[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 5275

SMIME Working Group                                           S. Turner
Internet Draft                                                     IECA
Document: draft-ietf-smime-symkeydist-02.txt           October 31, 2000
Expires:  April 2001


                   S/MIME Symmetric Key Distribution


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [1].

   This document is an Internet-Draft. Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups. Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This draft is being discussed on the 'ietf-smime' mailing list. To
   subscribe, send a message to ietf-smime-request@imc.org with the
   single word subscribe in the body of the message. There is a Web
   site for the mailing list at <http://www.imc.org/ietf-smime/>.


Abstract

   This document describes a mechanism to manage (i.e., setup,
   distribute, and rekey) keys used with symmetric cryptographic
   algorithms. Also defined herein is a mechanism to organize users
   into groups to support distribution of encrypted content using
   symmetric cryptographic algorithms. The mechanism uses the
   Cryptographic Message Syntax (CMS) protocol [2] and Certificate
   Management Message over CMS (CMC) protocol [3] to manage the
   symmetric keys. Any member of the group can then later use this
   distributed shared key to decrypt other CMS encrypted objects with
   the symmetric key. This mechanism has been developed to support
   S/MIME Mail List Agents (MLAs).





Turner                                                               1

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [4].

   1. INTRODUCTION....................................................3
   1.1 APPLICABILITY TO E-MAIL........................................4
   1.2 APPLICABILITY TO REPOSITORIES..................................4
   2. ARCHITECTURE....................................................5
   3. PROTOCOL INTERACTIONS...........................................6
   3.1 CONTROL ATTRIBUTES.............................................7
   3.1.1 GL USE KEK...................................................8
   3.1.2 GL DELETE...................................................10
   3.1.3 GL ADD MEMBER...............................................10
   3.1.4 GL DELETE MEMBERS...........................................11
   3.1.5 GL REKEY....................................................12
   3.1.6 GL ADD OWNER................................................13
   3.1.7 GL REMOVE OWNER.............................................13
   3.1.8 GL KEY COMPROMISE...........................................14
   3.1.9 GL KEY REFRESH..............................................14
   3.1.10 GL SUCCESS INFORMATION.....................................14
   3.1.11 GL FAIL INFORMATION........................................15
   3.1.12 GLA QUERY REQUEST..........................................17
   3.1.13 GLA QUERY RESPONSE.........................................17
   3.1.14 GL PROVIDE CERT............................................17
   3.1.15 GL UPDATE CERT.............................................18
   3.1.16 GL KEY.....................................................19
   3.2 USE OF CMC, CMS, AND PKIX.....................................20
   3.2.1 PROTECTION LAYERS...........................................20
   3.2.1.1 MINIMUM PROTECTION........................................21
   3.2.1.2 ADDITIONAL PROTECTION.....................................21
   3.2.2 COMBINING REQUESTS AND RESPONSES............................21
   3.2.3 GLA GENERATED MESSAGES......................................23
   3.2.4 CMC CONTROL ATTRIBUTES......................................24
   3.2.5 RESUBMITTED GL MEMBER MESSAGES..............................26
   3.2.6 PKIX........................................................26
   4 ADMINISTRATIVE MESSAGES.........................................26
   4.1 ASSIGN KEK TO GL..............................................26
   4.2 DELETE GL FROM GLA............................................29
   4.3 ADD MEMBERS TO GL.............................................31
   4.3.1 GLO INITIATED ADDITIONS.....................................32
   4.3.2 PROSPECTIVE MEMBER INITIATED ADDITIONS......................37
   4.4 DELETE MEMBERS FROM GL........................................39
   4.4.1 GLO INITIATED DELETIONS.....................................40
   4.4.2 MEMBER INITIATED DELETIONS..................................44
   4.5 REQUEST REKEY OF GL...........................................45
   4.5.1 GLO INITIATED REKEY REQUESTS................................46
   4.5.2 GLA INITIATED REKEY REQUESTS................................48
   4.6 CHANGE GLO....................................................48
   4.7 INDICATE KEK COMPROMISE.......................................50
   4.7.1 GL MEMBER INITIATED KEK COMPROMISE MESSAGE..................51

Turner                                                               2

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   4.7.2 GLO INITIATED KEK COMPROMISE MESSAGE........................52
   4.8 REQUEST KEK REFRESH...........................................53
   4.9 GLA QUERY REQUEST AND RESPONSE................................54
   4.10 UPDATE MEMBER CERTIFICATE....................................56
   4.10.1 GLO AND GLA INITIATED UPDATE MEMBER CERTIFICATE............56
   4.10.2 GL MEMBER INITIATED UPDATE MEMBER CERTIFICATE..............57
   5 DISTRIBUTION MESSAGE............................................58
   5.1 DISTRIBUTION PROCESS..........................................59
   6 ALGORITHMS......................................................60
   6.1 KEK GENERATION ALGORITHM......................................60
   6.2 SHARED KEK WRAP ALGORITHM.....................................60
   6.3 SHARED KEK ALGORITHM..........................................61
   7 TRANSPORT.......................................................61
   8 USING THE GROUP KEY.............................................61
   9 SECURITY CONSIDERATIONS.........................................61
   10 REFERENCES.....................................................61
   11 ACKNOWLEDGEMENTS...............................................62
   12 AUTHOR'S ADDRESSES.............................................62


1. Introduction

   With the ever-expanding use of secure electronic communications
   (e.g., S/MIME [2]), users require a mechanism to distribute
   encrypted data to multiple recipients (i.e., a group of users).
   There are essentially two ways to encrypt the data for recipients:
   using asymmetric algorithms with public key certificates (PKCs) or
   symmetric algorithms with symmetric keys.

   With asymmetric algorithms, the originator forms an originator-
   determined content-encryption key (CEK) and encrypts the content,
   using a symmetric algorithm. Then, using an asymmetric algorithm and
   the recipient's PKCs, the originator generates per-recipient
   information that either (a) encrypts the CEK for a particular
   recipient (ktri ReipientInfo CHOICE), or (b) transfers sufficient
   parameters to enable a particular recipient to independently
   generate the same KEK (kari RecipientInfo CHOICE). If the group is
   large, the amount of per-recipient information required may take
   quite some time to generate, not to mention the time required to
   collect and validate the PKCs for each of the recipients. Each
   recipient identifies their per-recipient information and uses the
   private key associated with the public key of their PKC to decrypt
   the CEK and hence gain access to the encrypted content.

   With symmetric algorithms, the origination process is the same as
   with asymmetric algorithms except for what encrypts the CEK. Instead
   of using PKCs, the originator uses a previously distributed secret
   key-encryption key (KEK) to encrypt the CEK (kekri RecipientInfo
   CHOICE). Only one copy of the encrypted CEK is required because all
   the recipients already have the shared KEK needed to decrypt the CEK
   and hence gain access to the encrypted content.


Turner                                                               3

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   The security provided by the shared KEK is only as good as the sum
   of the techniques employed by each member of the group to keep the
   KEK secret from nonmembers. These techniques are beyond the scope of
   this document. Only the members of the list and the key manager
   should have the KEK in order to maintain the secrecy of the group.
   Access control to the information protected by the KEK is determined
   by the entity that encrypts the information, as all members of the
   group have access. If the entity that is performing the encryption
   wants to ensure some subset of the group does not gain access to the
   information either a different KEK should be used (shared with this
   smaller group) or asymmetric algorithms should be used.


1.1 Applicability to E-mail

   One primary audience for this distribution mechanism is e-mail.
   Distribution lists sometimes referred to as mail lists, have been
   defined to support distribution of messages to recipients subscribed
   to the mail list. There are two models for how the mail list can be
   used. If the originator is a member of the mail list, the originator
   sends messages encrypted with the shared KEK to the mail list (e.g.,
   listserv or majordomo) and the message is distributed to the mail
   list members. If the originator is not a member of the mail list
   (does not have the shared KEK), the originator sends the message
   (encrypted for the MLA) to the mail list agent (MLA) and the MLA
   then forms the shared KEK needed to encrypt the message. In either
   case the recipients of the mail list use the previously distributed-
   shared KEK to decrypt the message.


1.2 Applicability to Repositories

   Objects can also be distributed via a repository (e.g., Light Weight
   Directory Protocol (LDAP) servers, X.500 Directory System Agents
   (DSAs), Web-based servers). If an object is stored in a repository
   encrypted with a symmetric key algorithm, any one with the shared
   KEK and access to that object can then decrypt that object. The
   encrypted object and the encrypted, shared KEK can be stored in the
   repository.














Turner                                                               4

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

2. Architecture

   Figure 1 depicts the architecture to support symmetric key
   distribution. The Group List Agent (GLA) supports two distinct
   functions with two different agents:

     - The Key Management Agent (KMA) which is responsible for
       generating the shared KEKs.

     - The Group Management Agent (GMA) which is responsible for
       managing the Group List (GL) to which the shared KEKs are
       distributed.

     +----------------------------------------------+
     |              Group List Agent                |    +-------+
     | +------------+    + -----------------------+ |    | Group |
     | |    Key     |    | Group Management Agent | |<-->| List  |
     | | Management |<-->|     +------------+     | |    | Owner |
     | |   Agent    |    |     | Group List |     | |    +-------+
     | +------------+    |     +------------+     | |
     |                   |       /  |  \          | |
     |                   +------------------------+ |
     +----------------------------------------------+
                              /     |      \
                 +----------+ +---------+ +----------+
                 | Member 1 | |   ...   | | Member n |
                 +----------+ +---------+ +----------+

          Figure 1 - Key Distribution Architecture


   A GLA may support multiple KMAs. A GLA in general supports only one
   GMA, but the GMA may support multiple GLs. Multiple KMAs may support
   a GMA in the same fashion as GLAs support multiple KMAs. Assigning a
   particular KMA to a GL is beyond the scope of this document.

   Modeling real world GL implementations shows that there are very
   restrictive GLs, where a human determines GL membership, and very
   open GLs, where there are no restrictions on GL membership. To
   support this spectrum, the mechanism described herein supports both
   managed (i.e., where access control is applied) and unmanaged (i.e.,
   where no access control is applied) GLs. The access control
   mechanism for managed lists is beyond the scope of this document.

   In either case, the GL must initially be constructed by an entity
   hereafter called the Group List Owner (GLO). There may be multiple
   entities who 'own' the GL and who are allowed to make changes the
   GL's properties or membership. The GLO determines if the GL will be
   managed or unmanaged and is the only entity that may delete the GL.
   GLO(s) may or may not be GL members.



Turner                                                               5

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   Though Figure 1 depicts the GLA as encompassing both the KMA and GMA
   functions, the two functions could be supported by the same entity
   or they could be supported by two different entities. If two
   entities are used, they could be located on one or two platforms.
   There is however a close relationship between the KMA and GMA
   functions. If the GMA stores all information pertaining to the GLs
   and the KMA merely generates keys, a corrupted GMA could cause
   havoc. To protect against a corrupted GMA, the KMA would be forced
   to double check the requests it receives to ensure the GMA did not
   tamper with them. These duplicative checks blur the functionality of
   the two components together. For this reason, the interactions
   between the KMA and GMA are beyond the scope of this document.
   Proprietary mechanisms may be used to separate the functions by
   strengthening the trust relationship between the two entities.
   Henceforth, the distinction between the two agents is omitted; the
   term GLA will be used to address both functions. It should be noted
   that corrupt GLA can always cause havoc.


3. Protocol Interactions

   There are existing mechanisms (e.g., listserv and majordomo) to
   support managing GLs; however, this document does not address
   securing these mechanisms, as they are not standardized. Instead, it
   defines protocol interactions, as depicted in Figure 2, used by the
   GL members, GLA, and GLO to manage GLs and distribute shared KEKs.
   The interactions have been divided into administration messages and
   distribution messages. The administrative messages are the request
   and response messages needed to setup the GL, delete the GL, add
   members to the GL, delete members of the GL, and request a group
   rekey, etc. The distribution messages are the messages that
   distribute the shared KEKs. The following paragraphs describe the
   ASN.1 for both the administration and distribution messages.
   Paragraph 4 describes how to use the administration messages and
   paragraph 5 describes how to use the distribution messages.

                    +-----+                   +----------+
                    | GLO | <---+      +----> | Member 1 |
                    +-----+     |      |      +----------+
                                |      |
                 +-----+ <------+      |      +----------+
                 | GLA | <-------------+----> |   ...    |
                 +-----+               |      +----------+
                                       |
                                       |      +----------+
                                       +----> | Member n |
                                              +----------+

                      Figure 2 - Protocol Interactions




Turner                                                               6

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

3.1 Control Attributes

   The messages are based on including control attributes in CMC's
   PKIData for requests and CMC's ResponseBody0 for responses. The
   content-types PKIData and PKIResponse are then encapsulated in CMS's
   SignedData or EnvelopedData, or a combination of the two (see
   paragraph 3.2). The following are the control attributes defined in
   this document:

         Control
        Attribute          OID          Syntax
   -------------------  ----------- -----------------
    glUseKEK            id-skd 1    GLUseKEK
    glDelete            id-skd 2    GeneralName
    glAddMember         id-skd 3    glAddMember
    glDeleteMember      id-skd 4    GLDeleteMember
    glRekey             id-skd 5    GLRekey
    glAddOwner          id-skd 6    GLOwnerAdministration
    glRemoveOwner       id-skd 7    GLOwnerAdministration
    glkCompromise       id-skd 8    GeneralName
    glkRefresh          id-skd 9    GeneralName
    glSuccessInfo       id-skd 10   GLSuccessInfo
    glFailInfo          id-skd 11   GLFailInfo
    glaQueryRequest     id-skd 12   GLAQueryRequest
    glaQueryResponse    id-skd 13   GLAQueryResponse
    glProvideCert       id-skd 14   GLProvideCert
    glUpdateCert        id-skd 15   GLUpdateCert
    glKey               id-skd 16   GLKey

   The following are the implementation requirements for the control
   attributes defined herein:

           Implementation Requirement         |   Control
     GLO    |        GLA          | GL Member |  Attribute
   O    R   | O      R       F    | O    R    |
   -------- | ------------------  | --------- | ----------
   MAY  N/A | N/A    MAY     N/A  | N/A  N/A  | glUseKEK
   MAY  N/A | N/A    MAY     N/A  | N/A  N/A  | glDelete
   MAY  MAY | N/A    MUST    MAY  | N/A  MUST | glAddMember
   MAY  MAY | N/A    MUST    MAY  | N/A  MUST | glDeleteMember
   MAY  N/A | N/A    MAY     N/A  | N/A  N/A  | glRekey
   MAY  N/A | N/A    MAY     N/A  | N/A  N/A  | glAddOwner
   MAY  N/A | N/A    MAY     N/A  | N/A  N/A  | glRemoveOwner
   MAY  MAY | N/A    MUST    MAY  | MUST N/A  | glkCompromise
   MAY  N/A | N/A    MUST    N/A  | MUST N/A  | glkRefresh
   N/A  MAY | MUST   N/A     N/A  | N/A  MUST | glSucessInfo
   N/A  MAY | MUST   N/A     N/A  | N/A  MUST | glFailInfo
   MAY  N/A | N/A    SHOULD  N/A  | MAY  MAY  | glaQueryRequest
   N/A  MAY | SHOULD N/A     N/A  | MAY  MAY  | glaQueryResponse
   MAY  N/A | MUST   N/A     MAY  | N/A  MUST | glProvideCert
   N/A  MAY | N/A    MUST    MAY  | MUST N/A  | glUpdateCert
   N/A  N/A | MUST   N/A     N/A  | N/A  MUST | glKey

Turner                                                               7

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


   glSuccessInfo, glFailInfo, glaQueryResponse, and gloResponse are
   responses and go into the PKIResponse content-type, all other
   control attributes are included in requests and go into the PKIData
   content-type. The exception is glUpdateCert which may be included in
   either PKIData or PKIResponse.


