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Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 4535

Internet Engineering Task Force
INTERNET-DRAFT                        H Harney, U Meth, A Colegrove (SPARTA)
                                                             A Schuett (NSA)
                                                           P McDaniel (AT&T)
                                                            G Kenny (Logica)
                                              H Cruickshank, S Iyengar (UoS)
draft-ietf-msec-gsakmp-sec-03.txt     SPARTA, Inc., National Security Agency
                                  AT&T Labs, LogicaCMG, University of Surrey
Expires:  Februrary 4, 2004                                         Aug 2003


                                   GSAKMP




                            Status of this memo



This document is an Internet-Draft and is in full conformance with all
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                                  Abstract

     This document specifies the Group Secure Association Key
    Management Protocol (GSAKMP). The GSAKMP provides a security
    framework for creating and managing cryptographic groups on a
    network.  It provides mechanisms to disseminate group policy and
    authenticate users, rules to perform access control decisions
    during group establishment and recovery, capabilities to recover
    from the compromise of group members, delegation of group security
    functions, and capabilities to destroy the group.  It also
    generates group keys.


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                              Copyright Notice

      Copyright (c) The Internet Society (2003).  All Rights Reserved.


















































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Contents

1 Overview                                                                 7
  1.1 GSAKMP Overview . . . . . . . . . . . . . . . . . . . . . . . . . .  7
  1.2 Protocol Considerations . . . . . . . . . . . . . . . . . . . . . .  8
  1.3 Document Organization . . . . . . . . . . . . . . . . . . . . . . .  8

2 Terminology                                                              8
3 Security Considerations                                                 10
  3.1 Security Assumptions  . . . . . . . . . . . . . . . . . . . . . . . 11
  3.2 GSAKMP Use of Other Protocols . . . . . . . . . . . . . . . . . . . 11
    3.2.1ISAKMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
    3.2.2FIPS Pub 196 . . . . . . . . . . . . . . . . . . . . . . . . . . 11
    3.2.3LKH  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
    3.2.4Diffie-Hellman . . . . . . . . . . . . . . . . . . . . . . . . . 12
  3.3 Denial of Service (DoS) Attack  . . . . . . . . . . . . . . . . . . 12
  3.4 Proof of Trust Hierarchy  . . . . . . . . . . . . . . . . . . . . . 12

4 Group Life Cycle                                                        13
  4.1 Group Definition  . . . . . . . . . . . . . . . . . . . . . . . . . 13
  4.2 Group Establishment . . . . . . . . . . . . . . . . . . . . . . . . 13
    4.2.1Standard Group Establishment . . . . . . . . . . . . . . . . . . 13
        4.2.1.1Request to Join  . . . . . . . . . . . . . . . . . . . . . 14
        4.2.1.2Key Download   . . . . . . . . . . . . . . . . . . . . . . 15
        4.2.1.3Notification   . . . . . . . . . . . . . . . . . . . . . . 16
    4.2.2Cookies - Group Establishment with Denial of Service Protection  17
  4.3 Group Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 19
    4.3.1Member Joins/Leaves  . . . . . . . . . . . . . . . . . . . . . . 19
    4.3.2Rekey Events . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5 Security Suite                                                          19
  5.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
  5.2 Definition Suite 1  . . . . . . . . . . . . . . . . . . . . . . . . 20

6 GSAKMP Payload Structure                                                21
  6.1 GSAKMP Header . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
  6.2 Generic Payload Header  . . . . . . . . . . . . . . . . . . . . . . 24
  6.3 Policy Token Payload  . . . . . . . . . . . . . . . . . . . . . . . 24
  6.4 Key Download Payload  . . . . . . . . . . . . . . . . . . . . . . . 26
  6.5 Rekey Event Payload . . . . . . . . . . . . . . . . . . . . . . . . 27
  6.6 Identification Payload  . . . . . . . . . . . . . . . . . . . . . . 28
  6.7 Certificate Payload . . . . . . . . . . . . . . . . . . . . . . . . 29
  6.8 Signature Payload . . . . . . . . . . . . . . . . . . . . . . . . . 30
  6.9 Notification Payload  . . . . . . . . . . . . . . . . . . . . . . . 33
    6.9.1Notification Data - Acknowledgement (ACK) Payload Type . . . . . 34
    6.9.2Notification Data - Cookie Request and Cookie Payload Type . . . 35
  6.10Key Creation Payload  . . . . . . . . . . . . . . . . . . . . . . . 36
  6.11Nonce Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

