Clearance attribute and Authority Clearance Constraint
   certificate extensions processing is the effective-clearance, which
   could also be an empty list; and success or failure with reason code
   for failure.

4.1. Collecting Constraints

   Authority Clearance Constraints are collected from the trust anchor
   and the intermediate PKCs in a certification path.

4.1.1. Certification Path Processing

   When processing Authority Clearance Constraints certificate extension
   for the purposes of validating Clearance attribute in the end PKC,
   the processing described in this section or an equivalent algorithm
   MUST be included in the certification path validation.  The
   processing is presented as additions to the certification path
   validation algorithm described in section 6 of [RFC5280].

4.1.1.1. Inputs

   Trust anchor information may include the
   AuthorityClearanceConstraints structure to specify Authority
   Clearance Constraints for the trust anchor.  The trust anchor may be
   constrained or unconstrained.

4.1.1.2. Initialization

   Examine the trust anchor information and verify that it does not
   contain more than one instance of AuthorityClearanceConstraints
   extension.  If the trust anchor information contains more than one
   instance of AuthorityClearanceConstraints extension, set effective-
   clearance to an empty list, set error code to "multiple extension
   instances", and exit with failure.

   If any of the Clearance attributes in the
   AuthorityClearanceConstraints extension contains more than one value,
   set effective-clearance to an empty list, set error code to "multiple
   values", and exit with failure.

   Create a state variable named permitted-clearances.  If the trust
   anchor contains an AuthorityClearanceConstraints extension, then the



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   initial value of permitted-clearances is the
   AuthorityClearanceConstraints extension from the trust anchor.

   Examine the permitted-clearances for the same Policy ID appearing
   more then once.  If a policyID appears more than once in the
   permitted-clearances state variable, set effective-clearance to an
   empty list, set error code to "multiple instances of same clearance",
   and exit with failure.

   If the trust anchor does not contain an AuthorityClearanceConstraints
   extension, the permitted-clearances variable is assigned the special
   value all-clearances.

4.1.1.3. Basic Certificate Processing

   If the PKC is the last PKC (i.e., certificate n), skip the steps
   listed in this section.

   Examine the PKC and verify that it does not contain more than one
   instance of AuthorityClearanceConstraints extension.  If the PKC
   contains more than one instance of AuthorityClearanceConstraints
   extension, set effective-clearance to an empty list, set error code
   to "multiple extension instances", and exit with failure.

   If any of the Clearance attributes in the
   AuthorityClearanceConstraints extension contains more than one value,
   set effective-clearance to an empty list, set error code to "multiple
   values", and exit with failure.

   If the AuthorityClearanceConstraints certificate extension is not
   present in the PKC, no action is taken, and the permitted-clearances
   value is unchanged.

   If the AuthorityClearanceConstraints certificate extension is present
   in the PKC, set the variable temp-clearances to
   AuthorityClearanceConstraints certificate extension.  Examine the
   temp-clearances for the same Policy ID appearing more then once.  If
   a policyID appears more than once in the temp-clearances state
   variable, set effective-clearance to an empty list, set error code to
   "multiple instances of same clearance", and exit with failure.

   If the AuthorityClearanceConstraints certificate extension is present
   in the PKC and permitted-clearances contains the all-clearances
   special value, then assign permitted-clearances the value of the
   temp-clearances.




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   If the AuthorityClearanceConstraints certificate extension is present
   in the PKC and permitted-clearances does not contain the all-
   clearances special value, take the intersection of temp-clearances
   and permitted-clearances by repeating the following steps for each
   clearance in the permitted-clearances state variable:

     - If the policyID associated with the clearance is absent in the
      temp-clearances, delete the clearance structure associated with
      the policyID from the permitted-clearances state variable.

     - If the policyID is present in the temp-clearances:

       -- For every classList bit, assign the classList bit a value of
          one (1) for the policyID in permitted-clearances state
          variable if the bit is one (1) in both the permitted-
          clearances state variable and the temp-clearances for that
          policyID; otherwise assign the bit a value of zero (0).

       -- If no bits are one (1) for the classList, delete the clearance
          structure associated with the policyID from the permitted-
          clearances state variable and skip the next step of processing
          securityCategories.