3.1.1 GL USE KEK

   The GLO uses glUseKEK to request that a shared KEK be assigned to a
   GL. glUseKEK messages MUST be signed by the GLO. The glUseKEK
   control attribute shall have the syntax GLUseKEK:

   GLUseKEK ::= SEQUENCE {
     glInfo                    GLInfo,
     glOwnerInfo               SEQUENCE SIZE (1..MAX) OF GLOwnerInfo,
     glAdministration          GLAdministration DEFAULT (1),
     glKeyAttributes       [0] GLKeyAttributes OPTIONAL }

   GLInfo ::= SEQUENCE {
     glName     GeneralName,
     glAddress  GeneralName }

   GLOwnerInfo ::= SEQUENCE {
     glOwnerName     GeneralName,
     glOwnerAddress  GeneralName }

   GLAdministration ::= INTEGER {
     unmanaged  (0),
     managed    (1),
     closed     (2) }

   GLKeyAttributes ::= SEQUENCE {
     rekeyControlledByGLO   [0] BOOLEAN DEFAULT FALSE,
     recipientMutuallyAware [1] BOOLEAN DEFAULT TRUE,
     duration               [2] INTEGER DEAULT (0),
     generationCounter      [3] INTEGER DEFAULT (2),
     requestedAlgorithm     [4] AlgorithmIdentifier
                                 DEFAULT (id-alg-CMS3DESwrap) OPTIONAL
   }


   The fields in GLUseKEK have the following meaning:

     - glInfo indicates the GL's name in glName and the GL's address in
       glAddress. In some instances the glName and glAddress may be the
       same, but this is not always the case. The name and address MUST
       be unique for a given GLA.

     - glOwnerInfo indicates the GL owner's name in glOwnerName and the
       GL owner's address in glOwnerAddress. One of the names in

Turner                                                               8

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

       glOwnerName MUST match one of the names in the certificate used
       to sign this SignedData.PKIData creating the GL (i.e., the
       immediate signer). Multiple GLOs MAY be indicated if
       glAdministration is set to managed or closed.

     - glAdministration indicates how the GL should be administered.
       The default is for the list to be managed. Three values are
       supported for glAdministration:

       - Unmanaged - When the GLO sets glAdministration to unmanaged,
         they are allowing prospective members to request being added
         and deleted from the GL without GLO intervention. They are
         also indicating that only one GLO may be associated at any one
         time with the GL.

       - Managed - When the GLO sets glAdministration to managed, they
         are allowing prospective members to request being added to and
         deleted from the GL, but the request is redirected by the GLA
         to GLO for review. The GLO makes the determination as to
         whether to honor the request.

       - Closed - When the GLO sets glAdministration to closed, they
         are not allowing prospective members to request being added to
         or deleted from the GL. The GLA will only accept glAddMember
         and glDeleteMember requests from the GLO.

     - glKeyAttributes indicates the attributes the GLO wants the GLA
       to assign to the shared KEK. If this field is omitted, GL rekeys
       will be controlled by the GLA, the recipients are allowed to
       know about one another, the algorithm will Triple-DES (see
       paragrpah 7), the shared KEK will be valid for a calendar month
       (i.e., first of the month until the last day of the month), and
       two shared KEKs will be distributed initially. The fields in
       glKeyAttributes have the following meaning:

       - rekeyControlledByGLO indicates whether the GL rekey messages
         will be generated by the GLO or by the GLA. The default is for
         the GLA to control rekeys. If GL rekey is controlled by the
         GLA, the GL will continue to be rekeyed until the GLO deletes
         the GL or changes the GL rekey to be GLO controlled.

       - recipientsMutuallyAware indicates that the GLO wants the GLA
         to distribute the shared KEK individually for each of the GL
         members (i.e., a separate glKey message is sent to each
         recipient). The default is for separate glKey message to not
         be required.

         NOTE: This supports lists where one member does not know the
         identities of the other members. For example, a list is
         configured granting submit permissions to only one member. All
         other members are 'listening.' The security policy of the list
         does not allow the members to know who else is on the list. If

Turner                                                               9

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

         a glKey is constructed for all of the GL members, information
         about each of the members may be derived from the information
         in RecipientInfos. To make sure the glkey message does not
         divulge information about the other recipients, a separate
         glKey message would be sent to each GL member.

       - duration indicates the length of time (in days) during which
         the shared KEK is considered valid. The value zero (0)
         indicates that the shared KEK is valid for a calendar month.
         For example if the duration is zero (0), if the GL shared KEK
         is requested on July 24, the first key will be valid until the
         end of July and the next key will be valid for the entire
         month of August. If the value is not zero (0), the shared KEK
         will be valid for the number of days indicated by the value.
         For example, if the value of duration is seven (7) and the
         shared KEK is requested on Monday but not generated until
         Tuesday (2359); the shared KEKs will be valid from Tuesday
         (2359) to Tuesday (2359). The exact time of the day is
         determined when the key is generated.

       - generationCounter indicates the number of keys the GLO wants
         the GLA to distribute. To ensure uninterrupted function of the
         GL two (2) shared KEKs at a minimum MUST be initially
         distributed. The second shared KEK is distributed with the
         first shared KEK, so that when the first shared KEK is no
         longer valid the second key can be used. If the GLA controls
         rekey then it also indicates the number of shared KEKs the GLO
         wants outstanding at any one time. See paragraphs 4.5 and 5
         for more on rekey.

       - requestedAlgorithm indicates the algorithm and any parameters
         the GLO wants the GLA to use to generate the shared KEK. See
         paragraph 7 for more on algorithms.


3.1.2 GL Delete

   GLOs use glDelete to request that a GL be deleted from the GLA. The
   glDelete control attribute shall have the syntax GeneralName. The
   name of the GL to be deleted is included in GeneralName. The
   glDelete message MUST be signed by the GLO.


3.1.3 GL Add Member

   GLOs use glAddMember to request addition of new members and
   prospective GL members use glAddMember to request being added to the
   GL. The glAddMember message must be signed by either the GLO or the
   prospective GL member. The glAddMember control attribute shall have
   the syntax GLAddMember:



Turner                                                              10

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   GLAddMember ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   GLMember ::= SEQUENCE {
     glMemberName     GeneralName,
     glMemberAddress  GeneralName,
     certificates     Certificates }

   Certificates ::= SEQUENCE {
      membersPKC         Certificate,
                                  -- See X.509
      membersAC          SEQUENCE OF AttributeCertificate OPTIONAL,
                                  -- See X.509
      certificationPath  CertificateSet OPTIONAL }
                                  -- From CMS [2]

   CertificateSet ::= SET OF CertificateChoices

   CertificateChoices ::= CHOICE {
     certificate              Certificate,    -- See X.509
     extendedCertificate  [0] IMPLICIT ExtendedCertificate,
                                              -- Obsolete
     attrCert             [1] IMPLICIT AttributeCertificate }
                                              -- See X.509 and X9.57


   The fields in GLAddMembers have the following meaning:

     - glName indicates the name of the GL to which the member should
       be added.

     - glMember indicates the particulars for the GL member.
       glMemberName indicates the name of the GL member and
       glMemberAddress indicates the GL member's address. In some
       instances the glMemberName and glMemberAddress may be the same,
       but this is not always the case. certificates.membersPKC
       includes the member's encryption certificate that will be used
       to at least initially encrypt the shared KEK for that member.
       certificates.membersAC MAY be included to convey any attribute
       certificate associated with the member's encryption certificate.
       certificates.certificationPath MAY also be included to convey
       the certification path corresponding to the member's encryption
       and attribute certificates. The certification path is optional
       because it may already be included elsewhere in the message
       (e.g., in the outer CMS layer).


3.1.4 GL Delete Members

   GLOs use glDeleteMember to request deletion of GL members and
   prospective non-GL members use glDeleteMember to request being

Turner                                                              11

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   removed from the GL. The glDeleteMember message must be signed by
   either the GLO or the prospective GL member. The glDeleteMember
   control attribute shall have the syntax GLDeleteMember:

   GLDeleteMember ::= SEQUENCE {
     glName            GeneralName,
     glMemberToDelete  GeneralName }


   The fields in GLDeleteMembers have the following meaning:

     - glName indicates the name of the GL from which the member should
       be removed.

     - glMemberToDelete indicates the name of the member to be deleted.


3.1.5 GL Rekey

   GLOs use the glRekey to request a GL rekey. The glRekey message MUST
   be signed by the GLO. The glRekey control attribute shall have the
   syntax GLRekey:

   GLRekey ::= SEQUENCE {
     glName              GeneralName,
     glAdministration    GLAdministration OPTIONAL,
     glNewKeyAttributes  GLNewKeyAttributes OPTIONAL }

   GLNewKeyAttributes ::= SEQUENCE {
     rekeyControlledByGLO   [0] BOOLEAN OPTIONAL,
     recipientMutuallyAware [1] BOOLEAN OPTIONAL,
     duration               [2] INTEGER OPTIONAL,
     generationCounter      [3] INTEGER OPTIONAL,
     requestedAlgorithm     [4] AlgorithmIdentifier OPTIONAL }


   The fields in GLRekey have the following meaning:

     - glName indicates the name of the GL to be rekeyed.

     - glAdministration indicates if there is any change to how the GL
       should be administered. See paragraph 3.1.1 for the three
       options. This field is only included if there is a change from
       the previously registered administered.

     - glNewKeyAttributes indicates whether the rekey of the GLO is
       controlled by the GLA or GL, what algorithm and parameters the
       GLO wishes to use, the duration of the key, and how many
       outstanding keys should be issued. The field is only included if
       there is a change from the previously registered
       glKeyAttributes. If the value zero (0) is specified in
       generationCounter the GLO is indicating that it wants all of the

Turner                                                              12

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

       outstanding GL shared KEKs rekeyed. For example, suppose the GLO
       used the glUseKEK with duration set to two (2) and the glRekey
       message is sent during the first duration with generationCounter
       set to zero (0). The GLA would know to generate a glKey message
       to replace both the shared KEK currently being used and the
       shared KEK for the second duration.


3.1.6 GL Add Owner

   GLOs use the glAddOwner to request that a new GLO be allowed to
   administer the GL. In addition, a registered GLO may use the request
   to update their certificate on the GLA. In this case, the new GLO
   certificate is signed by the old GLO certificate. The glAddOwner
   message MUST be signed a registered GLO. The glAddOwner control
   attribute shall have the syntax GLOwnerAdministration:

   GLOwnerAdministration ::= SEQUENCE {
     glName       GeneralName,
     glOwnerInfo  GLOwnerInfo }

   The fields in GLAddOwners have the following meaning:

     - glName indicates the name of the GL to which the new GLO should
       be associated.

     - glOwnerInfo indicates the name and address of the new GLO.


3.1.7 GL Remove Owner

   GLOs use the glRemoveOwner to request that a GLO be disassociated
   with the GL. The glRemoveOwner message MUST be signed a registered
   GLO. Unmanaged GLs may only have one GLO. If the GLA processes a
   glRemoveOwner for an unmanaged GL, only one GLO shall be associated
   with the GL at any given time. The glRemoveOwner control attribute
   shall have the syntax GLOwnerAdministration:

   GLOwnerAdministration ::= SEQUENCE {
     glName       GeneralName,
     glOwnerInfo  GLOwnerInfo }

   The fields in GLRemoveOwners have the following meaning:

     - glName indicates the name of the GL to which the GLO should be
       disassociated.

     - glOwnerInfo indicates the name and address of the GLO to be
       removed.




Turner                                                              13

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

3.1.8 GL Key Compromise

   GL members and GLOs use glkCompromise to indicate that the shared
   KEK possessed has been compromised. The glKeyCompromise control
   attribute shall have the syntax GeneralName. The name of the GL to
   which the compromised key is associated with is included in
   GeneralName. This message is always redirected by the GLA to the GLO
   for further action. The glkCompromise MUST NOT be included in an
   EnvelopedData generated with the compromised shared KEK.


3.1.9 GL Key Refresh

   GL members use the glkRefresh to request that the shared KEK be
   redistributed to them. The glKeyRefresh control attribute shall have
   the syntax GeneralName. The GL member includes the GL's name in
   GeneralName.


3.1.10 GL Success Information

   The GLA uses glSuccessInfo to indicate a successful result of an
   administrative message. A separate glSuccessInfo is returned for
   each action (e.g., if there are four successful glAddMember requests
   then four glSuccessInfo responses are generated). The glSuccessInfo
   message MUST be signed by the GLA. The glSucessInfo control
   attribute shall have the syntax GLSucessInfo:

   GLSuccessInfo ::= SEQUENCE {
     glInfo       GLInfo,
     glIdentifier GLIdentifier,
     action       Action }

   Action ::= SEQUENCE {
     actionCode     ActionCode,
     glMemberName   [0] GeneralName OPTIONAL,
     glOwnerName    [1] GeneralName OPTIONAL }

   ActionCode ::= INTEGER {
     assignedKEK   (0),
     deletedGL     (1),
     addedMember   (2),
     deletedMember (3),
     rekeyedGL     (4),
     addedGLO      (5),
     removedGLO    (6) }


   The fields in GLSuccessInfo have the following meaning:

     - glInfo indicates the GL's name in glName and the GL's address in
       glAddress.

Turner                                                              14

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


     - glIdentifier identifies GL's unique shared KEK.

