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Network Working Group S. Turner
Request for Comments: 5275 IECA
Category: Standards Track June 2008
CMS Symmetric Key Management and Distribution
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document describes a mechanism to manage (i.e., set up,
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 and Certificate
Management over CMS (CMC) protocol 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 Secure/Multipurpose Internet
Mail Extensions (S/MIME) Mail List Agents (MLAs).
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RFC 5275 CMS SymKeyDist June 2008
Table of Contents
1. Introduction ....................................................4
1.1. Conventions Used in This Document ..........................4
1.2. Applicability to E-mail ....................................5
1.3. Applicability to Repositories ..............................5
1.4. Using the Group Key ........................................5
2. Architecture ....................................................6
3. Protocol Interactions ...........................................7
3.1. Control Attributes .........................................8
3.1.1. GL Use KEK .........................................10
3.1.2. Delete GL ..........................................14
3.1.3. Add GL Member ......................................14
3.1.4. Delete GL Member ...................................15
3.1.5. Rekey GL ...........................................16
3.1.6. Add GL Owner .......................................16
3.1.7. Remove GL Owner ....................................17
3.1.8. GL Key Compromise ..................................17
3.1.9. GL Key Refresh .....................................18
3.1.10. GLA Query Request and Response ....................18
3.1.10.1. GLA Query Request ........................18
3.1.10.2. GLA Query Response .......................19
3.1.10.3. Request and Response Types ...............19
3.1.11. Provide Cert ......................................19
3.1.12. Update Cert .......................................20
3.1.13. GL Key ............................................21
3.2. Use of CMC, CMS, and PKIX .................................23
3.2.1. Protection Layers ..................................23
3.2.1.1. Minimum Protection ........................23
3.2.1.2. Additional Protection .....................24
3.2.2. Combining Requests and Responses ...................24
3.2.3. GLA Generated Messages .............................26
3.2.4. CMC Control Attributes and CMS Signed Attributes ...27
3.2.4.1. Using cMCStatusInfoExt ....................27
3.2.4.2. Using transactionId .......................30
3.2.4.3. Using Nonces and signingTime ..............30
3.2.4.4. CMC and CMS Attribute Support
Requirements ..............................31
3.2.5. Resubmitted GL Member Messages .....................31
3.2.6. PKIX Certificate and CRL Profile ...................31
4. Administrative Messages ........................................32
4.1. Assign KEK to GL ..........................................32
4.2. Delete GL from GLA ........................................36
4.3. Add Members to GL .........................................38
4.3.1. GLO Initiated Additions ............................39
4.3.2. Prospective Member Initiated Additions .............47
4.4. Delete Members from GL ....................................49
4.4.1. GLO Initiated Deletions ............................50
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4.4.2. Member Initiated Deletions .........................56
4.5. Request Rekey of GL .......................................57
4.5.1. GLO Initiated Rekey Requests .......................59
4.5.2. GLA Initiated Rekey Requests .......................62
4.6. Change GLO ................................................63
4.7. Indicate KEK Compromise ...................................65
4.7.1. GL Member Initiated KEK Compromise Message .........66
4.7.2. GLO Initiated KEK Compromise Message ...............67
4.8. Request KEK Refresh .......................................69
4.9. GLA Query Request and Response ............................70
4.10. Update Member Certificate ................................73
4.10.1. GLO and GLA Initiated Update Member Certificate ...73
4.10.2. GL Member Initiated Update Member Certificate .....75
5. Distribution Message ...........................................77
5.1. Distribution Process ......................................78
6. Algorithms .....................................................79
6.1. KEK Generation Algorithm ..................................79
6.2. Shared KEK Wrap Algorithm .................................79
6.3. Shared KEK Algorithm ......................................79
7. Message Transport ..............................................80
8. Security Considerations ........................................80
9. Acknowledgements ...............................................81
10. References ....................................................81
10.1. Normative References .....................................81
10.2. Informative References ...................................82
Appendix A. ASN.1 Module ..........................................83
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1. Introduction
With the ever-expanding use of secure electronic communications
(e.g., S/MIME [MSG]), 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 RecipientInfo 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,
processing of the per-recipient information may take quite some time,
not to mention the time required to collect and validate the PKCs for
each of the recipients. Each recipient identifies its per-recipient
information and uses the private key associated with the public key
of its PKC to decrypt the CEK and hence gain access to the encrypted
content.
With symmetric algorithms, the origination process is slightly
different. 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.
The techniques to protect the shared KEK 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 confidentiality. 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 performing the encryption wants to ensure that some
subset of the group does not gain access to the information, either a
different KEK should be used (shared only with this smaller group) or
asymmetric algorithms should be used.
1.1. 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 BCP 14, RFC 2119
[RFC2119].
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1.2. Applicability to E-mail
One primary audience for this distribution mechanism is e-mail.
Distribution lists, sometimes referred to as mail lists, support the
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 then the
MLA uses the shared KEK to encrypt the message for the members. In
either case, the recipients of the mail list use the previously
distributed-shared KEK to decrypt the message.
1.3. Applicability to Repositories
Objects can also be distributed via a repository (e.g., Lightweight
Directory Access 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, anyone 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.
1.4. Using the Group Key
This document was written with three specific scenarios in mind: two
supporting Mail List Agents and one for general message distribution.
Scenario 1 depicts the originator sending a public key (PK) protected
message to an MLA who then uses the shared KEK(s) to redistribute the
message to the members of the list. Scenario 2 depicts the
originator sending a shared KEK protected message to an MLA who then
redistributes the message to the members of the list (the MLA only
adds additional recipients). The key used by the originator could be
a key shared either amongst all recipients or just between the member
and the MLA. Note that if the originator uses a key shared only with
the MLA, then the MLA will need to decrypt the message and reencrypt
the message for the list recipients. Scenario 3 shows an originator
sending a shared KEK protected message to a group of recipients
without an intermediate MLA.
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+----> +----> +---->
PK +-----+ S | S +-----+ S | S |
----> | MLA | --+----> ----> | MLA | --+----> ----+---->
+-----+ | +-----+ | |
+----> +----> +---->
Scenario 1 Scenario 2 Scenario 3
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
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RFC 5275 CMS SymKeyDist June 2008
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.
Note: If the distribution for the list is performed by an entity
other than the originator (e.g., an MLA distributing a mail message),
this entity can also enforce access control rules.
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 to 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. GLO(s) may also set up lists
that are closed, where the GLO solely determines GL membership.
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 that 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 not discussed
further; the term GLA will be used to address both functions. It
should be noted that a corrupt GLA can always cause havoc.
3. Protocol Interactions
There are existing mechanisms (e.g., listserv and majordomo) to
manage 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(s) 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 set up the GL, delete the GL, add
members to the GL, delete members of the GL, request a group rekey,
add owners to the GL, remove owners of the GL, indicate a group key
compromise, refresh a group key, interrogate the GLA, and update
members' and owners' public key certificates. The distribution
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messages are the messages that distribute the shared KEKs. The
following sections describe the ASN.1 for both the administration and
distribution messages. Section 4 describes how to use the
administration messages, and Section 5 describes how to use the
distribution messages.
+-----+ +----------+
| GLO | <---+ +----> | Member 1 |
+-----+ | | +----------+
| |
+-----+ <------+ | +----------+
| GLA | <-------------+----> | ... |
+-----+ | +----------+
|
| +----------+
+----> | Member n |
+----------+
Figure 2 - Protocol Interactions
3.1. Control Attributes
To avoid creating an entirely new protocol, the Certificate
Management over CMS (CMC) protocol was chosen as the foundation of
this protocol. The main reason for the choice was the layering
aspect provided by CMC where one or more control attributes are
included in message, protected with CMS, to request or respond to a
desired action. The CMC PKIData structure is used for requests, and
the CMC PKIResponse structure is used for responses. The content-
types PKIData and PKIResponse are then encapsulated in CMS's
SignedData or EnvelopedData, or a combination of the two (see Section
3.2). The following are the control attributes defined in this
document:
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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 GLKRefresh
glaQueryRequest id-skd 11 GLAQueryRequest
glaQueryResponse id-skd 12 GLAQueryResponse
glProvideCert id-skd 13 GLManageCert
glUpdateCert id-skd 14 GLManageCert
glKey id-skd 15 GLKey
In the following conformance tables, the column headings have the
following meanings: O for originate, R for receive, and F for
forward. There are three types of implementations: GLOs, GLAs, and
GL members. The GLO is an optional component, hence all GLO O and
GLO R messages are optional, and GLA F messages are optional. The
first table includes messages that conformant implementations MUST
support. The second table includes messages that MAY be implemented.
The second table should be interpreted as follows: if the control
attribute is implemented by a component, then it must be implemented
as indicated. For example, if a GLA is implemented that supports the
glAddMember control attribute, then it MUST support receiving the
glAddMember message. Note that "-" means not applicable.
Required
Implementation Requirement | Control
GLO | GLA | GL Member | Attribute
O R | O R F | O R |
------- | ----------------- | --------- | ----------
MAY - | MUST - MAY | - MUST | glProvideCert
MAY MAY | - MUST MAY | MUST - | glUpdateCert
- - | MUST - - | - MUST | glKey
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Optional
Implementation Requirement | Control
GLO | GLA | GL Member | Attribute
O R | O R F | O R |
------- | ----------------- | --------- | ----------
MAY - | - MAY - | - - | glUseKEK
MAY - | - MAY - | - - | glDelete
MAY MAY | - MUST MAY | MUST - | glAddMember
MAY MAY | - MUST MAY | MUST - | glDeleteMember
MAY - | - MAY - | - - | glRekey
MAY - | - MAY - | - - | glAddOwner
MAY - | - MAY - | - - | glRemoveOwner
MAY MAY | - MUST MAY | MUST - | glkCompromise
MAY - | - MUST - | MUST - | glkRefresh
MAY - | - SHOULD - | MAY - | glaQueryRequest
- MAY | SHOULD - - | - MAY | glaQueryResponse
glaQueryResponse is carried in the CMC PKIResponse content-type, all
other control attributes are carried in the CMC PKIData content-type.
The exception is glUpdateCert, which can be carried in either PKIData
or PKIResponse.
Success and failure messages use CMC (see Section 3.2.4).
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 has the syntax GLUseKEK:
GLUseKEK ::= SEQUENCE {
glInfo GLInfo,
glOwnerInfo SEQUENCE SIZE (1..MAX) OF GLOwnerInfo,
glAdministration GLAdministration DEFAULT 1,
glKeyAttributes GLKeyAttributes OPTIONAL }
GLInfo ::= SEQUENCE {
glName GeneralName,
glAddress GeneralName }
GLOwnerInfo ::= SEQUENCE {
glOwnerName GeneralName,
glOwnerAddress GeneralName,
certificate Certificates OPTIONAL }
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Certificates ::= SEQUENCE {
pKC [0] Certificate OPTIONAL,
-- See [PROFILE]
aC [1] SEQUENCE SIZE (1.. MAX) OF
AttributeCertificate OPTIONAL,
-- See [ACPROF]
certPath [2] CertificateSet OPTIONAL }
-- From [CMS]
-- CertificateSet and CertificateChoices are included only
-- for illustrative purposes as they are imported from [CMS].
CertificateSet ::= SET SIZE (1..MAX) OF CertificateChoices
-- CertificateChoices supports X.509 public key certificates in
-- certificates and v2 attribute certificates in v2AttrCert.
GLAdministration ::= INTEGER {
unmanaged (0),
managed (1),
closed (2) }
GLKeyAttributes ::= SEQUENCE {
rekeyControlledByGLO [0] BOOLEAN DEFAULT FALSE,
recipientsNotMutuallyAware [1] BOOLEAN DEFAULT TRUE,
duration [2] INTEGER DEFAULT 0,
generationCounter [3] INTEGER DEFAULT 2,
requestedAlgorithm [4] AlgorithmIdentifier
DEFAULT { id-aes128-wrap } }
The fields in GLUseKEK have the following meaning:
- glInfo indicates the name of the GL in glName and the address of
the GL in glAddress. The glName and glAddress can be the same,
but this is not always the case. Both the name and address MUST
be unique for a given GLA.
- glOwnerInfo indicates:
-- glOwnerName indicates the name of the owner of the GL. One
of the names in glOwnerName MUST match one of the names in
the certificate (either the subject distinguished name or one
of the subject alternative names) used to sign this
SignedData.PKIData creating the GL (i.e., the immediate
signer).
-- glOwnerAddress indicates the GL owner's address.
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-- certificates MAY be included. It contains the following
three fields:
--- certificates.pKC includes the encryption certificate for
the GLO. It will be used to encrypt responses for the
GLO.