7 GSAKMP State Diagram                                                    39
A APPENDIX A -- Variable Length Payload Field Definitions                 42
  A.1 GSAKMP Header Fields  . . . . . . . . . . . . . . . . . . . . . . . 42


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  A.2 Key Download Payload Fields . . . . . . . . . . . . . . . . . . . . 42
    A.2.1GTEK Key Packet Fields . . . . . . . . . . . . . . . . . . . . . 42
    A.2.2Rekey Key Packet Fields  . . . . . . . . . . . . . . . . . . . . 42
  A.3 Rekey Event Payload Fields  . . . . . . . . . . . . . . . . . . . . 43
  A.4 Signature Payload Fields  . . . . . . . . . . . . . . . . . . . . . 43
    A.4.1Signature ID Data Field Format . . . . . . . . . . . . . . . . . 43

B APPENDIX B -- LKH Variable Length Payload Field Definitions             43
  B.1 LKH Rekey Key Packet Fields . . . . . . . . . . . . . . . . . . . . 43
  B.2 LKH Rekey Packet Data Format Fields . . . . . . . . . . . . . . . . 44
    B.2.1Rekey Event Header . . . . . . . . . . . . . . . . . . . . . . . 44
    B.2.2Rekey Event Packet Data(s) . . . . . . . . . . . . . . . . . . . 45
    B.2.3Key Pack Data  . . . . . . . . . . . . . . . . . . . . . . . . . 46
    B.2.4Pack Data Formats  . . . . . . . . . . . . . . . . . . . . . . . 47
        B.2.4.1GTEK Pack Data . . . . . . . . . . . . . . . . . . . . . . 47
        B.2.4.2LKH Pack Data  . . . . . . . . . . . . . . . . . . . . . . 47
    B.2.5Example  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
C APPENDIX C -- Change History                                            49
  C.1 Changes from GSAKMP-00 to GSAKMP-01 February 2003 . . . . . . . . . 49
  C.2 Changes from GSAKMP-01 to GSAKMP-02 June 2003 . . . . . . . . . . . 50
  C.3 Changes from GSAKMP-02 to GSAKMP-03 August 2003 . . . . . . . . . . 50

D References, Authors Addesses, and Acknowledgements                      50
  D.1 References  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
  D.2 Authors Addresses . . . . . . . . . . . . . . . . . . . . . . . . . 52
  D.3 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . . . 53



























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List of Figures

  1   GSAKMP Ladder Diagram . . . . . . . . . . . . . . . . . . . . . . . 14
  2   GSAKMP Ladder Diagram with Cookies  . . . . . . . . . . . . . . . . 18
  3   GSAKMP Header Format  . . . . . . . . . . . . . . . . . . . . . . . 22
  4   Generic Payload Header  . . . . . . . . . . . . . . . . . . . . . . 24
  5   Policy Token Payload Format . . . . . . . . . . . . . . . . . . . . 25
  6   Key Download Payload Format . . . . . . . . . . . . . . . . . . . . 26
  7   Rekey Event Payload Format  . . . . . . . . . . . . . . . . . . . . 27
  8   Identification Payload Format . . . . . . . . . . . . . . . . . . . 29
  9   Certificate Payload Format  . . . . . . . . . . . . . . . . . . . . 30
  10  Signature Payload Format  . . . . . . . . . . . . . . . . . . . . . 31
  11  Notification Payload Format . . . . . . . . . . . . . . . . . . . . 33
  12  Notification Data - Acknowledge Payload Type Format . . . . . . . . 35
  13  Key Creation Payload Format . . . . . . . . . . . . . . . . . . . . 36
  14  Nonce Payload Format  . . . . . . . . . . . . . . . . . . . . . . . 37
  15  GSAKMP State Diagram  . . . . . . . . . . . . . . . . . . . . . . . 39
  16   B. 1:  Rekey Event Header Format . . . . . . . . . . . . . . . . . 45
  17   B. 2:  Rekey Event Packet Data Format  . . . . . . . . . . . . . . 46
  18   B. 3:  Key Pack Data Format  . . . . . . . . . . . . . . . . . . . 46

