     - action indicates the successfully performed action.
       action.actionCode indicates whether the shared KEK was assigned
       to the GL, whether the GL was deleted, whether a member was
       added to a GL, whether a member was deleted from a GL, whether
       the GL was rekeyed, whether a new GLO was added, and whether a
       GLO was removed. If members were added to a GL or deleted from a
       GL the members MUST be indicated in glMemberName and glOwnerName
       MUST be omitted. If a GLO was added to a GL or deleted from a
       GL, the GLO MUST be indicated in glOwnerName and glMemberName
       MUST be omitted. If a shared KEK was assigned to a GL or a GL
       was deleted both glOwnerName and glMember MUST be omitted.


3.1.11 GL Fail Information

   The GLA uses glFailInfo to indicate that there was a problem
   performing a requested action. A separate glFailInfo is returned for
   each action (e.g., if there are four denied glAddMember requests
   then four glFailInfo responses are generated). The glFailInfo
   message MUST be signed by the GLA. The glFailInfo control attribute
   shall have the syntax GLFailInfo:

   GLFailInfo ::= SEQUENCE {
     glName        GeneralName,
     error         Error }

   Error ::= SEQUENCE {
     errorCode        ErrorCode,
     glMemberName [0] GeneralName OPTIONAL,
     glOwnerName  [1] GeneralName OPTIONAL }

   ErrorCode ::= INTEGER {
     unspecified (0),
     closedGL (1)
     unsupportedDuration (2)
     noGLACertificate (3),
     invalidCert (4),
     unsupportedAlgorithm (5),
     noGLONameMatch (6),
     invalidGLName (7),
     onlyOneGLOAllowed (8),
     nameAlreadyInUse (9),
     noSpam (10),
     deniedAccess (11),
     alreadyAMember (12),
     notAMember (13),
     alreadyAnOwner (14)
     notAnOwner (15) }


Turner                                                              15

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


   The fields in GLFailInfo have the following meaning:

     - glName indicates the name of the GL to which the error
       corresponds.

     - error indicates the reason why the GLA was unable to perform the
       request. It also indicates the GL member or GLO to which the
       error corresponds. If members were not added to a GL or deleted
       from a GL the members MUST be indicated in glMemberName. If a
       GLO was not added to a GL or deleted from a GL, the GLO MUST be
       indicated in glOwnerName. The errors are returned under the
       following conditions:

       - unspecified indicates that the GLA is unable or unwilling to
         perform the requested action and does not want to indicate
         why.

       - closedGL indicates that members can only be added or deleted
         by the GLO.

       - unsupportedDuration indicates the GLA does not support
         generating keys that are valid for the requested duration.

       - noGLACertificate indicates that the GLA does not have a valid
         certificate.

       - invalidCert indicates the member's encryption certificate was
         not verifiable (i.e., signature did not validate,
         certificate's serial number present on a CRL, etc.).

       - unsupportedAlgorithm indicates the GLA does not support the
         requested algorithm.

       - noGLONameMatch indicates that one of the names in the
         certificate used to sign a request does not match the name of
         a registered GLO.

       - invalidGLName indicates the GLA does not support the glName
         present in the request.

       - nameAlreadyInUse indicates the glName is already assigned on
         the GLA.

       - noSpam indicates the prospective GL member did not sign the
         request (i.e., if the name in glMember.glMemberName does not
         match one of the names in the certificate used to sign the
         request).

       - alreadyAMember indicates the prospective GL member is already
         a GL member.


Turner                                                              16

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

       - notAMember indicates the prospective non-GL member is not a GL
         member.

       - alreadyAnOwner indicates the prospective GLO is already a GLO.

       - notAnOwner indicates the prospective non-GLO is not a GLO.


3.1.12 GLA Query Request

   GLOs and GL members use the glaQueryRequest to ascertain information
   about the GLA. The glaQueryRequest control attribute shall have the
   syntax GLAQueryRequest:

   GLAQueryRequest ::= SEQUENCE {
     glaRequestType   OBJECT IDENTIFIER,
     glaRequestValue  ANY DEFINED BY glaResponseType }


   One request type is defined herein to support the GLO in determining
   the algorithms supported by the GLA:

   id-rt-algorithmSupported { id-tbd }

   There is no value defined for id-rt-algorithmSupported. Including
   the id-rt-algorithmSupport indicates that the GLO wishes to know the
   algorithms that the GLA supports.


3.1.13 GLA Query Response

   GLA's return the glaQueryResponse after receiving a GLAQueryRequest.
   The glaQueryResponse MUST be signed by a GLA. The glaQueryResponse
   control attribute shall have the syntax GLAQueryResponse:

   GLAQueryResponse ::= SEQUENCE {
     glaResponseType   OBJECT IDENTIFIER,
     glaResponseValue  ANY DEFINED BY glaResponseType }

   One response type is defined herein for the GLA to indicate the
   algorithms it supports:

   smimeCapabilities OBJECT IDENTIFIER ::=
   {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 15}
   -- Identifies the algorithms supported by the GLA (see MsgSpec [5])


3.1.14 GL Provide Cert

   GLAs and GLOs use glProvideCert to request that a GL member provide
   an updated or new encryption certificate. The glProvideCert message
   MUST be signed by either GLA or GLO. If the GL member's PKC has been

Turner                                                              17

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   revoked, the GLO or GLA MUST NOT use it to generate the
   EnvelopedData that encapsulates the glProvideCert request. The
   glProvideCert control attribute shall have the syntax GLProvideCert:

   GLProvideCert ::= SEQUENCE {
     glName        GeneralName,
     glMemberName  GeneralName}

   The fields in GLProvideCert have the following meaning:

     - glName indicates the name of the GL to which the GL member's new
       certificate should be associated.

     - glMemberName indicates name of the GL member.


3.1.15 GL Update Cert

   GL members use glUpdateCert to provide a new certificate for the GL.
   GL members may generate a glUpdateCert unsolicited or as a result of
   a glProvideCert message. GL members MUST sign the glUpdateCert. If
   the GL member's encryption certificate has been revoked, the GL
   member MUST NOT use it to generate the EnvelopedData that
   encapsulates the glUpdateCert request or response. The glUpdateCert
   control attribute shall have the syntax GLUpdateCert:

   GLUpdateCert ::= SEQUENCE {
     glName    GeneralName,
     glMember  GLMember }

   The fields in GLUpdateCert have the following meaning:

     - glName indicates the name of the GL to which the GL member's new
       certificate should be associated.

     - glMemberCert indicates the particulars for the GL member.
       glMemberName indicates the GL member's name and glMemberAddress
       indicates the GL member's address. certificates.membersPKC
       includes the member's encryption certificate that will be used
       to encrypt the shared KEK for that member.
       certificates.membersAC MAY be included to convey any attribute
       certificate associated with the member's encryption certificate.
       certificates.certificationPath MAY also be included to convey
       the certification path corresponding to the member's encryption
       and attribute certificates. The certification path is optional
       because it may already be included elsewhere in the message
       (e.g., in the outer CMS layer).






Turner                                                              18

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

3.1.16 GL Key

   The GLA uses glKey to distribute the shared KEK. The glKey message
   MUST be signed by the GLA. The glKey control attribute shall have
   the syntax GLKey:

   GLKey ::= SEQUENCE {
     glName        GeneralName,
     glIdentifier  OCTET STRING,
     glkWrapped    RecipientInfos,      -- See CMS [2]
     glkAlgorithm  AlgorithmIdentifier,
     glkNotBefore  GeneralizedTime,
     glkNotAfter   GeneralizedTime }


   The fields in GLKey have the following meaning:

     - glName is the name of the GL.

     - glIdentifier is the key identifier of the shared KEK. When GL
       members use the shared KEK to encrypt data objects for other GL
       members, they place the glIdentifier in
       RecipientInfo.kekri.kekid.keyIdentifier field. Two options are
       provided to generate a unique key identifier. The first choice
       concatenates the GLA's subject name from the digital signature
       certificate used to sign the glKey message and counter. The
       second choice concatenates the GLA's subjectKeyIdentifier, from
       the digital signature certificate used to sign the glKey
       message, and a counter. The second choice must be supported.

     - glkWrapped is the GL's wrapped shared KEK. The RecipientInfos
       shall be generated as specified in paragraph 6.2 of CMS [2]. The
       kari RecipientInfo choice MUST be supported. The EncryptedKey
       field, which is the shared KEK, MUST be generated according to
       the paragraph concerning random number generation in the
       security considerations of CMS [2].

     - glkAlgorithm identifies the algorithm the shared KEK is used
       with.

     - glkNotBefore indicates the date at which the shared KEK is
       considered valid. GeneralizedTime values MUST be expressed UTC
       (Zulu) and MUST include seconds (i.e., times are
       YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
       GeneralizedTime values MUST NOT include fractional seconds.

     - glkNotAfter indicates the date after which the shared KEK is
       considered invalid. GeneralizedTime values MUST be expressed UTC
       (Zulu) and MUST include seconds (i.e., times are
       YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
       GeneralizedTime values MUST NOT include fractional seconds.


Turner                                                              19

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   If the glKey message is in response to a glUseKEK message:

     - The GLA MUST generate separate glKey messages for each recipient
       if glUseKEK.glKeyAttributes.recipientMutuallyAware is set to
       FALSE.

     - The GLA MUST generate X number of glKey messages, where X is the
       value in glUseKEK.glKeyAttributes.generationCounter.

   If the glKey message is in response to a glRekey message:

     - The GLA MUST generate separate glKey messages for each recipient
       if glRekey.glNewKeyAttributes.recipientMutuallyAware is set to
       FALSE.

     - The GLA MUST generate X number of glKey messages, where X is the
       value in glUseKEK.glKeyAttributes.generationCounter. If the
       value is zero (0), the GLA MUST generate X number of glKey
       messages, where X is the number of outstanding shared KEKs for
       the GL (e.g., if there are two outstanding shared KEK and the
       generationCounter for the glUseKEK message was set to three then
       two glKey messages are generated).

   If the glKey message was not in response to a glRekey or glUseKEK
   (e.g., where the GLA controls rekey):

     - The GLA MUST generate separate glKey messages for each recipient
       if glUseKEK.glNewKeyAttributes.recipientMutuallyAware that set
       up the GL was set to FALSE.

     - The GLA MUST generate X glKey messages prior to the duration on
       the last outstanding shared KEK expiring, where X is the
       generationCounter minus one (1).


3.2 Use of CMC, CMS, and PKIX

   The following paragraphs outline the use of CMC, CMS, and PKIX.


3.2.1 Protection Layers

   The following paragraphs outline the protection required for the
   control attributes defined herein.









Turner                                                              20

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

3.2.1.1 Minimum Protection

   At a minimum, a SignedData MUST protect each request and response
   encapsulated in PKIData and PKIResponse. The following is a
   depiction of the minimum wrappings:

     Minimum Protection
     ------------------
     SignedData
      PKIData or PKIResponse
       controlSequence


   Prior to taking any action on any request or response SignedData(s)
   MUST be processed according to CMS [2].


3.2.1.2 Additional Protection

   An additional EnvelopedData MAY also be used to provide
   confidentiality of the request and response. An additional
   SignedData MAY also be added to provide authentication and integrity
   of the encapsulated EnvelopedData. The following is a depiction of
   the optional additional wrappings:

     Confidentiality Protection     A&I of Confidentiality Protection
     --------------------------     ---------------------------------
     EnvelopedData                  SignedData
      SignedData                     EnvelopedData
       PKIData or PKIResponse         SignedData
        controlSequence                PKIData or PKIResponse
                                        controlSequence


   If an incoming message was encrypted, the corresponding outgoing
   message MUST also be encrypted. All EnvelopedData objects MUST be
   processed as specified in CMS [2].

   If the GLO or GL member applies confidentiality to a request, the
   EnvelopedData MUST be encrypted for the GLA. If the GLA is to
   forward the GL member request to the GLO, the GLA decrypts the
   EnvelopedData, strips the confidentiality layer off, and applies its
   own confidentiality layer for the GLO.


3.2.2 Combining Requests and Responses

   Mutlipe requests and response corresponding to a GL MAY be included
   in one PKIData.controlSequence or PKIResponse.controlSequence.
   Requests and responses for multiple GLs MAY be combined in one
   PKIData or PKIResponse by using PKIData.cmsSequence and
   PKIResponse.cmsSequence. A separate cmsSequence MUST be used for

Turner                                                              21

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   different GLs (i.e., requests corresponding to two different GLs are
   included in different cmsSequences). The following is a diagram
   depicting multiple requests and responses combined in one PKIData
   and PKIResponse:

         Multiple Request and Response
     Request                        Response
     -------                        --------
     SignedData                      SignedData
      PKIData                         PKIResponse
       cmsSequence                     cmsSequence
        SignedData                      SignedData
         PKIData                         PKIResponse
          controlSequence                 controlSequence
           Zero or more requests          Zero or more responses
           corresponding to one GL.        corresponding to one GL.
        SignedData                      SignedData
         PKIData                         PKIResponse
          controlSequence                 controlSequence
           Zero or more requests          Zero or more responses
           corresponding to another GL.   corresponding to another GL.


   When applying confidentiality to multiple requests and responses,
   all of the requests/response MAY be included in one EnvelopedData.
   The following is a depiction:

       Confidentiality of Multiple Requests and Responses
     Wrapped Together
     ----------------
     EnvelopedData
      SignedData
       PKIData
        cmsSequence
         SignedData
          PKIResponse
           controlSequence
            Zero or more requests
            corresponding to one GL.
         SignedData
          PKIData
           controlSequence
            Zero or more requests
            corresponding to one GL.









Turner                                                              22

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   Certain combinations of requests in one PKIData.controlSequence and
   one PKIResponse.controlSequence are not allowed. The invalid
   combinations listed here MUST NOT be generated:

        Invalid Combinations
     ---------------------------
     glUseKEK   & glDeleteMember
     glUseKEK   & glRekey
     glUseKEK   & glDelete
     glDelete   & glAddMember
     glDelete   & glDeleteMember
     glDelete   & glRekey
     glDelete   & glAddOwner
     glDelete   & glRemoveOwner
     glFailInfo & glKey


   To avoid unnecessary errors, certain requests and responses should
   be processed prior to others. The following is the priority of
   message processing, if not listed it is an implementation decision
   as to which to process first: glUseKEK before glAddMember, glRekey
   before glAddMember, and glDeleteMember before glRekey.