--- certificates.aC MAY be included to convey any attribute
certificate (see [ACPROF]) associated with the
encryption certificate of the GLO included in
certificates.pKC.
--- certificates.certPath MAY also be included to convey
certificates that might aid the recipient in
constructing valid certification paths for the
certificate provided in certificates.pKC and the
attribute certificates provided in certificates.aC.
Theses certificates are optional because they might
already be included elsewhere in the message (e.g., in
the outer CMS layer).
-- glAdministration indicates how the GL ought to 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, it is allowing prospective members to request
addition and deletion from the GL without GLO
intervention.
--- Managed - When the GLO sets glAdministration to managed,
it is allowing prospective members to request addition
and deletion 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,
it is not allowing prospective members to request
addition or deletion 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 be
AES-128 (see Section 7), the shared KEK will be valid for a
calendar month (i.e., first of the month until the last day
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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.
--- recipientsNotMutuallyAware 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 not to 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 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 in the UTC Zulu time zone. 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 (13 May 2008);
the shared KEKs will be valid from Tuesday (13 May 2008)
to Tuesday (20 May 2008). The exact time of the day is
determined when the key is generated.
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--- 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 Sections 4.5 and 5 for
more on rekey.
--- requestedAlgorithm indicates the algorithm and any
parameters the GLO wants the GLA to use with the shared
KEK. The parameters are conveyed via the
SMIMECapabilities attribute (see [MSG]). See Section 6
for more on algorithms.
3.1.2. Delete GL
GLOs use glDelete to request that a GL be deleted from the GLA. The
glDelete control attribute has the syntax GeneralName. The glDelete
message MUST be signed by the GLO. The name of the GL to be deleted
is included in GeneralName:
DeleteGL ::= GeneralName
3.1.3. Add GL Member
GLOs use the glAddMember to request addition of new members, and
prospective GL members use the glAddMember to request their own
addition to the GL. The glAddMember message MUST be signed by either
the GLO or the prospective GL member. The glAddMember control
attribute has the syntax GLAddMember:
GLAddMember ::= SEQUENCE {
glName GeneralName,
glMember GLMember }
GLMember ::= SEQUENCE {
glMemberName GeneralName,
glMemberAddress GeneralName OPTIONAL,
certificates Certificates OPTIONAL }
The fields in GLAddMembers have the following meaning:
- glName indicates the name of the GL to which the member should be
added.
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- glMember indicates the particulars for the GL member. Both of
the following fields must be unique for a given GL:
-- glMemberName indicates the name of the GL member.
-- glMemberAddress indicates the GL member's address. It MUST
be included.
Note: In some instances, the glMemberName and glMemberAddress
may be the same, but this is not always the case.
-- certificates MUST be included. It contains the following
three fields:
--- certificates.pKC includes the member's encryption
certificate. It will be used, at least initially, to
encrypt the shared KEK for that member. If the message
is generated by a prospective GL member, the pKC MUST be
included. If the message is generated by a GLO, the pKC
SHOULD be included.
--- certificates.aC MAY be included to convey any attribute
certificate (see [ACPROF]) associated with the member's
encryption certificate.
--- certificates.certPath MAY also be included to convey
certificates that might aid the recipient in
constructing valid certification paths for the
certificate provided in certificates.pKC and the
attribute certificates provided in certificates.aC.
These certificates are optional because they might
already be included elsewhere in the message (e.g., in
the outer CMS layer).
3.1.4. Delete GL Member
GLOs use the glDeleteMember to request deletion of GL members, and GL
members use the glDeleteMember to request their own removal from the
GL. The glDeleteMember message MUST be signed by either the GLO or
the GL member. The glDeleteMember control attribute has the syntax
GLDeleteMember:
GLDeleteMember ::= SEQUENCE {
glName GeneralName,
glMemberToDelete GeneralName }
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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 or address of the member to
be deleted.
3.1.5. Rekey GL
GLOs use the glRekey to request a GL rekey. The glRekey message MUST
be signed by the GLO. The glRekey control attribute has the syntax
GLRekey:
GLRekey ::= SEQUENCE {
glName GeneralName,
glAdministration GLAdministration OPTIONAL,
glNewKeyAttributes GLNewKeyAttributes OPTIONAL,
glRekeyAllGLKeys BOOLEAN OPTIONAL }
GLNewKeyAttributes ::= SEQUENCE {
rekeyControlledByGLO [0] BOOLEAN OPTIONAL,
recipientsNotMutuallyAware [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 Section 3.1.1 for the three options.
This field is only included if there is a change from the
previously registered glAdministration.
- 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 keys
will be issued. The field is only included if there is a change
from the previously registered glKeyAttributes.
- glRekeyAllGLKeys indicates whether the GLO wants all of the
outstanding GL's shared KEKs rekeyed. If it is set to TRUE then
all outstanding KEKs MUST be issued. If it is set to FALSE then
all outstanding KEKs need not be reissued.
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3.1.6. Add GL Owner
GLOs use the glAddOwner to request that a new GLO be allowed to
administer the GL. The glAddOwner message MUST be signed by a
registered GLO. The glAddOwner control attribute has 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, address, and certificates of the
new GLO. As this message includes names of new GLOs, the
certificates.pKC MUST be included, and it MUST include the
encryption certificate of the new GLO.
3.1.7. Remove GL Owner
GLOs use the glRemoveOwner to request that a GLO be disassociated
with the GL. The glRemoveOwner message MUST be signed by a
registered GLO. The glRemoveOwner control attribute has 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. The certificates field SHOULD be omitted, as it will be
ignored.
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 has the syntax GeneralName. This message is always
redirected by the GLA to the GLO for further action. The
glkCompromise MAY be included in an EnvelopedData generated with the
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compromised shared KEK. The name of the GL to which the compromised
key is associated is placed in GeneralName:
GLKCompromise ::= GeneralName
3.1.9. GL Key Refresh
GL members use the glkRefresh to request that the shared KEK be
redistributed to them. The glkRefresh control attribute has the
syntax GLKRefresh.
GLKRefresh ::= SEQUENCE {
glName GeneralName,
dates SEQUENCE SIZE (1..MAX) OF Date }
Date ::= SEQUENCE {
start GeneralizedTime,
end GeneralizedTime OPTIONAL }
The fields in GLKRefresh have the following meaning:
- glName indicates the name of the GL for which the GL member wants
shared KEKs.
- dates indicates a date range for keys the GL member wants. The
start field indicates the first date the GL member wants and the
end field indicates the last date. The end date MAY be omitted
to indicate the GL member wants all keys from the specified start
date to the current date. Note that a procedural mechanism is
needed to restrict users from accessing messages that they are
not allowed to access.
3.1.10. GLA Query Request and Response
There are situations where GLOs and GL members may need to determine
some information from the GLA about the GL. GLOs and GL members use
the glaQueryRequest, defined in Section 3.1.10.1, to request
information and GLAs use the glaQueryResponse, defined in Section
3.1.10.2, to return the requested information. Section 3.1.10.3
includes one request and response type and value; others may be
defined in additional documents.
3.1.10.1. GLA Query Request
GLOs and GL members use the glaQueryRequest to ascertain information
about the GLA. The glaQueryRequest control attribute has the syntax
GLAQueryRequest:
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GLAQueryRequest ::= SEQUENCE {
glaRequestType OBJECT IDENTIFIER,
glaRequestValue ANY DEFINED BY glaRequestType }
3.1.10.2. GLA Query Response
GLAs return the glaQueryResponse after receiving a GLAQueryRequest.
The glaQueryResponse MUST be signed by a GLA. The glaQueryResponse
control attribute has the syntax GLAQueryResponse:
GLAQueryResponse ::= SEQUENCE {
glaResponseType OBJECT IDENTIFIER,
glaResponseValue ANY DEFINED BY glaResponseType }
3.1.10.3. Request and Response Types
Requests and responses are registered as a pair under the following
object identifier arc:
id-cmc-glaRR OBJECT IDENTIFIER ::= { id-cmc 99 }
This document defines one request/response pair for GL members and
GLOs to query the GLA for the list of algorithm it supports. The
following Object Identifier (OID) is included in the glaQueryType
field:
id-cmc-gla-skdAlgRequest OBJECT IDENTIFIER ::={ id-cmc-glaRR 1 }
SKDAlgRequest ::= NULL
If the GLA supports GLAQueryRequest and GLAQueryResponse messages,
the GLA may return the following OID in the glaQueryType field:
id-cmc-gla-skdAlgResponse OBJECT IDENTIFIER ::= { id-cmc-glaRR 2 }
The glaQueryValue has the form of the smimeCapabilities attributes as
defined in [MSG].
3.1.11. Provide Cert
GLAs and GLOs use the 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 revoked, the GLO or GLA MUST NOT use it to generate the
EnvelopedData that encapsulates the glProvideCert request. The
glProvideCert control attribute has the syntax GLManageCert:
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GLManageCert ::= SEQUENCE {
glName GeneralName,
glMember GLMember }
The fields in GLManageCert have the following meaning:
- glName indicates the name of the GL to which the GL member's new
certificate is to be associated.
- glMember indicates particulars for the GL member:
-- glMemberName indicates the GL member's name.
-- glMemberAddress indicates the GL member's address. It MAY be
omitted.
-- certificates SHOULD be omitted.
3.1.12 Update Cert
GL members and GLOs use the glUpdateCert to provide a new certificate
for the GL. GL members can generate an unsolicited glUpdateCert or
generate a response glUpdateCert as a result of receiving 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 has the syntax GLManageCert:
GLManageCert ::= SEQUENCE {
glName GeneralName,
glMember GLMember }
The fields in GLManageCert have the following meaning:
- glName indicates the name of the GL to which the GL member's new
certificate should be associated.
- glMember indicates the particulars for the GL member:
-- glMemberName indicates the GL member's name.
-- glMemberAddress indicates the GL member's address. It MAY be
omitted.
-- certificates MAY be omitted if the GLManageCert message is
sent to request the GL member's certificate; otherwise, it
MUST be included. It includes the following three fields:
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--- certificates.pKC includes the member's encryption
certificate that will be used to encrypt the shared KEK
for that member.
--- certificates.aC MAY be included to convey one or more
attribute certificates associated with the member's
encryption certificate.
--- certificates.certPath MAY also be included to convey
certificates that might aid the recipient in
constructing valid certification paths for the
certificate provided in certificates.pKC and the
attribute certificates provided in certificates.aC.
These certificates are optional because they might
already be included elsewhere in the message (e.g., in
the outer CMS layer).
3.1.13. GL Key
The GLA uses the glKey to distribute the shared KEK. The glKey
message MUST be signed by the GLA. The glKey control attribute has
the syntax GLKey:
GLKey ::= SEQUENCE {
glName GeneralName,
glIdentifier KEKIdentifier, -- See [CMS]
glkWrapped RecipientInfos, -- See [CMS]
glkAlgorithm AlgorithmIdentifier,
glkNotBefore GeneralizedTime,
glkNotAfter GeneralizedTime }
-- KEKIdentifier is included only for illustrative purposes as
-- it is imported from [CMS].
KEKIdentifier ::= SEQUENCE {
keyIdentifier OCTET STRING,
date GeneralizedTime OPTIONAL,
other OtherKeyAttribute OPTIONAL }
The fields in GLKey have the following meaning:
- glName is the name of the GL.
- glIdentifier is the key identifier of the shared KEK. See
Section 6.2.3 of [CMS] for a description of the subfields.
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- glkWrapped is the wrapped shared KEK for the GL for a particular
duration. The RecipientInfos MUST be generated as specified in
Section 6.2 of [CMS]. The ktri RecipientInfo choice MUST be
supported. The key in the EncryptedKey field (i.e., the
distributed shared KEK) MUST be generated according to the
section concerning random number generation in the security
considerations of [CMS].
- glkAlgorithm identifies the algorithm with which the shared KEK
is used. Since no encrypted data content is being conveyed at
this point, the parameters encoded with the algorithm should be
the structure defined for smimeCapabilities rather than encrypted
content.
- glkNotBefore indicates the date at which the shared KEK is
considered valid. GeneralizedTime values MUST be expressed in
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 in
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.
If the glKey message is in response to a glUseKEK message:
- The GLA MUST generate separate glKey messages for each recipient
if glUseKEK.glKeyAttributes.recipientsNotMutuallyAware is set to
TRUE. For each recipient, you want to generate a message that
contains that recipient's key (i.e., one message with one
attribute).
- The GLA MUST generate the requested number of glKey messages.
The value in glUseKEK.glKeyAttributes.generationCounter indicates
the number of glKey messages requested.
If the glKey message is in response to a glRekey message:
- The GLA MUST generate separate glKey messages for each recipient
if glRekey.glNewKeyAttributes.recipientsNotMutuallyAware is set
to TRUE.