       -- For the policyID in permitted-clearances, set the
          securityCategories to the intersection of securityCategories
          for the policyID in permitted-clearances and in temp-
          clearances using the algorithm described in Section 6.   Note
          that an empty SET is represented by simply omitting the SET.

4.1.1.4. Preparation for Certificate i+1

   No additional action associated with the Clearance attribute or
   AuthorityClearanceConstraints certificate extensions is taken during
   this phase of certification path validation as described in section 6
   of [RFC5280].

4.1.1.5. Wrap-up Procedure

   To complete the processing, perform the following steps for the last
   PKC (i.e., certificate n).

   Examine the PKC and verify that it does not contain more than one
   instance of Clearance attribute.  If the PKC contains more than one
   instance of Clearance attribute, set effective-clearance to an empty
   list, set error code to "multiple instances of an attribute", and
   exit with failure.



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   If the Clearance attribute is not present in the end PKC, set
   effective-clearance to an empty list and exit with success.

   Set effective-clearance to the Clearance attribute in the end PKC.

4.1.1.5.1. Wrap Up Clearance

   Examine effective-clearance and verify that it does not contain more
   than one value.  If effective-clearance contains more than one value,
   set effective-clearance to an empty list, set error code to "multiple
   values", and exit with failure.

   Let us say policyID in effective-clearance is X.

   If permitted-clearances is an empty list, set effective-clearance to
   an empty list and exit with success.

   If the permitted-clearances has special value of all-clearances, exit
   with success.

   If the policyID X in effective-clearance is absent from the
   permitted-clearances, set effective-clearance to an empty list and
   exit with success.

   Assign those classList bits in effective-clearance a value of one (1)
   that have a value of one (1) both in effective-clearance and in the
   clearance structure in permitted-clearances associated with policyID
   X.  Assign all other classList bits in effective-clearance a value of
   zero (0).

   If none of the classList bits have a value of one (1) in effective-
   clearance, set effective-clearance to an empty list and exit with
   success.

   Set the securityCategories in effective-clearance to the intersection
   of securityCategories in effective-clearance and in permitted-
   clearances using the algorithm described in Section 6.  Note that
   empty an SET is represented by simply omitting the SET.

   Exit with Success

4.1.1.6. Outputs

   If certification path validation processing succeeds, effective-
   clearance contains the effective clearance for the subject of the
   certification path.  Processing also returns success or failure
   indication and reason for failure, if applicable.


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5. Clearance and Authority Clearance Constraints Processing in AC

   This section describes the processing of certification path when
   Clearance is asserted in an AC.  Relevant to processing are: one TA;
   0 or more CA PKCs; 0 or 1 AA PKC; and 1 AC.

   Authority Clearance Constraints certificate extension and Clearance
   attribute processing determines the effective clearance (henceforth
   called effective-clearance) for the AC.  Authority Clearance
   Constraints certificate extension in the TA and in each PKC up to and
   including the AA PKC in a certification path impact the effective-
   clearance.  If there is more than one path to the AA PKC, each path
   is processed independently.  The process involves two steps:

     1) collecting the Authority Clearance Constraints; and

     2) using Authority Clearance Constraints in the PKC certification
       path and the Clearance in the AC to determine the effective-
       clearance for the subject of the AC.

   The effective-clearance for the subject of the AC is the intersection
   of Clearance in the subject AC, Authority Clearance Constraints, if
   present, in trust anchor and all Authority Clearance Constraints
   present in PKC certification path from the TA to the AA.  Any
   effective-clearance calculation algorithm that performs this
   calculation and provides the same outcome as the one from the
   algorithm described herein is considered compliant with the
   requirements of this RFC.

   Authority Clearance Constraints is maintained in one state variable:
   permitted-clearances.  When processing begins, permitted-clearances
   is initialized to the special value all-clearances if Authority
   Clearance Constraints certificate extension is not present in or
   associated with the trust anchor, otherwise this value is initialized
   to Authority Clearance Constraints associated with the trust anchor.
   The permitted-clearances state variable is updated each time a PKC
   (other than AC holder PKC) that contains an Authority Clearance
   Constraints certificate extension in the path is processed.