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List of Tables

  1   Request to Join Message Definition  . . . . . . . . . . . . . . . . 15
  2   Key Download Message Definition . . . . . . . . . . . . . . . . . . 16
  3   Notification Message Definition . . . . . . . . . . . . . . . . . . 16
  4   Cookie Download Message Definition  . . . . . . . . . . . . . . . . 17
  5   Rekey Event Message Definition  . . . . . . . . . . . . . . . . . . 20
  6   Group Identification Types  . . . . . . . . . . . . . . . . . . . . 22
  7   Payload Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
  8   Exchange Types  . . . . . . . . . . . . . . . . . . . . . . . . . . 23
  9   Policy Token Types  . . . . . . . . . . . . . . . . . . . . . . . . 25
  10  Key Download Data Types . . . . . . . . . . . . . . . . . . . . . . 27
  11  Rekey Event Types . . . . . . . . . . . . . . . . . . . . . . . . . 28
  12  Identification Types  . . . . . . . . . . . . . . . . . . . . . . . 29
  13  Certificate Payload Types . . . . . . . . . . . . . . . . . . . . . 30
  14  Signature Types . . . . . . . . . . . . . . . . . . . . . . . . . . 31
  15  Signature Types . . . . . . . . . . . . . . . . . . . . . . . . . . 32
  16  Authorization Types . . . . . . . . . . . . . . . . . . . . . . . . 32
  17  Notify Payload Types  . . . . . . . . . . . . . . . . . . . . . . . 34
  18  Notify Payload -- Status Types  . . . . . . . . . . . . . . . . . . 35
  19  Acknowledgement Types . . . . . . . . . . . . . . . . . . . . . . . 35
  20  Types Of Key Creation Information . . . . . . . . . . . . . . . . . 36
  21  Nonce Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
  22  GSAKMP States . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
  23  State Transition Events . . . . . . . . . . . . . . . . . . . . . . 41




























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1 Overview



1.1 GSAKMP Overview


Protecting group information requires the definition of a security
policy and the enforcement of that policy by all participating parties.
Controlling dissemination of cryptographic key is the primary mechanism to
enforce the access control policy.  It is the primary purpose of GSAKMP to
generate and disseminate a group key in a secure fashion.

GSAKMP separates group security management functions and responsibilities
into three major roles:  1) Group Owner, 2) Group Controller Key Server,
and 3) Group Member.  The Group Owner is responsible for creating the
security policy rules for a group and expressing these in the Policy Token.
The Group Controller Key Server (GCKS) is responsible for creating and
maintaining the keys and enforcing the group policy by granting access
to potential Group Members (GM) in accordance with the Policy Token.  To
enforce a group's policy the potential Group Members need to have knowledge
of the access control policy for the group, an unambiguous identification
of any party downloading keys to them, and verifiable chains of authority
for key download.  In other words, the Group Members need to know who
potentially will be in the group and to verify that the key disseminator is
authorized to act in that capacity.

In order to establish a Group Secure Association (GSA) to support these
activities, the identity of each party in the process MUST be unambiguously
asserted and authenticated.  It MUST also be verified that each party is
authorized, as defined by the Policy Token, to function in his role in the
protocol (e.g., GM or GCKS).