- The GLA MUST generate the requested number of glKey messages.
The value in glUseKEK.glKeyAttributes.generationCounter indicates
the number of glKey messages requested.
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- The GLA MUST generate one glKey message for each outstanding
shared KEKs for the GL when glRekeyAllGLKeys is set to TRUE.
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
when glUseKEK.glNewKeyAttributes.recipientsNotMutuallyAware that
set up the GL was set to TRUE.
- The GLA MAY generate glKey messages prior to the duration on the
last outstanding shared KEK expiring, where the number of glKey
messages generated is generationCounter minus one (1). Other
distribution mechanisms can also be supported to support this
functionality.
3.2. Use of CMC, CMS, and PKIX
The following sections outline the use of CMC, CMS, and the PKIX
certificate and CRL profile.
3.2.1. Protection Layers
The following sections outline the protection required for the
control attributes defined in this document.
Note: There are multiple ways to encapsulate SignedData and
EnvelopedData. The first is to use a MIME wrapper around each
ContentInfo, as specified in [MSG]. The second is not to use a MIME
wrapper around each ContentInfo, as specified in Transporting S/MIME
Objects in X.400 [X400TRANS].
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].
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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:
Authentication and Integrity
Confidentiality Protection of Confidentiality Protection
-------------------------- -----------------------------
EnvelopedData SignedData
SignedData EnvelopedData
PKIData or PKIResponse SignedData
controlSequence PKIData or PKIResponse
controlSequence
If an incoming message is encrypted, the confidentiality of the
message MUST be preserved. All EnvelopedData objects MUST be
processed as specified in [CMS]. If a SignedData is added over an
EnvelopedData, a ContentHints attribute SHOULD be added. See Section
2.9 of Extended Security Services for S/MIME [ESS].
If the GLO or GL member applies confidentiality to a request, the
EnvelopedData MUST include the GLA as a recipient. If the GLA
forwards the GL member request to the GLO, then the GLA MUST decrypt
the EnvelopedData content, strip the confidentiality layer, and apply
its own confidentiality layer as an EnvelopedData with the GLO as a
recipient.
3.2.2. Combining Requests and Responses
Multiple requests and responses 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
different GLs. That is, 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:
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Multiple Requests and Responses
Request Response
------- --------
SignedData SignedData
PKIData PKIResponse
cmsSequence cmsSequence
SignedData SignedData
PKIData PKIResponse
controlSequence controlSequence
One or more requests One or more responses
corresponding to one GL corresponding to one GL
SignedData SignedData
PKIData PKIResponse
controlSequence controlSequence
One or more requests One or more responses
corresponding to another GL corresponding to another GL
When applying confidentiality to multiple requests and responses, all
of the requests/responses 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
One or more requests
corresponding to one GL
SignedData
PKIData
controlSequence
One or more requests
corresponding to one GL
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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
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. Note that there is a
processing priority, but it does not imply an ordering within the
content.
3.2.3. GLA Generated Messages
When the GLA generates a success or fail message, it generates one
for each request. SKDFailInfo values of unsupportedDuration,
unsupportedDeliveryMethod, unsupportedAlgorithm, noGLONameMatch,
nameAlreadyInUse, alreadyAnOwner, and notAnOwner are not returned to
GL members.
If GLKeyAttributes.recipientsNotMutuallyAware is set to TRUE, a
separate PKIResponse.cMCStatusInfoExt and PKIData.glKey MUST be
generated for each recipient. However, it is valid to send one
message with multiple attributes to the same recipient.
If the GL has multiple GLOs, the GLA MUST send cMCStatusInfoExt
messages to the requesting GLO. The mechanism to determine which GLO
made the request is beyond the scope of this document.
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:
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GLA Forwarded Requests
----------------------
SignedData
PKIData
cmsSequence
SignedData
PKIData
controlSequence
3.2.4. CMC Control Attributes and CMS Signed Attributes
CMC carries control attributes as CMS signed attributes. These
attributes are defined in [CMC] and [CMS]. Some of these attributes
are REQUIRED; others are OPTIONAL. The required attributes are as
follows: cMCStatusInfoExt transactionId, senderNonce, recipientNonce,
queryPending, and signingTime. Other attributes can also be used;
however, their use is beyond the scope of this document. The
following sections specify requirements in addition to those already
specified in [CMC] and [CMS].
3.2.4.1. Using cMCStatusInfoExt
cMCStatusInfoExt is used by GLAs to indicate to GLOs and GL members
that a request was unsuccessful. Two classes of failure codes are
used within this document. Errors from the CMCFailInfo list, found
in Section 5.1.4 of CMC, are encoded as defined in CMC. Error codes
defined in this document are encoded using the ExtendedFailInfo field
of the cmcStatusInfoExt structure. If the same failure code applies
to multiple commands, a single cmcStatusInfoExt structure can be used
with multiple items in cMCStatusInfoExt.bodyList. The GLA MAY also
return other pertinent information in statusString. The SKDFailInfo
object identifier and value are:
id-cet-skdFailInfo OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) cet(15) skdFailInfo(1) }
SKDFailInfo ::= INTEGER {
unspecified (0),
closedGL (1),
unsupportedDuration (2),
noGLACertificate (3),
invalidCert (4),
unsupportedAlgorithm (5),
noGLONameMatch (6),
invalidGLName (7),
nameAlreadyInUse (8),
noSpam (9),
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-- obsolete (10),
alreadyAMember (11),
notAMember (12),
alreadyAnOwner (13),
notAnOwner (14) }
The values have the following meaning:
- unspecified indicates that the GLA is unable or unwilling to
perform the requested action and does not want to indicate the
reason.
- closedGL indicates that members can only be added or deleted by
the GLO.
- unsupportedDuration indicates that 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 that the member's encryption certificate
was not verifiable (i.e., signature did not validate,
certificate's serial number present on a CRL, the certificate
expired, 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 that the GLA does not support the glName
present in the request.
- nameAlreadyInUse indicates that the glName is already assigned on
the GLA.
- noSpam indicates that the prospective GL member did not sign the
request (i.e., if the name in glMember.glMemberName does not
match one of the names (either the subject distinguished name or
one of the subject alternative names) in the certificate used to
sign the request).
- alreadyAMember indicates that the prospective GL member is
already a GL member.
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- notAMember indicates that the prospective GL member to be deleted
is not presently a GL member.
- alreadyAnOwner indicates that the prospective GLO is already a
GLO.
- notAnOwner indicates that the prospective GLO to be deleted is
not presently a GLO.
cMCStatusInfoExt is used by GLAs to indicate to GLOs and GL members
that a request was successfully completed. If the request was
successful, the GLA returns a cMCStatusInfoExt response with
cMCStatus.success 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
cMCStatusInfoExt 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.
Additionally, the appropriate SKDFailInfo can be included in
cMCStatusInfoExt.extendedFailInfo.
cMCStatusInfoExt is used by GLOs, GLAs, and GL members to indicate
that signature verification failed. If the signature failed to
verify over any control attribute except a cMCStatusInfoExt, a
cMCStatusInfoExt 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.
GLOs and GL members who receive cMCStatusInfoExt messages whose
signatures are invalid SHOULD generate a new request to avoid
badMessageCheck message loops.
cMCStatusInfoExt 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 cMCStatusInfoExt
control attribute MUST be returned indicating cMCStatus.pending and
otherInfo.pendInfo. When requests are redirected to the GLO for
approval (for managed lists), the GLA MUST NOT return a
cMCStatusInfoExt indicating query pending.
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cMCStatusInfoExt is also used by GLAs to indicate that a
glaQueryRequest is not supported. If the glaQueryRequest is not
supported, the cMCStatusInfoExt control attribute MUST be returned
indicating cMCStatus.noSupport and statusString is optionally
returned to convey additional information.
cMCStatusInfoExt is also used by GL members, GLOs, and GLAs to
indicate that the signingTime (see Section 3.2.4.3) is not close
enough to the locally specified time. If the local time is not close
enough to the time specified in signingTime, a cMCStatus.failed and
otherInfo.failInfo.badTime MAY be returned.
3.2.4.2. Using transactionId
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 cMCStatusInfoExt response it generates one for the GLA with the
GLA's transactionId and one for the GL member with the GL member's
transactionId.
3.2.4.3. Using Nonces and signingTime
The use of nonces (see Section 5.6 of [CMC]) and an indication of
when the message was signed (see Section 11.3 of [CMS]) can be used
to provide application-level replay prevention.
To protect the GL, all messages MUST include the signingTime
attribute. Message originators and recipients can then use the time
provided in this attribute to determine whether they have previously
received the message.
If the originating message includes a senderNonce, the response to
the message MUST include the received senderNonce value as the
recipientNonce and a new value as the senderNonce value in the
response.
If a GLA aggregates multiple messages together or forwards a message
to a GLO, the GLA MAY optionally generate a new nonce value and
include that in the wrapping message. When the response comes back
from the GLO, the GLA builds a response to the originator(s) of the
message(s) and deals with each of the nonce values from the
originating messages.
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For these attributes, it is necessary to maintain state information
on exchanges to compare one result to another. The time period for
which this information is maintained is a local policy.
3.2.4.4. CMC and CMS Attribute Support Requirements
The following are the implementation requirements for CMC control
attributes and CMS signed attributes for an implementation to be
considered conformant to this specification:
Implementation Requirement |
GLO | GLA | GL Member | Attribute
O R | O R F | O R |
--------- | ------------- | --------- | ----------
MUST MUST | MUST MUST - | MUST MUST | cMCStatusInfoExt
MAY MAY | MUST MUST - | MAY MAY | transactionId
MAY MAY | MUST MUST - | MAY MAY | senderNonce
MAY MAY | MUST MUST - | MAY MAY | recepientNonce
MUST MUST | MUST MUST - | MUST MUST | SKDFailInfo
MUST MUST | MUST MUST - | MUST MUST | signingTime
3.2.5. Resubmitted GL Member Messages
When the GL is managed, the GLA forwards the GL member requests to
the GLO for GLO approval by creating a new request message containing
the GL member request(s) as a cmsSequence item. If the GLO approves
the request, it can either add a new layer of wrapping and send it
back to the GLA or create a new message and send it to the GLA.
(Note in this case there are now 3 layers of PKIData messages with
appropriate signing layers.)
3.2.6. PKIX Certificate and CRL Profile
Signatures, certificates, and CRLs are verified according to the PKIX
profile [PROFILE].
Name matching is performed according to the PKIX profile [PROFILE].
All distinguished name forms must follow the UTF8String convention
noted in the PKIX profile [PROFILE].
A certificate per GL would be issued to the GLA.
GL policy may mandate that the GL member's address be included in the
GL member's certificate.
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4. Administrative Messages
There are a number of administrative messages that must be exchanged
to manage a GL. The following sections describe each request and
response message combination in detail. The procedures defined in
this section are not prescriptive.
4.1. Assign KEK to GL
Prior to generating a group key, a GL needs to be set up and a shared
KEK assigned to the GL. Figure 3 depicts the protocol interactions
to set up and assign a shared KEK. Note that error messages are not
depicted in Figure 3. Additionally, behavior for the optional
transactionId, senderNonce, and recipientNonce CMC control attributes
is not addressed in these procedures.
+-----+ 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 recipientsNotMutuallyAware, the
requested algorithm to be used with the shared KEK in
requestedAlgorithm, the duration of the shared KEK, and how many
shared KEKs should be initially distributed in generationCounter.
The GLO MUST also include the signingTime attribute with this
request.
1.a - If the GLO knows of members to be added to the GL, the
glAddMember request(s) MAY be included in the same
controlSequence as the glUseKEK request (see Section 3.2.2).
The GLO indicates the same glName in the glAddMember request
as in glUseKEK.glInfo.glName. Further glAddMember procedures
are covered in Section 4.3.
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RFC 5275 CMS SymKeyDist June 2008
1.b - The GLO can apply confidentiality to the request by
encapsulating the SignedData.PKIData in an EnvelopedData (see
Section 3.2.1.2).
1.c - The GLO can also optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the request, the GLA checks the signingTime and
verifies the signature on the innermost SignedData.PKIData. If
an additional SignedData and/or EnvelopedData encapsulates the
request (see Sections 3.2.1.2 and 3.2.2), the GLA verifies the
outer signature(s) and/or decrypts the outer layer(s) prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
do not verify, the GLA returns a cMCStatusInfoExt response
indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures do verify but the GLA does not have a
valid certificate, the GLA returns a cMCStatusInfoExt with
cMCStatus.failed and otherInfo.extendedFailInfo.SKDFailInfo
value of noValidGLACertificate. Additionally, a signingTime
attribute is included with the response. Instead of
immediately returning the error code, the GLA attempts to get
a certificate, possibly using [CMC].