   When processing the AC, the value in the Clearance attribute in the
   AC is intersected with the permitted-clearances state variable.

   The output of Clearance and Authority Clearance Constraint
   certificate extensions processing is the effective-clearance, which
   could also be an empty list; and success or failure with reason code
   for failure.



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5.1. Collecting Constraints

   Authority Clearance Constraints are collected from the trust anchor
   and all the PKCs in a PKC certification path.

5.1.1. Certification Path Processing

   When processing Authority Clearance Constraints certificate extension
   for the purposes of validating Clearance in the AC, the processing
   described in this section or an equivalent algorithm MUST be included
   in the certification path validation.  The processing is presented as
   additions to the PKC certification path validation algorithm
   described in section 6 of [RFC5280] for the AA PKC certification path
   and the algorithm described in section 5 of [RFC3281] for the AC
   validation.

5.1.1.1. Inputs

   Same as Section 4.1.1.1.

   In addition, let us assume that the PKC certification path for the AA
   consists of n certificates.

5.1.1.2. Initialization

   Same as Section 4.1.1.2.

5.1.1.3. Basic PKC Processing

   Same as Section 4.1.1.3. except that the logic is applied to all n
   PKCs.

5.1.1.4. Preparation for Certificate i+1

   Same as Section 4.1.1.4.

5.1.1.5. Wrap-up Procedure

   To complete the processing, perform the following steps for the AC.

   Examine the AC and verify that it does not contain more than one
   instance of Clearance attribute.  If the AC contains more than one
   instance of Clearance attribute, set effective-clearance to an empty
   list, set error code to "multiple instances of an attribute", and
   exit with failure.




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   If the Clearance attribute is not present in the AC, set effective-
   clearance to an empty list and exit with success.

   Set effective-clearance to the Clearance attribute in the AC.

5.1.1.5.1. Wrap Up Clearance

   Same as Section 4.1.1.5.1.

5.1.1.6. Outputs

   Same as Section 4.1.1.6.

   In addition, apply AC processing rules described in Section 5 of
   [RFC3281].

6. Computing Intersection of securityCategories

   This section describes how to compute the intersection of
   securityCategories A and B.  It uses the state variable temp-set.

   Set the SET temp-set to empty.

   If SET A is empty (i.e., securityCategories is absent), return temp-
   set.

   If SET B is empty (i.e., securityCategories is absent), return temp-
   set.

   For every element (i.e., securityCategory) in the SET A carry out the
   following steps:

     1. If there is no element in SET B with the same Type OID as the
        type OID in the element from SET A, go to step 6.

     2. If there is an element in SET B with the same Type OID and value
        as in the element in SET A, carry out the following steps:

          a) Add an element containing the Type OID and the value to the
             SET temp-set.

          b) Delete all elements with the same Type OID and the same
             value from the SET B.

          c) Go to step 6.




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     3. If the processing semantics of Type OID in the element in SET A
        is not known, go to step 6.

     4. Perform Type OID specific intersection of the value in the
        element in SET A with the values in the applicable elements in
        SET B with the same Type OID.

     5. If the intersection is not empty, add and element containing the
        Type OID and intersection result as value to temp-set.

     6. If more elements remain in SET A, process the next element
        starting with step 1.

   Return temp-set.

7. Recommended securityCategories

   This RFC also include a recommended securityCategories as follows:

   SecurityCategory ::= SEQUENCE {
       type  [0]  OID id-TBSL,
       value [1]  BIT STRING
     }

   Note that Type specific intersection of two values for this Type will
   be simply setting the bits that are set in both values.  If the
   resulting intersection has none of the bits set, the intersection is
   considered empty.

8. Security Considerations

   Certificate issuers must recognize that absence of the
   AuthorityClearanceConstraints in a CA or AA certificate means that in
   terms of the clearance, the subject Authority is not constrained.

   Absence of Clearance attribute in a certificate means that the
   subject has not been assigned any clearance.

   If there is no Clearance associated with a TA, it means that the TA
   has not been assigned any clearance.

   If the local security policy considers the clearance held by a
   subject or those supported by a CA or AA to be sensitive, then the
   Clearance attribute or Authority Clearance Constraints should only be
   included if the subject's and Authority's certificate can be privacy
   protected.  Also in this case, distribution of trust anchors and



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   associated Authority Clearance Constraints extension or Clearance
   must also be privacy protected.