3.2.3 GLA Generated Messages

   When the GLA generates a glSuccessInfo, it generates one for each
   request. action.actionCode values of assignedKEK, deletedGL,
   rekeyedGL, addedGLO, and deletedGLO are not returned to GL members.
   Likewise, when the GLA generates glFailInfo it generates one each
   request. error values of unsupportedDuration,
   unsupportedDeliveryMethod, unsupportedAlgorithm, noGLONameMatch,
   nameAlreadyInUse, alreadyAnOwner, notAnOwner are not returned to GL
   members.

   If GLKeyAttributes.recipientMutuallyAware is set to FALSE, a
   separate PKIResponse.glSucessInfo, PKIResponse.glFailInfo, and
   PKIData.glKey MUST be generated for each recipient.

   If the GL has multiple GLOs, the GLA MUST send the glSuccessInfo and
   glFailInfo messages to the requesting GLO. The mechanism another GLO
   to determine which GLO made the request is beyond the scope of this
   document.










Turner                                                              23

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   If a GL is managed and the GLA receives a glAddMember,
   glDeleteMember, or glkCompromise message, the GLA redirects the
   request to the GLO for review. An additional, SignedData MUST be
   applied to the redirected request as follows:

     GLA Forwarded Requests
     ----------------------
     SignedData
      PKIData
        cmsSequence
          PKIData
            controlSequence


3.2.4 CMC Control Attributes

   Certain control attributes defined in CMC [3] are allowed; they are
   as follows: cMCStatusInfo, transactionId, senderNonce,
   recipientNonce, and queryPending.

   cMCStatusInfo is used by GLAs to indicate to GLOs and GL members
   whether a request was or was not successfully completed. If the
   request was successful, the GLA returns a cMCStatusInfo response
   with cMCStatus.success and optionally other pertinent information in
   stutsString. If the response was not successful, the GLA returns a
   cMCStatusInfo response with cMCStatus.failed and optionally other
   pertinent information in statusString.

   When the GL is managed and the GLO has reviewed GL member initiated
   glAddMember, glDeleteMember, and glkComrpomise requests, the GLO
   uses cMCStatusInfo to indicate the success or failure of the
   request. If the request is allowed, cMCStatus.success is returned
   and statusString is optionally returned to convey additional
   information. If the request is denied, cMCStatus.failed is returned
   and statusString is optionally returned to convey additional
   information.

   cMCStatusInfo is used by GLOs, GLAs, and GL members to indicate that
   signature verification failed. If the signature failed to verify,
   the cMCStatusInfo control attribute MUST be returned indicating
   cMCStatus.failed and otherInfo.failInfo.badMessageCheck. If the
   signature over the outermost PKIData failed, the bodyList value is
   zero (0). If the signature over any other PKIData failed the
   bodyList value is the bodyPartId value from the request or response.

   [Not sure the above is completely correct.]

   cMCStatusInfo is also used by GLOs and GLAs to indicate that a
   request could not be performed immediately. If the request could not
   be processed immediately by the GLA or GLO, the cMCStatusInfo
   control attribute MUST be returned indicating cMCStatus.pending and
   otherInfo.pendInfo. When requests are redirected to the GLO for

Turner                                                              24

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   approval (for managed lists), the GLA MUST NOT return a
   cMCStatusInfo indicating query pending.

   cMCStatusInfo is also used by GLAs to indicate that a
   glaQueryRequest is not supported. If the glaQueryRequest is not
   supported, the cMCStatusInfo control attribute MUST be returned
   indicating cMCStatus.noSupport and statusString is optionally
   returned to convey additional information.

   transactionId MAY be included by GLOs, GLAs, or GL members to
   identify a given transaction. All subsequent requests and responses
   related to the original request MUST include the same transactionId
   control attribute. If GL members include a transactionId and the
   request is redirected to the GLO, the GLA MAY include an additional
   transactionId in the outer PKIData. If the GLA included an
   additional transactionId in the outer PKIData, when the GLO
   generates a cMCStatusInfo response it generates one for the GLA with
   the GLA's transactionId and one for the GL member with the GL
   member's transactionId.

   senderNonce and recipientNonce (see paragraph 5.6 of [3]) MAY be
   used to provide application-level replay prevention. Originating
   messages include only a value for senderNonce. If a message includes
   a senderNonce, the response MUST include the transmitted value of
   the previously received senderNonce as recipientNonce and include a
   new value for senderNonce. If GL members include a senderNonce and
   the request is redirected to the GLO, the GLA MAY include an
   additional senderNonce in the outer PKIData. If the GLA included an
   additional senderNonce in the outer PKIData, when the GLO generates
   the response:

     - It generates one for the GLA by including the senderNonce from
       the GLA as the recipientNonce and includes a new value for
       senderNonce

     - It generates one for the GL member by including the senderNonce
       from the GL member as the recipientNonce and includes a new
       value for senderNonce. The value of this senderNonce MUST be
       different than the value in the senderNonce returned to the GLA.

   The following is the implementation requirement for the CMC control
   attributes:

           Implementation Requirement         |   Control
     GLO    |        GLA          | GL Member |  Attribute
   O    R   | O      R       F    | O    R    |
   -------- | ------------------  | --------- | ----------
   MUST MUST| MUST   MUST    N/A  | MUST MUST | cMCStatus
   MAY  MAY | MAY    MAY     N/A  | MAY  MAY  | transactionId
   MAY  MAY | MAY    MAY     N/A  | MAY  MAY  | senderNonce
   MAY  MAY | MAY    MAY     N/A  | MAY  MAY  | recepientNonce


Turner                                                              25

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


3.2.5 Resubmitted GL Member Messages

   When the GL is managed the GLA forwards GL member requests to the
   GLO for GLO approval. If the GLO approves the request it reforms the
   glAddMember, glDeleteMember, or glkCompromise message by stripping
   of the GL member's signature and resigning the request.


3.2.6 PKIX

   Signatures, certificates, and CRLs are verified according to PKIX
   [6].

   Name matching is performed according to PKIX [6].


4 Administrative Messages

   There are a number of administrative messages that must be performed
   to manage a GL. The following sections describe each of messages'
   request and response combinations in detail. The procedures defined
   in this paragraph are not prescriptive.


4.1 Assign KEK To GL

   Prior to generating a group key, a GL MUST be setup and a shared KEK
   assigned to the GL. Figure 3 depicts the protocol interactions to
   setup and assign a shared KEK. Note that error messages are not
   depicted in Figure 3.

                 +-----+   1    2  +-----+
                 | GLA | <-------> | GLO |
                 +-----+           +-----+

                Figure 3 - Create Group List


   The process is as follows:

     1 - The GLO is the entity responsible for requesting the creation
         of the GL. The GLO sends a
         SignedData.PKIData.controlSequence.glUseKEK request to the GLA
         (1 in Figure 3). The GLO MUST include: glName, glAddress,
         glOwnerName, glOwnerAddress, and glAdministration. The GLO MAY
         also include their preferences for the shared KEK in
         glKeyAttributes by indicating whether the GLO controls the
         rekey in rekeyControlledByGLO, whether separate glKey messages
         should be sent to each recipient in recipientMutuallyAware,
         the requested algorithm to be used with the shared KEK in
         requestedAlgorithm, the duration of the shared KEK, and how

Turner                                                              26

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

         many shared KEKs should be initially distributed in
         generationCounter.

     1.a - If the GLO knows of members to be added to the GL, the
           glAddMember request MAY be included in the same
           controlSequence as the glUseKEK request (see paragraph
           3.2.2). The GLO MUST indicate the same glName in the
           glAddMember request as in glUseKEK.glInfo.glName. Further
           glAddMember procedures are covered in paragraph 4.3.

     1.b - The GLO MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.c - The GLO MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the request, the GLA verifies the signature on
         the inner most SignedData.PKIData. If an additional SignedData
         and/or EnvelopedData encapsulates the request (see paragraphs
         3.2.1.2 and 3.2.2), the GLA MUST verify the outer signature(s)
         and/or decrypt the outer layer(S) prior to verifying the
         signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify but the GLA does not
           have a valid certificate, the GLA MUST return a
           glFailInfo.errorCode.noValidGLACertificate.

     2.c - If the signature(s) does(do) verify and the GLA does have a
           valid certificate, the GLA MUST check that one of the names
           in the certificate used to sign the request matches one of
           the names in glUseKEK.glOwnerInfo.glOwnerName.

     2.c.1 - If the names do not match, the GLA MUST return a response
             indicating glFailInfo.errorCode.noGLONameMatch.

     2.c.2 - If names do all match, the GLA MUST ensure the requested
             glName is not already in use. The GLA MUST also check any
             glAddMember included within the controlSequence with this
             glUseKEK. Further processing of the glAddMember is covered
             in paragraph 4.3.

     2.c.2.a - If the glName is already in use the GLA MUST return a
               response indicating
               glFailInfo.errorCode.nameAlreadyInUse.




Turner                                                              27

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.c.2.b - If the requestedAlgorithm is not supported, the GLA MUST
               return a response indicating
               glFailInfo.errorCode.unsupportedAlgorithm.

     2.c.2.c - If the duration is not supportable, determining this is
               beyond the scope of this document, the GLA MUST return a
               response indicating
               glFailInfo.errorCode.unsupportedDuration.

     2.c.2.d - If the glAdministration is set to closed (0) and there
               is more than one GLO in glOwner, the GLA MUST return a
               response indicating
               glFailInfo.errorCode.onlyOneGLOAllowed.

     2.c.2.e - If the GL is not supportable for other reasons, which
               the GLA does not wish to disclose, the GLA MUST return a
               response indicating glFailInfo.errorCode.unspecified.

     2.c.2.f - If the glName is not already in use, the duration is
               supportable, and the requestedAlgorithm is supported,
               the GLA MUST return a glSuccessInfo indicating the
               glName, the corresponding glIdentifier, and an
               action.actionCode.assignedKEK (2 in Figure 3). The GLA
               also takes administrative actions, which are beyond the
               scope of this document, to store the glName, glAddress,
               glKeyAttributes, glOwnerName, and glOwnerAddress. The
               GLA also sends a glKey message as described in paragraph
               5.

     2.c.2.f.1 - The GLA MUST apply confidentiality to the response by
                 encapsulating the SignedData.PKIResponse in an
                 EnvelopedData if the request was encapsulated in an
                 EnvelopedData (see paragraph 3.2.1.2).

     2.c.2.f.2 - The GLA MAY also optionally apply another SignedData
                 over the EnvelopedData (see paragraph 3.2.1.2).

     3 - Upon receipt of the glSuccessInfo or glFailInfo responses, the
         GLO verifies the GLA's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     3.a - If the signatures do not verify, the GLO MUST return a
           cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signatures do verify and the response was
           glSuccessInfo, the GLO has successfully created the GL.



Turner                                                              28

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     3.c - If the signatures do verify and the response was glFailInfo,
           the GLO MAY reattempt to create the GL using the information
           provided in the glFailInfo response. The GLO may also use
           the glaQueryRequest to determine the algorithms and other
           characteristics supported by the GLA (see paragraph 4.9).


4.2 Delete GL From GLA

   From time to time, there are instances when a GL is no longer
   needed. In this case the GLO must delete the GL. Figure 4 depicts
   that protocol interactions to delete a GL.

                  +-----+   1    2  +-----+
                  | GLA | <-------> | GLO |
                  +-----+           +-----+

                 Figure 4 - Delete Group List


   The process is as follows:

     1 - The GLO is the entity responsible for requesting the deletion
         of the GL. The GLO sends a
         SignedData.PKIData.controlSequence.glDelete request to the GLA
         (1 in Figure 4). The name of the GL to be deleted MUST be
         included in GeneralName.

     1.a - The GLO MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.b - The GLO MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the request the GLA verifies the signature on
         the inner most SignedData.PKIData. If an additional SignedData
         and/or EnvelopedData encapsulates the request (see paragraph
         3.2.1.2 or 3.2.2), the GLA MUST verify the outer signature
         and/or decrypt the outer layer prior to verifying the
         signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST make sure
           the GL is supported by checking the GL's Name matches a
           glName stored on the GLA.




Turner                                                              29

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.b.1 - If the glName is not supported by the GLA, the GLA MUST
             return a response indicating
             glFailInfo.errorCode.invalidGLName.

     2.b.2 - If the glName is supported by the GLA, the GLA MUST ensure
             a registered GLO signed the glDelete request by checking
             if one of the names present in the digital signature
             certificate used to sign the glDelete request matches a
             registered GLO.

     2.b.2.a - If the names do not match, the GLA MUST return a
               response indicating glFailInfo.errorCode.noGLONameMatch.

     2.b.2.b - If the names do match but the GL is not deletable for
               other reasons, which the GLA does not wish to disclose,
               the GLA MUST return a response indicating
               glFailInfo.errorCode.unspecified. Actions beyond the
               scope of this document must then be taken to delete the
               GL from the GLA.

     2.b.2.c - If the names do match, the GLA MUST return a
               glSuccessInfo indicating the glName, and an
               action.actionCode.deletedGL (2 in Figure 4).
               glMemberName and glOwnerName MUST be omitted. The GLA
               MUST not accept further requests for member additions,
               member deletions, or group rekeys for this GL.

     2.b.2.c.1 - The GLA MUST apply confidentiality to the response by
                 encapsulating the SignedData.PKIResponse in an
                 EnvelopedData if the request was encapsulated in an
                 EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.c.2 - The GLA MAY also optionally apply another SignedData
                 over the EnvelopedData (see paragraph 3.2.1.2).

     3 - Upon receipt of the glSuccessInfo or glFailInfo response, the
         GLO verifies the GLA's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signatures do verify and the response was
           glSuccessInfo, the GLO has successfully deleted the GL.

     3.c - If the signatures do verify and the response was glFailInfo,
           the GLO MAY reattempt to delete the GL using the information
           provided in the glFailInfo response.

Turner                                                              30

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000



4.3 Add Members To GL

   To add members to GLs, either the GLO or prospective members use the
   glAddMember request. The GLA processes GLO and prospective GL member
   requests differently though. GLOs can submit the request at any time
   to add members to the GL, and the GLA, once it has verified the
   request came from a registered GLO, should process it. If a
   prospective member sends the request, the GLA needs to determine how
   the GL is administered. When the GLO initially configured the GL,
   they set the GL to be unmanaged, managed, or closed (see paragraph
   3.1.1). In the unmanaged case, the GLA merely processes the member's
   request. For the managed case, the GLA forwards the requests from
   the prospective members to the GLO for review. Where there are
   multiple GLOs for a GL, which GLO the request is forwarded to is
   beyond the scope of this document. The GLO reviews the request and
   either rejects it or submits a reformed request to the GLA. In the
   closed case, the GLA will not accept requests from prospective
   members. The following paragraphs describe the processing for the
   GLO(s), GLA, and prospective GL members depending on where the
   glAddMeber request originated, either from a GLO or from prospective
   members. Figure 5 depicts the protocol interactions for the three
   options. Note that the error messages are not depicted.