2.d - Else the signatures are valid and the GLA does have a valid
certificate, the GLA checks that one of the names in the
certificate used to sign the request matches one of the names
in glUseKEK.glOwnerInfo.glOwnerName.
2.d.1 - If the names do not match, the GLA returns a response
indicating cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
noGLONameMatch. Additionally, a signingTime attribute is
included with the response.
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2.d.2 - Else if the names all match, the GLA checks that the
glName and glAddress are not already in use. The GLA
also checks any glAddMember included within the
controlSequence with this glUseKEK. Further processing
of the glAddMember is covered in Section 4.3.
2.d.2.a - If the glName is already in use, the GLA returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
nameAlreadyInUse. Additionally, a signingTime
attribute is included with the response.
2.d.2.b - Else if the requestedAlgorithm is not supported, the
GLA returns a response indicating cMCStatusInfoExt
with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unsupportedAlgorithm. Additionally, a signingTime
attribute is included with the response.
2.d.2.c - Else if the duration cannot be supported, determining
this is beyond the scope of this document, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unsupportedDuration. Additionally, a signingTime
attribute is included with the response.
2.d.2.d - Else if the GL cannot be supported for other reasons,
which the GLA does not wish to disclose, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unspecified. Additionally, a signingTime attribute
is included with the response.
2.d.2.e - Else if the glName is not already in use, the
duration can be supported, and the requestedAlgorithm
is supported, the GLA MUST return a cMCStatusInfoExt
indicating cMCStatus.success and a signingTime
attribute. (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
section 5.
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2.d.2.e.1 - The GLA can apply confidentiality to the response
by encapsulating the SignedData.PKIResponse in an
EnvelopedData if the request was encapsulated in
an EnvelopedData (see Section 3.2.1.2).
2.d.2.e.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see Section
3.2.1.2).
3 - Upon receipt of the cMCStatusInfoExt responses, the GLO checks
the signingTime and verifies the GLA signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
response (see Section 3.2.1.2 or 3.2.2), the GLO verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
do verify, the GLO MUST check that one of the names in the
certificate used to sign the response matches the name of the
GL.
3.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO should
not believe the response.
3.b.2 - Else if the name of the GL does match the name present in
the certificate and:
3.b.2.a - If the signatures do verify and the response was
cMCStatusInfoExt indicating cMCStatus.success, the
GLO has successfully created the GL.
3.b.2.b - Else if the signatures are valid and the response is
cMCStatusInfoExt.cMCStatus.failed with any reason,
the GLO can reattempt to create the GL using the
information provided in the response. The GLO can
also use the glaQueryRequest to determine the
algorithms and other characteristics supported by the
GLA (see Section 4.9).
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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 deletes the GL. Figure 4 depicts the protocol
interactions to delete a GL. Note that behavior for the optional
transactionId, senderNonce, and recipientNonce CMC control attributes
is not addressed in these procedures.
+-----+ 1 2 +-----+
| GLA | <-------> | GLO |
+-----+ +-----+
Figure 4 - Delete Group List
The process is as follows:
1 - The GLO is 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 is included in GeneralName. The GLO MUST also include
the signingTime attribute and can also include a transactionId
and senderNonce attributes.
1.a - The GLO can optionally apply confidentiality to the request
by encapsulating the SignedData.PKIData in an EnvelopedData
(see Section 3.2.1.2).
1.b - The GLO MAY optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the request, the GLA checks the signingTime and
verifies the signature on the innermost SignedData.PKIData. If
an additional SignedData and/or EnvelopedData encapsulates the
request (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
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2.c - Else if the signatures verify, the GLA makes sure the GL is
supported by checking the name of the GL matches a glName
stored on the GLA.
2.c.1 - If the glName is not supported by the GLA, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
2.c.2 - Else if the glName is supported by the GLA, the GLA
ensures that 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.c.2.a - If the names do not match, the GLA returns a response
indicating cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
noGLONameMatch. Additionally, a signingTime
attribute is included with the response.
2.c.2.b - Else if the names do match, but the GL cannot be
deleted for other reasons, which the GLA does not
wish to disclose, the GLA returns a response
indicating cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unspecified. Additionally, a signingTime attribute
is included with the response. Actions beyond the
scope of this document must then be taken to delete
the GL from the GLA.
2.c.2.c - Else if the names do match, the GLA returns a
cMCStatusInfoExt indicating cMCStatus.success and a
signingTime attribute (2 in Figure 4). The GLA ought
not accept further requests for member additions,
member deletions, or group rekeys for this GL.
2.c.2.c.1 - The GLA can apply confidentiality to the response
by encapsulating the SignedData.PKIResponse in an
EnvelopedData if the request was encapsulated in
an EnvelopedData (see Section 3.2.1.2).
2.c.2.c.2 - The GLA MAY optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
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3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
signingTime and verifies the GLA signature(s). If an additional
SignedData and/or EnvelopedData encapsulates the response (see
Section 3.2.1.2 or 3.2.2), the GLO verifies the outer signature
and/or decrypts the outer layer prior to verifying the signature
on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
verify, the GLO checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
3.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO should
not believe the response.
3.b.2 - Else if the name of the GL does match the name present in
the certificate and:
3.b.2.a - If the signatures verify and the response was
cMCStatusInfoExt indicating cMCStatus.success, the
GLO has successfully deleted the GL.
3.b.2.b - Else if the signatures do verify and the response was
cMCStatusInfoExt.cMCStatus.failed with any reason,
the GLO can reattempt to delete the GL using the
information provided in the response.
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, it
set the GL to be unmanaged, managed, or closed (see Section 3.1.1).
In the unmanaged case, the GLA merely processes the member's request.
In 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
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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 sections 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. Additionally, note that
behavior for the optional transactionId, senderNonce, and
recipientNonce CMC control attributes is not addressed in these
procedures.
+-----+ 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 can be rekeyed to maintain the confidentiality of the traffic
sent by group members. 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 Sections 4.5 and 5.
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 includes 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.pKC. The GLO can also include any
attribute certificates associated with the member's encryption
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certificate in glMember.certificates.aC, and the certification
path associated with the member's encryption and attribute
certificates in glMember.certificates.certPath. The GLO MUST
also include the signingTime attribute with this request.
1.a - The GLO can optionally apply confidentiality to the request
by encapsulating the SignedData.PKIData in an EnvelopedData
(see Section 3.2.1.2).
1.b - The GLO can also optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the request, the GLA checks the signingTime and
verifies the signature on the innermost SignedData.PKIData. If
an additional SignedData and/or EnvelopedData encapsulates the
request (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures verify, the glAddMember request is
included in a controlSequence with the glUseKEK request, and
the processing in Section 4.1 item 2.d is successfully
completed, the GLA returns a cMCStatusInfoExt indicating
cMCStatus.success and a signingTime attribute (2 in Figure
5).
2.c.1 - The GLA can apply confidentiality to the response by
encapsulating the SignedData.PKIData in an EnvelopedData
if the request was encapsulated in an EnvelopedData (see
Section 3.2.1.2).
2.c.2 - The GLA can also optionally apply another SignedData over
the EnvelopedData (see Section 3.2.1.2).
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2.d - Else if the signatures verify and the GLAddMember request is
not included in a controlSequence with the GLCreate request,
the GLA makes sure the GL is supported by checking that the
glName matches a glName stored on the GLA.
2.d.1 - If the glName is not supported by the GLA, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
2.d.2 - Else if the glName is supported by the GLA, the GLA
checks to see if the glMemberName is present on the GL.
2.d.2.a - If the glMemberName is present on the GL, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
alreadyAMember. Additionally, a signingTime
attribute is included with the response.
2.d.2.b - Else if the glMemberName is not present on the GL,
the GLA checks how the GL is administered.
2.d.2.b.1 - If the GL is closed, the GLA checks 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.d.2.b.1.a - If the names do not match, the GLA returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value
of noGLONameMatch. Additionally, a
signingTime attribute is included with the
response.
2.d.2.b.1.b - Else if the names match, the GLA verifies the
member's encryption certificate.
2.d.2.b.1.b.1 - If the member's encryption certificate
cannot be verified, the GLA can return a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo
value of invalidCert to the GLO.
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Additionally, a signingTime attribute is
included with the response. If the GLA
does not return a
cMCStatusInfoExt.cMCStatus.failed
response, the GLA issues a glProvideCert
request (see Section 4.10).
2.d.2.b.1.b.2 - Else if the member's certificate
verifies, the GLA returns a
cMCStatusInfoExt indicating
cMCStatus.success and a signingTime
attribute (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 also distributes the shared KEK
to the member via the mechanism described
in Section 5.
2.d.2.b.1.b.2.a - The GLA applies confidentiality to
the response by encapsulating the
SignedData.PKIData in an
EnvelopedData if the request was
encapsulated in an EnvelopedData (see
Section 3.2.1.2).
2.d.2.b.1.b.2.b - The GLA can also optionally apply
another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2.d.2.b.2 - Else if the GL is managed, the GLA checks 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 needs
to match a registered GLO. For the prospective
member, the name in glMember.glMemberName needs
to match one of the names in the certificate used
to sign the request.
2.d.2.b.2.a - If the signer is neither a registered GLO nor
the prospective GL member, the GLA returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value
of noSpam. Additionally, a signingTime
attribute is included with the response.
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2.d.2.b.2.b - Else if the signer is a registered GLO, the
GLA verifies the member's encryption
certificate.
2.d.2.b.2.b.1 - If the member's certificate cannot be
verified, the GLA can return a response
indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo
value of invalidCert. Additionally, a
signingTime attribute is included with
the response. If the GLA does not return
a cMCStatus.failed response, the GLA MUST
issue a glProvideCert request (see
Section 4.10).
2.d.2.b.2.b.2 - Else if the member's certificate
verifies, the GLA MUST return a
cMCStatusInfoExt indicating
cMCStatus.success and a signingTime
attribute 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 also
distributes the shared KEK to the member
via the mechanism described in Section 5.
The GL policy may mandate that the GL
member's address be included in the GL
member's certificate.
2.d.2.b.2.b.2.a - The GLA applies confidentiality to
the response by encapsulating the
SignedData.PKIData in an
EnvelopedData if the request was
encapsulated in an EnvelopedData (see
Section 3.2.1.2).
2.d.2.b.2.b.2.b - The GLA can also optionally apply
another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2.d.2.b.2.c - Else if the signer is the prospective member,
the GLA forwards the glAddMember request (see
Section 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 is beyond the scope of this
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document. Further processing of the
forwarded request by GLOs is addressed in 3
of Section 4.3.2.
2.d.2.b.2.c.1 - The GLA applies confidentiality to the
forwarded request by encapsulating the
SignedData.PKIData in an EnvelopedData if
the original request was encapsulated in
an EnvelopedData (see Section 3.2.1.2).
2.d.2.b.2.c.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
2.d.2.b.3 - Else if the GL is unmanaged, the GLA checks 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 needs
to match the name of a registered GLO. For the
prospective member, the name in
glMember.glMemberName needs to match one of the
names in the certificate used to sign the
request.
2.d.2.b.3.a - If the signer is neither a registered GLO nor
the prospective member, the GLA returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value
of noSpam. Additionally, a signingTime
attribute is included with the response.
2.d.2.b.3.b - Else if the signer is either a registered GLO
or the prospective member, the GLA verifies
the member's encryption certificate.
2.d.2.b.3.b.1 - If the member's certificate cannot be
verified, the GLA can return a response
indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo
value of invalidCert and a signingTime
attribute to either the GLO or the
prospective member depending on where the
request originated. If the GLA does not
return a cMCStatus.failed response, the
GLA issues a glProvideCert request (see
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Section 4.10) to either the GLO or
prospective member depending on where the
request originated.
2.d.2.b.3.b.2 - Else if the member's certificate
verifies, the GLA returns a
cMCStatusInfoExt indicating
cMCStatus.success and a signingTime
attribute 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. 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 also distributes the shared KEK to
the member via the mechanism described in
Section 5.
2.d.2.b.3.b.2.a - The GLA applies confidentiality to
the response by encapsulating the
SignedData.PKIData in an
EnvelopedData if the request was
encapsulated in an EnvelopedData (see
Section 3.2.1.2).
2.d.2.b.3.b.2.b - The GLA can also optionally apply
another SignedData over the
EnvelopedData (see Section 3.2.1.2).
3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
signingTime and verifies the GLA signature(s). If an additional
SignedData and/or EnvelopedData encapsulates the response (see
Section 3.2.1.2 or 3.2.2), the GLO verifies the outer signature
and/or decrypts the outer layer prior to verifying the signature
on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
verify, the GLO checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
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3.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO should
not believe the response.