The security features of the establishment protocol for the SA include


 -  Group policy identification

 -  Group policy dissemination

 -  GM to GCKS SA establishment to protect data

 -  Access control checking


GSAKMP provides mechanisms for cryptographic group creation and
management.  Other protocols may be used in conjunction with GSAKMP to
allow various applications to create functional groups according to their
application-specific requirements.  For example, in a small-scale video
conference the organizer might use a session invitation protocol like SIP
[RFC2543] to transmit information about the time of the conference, the
address of the session, and the formats to be used.  For a large-scale video

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transmission, the organizer might use a multicast announcement protocol like
SAP [RFC2974].

This document describes a useful default set of security algorithms and
configurations, Security Suite 1.  This suite allows an entire set of
algorithms and settings to be described to prospective group members in a
concise manner.  Other security suites MAY be defined as needed and MAY be
disseminated during the out-of-band announcement of a group.

Distributed architectures support large scale cryptographic groups.  Secure
distributed architectures require authorized delegation of GSA actions to
network resources.  The fully specified Policy Token is the mechanism to
facilitate this authorization.  Trasmission of this Policy Token to all
joining GMs allows GSAKMP to securely support distributed architectures and
multiple data sources.

Many-to-many group communications require multiple data sources.  Multiple
data sources are supported because the inclusion of a policy token and
policy payloads allow group members to review the group access control and
authorization parameters.  This member review process gives each member
(each potential source of data), the ability to determine if the group
provides adequate protection for member data.



1.2 Protocol Considerations


IANA has provided GSAKMP port number 3761 in both the UDP and TCP spaces.
All implementations MUST use this port assignment in the appropriate manner.


1.3 Document Organization


The remainder of this document is organized as follows:  Section 2 presents
the terminology and concepts used to present the requirements of this
protocol.  Section 3 outlines the security considerations with respect to
GSAKMP. Section 4 describes the group management life-cycle.  Section 5
describes the Security Suite Definition.  Section 6 presents the message
types and formats used during each phase of the life-cycle.  Section 7
defines the state diagram for the protocol.


2 Terminology


The following terminology is used throughout the GSAKMP paper.


Certificate:   A data structure used to verifiably bind an identity to a


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    cryptographic key (e.g., X.509v3).

Compromise Recovery:   The act of recovering a secure operating state
    after detecting that a group member cannot be trusted.  This can be
    accomplished by rekey.

Cryptographic Group:   A set of entities sharing or desiring to share a
    GSA.

Group Controller Key Server (GCKS):  A group member with authority to
    perform critical protocol actions including creating and distributing
    keys and building and maintaining the rekey structures.  As the group
    evolves, it MAY become desirable to have multiple controllers perform
    these functions.

Group Member (GM):  A Group Member is any entity with access to the group
    keys.  Regardless of how a member becomes a part of the group or how the
    group is structured, GMs will perform the following actions:



     -  Authenticate and validate the identities and the authorizations of
        entities performing security relevant actions

     -  Accept group keys from the GCKS

     -  Request group keys from the GCKS

     -  Enforce the cooperative group policies as stated in the group
        policy token

     -  Perform peer review of key management actions

     -  Manage local local key


Group Owner (GO):  A Group Owner is the entity authorized for generating
    and modifying an authenticatable policy token for the group, and
    notifying the GCKS to start the group.

Group Policy:   The Group Policy completely describes the protection
    mechanisms and security relevant behaviors of the group.  This policy
    MUST be commonly understood and enforced by the group for coherent
    secure operations.

Group Secure Association (GSA):  A GSA is a logical association of users or
    hosts that share cryptographic key(s).  This group may be established to
    support associations between applications or communication protocols.

Group Traffic Encryption Key (GTEK):  The key or keys created for
    encrypting the group data.