                +-----+  2,B{A}              3  +----------+
                | GLO | <--------+    +-------> | Member 1 |
                +-----+          |    |         +----------+
                         1       |    |
                +-----+ <--------+    |      3  +----------+
                | GLA |  A            +-------> |   ...    |
                +-----+ <-------------+         +----------+
                                      |
                                      |      3  +----------+
                                      +-------> | Member n |
                                                +----------+

                   Figure 5 - Member Addition

   An important decision that needs to be made on a group by group
   basis is whether to rekey the group every time a new member is
   added. Typically, unmanaged GLs should not be rekeyed when a new
   member is added, as the overhead associated with rekeying the group
   becomes prohibitive, as the group becomes large. However, managed
   and closed GLs MUST be rekeyed to maintain the secrecy of the group.
   An option to rekeying managed or closed GLs when a member is added
   is to generate a new GL with a different group key. Group rekeying
   is discussed in paragraphs 4.5 and 5.





Turner                                                              31

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

4.3.1 GLO Initiated Additions

   The process for GLO initiated glAddMember requests is as follows:

     1 - The GLO collects the pertinent information for the member(s)
         to be added (this MAY be done through an out of bands means).
         The GLO then sends a SignedData.PKIData.controlSequence with a
         separate glAddMember request for each member to the GLA (1 in
         Figure 5). The GLO MUST include: the GL name in glName, the
         member's name in glMember.glMemberName, the member's address
         in glMember.glMemberAddress, and the member's encryption
         certificate in glMember.certificates.membersPKC. The GLO MAY
         also include any attribute certificates associated with the
         member's encryption certificate in
         glMember.certificates.membersAC, and the certification path
         associated with the member's encryption and attribute
         certificates in glMember.certificates.certificationPath.

     1.a - The GLO MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.b - The GLO MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the request, the GLA verifies the signature on
         the inner most SignedData.PKIData. If an additional SignedData
         and/or EnvelopedData encapsulates the request (see paragraph
         3.2.1.2 or 3.2.2), the GLA MUST verify the outer signature
         and/or decrypt the outer layer prior to verifying the
         signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the glAddMember request
           is included in a controlSequence with the glUseKEK request,
           and the processing in paragraph 4.1 item 2.e is successfully
           completed the GLA MUST return a glSuccessInfo indicating the
           glName, the corresponding glIdentifier, an
           action.actionCode.addedMember, and action.glMemberName (2 in
           Figure 5).

     2.b.1 - The GLA MUST apply confidentiality to the response by
             encapsulating the SignedData.PKIData in an EnvelopedData
             if the request was encapsulated in an EnvelopedData (see
             paragraph 3.2.1.2).

     2.b.2 - The GLA MAY also optionally apply another SignedData over
             the EnvelopedData (see paragraph 3.2.1.2).


Turner                                                              32

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.c - If the signature(s) does(do) verify and the GLAddMember
           request is not included in a controlSequence with the
           GLCreate request, the GLA MUST make sure the GL is supported
           by checking that the glName matches a glName stored on the
           GLA.

     2.c.1 - If the glName is not supported by the GLA, the GLA MUST
             return a response indicating
             glFailInfo.errorCode.invalidGLName.

     2.c.2 - If the glName is supported by the GLA, the GLA MUST check
             to see if the glMemberName is present on the GL.

     2.c.2.a - If the glMemberName is present on the GL, the GLA MUST
               return a response indicating
               glFailInfo.errorCode.alreadyAMember.

     2.c.2.b - If the glMemberName is not present on the GL, the GLA
               MUST check how the GL is administered.

     2.c.2.b.1 - If the GL is closed, the GLA MUST check that a
                 registered GLO signed the request by checking that one
                 of the names in the digital signature certificate used
                 to sign the request matches a registered GLO.

     2.c.2.b.1.a - If the names do not match, the GLA MUST return a
                   response indicating
                   glFailInfo.errorCode.noGLONameMatch.

     2.c.2.b.1.b - If the names do match, the GLA MUST verify the
                   member's encryption certificate.

     2.c.2.b.1.b.1 - If the member's encryption certificate does not
                     verify, the GLA MAY return a response indicating
                     glFailInfo.errorCode.invalidCert to the GLO. If
                     the GLA does not return a glFailInfo response, the
                     GLA MUST issue a glProvideCert request (see
                     paragraph 4.10).

     2.c.2.b.1.b.2 - If the member's certificate does verify, the GLA
                     MUST return a glSuccessInfo to the GLO indicating
                     the glName, the corresponding glIdentifier, an
                     action.actionCode.addedMember, and
                     action.glMemberName (2 in Figure 5). The GLA also
                     takes administrative actions, which are beyond the
                     scope of this document, to add the member to the
                     GL stored on the GLA. The GLA MUST also distribute
                     the shared KEK to the member via the mechanism
                     described in paragraph 5.

     2.c.2.b.1.b.2.a - The GLA MUST apply confidentiality to the
                       response by encapsulating the SignedData.PKIData

Turner                                                              33

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

                       in an EnvelopedData if the request was
                       encapsulated in an EnvelopedData (see paragraph
                       3.2.1.2).

     2.c.2.b.1.b.2.b - The GLA MAY also optionally apply another
                       SignedData over the EnvelopedData (see paragraph
                       3.2.1.2).

     2.c.2.b.2 - If the GL is managed, the GLA MUST check that either a
                 registered GLO or the prospective member signed the
                 request. For GLOs, one of the names in the certificate
                 used to sign the request MUST match a registered GLO.
                 For the prospective member, the name in
                 glMember.glMemberName MUST match one of the names in
                 the certificate used to sign the request.

     2.c.2.b.2.a - If the signer is neither a registered GLO nor the
                   prospective GL member, the GLA MUST return a
                   response indicating glFailInfo.errorCode.noSpam.

     2.c.2.b.2.b - If the signer is a registered GLO, the GLA MUST
                   verify the member's encryption certificate.

     2.c.2.b.2.b.1 - If the member's certificate does not verify, the
                     GLA MAY return a response indicating
                     glFailInfo.errorCode.invalidCert. If the GLA does
                     not return a glFailInfo response, the GLA MUST
                     issue a glProvideCert request (see paragraph
                     4.10).

     2.c.2.b.2.b.2 - If the member's certificate does verify, the GLA
                     MUST return glSuccessInfo indicating the glName,
                     the corresponding glIdentifier, an
                     action.actionCode.addedMember, and
                     action.glMemberName to the GLO (2 in Figure 5).
                     The GLA also takes administrative actions, which
                     are beyond the scope of this document, to add the
                     member to the GL stored on the GLA. The GLA MUST
                     also distribute the shared KEK to the member via
                     the mechanism described in paragraph 5.

     2.c.2.b.2.b.2.a - The GLA MUST apply confidentiality to the
                       response by encapsulating the SignedData.PKIData
                       in an EnvelopedData if the request was
                       encapsulated in an EnvelopedData (see paragraph
                       3.2.1.2).

     2.c.2.b.2.b.2.b - The GLA MAY also optionally apply another
                       SignedData over the EnvelopedData (see paragraph
                       3.2.1.2).



Turner                                                              34

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.c.2.b.2.c - If the signer is the prospective member, the GLA
                   MUST forward the glAddMember request (see paragraph
                   3.2.3) to a registered GLO (B{A} in Figure 5). If
                   there is more than one registered GLO, the GLO to
                   which the request is forwarded to is beyond the
                   scope of this document. Further processing of the
                   forwarded request by GLOs is addressed in 3 of
                   paragraph 4.3.2.

     2.c.2.b.2.c.1 - The GLA MUST apply confidentiality to the
                     forwarded request by encapsulating the
                     SignedData.PKIData in an EnvelopedData if the
                     original request was encapsulated in an
                     EnvelopedData (see paragraph 3.2.1.2).

     2.c.2.b.2.c.2 - The GLA MAY also optionally apply another
                     SignedData over the EnvelopedData (see paragraph
                     3.2.1.2).

     2.c.2.b.3 - If the GL is unmanaged, the GLA MUST check that either
                 a registered GLO or the prospective member signed the
                 request. For GLOs, one of the names in the certificate
                 used to sign the request MUST match the name of a
                 registered GLO. For the prospective member, the name
                 in glMember.glMemberName MUST match one of the names
                 in the certificate used to sign the request.

     2.c.2.b.3.a - If the signer is neither a registered GLO nor the
                   prospective member, the GLA MUST return a response
                   indicating glFailInfo.errorCode.noSpam.

     2.c.2.b.3.b - If the signer is either a registered GLO or the
                   prospective member, the GLA MUST verify the member's
                   encryption certificate.

     2.c.2.b.3.b.1 - If the member's certificate does not verify, the
                     GLA MAY return a response indicating
                     glFailInfo.errorCode.invalidCert to either the GLO
                     or the prospective member depending on where the
                     request originated. If the GLA does not return a
                     glFailInfo response, the GLA MUST issue a
                     glProvideCert request (see paragraph 4.10) to
                     either the GLO or prospective member depending on
                     where the request originated.

     2.c.2.b.3.b.2 - If the member's certificate does verify, the GLA
                     MUST return a glSuccessInfo indicating the glName,
                     the corresponding glIdentifier, an
                     action.actionCode.addedMember, and
                     action.glMemberName to the GLO (2 in Figure 5) if
                     the GLO signed the request and to the GL member (3
                     in Figure 5) if the GL member signed the request.

Turner                                                              35

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

                     The GLA also takes administrative actions, which
                     are beyond the scope of this document, to add the
                     member to the GL stored on the GLA. The GLA MUST
                     also distribute the shared KEK to the member via
                     the mechanism described in paragraph 5.

     2.c.2.b.3.b.2.a - The GLA MUST apply confidentiality to the
                       response by encapsulating the SignedData.PKIData
                       in an EnvelopedData if the request was
                       encapsulated in an EnvelopedData (see paragraph
                       3.2.1.2).

     2.c.2.b.3.b.2.b - The GLA MAY also optionally apply another
                       SignedData over the EnvelopedData (see paragraph
                       3.2.1.2).

     3 - Upon receipt of the glSuccessInfo or glFailInfo response, the
         GLO verifies the GLA's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     3.a - If the signature(s) does (do) not verify, the GLO MUST
           return a cMCStatusInfo response indicating cMCStatus.failed
           and otherInfo.failInfo.badMessageCheck.

     3.b - If the signature(s) does(do) verify and the response is
           glSuccessInfo, the GLO has added the member to the GL. If
           member was added to a managed list and the original request
           was signed by the member, the GLO MUST send a
           cMCStatusInfo.cMCStatus.success to the GL member.

     3.c - If the GLO received a glFailInfo, for any reason, the GLO
           MAY reattempt to add the member to the GL using the
           information provided in the glFailInfo response.

     4 - Upon receipt of the glSuccessInfo, glFailInfo, or cMCStatus
         response, the prospective member verifies the GLA's
         signature(s) or GLO's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     4.a - If the signatures do not verify, the prospective member MUST
           return a cMCStatusInfo response indicating cMCStatus.failed
           and otherInfo.failInfo.badMessageCheck.

     4.b - If the signatures do verify, the prospective member has been
           added to the GL.


Turner                                                              36

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     4.c - If the prospective member received a glFailInfo, for any
           reason, the prospective member MAY reattempt to add
           themselves to the GL using the information provided in the
           glFailInfo response.


4.3.2 Prospective Member Initiated Additions

   The process for prospective member initiated glAddMember requests is
   as follows:

     1 - The prospective GL member sends a
         SignedData.PKIData.controlSequence.glAddMember request to the
         GLA (A in Figure 5). The prospective GL member MUST include:
         the GL name in glName, their name in glMember.glMemberName,
         their address in glMember.glMemberAddress, and their
         encryption certificate in glMember.certificates.membersPKC.
         The prospective GL member MAY also include any attribute
         certificates associated with their encryption certificate in
         glMember.certificates.membersAC, and the certification path
         associated with their encryption and attribute certificates in
         glMember.certificates.certificationPath.

     1.a - The prospective GL member MAY optionally apply
           confidentiality to the request by encapsulating the
           SignedData.PKIData in an EnvelopedData (see paragraph
           3.2.1.2).

     1.b - The prospective GL member MAY also optionally apply another
           SignedData over the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the request, the GLA verifies the request as
         per 2 in paragraph 4.3.1.

     3 - Upon receipt of the forwarded request, the GLO verifies the
         prospective GL member's signature on the inner most
         SignedData.PKIData and the GLA's signature on the outer layer.
         If an EnvelopedData encapsulates the inner most layer (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST decrypt the outer
         layer prior to verifying the signature on the inner most
         SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signature(s) does(do) verify, the GLO MUST check to
           make sure one of the names in the certificate used to sign
           the request matches the name in glMember.glMemberName.

     3.b.1 - If the names do not match, the GLO MAY send a
             SignedData.PKIResponse.controlSequence message back to the

Turner                                                              37

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

             prospective member with cMCStatusInfo.cMCStatus.failed
             indicating why the prospective member was denied in
             cMCStausInfo.statusString. This stops people from adding
             people to GLs without their permission.

     3.b.2 - If the names do match, the GLO determines whether the
             prospective member is allowed to be added. The mechanism
             is beyond the scope of this document; however, the GLO
             should check to see that the glMember.glMemberName is not
             already on the GL.

     3.b.2.a - If the GLO determines the prospective member is not
               allowed to join the GL, the GLO MAY return a
               SignedData.PKIResponse.controlSequence message back to
               the prospective member with
               cMCStatusInfo.cMCtatus.failed indicating why the
               prospective member was denied in cMCStatus.statusString.

     3.b.2.b - If GLO determines the prospective member is allowed to
               join the GL, the GLO MUST verify the member's encryption
               certificate.

     3.b.2.b.1 - If the member's certificate does not verify, the GLO
                 MAY return a SignedData.PKIResponse.controlSequence
                 back to the prospective member with
                 cMCStatusInfo.cMCtatus.failed indicating that the
                 member's encryption certificate did not verify in
                 cMCStatus.statusString. If the GLO does not return a
                 cMCStatusInfo response, the GLO MUST send a
                 SignedData.PKIData.controlSequence.glProvideCert
                 message to the prospective member requesting a new
                 encryption certificate (see paragraph 4.10).

     3.b.2.b.2 - If the member's certificate does verify, the GLO
                 resubmits the glAddMember request (see paragraph
                 3.2.5) to the GLA (1 in Figure 5).