3.b.2 - Else if the name of the GL matches the name present in
the certificate and:
3.b.2.a - If the signatures verify and the response is
cMCStatusInfoExt indicating cMCStatus.success, the
GLA has added the member to the GL. If the member
was added to a managed list and the original request
was signed by the member, the GLO sends a
cMCStatusInfoExt.cMCStatus.success and a signingTime
attribute to the GL member.
3.b.2.b - Else if the GLO received a
cMCStatusInfoExt.cMCStatus.failed with any reason,
the GLO can reattempt to add the member to the GL
using the information provided in the response.
4 - Upon receipt of the cMCStatusInfoExt response, the prospective
member checks the signingTime and verifies the GLA signatures or
GLO signatures. If an additional SignedData and/or EnvelopedData
encapsulates the response (see Section 3.2.1.2 or 3.2.2), the GLO
verifies the outer signature and/or decrypts the outer layer
prior to verifying the signature on the innermost SignedData.
4.a - If the signingTime attribute value is not within the locally
accepted time window, the prospective member MAY return a
response indicating cMCStatus.failed and
otherInfo.failInfo.badTime and a signingTime attribute.
4.b - Else if signature processing continues and if the signatures
verify, the GL member checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
4.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GL member
should not believe the response.
4.b.2 - Else if the name of the GL matches the name present in the
certificate and:
4.b.2.a - If the signatures verify, the prospective member has
been added to the GL.
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4.b.2.b - Else if the prospective member received a
cMCStatusInfoExt.cMCStatus.failed, for any reason,
the prospective member MAY reattempt to add itself to
the GL using the information provided in the
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 includes: the GL name
in glName, their name in glMember.glMemberName, their address in
glMember.glMemberAddress, and their encryption certificate in
glMember.certificates.pKC. The prospective GL member can also
include any attribute certificates associated with their
encryption certificate in glMember.certificates.aC, and the
certification path associated with their encryption and attribute
certificates in glMember.certificates.certPath. The prospective
member MUST also include the signingTime attribute with this
request.
1.a - The prospective GL member can optionally apply
confidentiality to the request by encapsulating the
SignedData.PKIData in an EnvelopedData (see Section 3.2.1.2).
1.b - The prospective GL member MAY optionally apply another
SignedData over the EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the request, the GLA verifies the request as per
2 in Section 4.3.1.
3 - Upon receipt of the forwarded request, the GLO checks the
signingTime and verifies the prospective GL member signature on
the innermost SignedData.PKIData and the GLA signature on the
outer layer. If an EnvelopedData encapsulates the innermost
layer (see Section 3.2.1.2 or 3.2.2), the GLO decrypts the outer
layer prior to verifying the signature on the innermost
SignedData.
Note: For cases where the GL is closed and either a) a
prospective member sends directly to the GLO or b) the GLA has
mistakenly forwarded the request to the GLO, the GLO should first
determine whether to honor the request.
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3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime.
3.b - Else if signature processing continues and if the signatures
verify, the GLO checks 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 sends a
SignedData.PKIResponse.controlSequence message back to
the prospective member with
cMCStatusInfoExt.cMCStatus.failed indicating why the
prospective member was denied in
cMCStausInfo.statusString. This stops people from adding
people to GLs without their permission. Additionally, a
signingTime attribute is included with the response.
3.b.2 - Else if the names 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 can return a
SignedData.PKIResponse.controlSequence message back
to the prospective member with
cMCStatusInfoExt.cMCtatus.failed indicating why the
prospective member was denied in
cMCStatus.statusString. Additionally, a signingTime
attribute is included with the response.
3.b.2.b - Else if the GLO determines the prospective member is
allowed to join the GL, the GLO verifies the member's
encryption certificate.
3.b.2.b.1 - If the member's certificate cannot be verified,
the GLO returns a
SignedData.PKIResponse.controlSequence back to
the prospective member with
cMCStatusInfoExt.cMCtatus.failed indicating that
the member's encryption certificate did not
verify in cMCStatus.statusString. Additionally,
a signingTime attribute is included with the
response. If the GLO does not return a
cMCStatusInfoExt response, the GLO sends a
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SignedData.PKIData.controlSequence.glProvideCert
message to the prospective member requesting a
new encryption certificate (see Section 4.10).
3.b.2.b.2 - Else if the member's certificate verifies, the
GLO resubmits the glAddMember request (see
Section 3.2.5) to the GLA (1 in Figure 5).
3.b.2.b.2.a - The GLO applies confidentiality to the new
GLAddMember request by encapsulating the
SignedData.PKIData in an EnvelopedData if the
initial request was encapsulated in an
EnvelopedData (see Section 3.2.1.2).
3.b.2.b.2.b - The GLO can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
4 - Processing continues as in 2 of Section 4.3.1.
4.4. Delete Members from GL
To delete members from GLs, either the GLO or members to be removed
use the glDeleteMember request. The GLA processes the GLO, and
members requesting their own removal make 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 member sends the request, the
GLA needs to determine how the GL is administered. When the GLO
initially configured the GL, it set the GL to be unmanaged, managed,
or closed (see Section 3.1.1). In the unmanaged case, the GLA merely
processes the member's request. In the managed case, the GLA
forwards the requests from the member 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 members. The
following sections describe the processing for the GLO(s), GLA, and
GL members depending on where the request originated, either from a
GLO or from members wanting to be removed. Figure 6 depicts the
protocol interactions for the three options. Note that the error
messages are not depicted. Additionally, behavior for the optional
transactionId, senderNonce, and recipientNonce CMC control attributes
is not addressed in these procedures.
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+-----+ 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, it 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 itself back on the GL
under a different name. For managed and closed GLs, the GLO needs to
take steps to ensure that the member being deleted is not on the GL
twice. After ensuring this, managed and closed GLs can be rekeyed to
maintain the confidentiality of the traffic sent by group members.
If the GLO is sure the member has been deleted, the group rekey
mechanism can be used to distribute the new key (see Sections 4.5 and
5).
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 can be done through an out-of-band 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 is a closed or managed GL, the GLO MUST
also generate a glRekey request and include it with the
glDeletemember request (see Section 4.5). The GLO MUST also
include the signingTime attribute with this request.
1.a - The GLO can optionally apply confidentiality to the request
by encapsulating the SignedData.PKIData in an EnvelopedData
(see Section 3.2.1.2).
1.b - The GLO can also optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
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2 - Upon receipt of the request, the GLA checks the signingTime
attribute and verifies the signature on the innermost
SignedData.PKIData. If an additional SignedData and/or
EnvelopedData encapsulates the request (see Section 3.2.1.2 or
3.2.2), the GLA verifies the outer signature and/or decrypts the
outer layer prior to verifying the signature on the innermost
SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures verify, the GLA makes sure the GL is
supported by the GLA 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
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
2.c.2 - Else if the glName is supported by the GLA, the GLA
checks to see if the glMemberName is present on the GL.
2.c.2.a - If the glMemberName is not present on the GL, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
notAMember. Additionally, a signingTime attribute is
included with the response.
2.c.2.b - Else if the glMemberName is already on the GL, the
GLA checks how the GL is administered.
2.c.2.b.1 - If the GL is closed, the GLA checks 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.
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2.c.2.b.1.a - If the names do not match, the GLA returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value
of closedGL. Additionally, a signingTime
attribute is included with the response.
2.c.2.b.1.b - Else if the names do match, the GLA returns a
cMCStatusInfoExt.cMCStatus.success and a
signingTime attribute (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. Note that the GL also needs to be
rekeyed as described in Section 5.
2.c.2.b.1.b.1 - The GLA applies confidentiality to the
response by encapsulating the
SignedData.PKIData in an EnvelopedData if
the request was encapsulated in an
EnvelopedData (see Section 3.2.1.2).
2.c.2.b.1.b.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
2.c.2.b.2 - Else if the GL is managed, the GLA checks 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 needs
to match a registered GLO. For the prospective
member, the name in glMember.glMemberName needs
to 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 returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value
of noSpam. Additionally, a signingTime
attribute is included with the response.
2.c.2.b.2.b - Else if the signer is a registered GLO, the
GLA returns a
cMCStatusInfoExt.cMCStatus.success and a
signingTime attribute(2 in Figure 6). The
GLA also takes administrative actions, which
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are beyond the scope of this document, to
delete the member with the GL stored on the
GLA. Note that the GL will also be rekeyed
as described in Section 5.
2.c.2.b.2.b.1 - The GLA applies confidentiality to the
response by encapsulating the
SignedData.PKIData in an EnvelopedData if
the request was encapsulated in an
EnvelopedData (see Section 3.2.1.2).
2.c.2.b.2.b.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
2.c.2.b.2.c - Else if the signer is the prospective member,
the GLA forwards the glDeleteMember request
(see Section 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 Section 4.4.2.
2.c.2.b.2.c.1 - The GLA applies confidentiality to the
forwarded request by encapsulating the
SignedData.PKIData in an EnvelopedData if
the request was encapsulated in an
EnvelopedData (see Section 3.2.1.2).
2.c.2.b.2.c.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
2.c.2.b.3 - Else if the GL is unmanaged, the GLA checks 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 needs
to match the name of a registered GLO. For the
prospective member, the name in
glMember.glMemberName needs to match one of the
names in the certificate used to sign the
request.
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2.c.2.b.3.a - If the signer is neither the GLO nor the
prospective member, the GLA returns a
response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value
of noSpam. Additionally, a signingTime
attribute is included with the response.
2.c.2.b.3.b - Else if the signer is either a registered GLO
or the member, the GLA returns a
cMCStatusInfoExt.cMCStatus.success and a
signingTime attribute 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.c.2.b.3.b.1 - The GLA applies confidentiality to the
response by encapsulating the
SignedData.PKIData in an EnvelopedData if
the request was encapsulated in an
EnvelopedData (see Section 3.2.1.2).
2.c.2.b.3.b.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
signingTime and verifies the GLA signatures. If an additional
SignedData and/or EnvelopedData encapsulates the response (see
Section 3.2.1.2 or 3.2.2), the GLO verifies the outer signature
and/or decrypts the outer layer prior to verifying the signature
on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
do verify, the GLO checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
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3.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO should
not believe the response.
3.b.2 - Else if the name of the GL matches the name present in
the certificate and:
3.b.2.a - If the signatures verify and the response is
cMCStatusInfoExt.cMCStatus.success, 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 sends a
cMCStatusInfoExt.cMCStatus.success and a signingTime
attribute to the GL member.
3.b.2.b - Else if the GLO received a
cMCStatusInfoExt.cMCStatus.failed with any reason,
the GLO may reattempt to delete the member from the
GL using the information provided in the response.
4 - Upon receipt of the cMCStatusInfoExt response, the member checks
the signingTime and verifies the GLA signature(s) or GLO
signature(s). If an additional SignedData and/or EnvelopedData
encapsulates the response (see Section 3.2.1.2 or 3.2.2), the GLO
verifies the outer signature and/or decrypts the outer layer
prior to verifying the signature on the innermost SignedData.
4.a - If the signingTime attribute value is not within the locally
accepted time window, the prospective member MAY return a
response indicating cMCStatus.failed and
otherInfo.failInfo.badTime and a signingTime attribute.
4.b - Else if signature processing continues and if the signatures
verify, the GL member checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
4.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GL member
should not believe the response.
4.b.2 - Else if the name of the GL matches the name present in
the certificate and:
4.b.2.a - If the signature(s) verify, the member has been
deleted from the GL.
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4.b.2.b - Else if the member received a
cMCStatusInfoExt.cMCStatus.failed with any reason,
the member can reattempt to delete itself from the GL
using the information provided in the response.
4.4.2. Member Initiated Deletions
The process for member initiated deletion of its own membership using
the glDeleteMember requests is as follows:
1 - The member sends a
SignedData.PKIData.controlSequence.glDeleteMember request to the
GLA (A in Figure 6). The member includes the name of the GL in
glName and the member's own name in glMemberToDelete. The GL
member MUST also include the signingTime attribute with this
request.
1.a - The member can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIData in an
EnvelopedData (see Section 3.2.1.2).
1.b - The member can also optionally apply another SignedData over
the EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the request, the GLA verifies the request as per
2 in Section 4.4.1.
3 - Upon receipt of the forwarded request, the GLO checks the
signingTime and verifies the member signature on the innermost
SignedData.PKIData and the GLA signature on the outer layer. If
an EnvelopedData encapsulates the innermost layer (see Section
3.2.1.2 or 3.2.2), the GLO decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
Note: For cases where the GL is closed and either (a) a
prospective member sends directly to the GLO or (b) the GLA has
mistakenly forwarded the request to the GLO, the GLO should first
determine whether to honor the request.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
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3.b - Else if signature processing continues if the signatures
cannot be verified, the GLO returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck and a signingTime
attribute.