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Logical Key Hierarchy (LKH) Array:   The group of keys created to
    facilitate the LKH compromise recovery methodology.

Policy Token:   The policy token is a data structure used to disseminate
    group policy and the mechanisms to enforce it.  The policy token
    is issued and signed by an authorized source.  Each member of the
    group MUST verify the token, meet the group join policy, and enforce
    the policy of the group, (e.g., encrypt application data with a
    specific algorithm).  The group policy token will contain a variety of
    information including:



     -  GSAKMP protocol version

     -  Key creation method

     -  Key dissemination policy

     -  Access control policy

     -  Group authorization policy

     -  Compromise recovery policy

     -  Data protection mechanisms


    An example of a policy token is specified in [HCLM00].

Rekey:   The act of changing keys within a group.

Subordinate Group Controller Key Server (SGCKS):  Any group member having
    the appropriate processing and trust characteristics as defined in the
    group policy that has the potential to act as a SGCKS. This will allow
    the group processing and communication requirements to be distributed
    equitably throughout the network (e.g., distribute group key).  The
    optional use of GSAKMP with Subordinate Group Controller Key Servers
    will be documented in a separate paper.


3 Security Considerations


In addition to the specification of GSAKMP itself, the security of an
implemented GSAKMP system is affected by supporting factors.  These are
discussed here.






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3.1 Security Assumptions


The following assumptions are made as the basis for the security discussion



1.  GSAKMP assumes its supporting platform can provide the process and data
    separation services at the appropriate assurance level to support its
    groups.

2.  The key generation function of the cryptographic engine will only
    generate strong keys.

3.  The security of this protocol is critically dependent on the randomness
    of the randomly chosen parameters.  These should be generated by a
    strong random or properly seeded pseudo-random source.


3.2 GSAKMP Use of Other Protocols


GSAKMP is based upon two (2) existing protocols:  ISAKMP [MSST98] and FIPS
Pub 196 [FIPS 196].  GSAKMP MAY use Diffie-Hellman key exchange [DH77] for
two party key creation and MAY use LKH for rekey capability.


3.2.1 ISAKMP


ISAKMP provides a flexible structure of chained payloads in support of
authenticated key exchange and security association management for pairwise
communications.  GSAKMP expands upon these features to provide policy
enforcement features in support of diverse group communications.


3.2.2 FIPS Pub 196


FIPS Pub 196 provides a mutual authentication protocol.


3.2.3 LKH


GSAKMP relies upon a rekey capability, i.e., LKH, to enable group recovery
after a compromise.






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3.2.4 Diffie-Hellman


GSAKMP MAY rely upon two party key creation mechanisms, i.e.,
Diffie-Hellman, to protect sensitive data during download.

The information in this section is borrowed heavily from [IKEv2] as this
protocol has already worked through this issue and GSAKMP is using the
same security considerations for its purposes.  This section will contain
paraphrased sections of [IKEv2] modified for GSAKMP as appropriate.

The strength of a key derived from a Diffie-Hellman exchange using specific
p and g values depends on the inherent strength of the values, the size of
the exponent used, and the entropy provided by the random number generator
used.  Security Suite 1 defined in section 5, based on [IKEv2] Group 2,
with a strong random number generator and an exponent no less than 200 bits
is sufficient to use for 3DES. An implementation should make note of this
conservative estimate when establishing policy and negotiating security
parameters.

Note that these limitations are on the Diffie-Hellman values themselves.
There is nothing in GSAKMP which prohibits using stronger values nor is
there anything which will dilute the strength obtained from stronger values.
In fact, the extensible framework of GSAKMP encourages the definition of
more Security Suites.

It is assumed that the Diffie-Hellman exponents in this exchange are erased
from memory after use.  In particular, these exponents MUST NOT be derived
from long-lived secrets like the seed to a pseudo-random generator that is
not erased after use.