     3.b.2.b.2.a - The GLO MUST apply confidentiality to the new
                   GLAddMember request by encapsulating the
                   SignedData.PKIData in an EnvelopedData if the
                   initial request was encapsulated in an EnvelopedData
                   (see paragraph 3.2.1.2).

     3.b.2.b.2.b - The GLO MAY also optionally apply another SignedData
                   over the EnvelopedData (see paragraph 3.2.1.2).

     4 - Processing continues as in 2 of paragraph 4.3.1.






Turner                                                              38

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

4.4 Delete Members From GL

   To delete members from GLs, either the GLO or prospective non-
   members use the glDeleteMember request. The GLA processes GLO and
   prospective non-GL member requests differently. The GLO can submit
   the request at any time to delete members from the GL, and the GLA,
   once it has verified the request came from a registered GLO, should
   delete the member. If a prospective member sends the request, the
   GLA needs to determine how the GL is administered. When the GLO
   initially configured the GL, they set the GL to be unmanaged,
   managed, or closed (see paragraph 3.1.1). In the unmanaged case, the
   GLA merely processes the member's request. For the managed case, the
   GLA forwards the requests from the prospective members to the GLO
   for review. Where there are multiple GLOs for a GL, which GLO the
   request is forwarded to is beyond the scope of this document. The
   GLO reviews the request and either rejects it or submits a reformed
   request to the GLA. In the closed case, the GLA will not accept
   requests from prospective members. The following paragraphs describe
   the processing for the GLO(s), GLA, and prospective non-GL members
   depending on where the request originated, either from a GLO or from
   prospective non-members. Figure 6 depicts the protocol interactions
   for the three options. Note that the error messages are not
   depicted.

                +-----+  2,B{A}              3  +----------+
                | GLO | <--------+    +-------> | Member 1 |
                +-----+          |    |         +----------+
                         1       |    |
                +-----+ <--------+    |      3  +----------+
                | GLA |  A            +-------> |   ...    |
                +-----+ <-------------+         +----------+
                                      |
                                      |      3  +----------+
                                      +-------> | Member n |
                                                +----------+

                   Figure 6 - Member Deletion

   If the member is not removed from the GL, they will continue to
   receive and be able to decrypt data protected with the shared KEK
   and will continue to receive rekeys. For unmanaged lists, there is
   no point to a group rekey because there is no guarantee that the
   member requesting to be removed has not already added themselves
   back on the GL under a different name. For managed and closed GLs,
   the GLO MUST take steps to ensure the member being deleted is not on
   the GL twice. After ensuring this, managed and closed GLs MUST be
   rekeyed to maintain the secrecy of the group. If the GLO is sure the
   member has been deleted the group rekey mechanism MUST be used to
   distribute the new key (see paragraphs 4.5 and 5).




Turner                                                              39

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

4.4.1 GLO Initiated Deletions

   The process for GLO initiated glDeleteMember requests is as follows:

     1 - The GLO collects the pertinent information for the member(s)
         to be deleted (this MAY be done through an out of bands
         means). The GLO then sends a
         SignedData.PKIData.controlSequence with a separate
         glDeleteMember request for each member to the GLA (1 in Figure
         6). The GLO MUST include: the GL name in glName and the
         member's name in glMemberToDelete. If the GL from which the
         member is being deleted in a closed or managed GL, the GLO
         MUST also generate a glRekey request and include it with the
         glDeletemember request (see paragraph 4.5).

     1.a - The GLO MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.b - The GLO MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the request, the GLA verifies the signature on
         the inner most SignedData.PKIData. If an additional SignedData
         and/or EnvelopedData encapsulates the request (see paragraph
         3.2.1.2 or 3.2.2), the GLA MUST verify the outer signature
         and/or decrypt the outer layer prior to verifying the
         signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST make sure
           the GL is supported by the GLA by checking that the glName
           matches a glName stored on the GLA.

     2.b.1 - If the glName is not supported by the GLA, the GLA MUST
             return a response indicating
             glFailInfo.errorCode.invalidGLName.

     2.b.2 - If the glName is supported by the GLA, the GLA MUST check
             to see if the glMemberName is present on the GL.

     2.b.2.a - If the glMemberName is not present on the GL, the GLA
               MUST return a response indicating
               glFailInfo.errorCode.notAMember.

     2.b.2.b - If the glMemberName is already on the GL, the GLA MUST
               check how the GL is administered.



Turner                                                              40

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.b.2.b.1 - If the GL is closed, the GLA MUST check that the
                 registered GLO signed the request by checking that one
                 of the names in the digital signature certificate used
                 to sign the request matches the registered GLO.

     2.b.2.b.1.a - If the names do not match, the GLA MUST return a
                   response indicating
                   glFailInfo.errorCode.noGLONameMatch.

     2.b.2.b.1.b - If the names do match, the GLA MUST return a
                   glSuccessInfo indicating the glName, the
                   corresponding glIdentifier, an
                   action.actionCode.deletedMember, and
                   action.glMemberName (2 in Figure 5). The GLA also
                   takes administrative actions, which are beyond the
                   scope of this document, to delete the member with
                   the GL stored on the GLA. The GLA MUST also rekey
                   group as described in paragraph 5.

     2.b.2.b.1.b.1 - The GLA MUST apply confidentiality to the response
                     by encapsulating the SignedData.PKIData in an
                     EnvelopedData if the request was encapsulated in
                     an EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.b.1.b.2 - The GLA MAY also optionally apply another
                     SignedData over the EnvelopedData (see paragraph
                     3.2.1.2).

     2.b.2.b.2 - If the GL is managed, the GLA MUST check that either a
                 registered GLO or the prospective member signed the
                 request. For GLOs, one of the names in the certificate
                 used to sign the request MUST match a registered GLO.
                 For the prospective member, the name in
                 glMember.glMemberName MUST match one of the names in
                 the certificate used to sign the request.

     2.b.2.b.2.a - If the signer is neither a registered GLO nor the
                   prospective GL member, the GLA MUST return a
                   response indicating glFailInfo.errorCode.noSpam.

     2.b.2.b.2.b - If the signer is a registered GLO, the GLA MUST
                   return a glSuccessInfo to the GLO indicating the
                   glName, the corresponding glIdentifier, an
                   action.actionCode.deletedMember, and
                   action.glMemberName (2 in Figure 6). The GLA also
                   takes administrative actions, which are beyond the
                   scope of this document, to delete the member with
                   the GL stored on the GLA. The GLA will also rekey
                   group as described in paragraph 5.

     2.b.2.b.2.b.1 - The GLA MUST apply confidentiality to the response
                     by encapsulating the SignedData.PKIData in an

Turner                                                              41

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

                     EnvelopedData if the request was encapsulated in
                     an EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.b.2.b.2 - The GLA MAY also optionally apply another
                     SignedData over the EnvelopedData (see paragraph
                     3.2.1.2).

     2.b.2.b.2.c - If the signer is the prospective member, the GLA
                   forwards the glDeleteMember request (see paragraph
                   3.2.3) to the GLO (B{A} in Figure 6). If there is
                   more than one registered GLO, the GLO to which the
                   request is forwarded to is beyond the scope of this
                   document. Further processing of the forwarded
                   request by GLOs is addressed in 3 of paragraph
                   4.4.2.

     2.b.2.b.2.c.1 - The GLA MUST apply confidentiality to the
                     forwarded request by encapsulating the
                     SignedData.PKIData in an EnvelopedData if the
                     request was encapsulated in an EnvelopedData (see
                     paragraph 3.2.1.2).

     2.b.2.b.2.c.2 - The GLA MAY also optionally apply another
                     SignedData over the EnvelopedData (see paragraph
                     3.2.1.2).

     2.b.2.b.3 - If the GL is unmanaged, the GLA MUST check that either
                 a registered GLO or the prospective member signed the
                 request. For GLOs, one of the names in the certificate
                 used to sign the request MUST match the name of a
                 registered GLO. For the prospective member, the name
                 in glMember.glMemberName MUST match one of the names
                 in the certificate used to sign the request.

     2.b.2.b.3.a - If the signer is neither the GLO nor the prospective
                   member, the GLA MUST return a response indicating
                   glFailInfo.errorCode.noSpam.

     2.b.2.b.3.b - If the signer is either a registered GLO or the
                   member, the GLA MUST return a glSuccessInfo
                   indicating the glName, the corresponding
                   glIdentifier, an action.actionCode.deletedMember,
                   and action.glMemberName to the GLO (2 in Figure 6)
                   if the GLO signed the request and to the GL member
                   (3 in Figure 6) if the GL member signed the request.
                   The GLA also takes administrative actions, which are
                   beyond the scope of this document, to delete the
                   member with the GL stored on the GLA.

     2.b.2.b.3.b.1 - The GLA MUST apply confidentiality to the response
                     by encapsulating the SignedData.PKIData in an


Turner                                                              42

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

                     EnvelopedData if the request was encapsulated in
                     an EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.b.3.b.2 - The GLA MAY also optionally apply another
                     SignedData over the EnvelopedData (see paragraph
                     3.2.1.2).

     3 - Upon receipt of the glSuccessInfo or glFailInfo response, the
         GLO verifies the GLA's signatures. If an additional SignedData
         and/or EnvelopedData encapsulates the response (see paragraph
         3.2.1.2 or 3.2.2), the GLO MUST verify the outer signature
         and/or decrypt the outer layer prior to verifying the
         signature on the inner most SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signature(s) does(do) verify and the response is
           glSuccessInfo, the GLO has deleted the member from the GL.
           If member was deleted from a managed list and the original
           request was signed by the member, the GLO MUST send a
           cMCStatusInfo.cMCStatus.success to the GL member.

     3.c - If the GLO received a glFailInfo, for any reason, the GLO
           may reattempt to delete the member from the GL using the
           information provided in the glFailInfo response.

     4 - Upon receipt of the glSuccessInfo, glFailInfo, or cMCStatus
         response, the prospective member verifies the GLA's
         signature(s) or GLO's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     4.a - If the signature(s) does(do) not verify, the prospective
           member MUST return a cMCStatusInfo response indicating
           cMCStatus.failed and otherInfo.failInfo.badMessageCheck.

     4.b - If the signature(s) does(do) verify, the prospective member
           has been deleted from the GL.

     4.c - If the prospective member received a glFailInfo, for any
           reason, the prospective member MAY reattempt to delete
           themselves from the GL using the information provided in the
           glFailInfo response.






Turner                                                              43

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

4.4.2 Member Initiated Deletions

   The process for prospective non-member initiated glDeleteMember
   requests is as follows:

     1 - The prospective non-GL member sends a
         SignedData.PKIData.controlSequence.glDeleteMember request to
         the GLA (A in Figure 6). The prospective non-GL member MUST
         include: the GL name in glName and their name in
         glMemberToDelete.

     1.a - The prospective non-GL member MAY optionally apply
           confidentiality to the request by encapsulating the
           SignedData.PKIData in an EnvelopedData (see paragraph
           3.2.1.2).

     1.b - The prospective non-GL member MAY also optionally apply
           another SignedData over the EnvelopedData (see paragraph
           3.2.1.2).

     2 - Upon receipt of the request, the GLA verifies the request as
         per 2 in paragraph 4.4.1.

     3 - Upon receipt of the forwarded request, the GLO verifies the
         prospective non-member's signature on the inner most
         SignedData.PKIData and the GLA's signature on the outer layer.
         If an EnvelopedData encapsulates the inner most layer (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST decrypt the outer
         layer prior to verifying the signature on the inner most
         SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signature(s) does(do) verify, the GLO MUST check to
           make sure one of the names in the certificates used to sign
           the request matches the name in glMemberToDelete.

     3.b.1 - If the names do not match, the GLO MAY send a
             SignedData.PKIResponse.controlSequence message back to the
             prospective member with cMCStatusInfo.cMCtatus.failed
             indicating why the prospective member was denied in
             cMCStatusInfo.statusString. This stops people from adding
             people to GLs without their permission.

     3.b.2 - If the names do match, the GLO resubmits the
             glDeleteMember request (see paragraph 3.2.5) to the GLA (1
             in Figure 6). The GLO MUST make sure the glMemberName is
             already on the list and only on the list once. The GLO
             MUST also generate a glRekey request and include it with
             the GLDeleteMember request (see paragraph 4.5).

Turner                                                              44

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


     3.b.2.a - The GLO MUST apply confidentiality to the new
               GLDeleteMember request by encapsulating the
               SignedData.PKIData in an EnvelopedData if the initial
               request was encapsulated in an EnvelopedData (see
               paragraph 3.2.1.2).

     3.b.2.b - The GLO MAY also optionally apply another SignedData
               over the EnvelopedData (see paragraph 3.2.1.2).

     4 - Further processing is as in 2 of paragraph 4.4.1.


4.5 Request Rekey Of GL

   From time to time the GL will need to be rekeyed. Some situations
   are as follows:

     - When a member is removed from a closed or managed GL. In this
       case, the PKIData.controlSequence containing the glDeleteMember
       should contain a glRekey request.

     - Depending on policy, when a member is removed from an unmanaged
       GL. If the policy is to rekey the GL, the
       PKIData.controlSequence containing the glDeleteMember could also
       contain a glRekey request or an out of bands means could be used
       to tell the GLA to rekey the GL. Rekeying of unmanaged GLs when
       members are deleted is not advised.

     - When the current shared KEK has been compromised.

     - When the current shared KEK is about to expire.

       - If the GLO controls the GL rekey, the GLA should not assume
         that a new shared KEK should be distributed, but instead wait
         for the glRekey message.

       - If the GLA controls the GL rekey, the GLA should initiate a
         glKey message as specified in paragraph 5.

   If the generationCounter (see paragraph 3.1.1) is set to a value
   greater than one (1) and the GLO controls the GL rekey, the GLO may
   generate a glRekey any time before the last shared KEK has expired.
   To be on the safe side, the GLO should request a rekey one (1)
   duration before the last shared KEK expires.

   The GLA and GLO are the only entities allowed to initiate a GL
   rekey. The GLO indicated whether they are going control rekeys or
   whether the GLA is going to control rekeys when the assigned the
   shared KEK to GL (see paragraph 3.1.1). The GLO MAY initiate a GL
   rekey at any time. The GLA MAY be configured to automatically rekey
   the GL prior to the expiration of the shared KEK (the length of time

Turner                                                              45

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   before the expiration is an implementation decision). Figure 7
   depicts the protocol interactions to request a GL rekey. Note that
   error messages are not depicted.