3.c - Else if the signatures verify, the GLO checks to make sure
one of the names in the certificates used to sign the request
matches the name in glMemberToDelete.
3.c.1 - If the names do not match, the GLO sends a
SignedData.PKIResponse.controlSequence message back to
the prospective member with
cMCStatusInfoExt.cMCtatus.failed indicating why the
prospective member was denied in
cMCStatusInfoExt.statusString. This stops people from
adding people to GLs without their permission.
Additionally, a signingTime attribute is included with
the response.
3.c.2 - Else if the names match, the GLO resubmits the
glDeleteMember request (see Section 3.2.5) to the GLA (1
in Figure 6). The GLO makes sure the glMemberName is
already on the GL. The GLO also generates a glRekey
request and include it with the GLDeleteMember request
(see Section 4.5).
3.c.2.a - The GLO applies confidentiality to the new
GLDeleteMember request by encapsulating the
SignedData.PKIData in an EnvelopedData if the initial
request was encapsulated in an EnvelopedData (see
Section 3.2.1.2).
3.c.2.b - The GLO can also optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
4 - Further processing is as in 2 of Section 4.4.1.
4.5. Request Rekey of GL
From time to time, the GL will need to be rekeyed. Some situations
follow:
- When a member is removed from a closed or managed GL. In this
case, the PKIData.controlSequence containing the glDeleteMember
ought to contain a glRekey request.
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- 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. Consider two
cases:
-- 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 Section 5.
If the generationCounter (see Section 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 ought to 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 to control rekeys or whether
the GLA is going to control rekeys when they assigned the shared KEK
to GL (see Section 3.1.1). The GLO initiates a GL rekey at any time.
The GLA can be configured to automatically rekey the GL prior to the
expiration of the shared KEK (the length of time before the
expiration is an implementation decision). The GLA can also
automatically rekey GLs that have been compromised, but this is
covered in Section 5. Figure 7 depicts the protocol interactions to
request a GL rekey. Note that error messages are not depicted.
Additionally, behavior for the optional transactionId, senderNonce,
and recipientNonce CMC control attributes is not addressed in these
procedures.
+-----+ 1 2,A +-----+
| GLA | <-------> | GLO |
+-----+ +-----+
Figure 7 - GL Rekey Request
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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 includes 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, it includes the glRekeyAllGLKeys set to TRUE. The
GLO MUST also include a signingTime attribute with this request.
1.a - The GLO can optionally apply confidentiality to the request
by encapsulating the SignedData.PKIData in an EnvelopedData
(see Section 3.2.1.2).
1.b - The GLO can also optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the request, the GLA checks the signingTime and
verifies the signature on the innermost SignedData.PKIData. If
an additional SignedData and/or EnvelopedData encapsulates the
request (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
do not verify, the GLA returns a cMCStatusInfoExt response
indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures do verify, the GLA makes sure the GL
is supported by the GLA by checking that the glName matches a
glName stored on the GLA.
2.c.1 - If the glName present does not match a GL stored on the
GLA, the GLA returns a response indicating
cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
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2.c.2 - Else if the glName present matches a GL stored on the
GLA, the GLA checks that a registered GLO signed the
request by checking that one of the names in the
certificate used to sign the request is a registered GLO.
2.c.2.a - If the names do not match, the GLA returns a response
indicating cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
noGLONameMatch. Additionally, a signingTime
attribute is included with the response.
2.c.2.b - Else if the names match, the GLA checks the
glNewKeyAttribute values.
2.c.2.b.1 - If the new value for requestedAlgorithm is not
supported, the GLA returns a response indicating
cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unsupportedAlgorithm. Additionally, a
signingTime attribute is included with the
response.
2.c.2.b.2 - Else if the new value duration is not supportable
(determining this is beyond the scope of this
document), the GLA returns a response indicating
cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unsupportedDuration. Additionally, a signingTime
attribute is included with the response.
2.c.2.b.3 - Else if the GL is not supportable for other
reasons that the GLA does not wish to disclose,
the GLA returns a response indicating
cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
unspecified. Additionally, a signingTime
attribute is included with the response.
2.c.2.b.4 - Else if the new requestedAlgorithm and duration
are supportable or the glNewKeyAttributes was
omitted, the GLA returns a
cMCStatusInfoExt.cMCStatus.success and a
sigingTime attribute (2 in Figure 7). The GLA
also uses the glKey message to distribute the
rekey shared KEK (see Section 5).
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2.c.2.b.4.a - The GLA applies confidentiality to response
by encapsulating the SignedData.PKIData in an
EnvelopedData if the request was encapsulated
in an EnvelopedData (see Section 3.2.1.2).
2.c.2.b.4.b - The GLA can also optionally apply another
SignedData over the EnvelopedData (see
Section 3.2.1.2).
3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
signingTime and verifies the GLA signature(s). If an additional
SignedData and/or EnvelopedData encapsulates the forwarded
response (see Section 3.2.1.2 or 3.2.2), the GLO verifies the
outer signature and/or decrypts the forwarded response prior to
verifying the signature on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
verify, the GLO checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
3.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO should
not believe the response.
3.b.2 - Else if the name of the GL matches the name present in
the certificate and:
3.b.2.a - If the signatures verify and the response is
cMCStatusInfoExt.cMCStatus.success, the GLO has
successfully rekeyed the GL.
3.b.2.b - Else if the GLO received a
cMCStatusInfoExt.cMCStatus.failed with any reason,
the GLO can reattempt to rekey the GL using the
information provided in the response.
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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 Section 5). In addition the GLA will
generate a cMCStatusInfoExt to indicate to the GL that a successful
rekey has occurred. The process for GLA initiated rekey is as
follows:
1 - The GLA generates for all GLOs a
SignedData.PKIData.controlSequence.cMCStatusInfoExt.cMCStatus
success and includes a signingTime attribute (A in Figure 7).
1.a - The GLA can optionally apply confidentiality to the request
by encapsulating the SignedData.PKIData in an EnvelopedData
(see Section 3.2.1.2).
1.b - The GLA can also optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the cMCStatusInfoExt.cMCStatus.success response,
the GLO checks the signingTime and verifies the GLA signature(s).
If an additional SignedData and/or EnvelopedData encapsulates the
forwarded response (see Section 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 innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
verify, the GLO checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
2.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO ought
not believe the response.
2.b.2 - Else if the name of the GL does match the name present in
the certificate and the response is
cMCStatusInfoExt.cMCStatus.success, the GLO knows the GLA
has successfully rekeyed the GL.
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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. Note that error messages are not shown.
Additionally, behavior for the optional transactionId, senderNonce,
and recipientNonce CMC control attributes is not addressed in these
procedures.
+-----+ 1 2 +-----+
| GLA | <-------> | GLO |
+-----+ +-----+
Figure 8 - GLO Add and 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
includes the GL name in glName, and the name and address of the
GLO in glOwnerName and glOwnerAddress, respectively. The GLO
MUST also include the signingTime attribute with this request.
1.a - The GLO can optionally apply confidentiality to the request
by encapsulating the SignedData.PKIData in an EnvelopedData
(see Section 3.2.1.2).
1.b - The GLO can also optionally apply another SignedData over the
EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the glAddOwner or glRemoveOwner request, the GLA
checks the signingTime and verifies the GLO signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
request (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
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2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures verify, the GLA makes 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
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
2.c.2 - Else if the glName is supported by the GLA, the GLA
ensures that 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.c.2.a - If the names do not match, the GLA returns a response
indicating cMCStatusInfoExt with cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
noGLONameMatch. Additionally, a signingTime
attribute is included with the response.
2.c.2.b - Else if the names match, the GLA returns a
cMCStatusInfoExt.cMCStatus.success and a signingTime
attribute (2 in Figure 4). The GLA also takes
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.c.2.b.1 - The GLA applies confidentiality to the response
by encapsulating the SignedData.PKIResponse in an
EnvelopedData if the request was encapsulated in
an EnvelopedData (see Section 3.2.1.2).
2.c.2.b.2 - The GLA can also optionally apply another
SignedData over the EnvelopedData (see Section
3.2.1.2).
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3 - Upon receipt of the cMCStatusInfoExt response, the GLO checks the
signingTime and verifies the GLA's signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
response (see Section 3.2.1.2 or 3.2.2), the GLO verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
verify, the GLO checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
3.b.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO should
not believe the response.
3.b.2 - Else if the name of the GL does match the name present in
the certificate and:
3.b.2.a - If the signatures verify and the response was
cMCStatusInfoExt.cMCStatus.success, the GLO has
successfully added or removed the GLO.
3.b.2.b - Else if the signatures verify and the response was
cMCStatusInfoExt.cMCStatus.failed with any reason,
the GLO can reattempt to add or delete the GLO using
the information provided in the response.
4.7. Indicate KEK Compromise
There 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. Note that error messages are not shown.
Additionally, behavior for the optional transactionId, senderNonce,
and recipientNonce CMC control attributes is not addressed in these
procedures.
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+-----+ 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 includes the name of the GL
in GeneralName. The GL member MUST also include the signingTime
attribute with this request.
1.a - The GL member can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIData in an
EnvelopedData (see Section 3.2.1.2). The glkCompromise can
be included in an EnvelopedData generated with the
compromised shared KEK.
1.b - The GL member can also optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the glkCompromise request, the GLA checks the
signingTime and verifies the GL member signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
request (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
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2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures verify, the GLA makes sure the GL is
supported by checking that the indicated GL name matches a
glName stored on the GLA.
2.c.1 - If the glName is not supported by the GLA, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
2.c.2 - Else if the glName is supported by the GLA, the GLA
checks who signed the request. For GLOs, one of the
names in the certificate used to sign the request needs
to match a registered GLO. For the member, the name in
glMember.glMemberName needs to match one of the names in
the certificate used to sign the request.
2.c.2.a - If the GLO signed the request, the GLA generates a
glKey message as described in Section 5 to rekey the
GL (4 in Figure 9).
2.c.2.b - Else if someone other than the GLO signed the
request, the GLA forwards the glkCompromise message
(see Section 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 Section 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 includes the name of the GL
in GeneralName. The GLO MUST also include a signingTime
attribute with this request.
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1.a.1 - The GLO can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIData in an
EnvelopedData (see Section 3.2.1.2). The glkCompromise
can be included in an EnvelopedData generated with the
compromised shared KEK.
1.a.2 - The GLO can also optionally apply another SignedData over
the EnvelopedData (see Section 3.2.1.2).
1.b - Otherwise, checks the signingTime and verifies the GLA and GL
member signatures on the forwarded glkCompromise message. If
an additional SignedData and/or EnvelopedData encapsulates
the request (see Section 3.2.1.2 or 3.2.2), the GLO verifies
the outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
1.b.1 - If the signingTime attribute value is not within the
locally accepted time window, the GLO MAY return a
response indicating cMCStatus.failed and
otherInfo.failInfo.badTime and a signingTime attribute.
1.b.2 - Else if signature processing continues and if the
signatures cannot be verified, the GLO returns a
cMCStatusInfoExt response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
1.b.2.a - If the signatures verify, the GLO checks that the
names in the certificate match the name of the signer
(i.e., the name in the certificate used to sign the
GL member's request is the GL member).
1.b.2.a.1 - If either name does not match, the GLO ought not
trust the signer and it ought not forward the
message to the GLA.
1.b.2.a.2 - Else if the names match and the signatures
verify, the GLO determines whether to forward the
glkCompromise message back to the GLA (3{1} in
Figure 9). Further processing by the GLA is in 2
of Section 4.7.1. The GLO can also return a
response to the prospective member with
cMCStatusInfoExt.cMCtatus.success indicating that
the glkCompromise message was successfully
received.
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4.8. Request KEK Refresh
There will be times when GL members have irrecoverably lost 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. Note that
error messages are not shown. Additionally, behavior for the
optional transactionId, senderNonce, and recipientNonce CMC control
attributes is not addressed in these procedures.
+-----+ 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 includes name of the GL in
GeneralName. The GL member MUST also include a signingTime
attribute with this request.
1.a - The GL member can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIData in an
EnvelopedData (see Section 3.2.1.2).
1.b - The GL member can also optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the glkRefresh request, the GLA checks the
signingTime and verifies the GL member signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
request (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypt the outer layer prior to verifying
the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
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2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures verify, the GLA makes sure the GL is
supported by checking that the GLGeneralName matches a glName
stored on the GLA.
2.c.1 - If the name of the GL is not supported by the GLA, the
GLA returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
invalidGLName. Additionally, a signingTime attribute is
included with the response.