3.3 Denial of Service (DoS) Attack


This GSAKMP specification addresses the mitigation for a distributed IP
spoofing attack (a subset of possible DoS attacks) in section  4.2.2,
Cookies.


3.4 Proof of Trust Hierarchy


As defined by [HCM], security group policy MUST be defined in a verifiable
manner.  GSAKMP anchors its trust in the creator of the group, the GO.

The Policy Token explicitly defines all the parameters that create a secure
verifiable infrastructure.  The GSAKMP Policy Token is issued and signed by
the GO. The GCKS will verify it and grant access to GMs only if they meet
the rules of the Policy Token.  The new GMs will accept access only if 1)
the token verifies, 2) the GCKS is an authorized disseminator, and 3) the

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group mechanisms are acceptable for protecting the GMs data.



4 Group Life Cycle


The management of a cryptographic group follows a life-cycle:  group
definition, group establishment, and security relevant group maintenance.
Group definition involves defining the parameters necessary to support
a secure group, including its policy token.  Group establishment is the
process of granting access to new members.  Security relevant group
maintenance messages include rekey, policy changes and member deletion.
Each of these life-cycle phases is discussed in the following sections.


4.1 Group Definition


A cryptographic group is established to support secure communications among
a group of individuals.  The activities necessary to create a Policy Token
in support of a cryptographic group include


 -  Determine Access Policy - identify the entities that are authorized to
    receive the group key.

 -  Determine Authorization Policy - identify which entities are authorized
    to perform security relevant actions, including key dissemination,
    policy creation, and initiation of security management actions.

 -  Determine Mechanisms - define the algorithms and protocols used by
    GSAKMP to secure the group.

 -  Create Group Policy Token - format the policies and mechanisms into a
    Policy Token and apply the GO signature.



4.2 Group Establishment


4.2.1 Standard Group Establishment


After the out-of-band receipt of a Policy Token, a potential Group
Controller Key Server (GCKS) verifies the token and its rules.  This entity
then establishes that eligibility rules for GCKS creation have been met.
The GCKS is then permitted to create any needed group keys and begin to
establish the group.

The GSAKMP Ladder Diagram, Figure 1, is presented to illustrate the process

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of establishing a cryptographic group.  The left side of the diagram
represents the actions of the GCKS. The right side of the diagram represents
the actions of the GMs.  The components of each message shown in the diagram
are presented in sections 4.2.1.1 -  4.2.1.3.

          CONTROLLER                  MESSAGE                  MEMBER

                    !<------------Request to Join-------------!
      <Process RTJ> !                                         !
                    !-------------Key Download--------------->!
                    !                                         ! <Process KD>
                    !<------Notification - Ack/Failure--------!
   <Process Notif>  !                                         !
                    !<=======SHARED KEYED GROUP SESSION======>!




                      Figure 1:  GSAKMP Ladder Diagram

To facilitate a well ordered group creation, the GCKS MUST send security
policy information to the GM using a group policy token.  The group policy
token MUST include the group's identification, group permissions, group join
policy, group controller key server identity, group management information,
and digital signature of the policy creation authority.  This will allow the
GM to determine wether group policy is compatible with local policy.

Standard design principles for secure protocols mandate the use of explicit
identification of senders and recipients of messages.  The signature payload
of each message identifies the signer of the message and therefore satisfies
the sender requirement.  Within the GSAKMP header is a group ID. Because
the member may be served by any Key Server within a group, this ID provides
sufficient granularity for the recipient ID for the Request to Join message.
Other messages sent by the potential member will contain the recipient ID
for the GCKS serving that member.

If the GCKS is unable to correctly process the Notification message, the
GCKS MUST remove this GM from the group and handle according to policy.

For the following message structure sections, details about payload formats
can be found in Section  6.


4.2.1.1 Request to Join


The components of a Request to Join Message are shown in Table 1.