9. IANA Considerations

   None.  Please remove this section prior to publication as an RFC.

10. References

10.1. Normative References

   [PKI-ASN]   Hoffman, P., and J. Schaad, "New ASN.1 Modules for PKIX",
               draft-ietf-pkix-new-asn1, work-in-progress.

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

   [RFC3281]   Farrell, S., and Housley, R., "An Internet Attribute
               Certificate Profile for Authorization", RFC 3281, April
               2002.

   [3281bis]   Farrell, S., Housely, R., and S. Turner, "An Internet
               Attribute Certificate Profile for Authorization: Update",
               draft-ietf-pkix-3281update-01, work-in-progress.

   [RFC5280]   Cooper, D. et. al., "Internet X.509 Public Key
               Infrastructure Certificate and Certification Revocation
               List (CRL) Profile", RFC 5280, May 2008.

   [X.680]     ITU-T Recommendation X.680 (2004) | ISO/IEC 8824-1:2004.
               Information Technology - Abstract Syntax Notation One.

10.2. Informative References

   [RFC3114]   Nicolls, W., "Implementing Company Classification Policy
               with S/MIME Security Label", RFC3114, May 2002.

   [RFC3739]   Santesson, S. et. al., "Internet X.509 Public Key
               Infrastructure: Qualified Certificate Profile", RFC 3739,
               March 2004.









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Appendix A. ASN.1 Module

   This appendix provides the normative ASN.1 definitions for
   the structures described in this specification using ASN.1 as defined
   in X.680.

   Clearance-AuthorityClearanceConstraints93 { id-TBSL }

   DEFINITIONS IMPLICIT TAGS ::=

   BEGIN

   -- EXPORTS ALL --

   IMPORTS

   -- IMPORTS from [PKI-ASN]

   id-at-clearance, Clearance
      FROM PKIXAttributeCertificate
      { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-mod(0)
        id-mod-attribute-cert(12)
      }

   -- IMPORTS from [PKI-ASN]

   EXTENSION
     FROM PKIX-CommonTypes
      { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-mod(0)
        id-mod-pkixCommon(43)
      }
   ;

   -- Clearance attribute OID and syntax

   -- The following is a '93 version for clearance.
   -- It is included for convenience.

   -- id-at-clearance OBJECT IDENTIFIER ::=
   --  { joint-iso-ccitt(2) ds(5) module(1) selected-attribute-types(5)
   --    clearance (55)
   --  }





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   -- Clearance  ::=  SEQUENCE {
   --   policyId            OBJECT IDENTIFIER,
   --   classList           ClassList DEFAULT {unclassified},
   --   securityCategories  SET OF SecurityCategory  OPTIONAL
   -- }

   -- ClassList  ::=  BIT STRING {
   --   unmarked      (0),
   --   unclassified  (1),
   --   restricted    (2),
   --   confidential  (3),
   --   secret        (4),
   --   topSecret     (5)
   -- }

   -- SECURITY-CATEGORY ::= TYPE-IDENTIFIER

   -- SecurityCategory ::= SEQUENCE {
   --   type  [0]
   --      TYPE-IDENTIFIER.&id({SupportedSecurityCategories}),
   --   value [1]
   --      EXPLICIT TYPE-IDENTIFIER.&Type
   --                           ({SupportedSecurityCategories}{@type})
   -- }

   -- Authority Clearance Constraints certificate extension OID
   -- and syntax

   id-ce-authorityClearanceConstraints OBJECT IDENTIFIER ::= { id-TBSL }

   authorityClearanceConstraints EXTENSION ::= {
     SYNTAX         AuthorityClearanceConstraints
     IDENTIFIED BY  id-ce-AuthorityClearanceConstraints
   }

   AuthorityClearanceConstraints ::= SEQUENCE SIZE (1..MAX) OF Clearance

   END











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Author's Addresses

   Sean Turner

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

   EMail: turners@ieca.com

   Santosh Chokhani
   CygnaCom Solutions, Inc.

   Email: SChokhani@cygnacom.com


































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