2.c.2 - Else if the glName is supported by the GLA, the GLA
ensures that the GL member is on the GL.
2.c.2.a - If the glMemberName is not present on the GL, the GLA
returns a response indicating cMCStatusInfoExt with
cMCStatus.failed and
otherInfo.extendedFailInfo.SKDFailInfo value of
noSpam. Additionally, a signingTime attribute is
included with the response.
2.c.2.b - Else if the glMemberName is present on the GL, the
GLA returns a cMCStatusInfoExt.cMCStatus.success, a
signingTime attribute, and a glKey message (2 in
Figure 10) as described in Section 5.
4.9. GLA Query Request and Response
There will be certain times when a GLO is having trouble setting up a
GL because it does not know the algorithm(s) or some other
characteristic that the GLA supports. There can also be times when
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 messages have been defined to
support determining this information. Figure 11 depicts the protocol
interactions for glaQueryRequest and glaQueryResponse. Note that
error messages are not shown. Additionally, behavior for the
optional transactionId, senderNonce, and recipientNonce CMC control
attributes is not addressed in these procedures.
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+-----+ 1 2 +------------------+
| GLA | <-------> | GLO or GL Member |
+-----+ +------------------+
Figure 11 - GLA Query Request and 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 it is interested in receiving
from the GLA. Additionally, a signingTime attribute is included
with this request.
1.a - The GLO, GL member, or prospective GL member can optionally
apply confidentiality to the request by encapsulating the
SignedData.PKIData in an EnvelopedData (see Section 3.2.1.2).
1.b - The GLO, GL member, or prospective GL member can also
optionally apply another SignedData over the EnvelopedData
(see Section 3.2.1.2).
2 - Upon receipt of the glaQueryRequest, the GLA determines if it
accepts glaQueryRequest messages.
2.a - If the GLA does not accept glaQueryRequest messages, the GLA
returns a cMCStatusInfoExt response indicating
cMCStatus.noSupport and any other information in
statusString.
2.b - Else if the GLA does accept GLAQueryRequests, the GLA checks
the signingTime and verifies the GLO, GL member, or
prospective GL member signature(s). If an additional
SignedData and/or EnvelopedData encapsulates the request (see
Section 3.2.1.2 or 3.2.2), the GLA verifies the outer
signature and/or decrypts the outer layer prior to verifying
the signature on the innermost SignedData.
2.b.1 - If the signingTime attribute value is not within the
locally accepted time window, the GLA MAY return a
response indicating cMCStatus.failed and
otherInfo.failInfo.badTime and a signingTime attribute.
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2.b.2 - Else if the signature processing continues and if the
signatures cannot be verified, the GLA returns a
cMCStatusInfoExt response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.b.3 - Else if the signatures verify, the GLA returns a
glaQueryResponse (2 in Figure 11) with the correct
response if the glaRequestType is supported or returns a
cMCStatusInfoExt response indicating cMCStatus.noSupport
if the glaRequestType is not supported. Additionally, a
signingTime attribute is included with the response.
2.b.3.a - The GLA applies confidentiality to the response by
encapsulating the SignedData.PKIResponse in an
EnvelopedData if the request was encapsulated in an
EnvelopedData (see Section 3.2.1.2).
2.b.3.b - The GLA can also optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
3 - Upon receipt of the glaQueryResponse, the GLO, GL member, or
prospective GL member checks the signingTime and verifies the GLA
signature(s). If an additional SignedData and/or EnvelopedData
encapsulates the response (see Section 3.2.1.2 or 3.2.2), the
GLO, GL member, or prospective GL member verifies the outer
signature and/or decrypts the outer layer prior to verifying the
signature on the innermost SignedData.
3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO, GL member, or prospective GL
member MAY return a response indicating cMCStatus.failed and
otherInfo.failInfo.badTime and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
do not verify, the GLO, GL member, or prospective GL member
returns a cMCStatusInfoExt response indicating
cMCStatus.failed and otherInfo.failInfo.badMessageCheck.
Additionally, a signingTime attribute is included with the
response.
3.c - Else if the signatures verify, then the GLO, GL member, or
prospective GL member checks that one of the names in the
certificate used to sign the response matches the name of the
GL.
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3.c.1 - If the name of the GL does not match the name present in
the certificate used to sign the message, the GLO ought
not believe the response.
3.c.2 - Else if the name of the GL matches the name present in
the certificate and the response was glaQueryResponse,
then the GLO, GL member, or prospective GL member may use
the information contained therein.
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 can
be instances when the 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 might also be
times when the GL member knows that its certificate is about to
expire or has been revoked, and GL member will not be able to receive
GL rekeys. Behavior for the optional transactionId, senderNonce, and
recipientNonce CMC control attributes is not addressed in these
procedures.
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 name in glMemberName. Additionally, a signingTime
attribute is included with this request.
1.a - The GLO or GLA can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIData in an
EnvelopedData (see Section 3.2.1.2). If the GL member's PKC
has been revoked, the GLO or GLA ought not use it to generate
the EnvelopedData that encapsulates the glProvideCert
request.
1.b - The GLO or GLA can also optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
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2 - Upon receipt of the glProvideCert message, the GL member checks
the signingTime and verifies the GLO or GLA signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
response (see Section 3.2.1.2 or 3.2.2), the GL member verifies
the outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GL member MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
cannot be verified, the GL member returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
2.c - Else if the signatures verify, the GL member generates a
Signed.PKIResponse.controlSequence.glUpdateCert that includes
the GL name in glName, the member's name in
glMember.glMemberName, the member's encryption certificate in
glMember.certificates.pKC. The GL member can also include
any attribute certificates associated with the member's
encryption certificate in glMember.certificates.aC, and the
certification path associated with the member's encryption
and attribute certificates in glMember.certificates.certPath.
Additionally, a signingTime attribute is included with the
response.
2.c.1 - The GL member can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIResponse in an
EnvelopedData (see Section 3.2.1.2). If the GL member's
PKC has been revoked, the GL member ought not use it to
generate the EnvelopedData that encapsulates the
glProvideCert request.
2.c.2 - The GL member can also optionally apply another
SignedData over the EnvelopedData (see Section 3.2.1.2).
3 - Upon receipt of the glUpdateCert message, the GLO or GLA checks
the signingTime and verifies the GL member signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
response (see Section 3.2.1.2 or 3.2.2), the GL member verifies
the outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
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3.a - If the signingTime attribute value is not within the locally
accepted time window, the GLO or GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
3.b - Else if signature processing continues and if the signatures
cannot be verified, the GLO or GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
3.c - Else if the signatures verify, the GLO or GLA verifies the
member's encryption certificate.
3.c.1 - If the member's encryption certificate cannot be
verified, the GLO returns either another glProvideCert
request or a cMCStatusInfoExt with cMCStatus.failed and
the reason why in cMCStatus.statusString. glProvideCert
should be returned only a certain number of times is
because if the GL member does not have a valid
certificate it will never be able to return one.
Additionally, a signingTime attribute is included with
either response.
3.c.2 - Else if the member's encryption certificate cannot be
verified, the GLA returns another glProvideCert request
to the GL member or a cMCStatusInfoExt 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 it will never
be able to return one. Additionally, a signingTime
attribute is included with the response.
3.c.3 - Else if the member's encryption certificate verifies, 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 includes the GL name in glName, the member's name in
glMember.glMemberName, the member's encryption certificate in
glMember.certificates.pKC. The GL member can also include any
attribute certificates associated with the member's encryption
certificate in glMember.certificates.aC, and the certification
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path associated with the member's encryption and attribute
certificates in glMember.certificates.certPath. The GL member
MUST also include a signingTime attribute with this request.
1.a - The GL member can optionally apply confidentiality to the
request by encapsulating the SignedData.PKIData in an
EnvelopedData (see Section 3.2.1.2). If the GL member's PKC
has been revoked, the GLO or GLA ought not use it to generate
the EnvelopedData that encapsulates the glProvideCert
request.
1.b - The GL member can also optionally apply another SignedData
over the EnvelopedData (see Section 3.2.1.2).
2 - Upon receipt of the glUpdateCert message, the GLA checks the
signingTime and verifies the GL member signature(s). If an
additional SignedData and/or EnvelopedData encapsulates the
response (see Section 3.2.1.2 or 3.2.2), the GLA verifies the
outer signature and/or decrypts the outer layer prior to
verifying the signature on the innermost SignedData.
2.a - If the signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
cannot be verified, the GLA returns a cMCStatusInfoExt
response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck.
2.c - Else if the signatures verify, the GLA verifies the member's
encryption certificate.
2.c.1 - If the member's encryption certificate cannot be
verified, the GLA returns another glProvideCert request
to the GL member or a cMCStatusInfoExt with
cMCStatus.failed and the reason why in
cMCStatus.statusString to the GLO. glProvideCert ought
not be returned indefinitely; if the GL member does not
have a valid certificate it will never be able to return
one. Additionally, a signingTime attribute is included
with the response.
2.c.2 - Else if the member's encryption certificate verifies, the
GLA will use it in subsequent glAddMember requests and
glKey messages associated with the GL member. The GLA
also forwards the glUpdateCert message to the GLO.
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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
cMCStatusInfoExt response for the respective request. Figure 12
depicts the protocol interactions to send out glKey messages. Unlike
the procedures defined for the administrative messages, the
procedures defined in this section MUST be implemented by GLAs for
origination and by GL members on reception. Note that error messages
are not shown. Additionally, behavior for the optional
transactionId, senderNonce, and recipientNonce CMC control attributes
is not addressed in these procedures.
1 +----------+
+-------> | Member 1 |
| +----------+
+-----+ | 1 +----------+
| GLA | ----+-------> | ... |
+-----+ | +----------+
| 1 +----------+
+-------> | Member n |
+----------+
Figure 12 - GL Key Distribution
If the GL was set up with GLKeyAttributes.recipientsNotMutuallyAware
set to TRUE, a separate glKey message MUST be sent to each GL member
so as not to 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 GL's glAdministration set to
managed or closed, and
- glRekey request with generationCounter set to zero (0).
The GLA MUST use either the kari (see Section 12.3.2 of [CMS]) or
ktri (see Section 12.3.1 of [CMS]) choice in
glKey.glkWrapped.RecipientInfo to ensure that only the intended
recipients receive the shared KEK. The GLA MUST support the ktri
choice.
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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 Section 12.3.3
of [CMS]) in glKey.glkWrapped.RecipientInfo to ensure that only the
intended recipients receive the shared KEK. The GLA MUST support the
RecipientInfo.ktri 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 cannot
generate a glKey message for the GL member because the GL
member's PKC has expired or is otherwise invalid, the GLA MAY
send a glUpdateCert to the GL member requesting a new certificate
be provided (see Section 4.10). The number of glKey messages
generated for the GL is described in Section 3.1.13.
Additionally, a signingTime attribute is included with the
distribution message(s).
1.a - The GLA MAY optionally apply another confidentiality layer to
the message by encapsulating the SignedData.PKIData in
another EnvelopedData (see Section 3.2.1.2).
1.b - The GLA MAY also optionally apply another SignedData over the
EnvelopedData.SignedData.PKIData (see Section 3.2.1.2).
2 - Upon receipt of the glKey message, the GL members MUST check the
signingTime and verify the signature over the innermost
SignedData.PKIData. If an additional SignedData and/or
EnvelopedData encapsulates the message (see Section 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 signingTime attribute value is not within the locally
accepted time window, the GLA MAY return a response
indicating cMCStatus.failed and otherInfo.failInfo.badTime
and a signingTime attribute.
2.b - Else if signature processing continues and if the signatures
cannot be verified, the GL member MUST return a
cMCStatusInfoExt response indicating cMCStatus.failed and
otherInfo.failInfo.badMessageCheck. Additionally, a
signingTime attribute is included with the response.
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2.c - Else if the signatures verify, the GL member processes the
RecipientInfos according to [CMS]. 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. Additionally, the GL member MUST return a
cMCStatusInfoExt indicating cMCStatus.success to tell the GLA
the KEK was received.
6. Algorithms
This section lists the algorithms that MUST be implemented.
Additional algorithms that SHOULD be implemented are also included.
Further algorithms MAY also be implemented.
6.1. KEK Generation Algorithm
Implementations MUST randomly generate content-encryption keys,
message-authentication keys, initialization vectors (IVs), and
padding. Also, the generation of public/private key pairs relies on
a random numbers. The use of inadequate pseudo-random number
generators (PRNGs) to generate cryptographic keys can result in
little or no security. An attacker may find it much easier to
reproduce the PRNG environment that produced the keys, searching the
resulting small set of possibilities, rather than brute force
searching the whole key space. The generation of quality random
numbers is difficult. RFC 4086 [RANDOM] offers important guidance in
this area, and Appendix 3 of FIPS Pub 186 [FIPS] provides one quality
PRNG technique.