As shown by Figure 1, potential GMs join a group by initiating a request for
permission to join.  In response, the GCKS accepts or denies the request
based on local configuration.  <Process RTJ> indicates the GCKS actions


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                Table 1:  Request to Join Message Definition

    Message Name  : Request to Join (RTJ)
    Dissection    : {HDR-GrpID, Key Creation, Nonce_I, [Notification]}
                    SigM, [Cert]
    Payload Types : GSAKMP Header, Key Creation, Nonce, Signature,
                    [Certificate], [Notification]

       SigM       : Signature of Group Member
       Cert       : Necessary Certificates, zero or more
       {}SigX      :Indicates minimum fields used in Signature
       []         : Indicate an optional data item

that will determine if the RTJ will be acted upon.  Reasons for refusal
of action can include:  malformed RTJ, unverifiable RTJ, GCKS processing
issues, and state violations.  NOTE: At any one time, a GCKS MUST process no
more that one (1) valid RTJ from a single GM per group.  If the results of
<Process RTJ> indicate that the GCKS should reject the request, the session
MUST be terminated.

The GCKS processes the Request to Join.  In this procedure, the GCKS will
verify the signature on the message to ensure its authenticity.  The GCKS
MUST used verified and trusted authentication material from a known root.
If the message signature does not verify, the session MUST be terminated.
If the message signature verifies, then the identity of the sender is
extracted from the Signature Payload.  This identity information will be
used the Key Download message.

The GCKS then confirms that all required payloads are present and
properly formatted based upon the mechanisms announced with the group
characteristics.  If not, the session MUST be terminated.

If the message signature is verified, and the GM passes the GCKS's access
control checks, the GCKS will create and send the Key Download message as
described in section  4.2.1.2.

The OPTIONAL Notification payload will be used when the GCKS requires
cookies in the Request to Join message.  The use of this payload will be
defined in section  4.2.2.


4.2.1.2 Key Download


The components of a Key Download Message are shown in Table 2:

The GM receives this message and verifies the following information:
signature on the message to ensure its authenticity, the contents of the
nonce responder and combined payloads, the contents of the key creation
payload, and verify the identity information.  If the message signature,


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                 Table 2:  Key Download Message Definition

    Message Name  : Key Download (KD)
    Dissection    : {HDR-GrpID, Member ID, Nonce_R, Nonce_C, Key
                    Creation, (Policy Token)*, (Key Download)*} SigC,
                    [Cert]
    Payload Types : GSAKMP Header, Identification, Nonce, Key
                    Creation, Policy Token, Key Download, Signature,
                    [Certificate]

       SigC       : Signature of Group Controller Key Server
       Cert       : Necessary Certificates, zero or more
       {}SigX      :Indicates minimum fields used in Signature
       []         : Indicate an optional data item
       (data)*    : Indicates encrypted information

nonce, or identification information does not verify, the session MUST
be terminated.  GSAKMP sends a properly authenticated message with a
Notification Payload of type NACK to indicate termination.

The Policy Token and Key Download payloads are sent encrypted in the KEK
generated by the Key Creation payload information using the mechanisms
defined in the group announcment.  This guarantees that the sensitive policy
and key data for the group and potential rekey data for this individual
cannot be read by anyone but the intended recipient.


4.2.1.3 Notification


The components of a Notification Message are shown in Table 3:


                 Table 3:  Notification Message Definition

    Message Name  : Notification
    Dissection    : {HDR-GrpID, Nonce_C, ACK}SigM
    Payload Types : GSAKMP Header, Nonce, Notification, Signature
       SigM       : Signature of Group Member
       {}SigX      :Indicates minimum fields used in Signature


The GCKS receives the signed notification and will verify the signature on
the message to ensure its authenticity and the nonce value.  If the message
signature or nonce does not verify, the session MUST be terminated.

If the message signature and nonce are verified, then the GCKS and GM have
established a GSA.