                  +-----+  1   2,A  +-----+
                  | GLA | <-------> | GLO |
                  +-----+           +-----+

                     Figure 7 - GL Rekey Request


4.5.1 GLO Initiated Rekey Requests

   The process for GLO initiated glRekey requests is as follows:

     1 - The GLO sends a SignedData.PKIData.controlSequence.glRekey
         request to the GLA (1 in Figure 7). The GLO MUST include the
         glName. If glAdministration and glKeyNewAttributes are omitted
         then there is no change from the previously registered GL
         values for these fields. If the GLO wants to force a rekey for
         all outstanding shared KEKs the
         glNewKeyAttributes.generationCounter MUST be set to zero (0)

     1.a - The GLO MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.b - The GLO MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the request, the GLA verifies the signature on
         the inner most SignedData.PKIData. If an additional SignedData
         and/or EnvelopedData encapsulates the request (see paragraph
         3.2.1.2 or 3.2.2), the GLA MUST verify the outer signature
         and/or decrypt the outer layer prior to verifying the
         signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST make sure
           the GL is supported by the GLA by checking that the glName
           matches a glName stored on the GLA.

     2.b.1 - If the glName present does not match a GL stored on the
             GLA, the GLA MUST return a response indicating
             glFailInfo.errorCode.invalidGLName.

     2.b.2 - If the glName present does match a GL stored on the GLA,
             the GLA MUST check that a registered GLO signed the


Turner                                                              46

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

             request by checking that one of the names in the
             certificate used to sign the request is a registered GLO.

     2.b.2.a - If the names do not match, the GLA MUST return a
               response indicating glFailInfo.errorCode.noGLONameMatch.

     2.b.2.b - If the names do match, the GLA MUST check the
               glNewKeyAttribute values.

     2.b.2.b.1 - If the new value for requestedAlgorithm is not
                 supported, the GLA MUST return a response indicating
                 glFailInfo.errorCode.unsupportedAlgorithm

     2.b.2.b.2 - If the new value duration is not supportable,
                 determining this is beyond the scope this document,
                 the GLA MUST return a response indicating
                 glFailInfo.errorCode.unsupportedDuration.

     2.b.2.b.3 - If the GL is not supportable for other reasons, which
                 the GLA does not wish to disclose, the GLA MUST return
                 a response indicating
                 glFailInfo.errorCode.unspecified.

     2.b.2.b.4 - If the new requestedAlgorithm and duration are
                 supportable or the glNewKeyAttributes was omitted, the
                 GLA MUST return a glSuccessInfo to the GLO indicating
                 the glName, the new glIdentifier, and an
                 action.actionCode.rekeyedGL (2 in Figure 7). The GLA
                 also uses the glKey message to distribute the rekey
                 shared KEK (see paragraph 5).

     2.b.2.b.4.a - The GLA MUST apply confidentiality to response by
                   encapsulating the SignedData.PKIData in an
                   EnvelopedData if the request was encapsulated in an
                   EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.b.4.b - The GLA MAY also optionally apply another SignedData
                   over the EnvelopedData (see paragraph 3.2.1.2).

     3 - Upon receipt of the glSuccessInfo or glFailInfo response, the
         GLO verifies the GLA's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the forwarded
         response (see paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify
         the outer signature and/or decrypt the forwarded response
         prior to verifying the signature on the inner most SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signatures verifies and the response is
           glSuccessInfo, the GLO has successfully rekeyed the GL.

Turner                                                              47

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


     3.c - If the GLO received a glFailInfo, for any reason, the GLO
           may reattempt to rekey the GL using the information provided
           in the glFailInfo response.


4.5.2 GLA Initiated Rekey Requests

   If the GLA is in charge of rekeying the GL the GLA will
   automatically issue a glKey message (see paragraph 5). In addition
   the GLA will generate a glSuccessInfo to indicate to the GL that a
   successful rekey has occurred. The process for GLA initiated rekey
   is as follows:

     1 - The GLA MUST generate for all GLOs a
         SignedData.PKIData.controlSequence.glSuccessInfo indicating
         the glName, the new glIdentifier, and actionCode.rekeyedGL (A
         in Figure 7). glMemberName and glOwnerName are omitted.

     1.a - The GLA MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.b - The GLA MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the glSuccessInfo response, the GLO verifies
         the GLA's signature(s). If an additional SignedData and/or
         EnvelopedData encapsulates the forwarded response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     2.a - If the signatures do not verify, the GLO MUST return a
           cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signatures verifies and the response is
           glSuccessInfo, the GLO knows the GLA has successfully
           rekeyed the GL.


4.6 Change GLO

   Management of managed and closed GLs can become difficult for one
   GLO if the GL membership grows large. To support distributing the
   workload, GLAs support having GLs be managed by multiple GLOs. The
   glAddOwner and glRemoveOwner messages are designed to support adding
   and removing registered GLOs. Figure 8 depicts the protocol
   interactions to send glAddOwner and glRemoveOwner messages and the
   resulting response messages.


Turner                                                              48

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


                      +-----+   1    2  +-----+
                      | GLA | <-------> | GLO |
                      +-----+           +-----+

                 Figure 8 - GLO Add & Delete Owners

   The process for glAddOwner and glDeleteOwner is as follows:

     1 - The GLO sends a SignedData.PKIData.controlSequence.glAddOwner
         or glRemoveOwner request to the GLA (1 in Figure 8). The GLO
         MUST include: the GL name in glName, the GLO's name in
         glOwnerName, and the GLO's address in glOwnerAddress.

     1.a - The GLO MAY optionally apply confidentiality to the request
           by encapsulating the SignedData.PKIData in an EnvelopedData
           (see paragraph 3.2.1.2).

     1.b - The GLO MAY also optionally apply another SignedData over
           the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the glAddOwner or glRemoveOwner request, the
         GLA verifies the GLO's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the request (see
         paragraph 3.2.1.2 or 3.2.2), the GLA MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST make sure
           the GL is supported by checking that the glName matches a
           glName stored on the GLA.

     2.b.1 - If the glName is not supported by the GLA, the GLA MUST
             return a response indicating
             glFailInfo.errorCode.invalidGLName.

     2.b.2 - If the glName is supported by the GLA, the GLA MUST ensure
             a registered GLO signed the glAddOwner or glRemoveOwner
             request by checking that one of the names present in the
             digital signature certificate used to sign the glAddOwner
             or glDeleteOwner request matches the name of a registered
             GLO.

     2.b.2.a - If the names do not match, the GLA MUST return a
               response indicating glFailInfo.errorCode.noGLONameMatch.

     2.b.2.b - If the names do match, the GLA MUST return a
               glSuccessInfo indicating the glName, the corresponding

Turner                                                              49

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

               glIdentifier (for glAddOwner), an
               action.actionCode.addedGLO or removedGLO, and the
               respective GLO name in glOwnerName (2 in Figure 4). The
               GLA MUST also take administrative actions to associate
               the new glOwnerName with the GL in the case of
               glAddOwner or to disassociate the old glOwnerName with
               the GL in the cased of glRemoveOwner.

     2.b.2.b.1 - The GLA MUST apply confidentiality to the response by
                 encapsulating the SignedData.PKIResponse in an
                 EnvelopedData if the request was encapsulated in an
                 EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.b.2 - The GLA MAY also optionally apply another SignedData
                 over the EnvelopedData (see paragraph 3.2.1.2).

     3 - Upon receipt of the glSuccessInfo or glFailInfo response, the
         GLO verifies the GLA's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GLO MUST verify the outer
         signature and/or decrypt the outer layer prior to verifying
         the signature on the inner most SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signatures do verify and the response was
           glSuccessInfo, the GLO has successfully added or removed the
           GLO.

     3.c - If the signatures do verify and the response was glFailInfo,
           the GLO MAY reattempt to add or delete the GLO using the
           information provided in the glFailInfo response.


4.7 Indicate KEK Compromise

   The will be times when the shared KEK is compromised. GL members and
   GLOs use glkCompromise to tell the GLA that the shared KEK has been
   compromised. Figure 9 depicts the protocol interactions for GL Key
   Compromise.











Turner                                                              50

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

                +-----+  2{1}                  4  +----------+
                | GLO | <----------+    +-------> | Member 1 |
                +-----+  5,3{1}    |    |         +----------+
                +-----+ <----------+    |      4  +----------+
                | GLA |  1              +-------> |   ...    |
                +-----+ <---------------+         +----------+
                                        |      4  +----------+
                                        +-------> | Member n |
                                                  +----------+

                   Figure 9 - GL Key Compromise

4.7.1 GL Member Initiated KEK Compromise Message

   The process for GL member initiated glkCompromise messages is as
   follows:

     1 - The GL member sends a
         SignedData.PKIData.controlSequence.glkCompromise request to
         the GLA (1 in Figure 9). The GL member MUST include the GL's
         name in GeneralName.

     1.a - The GL member MAY optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see paragraph 3.2.1.2). The glkCompromise
           MUST NOT be included in an EnvelopedData generated with the
           compromised shared KEK.

     1.b - The GL member MAY also optionally apply another SignedData
           over the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the glkCompromise requst, the GLA verifies the
         GL member's signature(s). If an additional SignedData and/or
         EnvelopedData encapsulates the request (see paragraph 3.2.1.2
         or 3.2.2), the GLA MUST verify the outer signature and/or
         decrypt the outer layer prior to verifying the signature on
         the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST make sure
           the GL is supported by checking  that the indicated GL name
           matches a glName stored on the GLA.

     2.b.1 - If the glName is not supported by the GLA, the GLA MUST
             return a response indicating
             glFailInfo.errorCode.invalidGLName.

     2.b.2 - If the glName is supported by the GLA, the GLA MUST check
             who signed the request. For GLOs, one of the names in the

Turner                                                              51

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

             certificate used to sign the request MUST match a
             registered GLO. For the prospective member, the name in
             glMember.glMemberName MUST match one of the names in the
             certificate used to sign the request.

     2.b.2.a - If the GLO signed the request, the GLA MUST generate a
               glKey message as described in paragraph 5 to rekey the
               GL (4 in Figure 9).

     2.b.2.b - If anyone else signed the request, the GLA MUST forward
               the glkCompromise message (see paragraph 3.2.3) to the
               GLO (2{1} in Figure 9). If there is more than one GLO,
               to which GLO the request is forwarded is beyond the
               scope of this document. Further processing by the GLO is
               discussed in paragraph 4.7.2.


4.7.2 GLO Initiated KEK Compromise Message

   The process for GLO initiated glkCompromise messages is as follows:

     1 - The GLO either:

     1.a - Generates the glkCompromise message itself by sending a
           SignedData.PKIData.controlSequence.glkCompromise request to
           the GLA (5 in Figure 9). The GLO MUST include the name of
           the GL in GeneralName.

     1.a.1 - The GLO MAY optionally apply confidentiality to the
             request by encapsulating the SignedData.PKIData in an
             EnvelopedData (see paragraph 3.2.1.2). The glkCompromise
             MUST NOT be included in an EnvelopedData generated with
             the compromised shared KEK.

     1.a.2 - The GLO MAY also optionally apply another SignedData over
             the EnvelopedData (see paragraph 3.2.1.2).

     1.b - Verifies the GLA's and GL member's signatures on the
           forwarded glkCompromise message. If an additional SignedData
           and/or EnvelopedData encapsulates the request (see paragraph
           3.2.1.2 or 3.2.2), the GLO MUST verify the outer signature
           and/or decrypt the outer layer prior to verifying the
           signature on the inner most SignedData.

     1.b.1 - If the signatures do not verify, the GLO MUST return a
             cMCStatusInfo response indicating cMCStatus.failed and
             otherInfo.failInfo.badMessageCheck.

     1.b.2 - If the signatures do verify, the GLO MUST determine
             whether to forward the glkCompromise message back to the
             GLA (3{1} in Figure 9). Further processing by the GLA is
             in 2 of paragraph 4.7.1. The GLO MAY also return a the

Turner                                                              52

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

             prospective member with cMCStatusInfo.cMCtatus.success
             indicating that the glkCompromise message was successfully
             received.


4.8 Request KEK Refresh

   There will be times when GL members have misplaced their shared KEK.
   The shared KEK is not compromised and a rekey of the entire GL is
   not necessary. GL members use the glkRefresh message to request that
   the shared KEK(s) be redistributed to them. Figure 10 depicts the
   protocol interactions for GL Key Refresh.

                      +-----+   1       2   +----------+
                      | GLA | <---+-------> |  Member  |
                      +-----+               +----------+

                         Figure 10 - GL KEK Refresh


   The process for glkRefresh is as follows:

     1 - The GL member sends a
         SignedData.PKIData.controlSequence.glkRefresh request to the
         GLA (1 in Figure 10). The GL member MUST include name of the
         GL in GeneralName.

     1.a - The GL member MAY optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see paragraph 3.2.1.2).

     1.b - The GL member MAY also optionally apply another SignedData
           over the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the glkRefresh request, the GLA verifies the
         GL member's signature(s). If an additional SignedData and/or
         EnvelopedData encapsulates the request (see paragraph 3.2.1.2
         or 3.2.2), the GLA MUST verify the outer signature and/or
         decrypt the outer layer prior to verifying the signature on
         the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST make sure
           the GL is supported by checking that the GL's GeneralName
           matches a glName stored on the GLA.

     2.b.1 - If the GL's name is not supported by the GLA, the GLA MUST
             return a response indicating
             glFailInfo.errorCode.invalidGLName.

Turner                                                              53

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000


     2.b.2 - If the glName is supported by the GLA, the GLA MUST ensure
             the GL member is on the GL.

     2.b.2.a - If the glMemberName is not present on the GL, the GLA
               MUST return a response indicating
               glFailInfo.errorCode.noSpam.

     2.b.2.b - If the glMemberName is present on the GL, the GLA MUST
               return a glKey message (2 in Figure 10) as described in
               paragraph 5.


4.9 GLA Query Request and Response

   There will be certain times when a GLO is having trouble setting up
   a GLO because they do not know the algorithm(s) or some other
   characteristic that the GLA supports. There may also be times when
   the prospective GL members or GL members need to know something
   about the GLA (these requests are not defined in the document). The
   glaQueryRequest and glaQueryResponse message have been defined to
   support determining this information. Figure 11 depicts the protocol
   interactions for glaQueryRequest and glaQueryResponse.

                      +-----+   1    2  +------------------+
                      | GLA | <-------> | GLO or GL Member |
                      +-----+           +------------------+

                Figure 11 - GLA Query Request & Response


   The process for glaQueryRequest and glaQueryResponse is as follows:

     1 - The GLO, GL member, or prospective GL member sends a
         SignedData.PKIData.controlSequence.glaQueryRequest request to
         the GLA (1 in Figure 11). The GLO, GL member, or prospective
         GL member indicates the information they are interested in
         receiving from the GLA.