6.2. Shared KEK Wrap Algorithm
In the mechanisms described in Section 5, the shared KEK being
distributed in glkWrapped MUST be protected by a key of equal or
greater length (e.g., if an AES 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 [CMSALG] and [CMSAES].
6.3. Shared KEK Algorithm
The shared KEK distributed and indicated in glkAlgorithm MUST support
the symmetric key-encryption algorithms as specified in [CMSALG] and
[CMSAES].
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7. Message Transport
SMTP [SMTP] MUST be supported. Other transport mechanisms MAY also
be supported.
8. Security Considerations
As GLOs control setting up and tearing down the GL and rekeying the
GL, and can control member additions and deletions, GLOs play an
important role in the management of the GL, and only "trusted" GLOs
should be used.
If a member is deleted or removed from a closed or a managed GL, the
GL needs to be rekeyed. If the GL is not rekeyed after a member is
removed or deleted, the member still possesses the group key and will
be able to continue to decrypt any messages that can be obtained.
Members who store KEKs MUST associate the name of the GLA that
distributed the key so that the members can make sure subsequent
rekeys are originated from the same entity.
When generating keys, care should be taken to ensure that the key
size is not too small and duration too long because attackers will
have more time to attack the key. Key size should be selected to
adequately protect sensitive business communications.
GLOs and GLAs need to make sure that the generationCounter and
duration are not too large. For example, if the GLO indicates that
the generationCounter is 14 and the duration is one year, then 14
keys are generated each with a validity period of a year. An
attacker will have at least 13 years to attack the final key.
Assume that two or more parties have a shared KEK, and the shared KEK
is used to encrypt a second KEK for confidential distribution to
those parties. The second KEK might be used to encrypt a third KEK,
the third KEK might be used to encrypt a fourth KEK, and so on. If
any of the KEKs in such a chain is compromised, all of the subsequent
KEKs in the chain MUST also be considered compromised.
An attacker can attack the group's shared KEK by attacking one
member's copy of the shared KEK or attacking multiple members' copies
of the shared KEK. For the attacker, it may be easier to either
attack the group member with the weakest security protecting its copy
of the shared KEK or attack multiple group members.
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An aggregation of the information gathered during the attack(s) may
lead to the compromise of the group's shared KEK. Mechanisms to
protect the shared KEK should be commensurate with value of the data
being protected.
The nonce and signingTime attributes are used to protect against
replay attacks. However, these provisions are only helpful if
entities maintain state information about the messages they have sent
or received for comparison. If sufficient information is not
maintained on each exchange, nonces and signingTime are not helpful.
Local policy determines the amount and duration of state information
that is maintained. Additionally, without a unified time source,
there is the possibility of clocks drifting. Local policy determines
the acceptable difference between the local time and signingTime,
which must compensate for unsynchronized clocks. Implementations
MUST handle messages with siginingTime attributes that indicate they
were created in the future.
9. Acknowledgements
Thanks to Russ Housley and Jim Schaad for providing much of the
background and review required to write this document.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", RFC
3852, July 2004.
[CMC] Schaad, J. and M. Myers, "Certificate Management over
CMS (CMC)", RFC 5272, June 2008.
[PROFILE] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation
List (CRL) Profile", RFC 5280, May 2008.
[ACPROF] Farrell, S. and R. Housley, "An Internet Attribute
Certificate Profile for Authorization", RFC 3281, April
2002.
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[MSG] Ramsdell, B., Ed., "Secure/Multipurpose Internet Mail
Extensions (S/MIME) Version 3.1 Message Specification",
RFC 3851, July 2004.
[ESS] Hoffman, P., Ed., "Enhanced Security Services for
S/MIME", RFC 2634, June 1999.
[CMSALG] Housley, R., "Cryptographic Message Syntax (CMS)
Algorithms", RFC 3370, August 2002.
[CMSAES] Schaad, J., "Use of the Advanced Encryption Standard
(AES) Encryption Algorithm in Cryptographic Message
Syntax (CMS)", RFC 3565, July 2003.
[SMTP] Klensin, J., Ed., "Simple Mail Transfer Protocol", RFC
2821, April 2001.
10.2. Informative References
[X400TRANS] Hoffman, P. and C. Bonatti, "Transporting
Secure/Multipurpose Internet Mail Extensions (S/MIME)
Objects in X.400", RFC 3855, July 2004.
[RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC
4086, June 2005.
[FIPS] National Institute of Standards and Technology, FIPS Pub
186-2: Digital Signature Standard, January 2000.
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Appendix A. ASN.1 Module
SMIMESymmetricKeyDistribution
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) symkeydist(12) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS All --
-- The types and values defined in this module are exported for use
-- in the other ASN.1 modules. Other applications may use them for
-- their own purposes.
IMPORTS
-- PKIX Part 1 - Implicit [PROFILE]
GeneralName
FROM PKIX1Implicit88 { iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-implicit(19) }
-- PKIX Part 1 - Explicit [PROFILE]
AlgorithmIdentifier, Certificate
FROM PKIX1Explicit88 { iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-explicit(18) }
-- Cryptographic Message Syntax [CMS]
RecipientInfos, KEKIdentifier, CertificateSet
FROM CryptographicMessageSyntax2004 {iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0)
cms-2004(24) }
-- Advanced Encryption Standard (AES) with CMS [CMSAES]
id-aes128-wrap
FROM CMSAesRsaesOaep { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0)
id-mod-cms-aes(19) }
-- Attribute Certificate Profile [ACPROF]
AttributeCertificate FROM
PKIXAttributeCertificate { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-mod-attribute-cert(12) };
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-- This defines the GL symmetric key distribution object identifier
-- arc.
id-skd OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) skd(8) }
-- This defines the GL Use KEK control attribute.
id-skd-glUseKEK OBJECT IDENTIFIER ::= { id-skd 1 }
GLUseKEK ::= SEQUENCE {
glInfo GLInfo,
glOwnerInfo SEQUENCE SIZE (1..MAX) OF GLOwnerInfo,
glAdministration GLAdministration DEFAULT 1,
glKeyAttributes GLKeyAttributes OPTIONAL }
GLInfo ::= SEQUENCE {
glName GeneralName,
glAddress GeneralName }
GLOwnerInfo ::= SEQUENCE {
glOwnerName GeneralName,
glOwnerAddress GeneralName,
certificates Certificates OPTIONAL }
GLAdministration ::= INTEGER {
unmanaged (0),
managed (1),
closed (2) }
GLKeyAttributes ::= SEQUENCE {
rekeyControlledByGLO [0] BOOLEAN DEFAULT FALSE,
recipientsNotMutuallyAware [1] BOOLEAN DEFAULT TRUE,
duration [2] INTEGER DEFAULT 0,
generationCounter [3] INTEGER DEFAULT 2,
requestedAlgorithm [4] AlgorithmIdentifier
DEFAULT { id-aes128-wrap } }
-- This defines the Delete GL control attribute.
-- It has the simple type GeneralName.
id-skd-glDelete OBJECT IDENTIFIER ::= { id-skd 2 }
DeleteGL ::= GeneralName
-- This defines the Add GL Member control attribute.
id-skd-glAddMember OBJECT IDENTIFIER ::= { id-skd 3 }
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GLAddMember ::= SEQUENCE {
glName GeneralName,
glMember GLMember }
GLMember ::= SEQUENCE {
glMemberName GeneralName,
glMemberAddress GeneralName OPTIONAL,
certificates Certificates OPTIONAL }
Certificates ::= SEQUENCE {
pKC [0] Certificate OPTIONAL,
-- See [PROFILE]
aC [1] SEQUENCE SIZE (1.. MAX) OF
AttributeCertificate OPTIONAL,
-- See [ACPROF]
certPath [2] CertificateSet OPTIONAL }
-- From [CMS]
-- This defines the Delete GL Member control attribute.
id-skd-glDeleteMember OBJECT IDENTIFIER ::= { id-skd 4 }
GLDeleteMember ::= SEQUENCE {
glName GeneralName,
glMemberToDelete GeneralName }
-- This defines the Delete GL Member control attribute.
id-skd-glRekey OBJECT IDENTIFIER ::= { id-skd 5 }
GLRekey ::= SEQUENCE {
glName GeneralName,
glAdministration GLAdministration OPTIONAL,
glNewKeyAttributes GLNewKeyAttributes OPTIONAL,
glRekeyAllGLKeys BOOLEAN OPTIONAL }
GLNewKeyAttributes ::= SEQUENCE {
rekeyControlledByGLO [0] BOOLEAN OPTIONAL,
recipientsNotMutuallyAware [1] BOOLEAN OPTIONAL,
duration [2] INTEGER OPTIONAL,
generationCounter [3] INTEGER OPTIONAL,
requestedAlgorithm [4] AlgorithmIdentifier OPTIONAL }
-- This defines the Add and Delete GL Owner control attributes.
id-skd-glAddOwner OBJECT IDENTIFIER ::= { id-skd 6 }
id-skd-glRemoveOwner OBJECT IDENTIFIER ::= { id-skd 7 }
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GLOwnerAdministration ::= SEQUENCE {
glName GeneralName,
glOwnerInfo GLOwnerInfo }
-- This defines the GL Key Compromise control attribute.
-- It has the simple type GeneralName.
id-skd-glKeyCompromise OBJECT IDENTIFIER ::= { id-skd 8 }
GLKCompromise ::= GeneralName
-- This defines the GL Key Refresh control attribute.
id-skd-glkRefresh OBJECT IDENTIFIER ::= { id-skd 9 }
GLKRefresh ::= SEQUENCE {
glName GeneralName,
dates SEQUENCE SIZE (1..MAX) OF Date }
Date ::= SEQUENCE {
start GeneralizedTime,
end GeneralizedTime OPTIONAL }
-- This defines the GLA Query Request control attribute.
id-skd-glaQueryRequest OBJECT IDENTIFIER ::= { id-skd 11 }
GLAQueryRequest ::= SEQUENCE {
glaRequestType OBJECT IDENTIFIER,
glaRequestValue ANY DEFINED BY glaRequestType }
-- This defines the GLA Query Response control attribute.
id-skd-glaQueryResponse OBJECT IDENTIFIER ::= { id-skd 12 }
GLAQueryResponse ::= SEQUENCE {
glaResponseType OBJECT IDENTIFIER,
glaResponseValue ANY DEFINED BY glaResponseType }
-- This defines the GLA Request/Response (glaRR) arc for
-- glaRequestType/glaResponseType.
id-cmc-glaRR OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) cmc(7) glaRR(99) }
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-- This defines the Algorithm Request.
id-cmc-gla-skdAlgRequest OBJECT IDENTIFIER ::= { id-cmc-glaRR 1 }
SKDAlgRequest ::= NULL
-- This defines the Algorithm Response.
id-cmc-gla-skdAlgResponse OBJECT IDENTIFIER ::= { id-cmc-glaRR 2 }
-- Note that the response for algorithmSupported request is the
-- smimeCapabilities attribute as defined in MsgSpec [MSG].
-- This defines the control attribute to request an updated
-- certificate to the GLA.
id-skd-glProvideCert OBJECT IDENTIFIER ::= { id-skd 13 }
GLManageCert ::= SEQUENCE {
glName GeneralName,
glMember GLMember }
-- This defines the control attribute to return an updated
-- certificate to the GLA. It has the type GLManageCert.
id-skd-glManageCert OBJECT IDENTIFIER ::= { id-skd 14 }
-- This defines the control attribute to distribute the GL shared
-- KEK.
id-skd-glKey OBJECT IDENTIFIER ::= { id-skd 15 }
GLKey ::= SEQUENCE {
glName GeneralName,
glIdentifier KEKIdentifier, -- See [CMS]
glkWrapped RecipientInfos, -- See [CMS]
glkAlgorithm AlgorithmIdentifier,
glkNotBefore GeneralizedTime,
glkNotAfter GeneralizedTime }
-- This defines the CMC error types.
id-cet-skdFailInfo OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) cet(15) skdFailInfo(1) }
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SKDFailInfo ::= INTEGER {
unspecified (0),
closedGL (1),
unsupportedDuration (2),
noGLACertificate (3),
invalidCert (4),
unsupportedAlgorithm (5),
noGLONameMatch (6),
invalidGLName (7),
nameAlreadyInUse (8),
noSpam (9),
-- obsolete (10),
alreadyAMember (11),
notAMember (12),
alreadyAnOwner (13),
notAnOwner (14) }
END -- SMIMESymmetricKeyDistribution
Author's Address
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
EMail: turners@ieca.com
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Full Copyright Statement
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contained in BCP 78, and except as set forth therein, the authors
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