     1.a - The GLO, GL member, or prospective GL member MAY optionally
           apply confidentiality to the request by encapsulating the
           SignedData.PKIData in an EnvelopedData (see paragraph
           3.2.1.2).

     1.b - The GLO, GL member, or prospective GL member MAY also
           optionally apply another SignedData over the EnvelopedData
           (see paragraph 3.2.1.2).

     2 - Upon receipt of the glaQueryRequest, the GLA determines if it
         accepts glaQueryRequest messages.



Turner                                                              54

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.a - If the GLA does not accept glaQueryRequest messages, the GLA
           MUST return a cMCStatusInfo response indicating
           cMCStatus.noSupport and any other information in
           statusString.

     2.b - If the GLA does accept GLAQueryReuests, the GLA MUST verify
           the GLO's, GL member's, or prospective GL member's
           signature(s). If an additional SignedData and/or
           EnvelopedData encapsulates the request (see paragraph
           3.2.1.2 or 3.2.2), the GLA MUST verify the outer signature
           and/or decrypt the outer layer prior to verifying the
           signature on the inner most SignedData.

     2.b.1 - If the signature(s) does(do) not verify, the GLA MUST
             return a cMCStatusInfo response indicating
             cMCStatus.failed and otherInfo.failInfo.badMessageCheck.

     2.b.2 - If the signature(s) does(do) verify, the GLA MUST return a
             glaQueryResponse (2 in Figure 11) indicating the the
             requested information if the glaRequestType is supported
             or return a cMCStatusInfo response indicating
             cMCStatus.noSupport if the glaRequestType is not
             supported.

     2.b.2.a - The GLA MUST apply confidentiality to the response by
               encapsulating the SignedData.PKIResponse in an
               EnvelopedData if the request was encapsulated in an
               EnvelopedData (see paragraph 3.2.1.2).

     2.b.2.b - The GLA MAY also optionally apply another SignedData
               over the EnvelopedData (see paragraph 3.2.1.2).

     3 - Upon receipt of the glaQueryResponse, the GLO, GL member, or
         prospective GL member verifies the GLA's signature(s). If an
         additional SignedData and/or EnvelopedData encapsulates the
         response (see paragraph 3.2.1.2 or 3.2.2), the GLO, GL member,
         or prospective GL member MUST verify the outer signature
         and/or decrypt the outer layer prior to verifying the
         signature on the inner most SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO, GL member,
           or prospective GL member MUST return a cMCStatusInfo
           response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     3.b - If the signatures do verify and the response was
           glaQueryResponse, the GLO, GL member, or prospective GL
           member may use the information contained therein.





Turner                                                              55

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

4.10 Update Member Certificate

   When the GLO generates a glAddMember request, when the GLA generates
   a glKey message, or when the GLA processes a glAddMember there may
   be instances when GL member's certificate has expired or is invalid.
   In these instances the GLO or GLA may request that the GL member
   provide a new certificate to avoid the GLA from being unable to
   generate a glKey message for the GL member. There may also be times
   when the GL member knows their certificate is about to expire or has
   been revoked and they will not be able to receive GL rekeys.

4.10.1 GLO and GLA Initiated Update Member Certificate

   The process for GLO initiated glUpdateCert is as follows:

     1 - The GLO or GLA sends a
         SignedData.PKIData.controlSequence.glProvideCert request to
         the GL member. The GLO or GLA indicates the GL name in glName
         and the GL member's name in glMemberName.

     1.a - The GLO or GLA MAY optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see paragraph 3.2.1.2). If the GL member's
           PKC has been revoked, the GLO or GLA MUST NOT use it to
           generate the EnvelopedData that encapsulates the
           glProvideCert request.

     1.b - The GLO or GLA MAY also optionally apply another SignedData
           over the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the glProvideCert message, the GL member
         verifies the GLO's or GLA's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GL member MUST verify the
         outer signature and/or decrypt the outer layer prior to
         verifying the signature on the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GL member MUST
           return a cMCStatusInfo response indicating cMCStatus.failed
           and otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GL member generates
           a Signed.PKIResponse.controlSequence.glUpdateCert that MUST
           include the GL name in glName, the member's name in
           glMember.glMemberName, their encryption certificate in
           glMember.certificates.membersPKC. The GL member MAY also
           include any attribute certificates associated with their
           encryption certificate in glMember.certificates.membersAC,
           and the certification path associated with their encryption
           and attribute certificates in
           glMember.certificates.certificationPath.


Turner                                                              56

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

     2.a - The GL member MAY optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIResponse in an
           EnvelopedData (see paragraph 3.2.1.2). If the GL member's
           PKC has been revoked, the GL member MUST NOT use it to
           generate the EnvelopedData that encapsulates the
           glProvideCert request.

     2.b - The GL member MAY also optionally apply another SignedData
           over the EnvelopedData (see paragraph 3.2.1.2).

     3 - Upon receipt of the glUpdateCert message, the GLO or GLA
         verifies the GL member's signature(s). If an additional
         SignedData and/or EnvelopedData encapsulates the response (see
         paragraph 3.2.1.2 or 3.2.2), the GL member MUST verify the
         outer signature and/or decrypt the outer layer prior to
         verifying the signature on the inner most SignedData.

     3.a - If the signature(s) does(do) not verify, the GLO or GLA MUST
           return a cMCStatusInfo response indicating cMCStatus.failed
           and otherInfo.failInfo.badMessageCheck.

     3.b - If the signature(s) does(do) verify, the GLO or GLA MUST
           verify the member's encryption certificate.

     3.b.1 - If the member's encryption certificate does not verify,
             the GLO MAY return either another glProvideCert request or
             a cMCStatusInfo with cMCStatus.failed and the reason why
             in cMCStatus.statusString. glProvideCert should be
             returned only a certain number of times because if the GL
             member does not have a valid certificate they will never
             be able to return one.

     3.b.2 - If the member's encryption certificate does not verify,
             the GLA MAY return another glProvideCert request to the GL
             member or a cMCStatusInfo with cMCStatus.failed and the
             reason why in cMCStatus.statusString to the GLO.
             glProvideCert should be returned only a certain number of
             times because if the GL member does not have a valid
             certificate they will never be able to return one.

     3.b.3 - If the member's encryption certificate does verify, the
             GLO or GLA will use it in subsequent glAddMember requests
             and glKey messages associated with the GL member.


4.10.2 GL Member Initiated Update Member Certificate

   The process for an unsolicited GL member glUpdateCert is as follows:

     1 - The GL member sends a
         Signed.PKIData.controlSequence.glUpdateCert that MUST include
         the GL name in glName, the member's name in

Turner                                                              57

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

         glMember.glMemberName, their encryption certificate in
         glMember.certificates.membersPKC. The GL member MAY also
         include any attribute certificates associated with their
         encryption certificate in glMember.certificates.membersAC, and
         the certification path associated with their encryption and
         attribute certificates in
         glMember.certificates.certificationPath.

     1.a - The GL member MAY optionally apply confidentiality to the
           request by encapsulating the SignedData.PKIData in an
           EnvelopedData (see paragraph 3.2.1.2). If the GL member's
           PKC has been revoked, the GLO or GLA MUST NOT use it to
           generate the EnvelopedData that encapsulates the
           glProvideCert request.

     1.b - The GL member MAY also optionally apply another SignedData
           over the EnvelopedData (see paragraph 3.2.1.2).

     2 - Upon receipt of the glUpdateCert message, the GLA verifies the
         GL member's signature(s). If an additional SignedData and/or
         EnvelopedData encapsulates the response (see paragraph 3.2.1.2
         or 3.2.2), the GLA MUST verify the outer signature and/or
         decrypt the outer layer prior to verifying the signature on
         the inner most SignedData.

     2.a - If the signature(s) does(do) not verify, the GLA MUST return
           a cMCStatusInfo response indicating cMCStatus.failed and
           otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GLA MUST verify the
           member's encryption certificate.

     2.b.1 - If the member's encryption certificate does not verify,
             the GLA MAY return another glProvideCert request to the GL
             member or a cMCStatusInfo with cMCStatus.failed and the
             reason why in cMCStatus.statusString to the GLO.
             glProvideCert should be returned only a certain number of
             times because if the GL member does not have a valid
             certificate they will never be able to return one.

     2.b.2 - If the member's encryption certificate does verify, the
             GLA will use it in subsequent glAddMember requests and
             glKey messages associated with the GL member. The GLA MUST
             also forward the glUpdateCert message to the GLO.


5 Distribution Message

   The GLA uses the glKey message to distribute new, shared KEK(s)
   after receiving glAddMember, glDeleteMember (for closed and managed
   GLs), glRekey, glkCompromise, or glkRefresh requests and returning a
   glSuccessInfo response for the respective request. Figure 12 depicts

Turner                                                              58

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

   the protocol interactions to send out glKey messages. The procedures
   defined in this paragraph MUST be implemented.

                                        1   +----------+
                                  +-------> | Member 1 |
                                  |         +----------+
                      +-----+     |     1   +----------+
                      | GLA | ----+-------> |   ...    |
                      +-----+     |         +----------+
                                  |     1   +----------+
                                  +-------> | Member n |
                                            +----------+

                   Figure 12 - GL Key Distribution


   If the GL was setup with GLKeyAttributes.recipientsMutuallyAware set
   to FALSE, a separate glKey message MUST be sent to each GL member so
   as to not divulge information about the other GL members.

   When the glKey message is generated as a result of a:

     - glAddMember request,
     - glkComrpomise indication,
     - glkRefresh request,
     - glDeleteMember request with the the GL's glAdministration set to
       managed or closed,
     - glRekey request with generationCounter set to zero (0)

   The GLA MUST use either the kari (see paragraph 12.3.2 of CMS [2])
   or ktri (see paragraph 12.3.1 of CMS [2]) choice in
   glKey.glkWrapped.RecipientInfo to ensure only the intended
   recipients receive the shared KEK. The GLA MUST support the kari
   choice.

   When the glKey message is generated as a result of a glRekey request
   with generationCounter greater than zero (0) or when the GLA
   controls rekeys, the GLA MAY use the kari, ktri, or kekri (see
   paragraph 12.3.3 of CMS [2]) in glKey.glkWrapped.RecipientInfo to
   ensure only the intended recipients receive the shared KEK. The GLA
   MUST support the RecipientInfo.kari choice.


5.1 Distribution Process

   When a glKey message is generated the process is as follows:

     1 - The GLA MUST send a SignedData.PKIData.controlSequence.glKey
         to each member by including: glName, glIdentifier, glkWrapped,
         glkAlgorithm, glkNotBefore, and glkNotAfter. If the GLA can
         not generate a glKey message for the GL member because the GL
         member's PKC has expired or is invalid, the GLA MAY send a

Turner                                                              59

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000

         glUpdateCert to the GL member requesting a new certificate be
         provided (see paragraph 4.10). The number of glKey messages
         generated for the GL is described in paragraph 3.1.16.

     1.a - The GLA MAY optionally apply another confidentiality layer
           to the message by encapsulating the SignedData.PKIData in
           another EnvelopedData (see paragraph 3.2.1.2).

     1.b - The GLA MAY also optionally apply another SignedData over
           the EnvelopedData.SignedData.PKIData (see paragraph
           3.2.1.2).

     2 - Upon receipt of the message, the GL members MUST verify the
         signature over the inner most SignedData.PKIData. If an
         additional SignedData and/or EnvelopedData encapsulates the
         message (see paragraph 3.2.1.2 or 3.2.2), the GL Member MUST
         verify the outer signature and/or decrypt the outer layer
         prior to verifying the signature on the
         SignedData.PKIData.controlSequence.glKey.

     2.a - If the signature(s) does(do) not verify, the GL member MUST
           return a cMCStatusInfo response indicating cMCStatus.failed
           and otherInfo.failInfo.badMessageCheck.

     2.b - If the signature(s) does(do) verify, the GL member process
           the RecipientInfos according to CMS [2]. Once unwrapped the
           GL member should store the shared KEK in a safe place. When
           stored, the glName, glIdentifier, and shared KEK should be
           associated.


6 Algorithms

   This section lists the algorithms that must be implemented.
   Additional algorithms that should be implemented are also included.


6.1 KEK Generation Algorithm

   The shared KEK MUST be generated according to the security
   considerations paragraph in CMS [2].


6.2 Shared KEK Wrap Algorithm

   In the mechanisms described in paragraphs 5, the shared KEK being
   distributed in glkWrapped MUST be protected by a key of equal or
   greater length (i.e., if a RC2 128-bit key is being distributed a
   key of 128-bits or greater must be used to protect the key).

   The algorithm object identifiers included in glkWrapped are as
   specified in 12.3 of CMS [2].

Turner                                                              60

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000



6.3 Shared KEK Algorithm

   The shared KEK distributed and indicated in glkAlgorithm MUST
   support the symmetric key-encryption algorithms as specified in
   paragraph 12.3.3 of CMS [2]


7 Transport

   SMTP [7] MUST be supported. All other transport mechanisms MAY be
   supported.


8 Using the Group Key

   TBSL


9 Security Considerations

   Don't have too many GLOs because they could start willie nillie
   adding people you don't like.

   Need to rekey closed and managed GLs if a member is deleted.

   GL members have to store some kind of information about who
   distributed the shared KEK to them so that they can make sure
   subsequent rekeys are originated from the same entity.

   Need to make sure you don't make the key size too small and duration
   long because people will have more time to attack the key.

   Need to make sure you don't make the generationCounter to large
   because then people can attack the last key. If there are 14 keys
   outstanding each with a year's duration attackers might be able
   determine the 14th key.


10 References


   1  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
      9, RFC 2026, October 1996.

   2  Housley, R., "Cryptographic Message Syntax," RFC 2630, June 1999.

   3  Myers, M., Liu, X., Schadd, J., Weinsten, J., "Certificate
      Management Message over CMS," draft-ietf-pkix-cmc-05.txt, July
      1999.


Turner                                                              61

Internet-Draft    S/MIME Symmetric Key Distribution    August 20, 2000



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

   5  Ramsdale, B., "S/MIME Version 3 Message Specification," RFC 2633,
      June 1999.

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

   7  Postel, j., "Simple Mail Transport Protocol," RFC 821, August
      1982.




11 Acknowledgements

   Thanks to Russ Housley and Jim Schaad for providing much of the
   background and review required to write this draft.


12 Author's Addresses

   Sean Turner
   IECA, Inc.
   9010 Edgepark Road
   Vienna, VA 22182
   Phone: +1.703.628.3180
   Email: turners@ieca.com





   Expires April 2001















Turner                                                              62


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/