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4.2.2 Cookies - Group Establishment with Denial of Service Protection


This section defines an OPTIONAL capability that MAY be implemented into
GSAKMP. The information in this section is borrowed heavily from [IKEv2] as
this protocol has already worked through this issue and GSAKMP is copying
this concept.  This section will contain paraphrased sections of [IKEv2]
modified for GSAKMP to define the purpose of Cookies.

An optional Cookie mode is being defined for the GSAKMP to help against DoS
attacks.

The term "cookies" originates with Karn and Simpson [RFC 2522] in Photuris,
an early proposal for key management with IPsec.  The ISAKMP fixed message
header includes two eight octet fields titled "cookies".  Instead of placing
this cookie data in the header, this data is moved into a Notification
payload.

An expected attack against GSAKMP is state and CPU exhaustion, where
the target GCKS is flooded with Request to Join requests from forged IP
addresses.  This attack can be made less effective if a GCKS implementation
uses minimal CPU and commits no state to the communication until it knows
the initiator potential GM can receive packets at the address from which
it claims to be sending them.  To accomplish this, the GCKS when operating
in Cookie mode, SHOULD reject initial Request to Join messages unless they
contain a Notification payload of type "cookie".  It SHOULD instead send
a Cookie Download message as a response to the RTJ and include a cookie in
a notify payload of type Cookie_Requested.  Potential GMs who receive such
responses MUST retry the Request to Join message with the responder GCKS
supplied cookie in its notification payload of type Cookie, as defined by
the optional Notification payload of the Request to Join Msg as defined in
section 4.2.1.1.  This initial exchange will then be as shown in Figure 2
with the components of the new message Cookie Download shown in Table 4.


                Table 4:  Cookie Download Message Definition

    Message Name  : Cookie Download
    Dissection    : {HDR-GrpID, COOKIE_REQUIRED}
    Payload Types : GSAKMP Header, Notification, Signature


The first two messages do not affect any GM or GCKS state except for
communicating the cookie.

A GSAKMP implementation SHOULD implement its GCKS cookie generation in such
a way as to not require any saved state to recognize its valid cookie when
the second Request to Join message arrives.  The exact algorithms and syntax
they use to generate cookies does not affect interoperability and hence is
not specified here.  The following is an example of how an endpoint could
use cookies to implement limited DoS protection.


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          CONTROLLER                  MESSAGE                  MEMBER
        in Cookie Mode
                    !<--Request to Join without Cookie Info---!
   <Gen Cookie Rsp> !                                         !
                    !----------Cookie Download--------------->!
                    !                                         ! <Process CD>
                    !<----Request to Join with Cookie Info----!
      <Process RTJ> !                                         !
                    !-------------Key Download--------------->!
                    !                                         ! <Process KD>
                    !<------Notification - Ack/Failure--------!
   <Process Notif>  !                                         !
                    !<=======SHARED KEYED GROUP SESSION======>!




               Figure 2:  GSAKMP Ladder Diagram with Cookies


A good way to do this is to set the cookie to be:



    Cookie = <SecretVersionNumber> ! Hash(Ni ! IPi ! <secret>)



where <secret> is a randomly generated secret known only to the responder
GCKS and periodically changed, Ni is the Nonce value taken from the
initiator potential GM, IPi is the supposed IP of the initiator potential
GM. <SecretVersionNumber> should be changed whenever <secret> is
regenerated.  The cookie can be recomputed when the "Request to Join with
Cookie Info" arrives and compared to the cookie in the received message.
If it matches, the responder GCKS knows that all values have been computed
since the last change to <secret> and that IPi MUST be the same as the
source address it saw the first time.  Incorporating Ni into the hash
assures that an attacker who sees only the Cookie_Download message cannot
successfully forge a "Request to Join with Cookie Info" message.  This Ni
value MUST be the same Ni value from the original "Request to Join" message
for the calculation to be successful.

If a new value for <secret> is chosen while there are connections in the
process of being initialized, a "Request to Join with Cookie Info" might be
returned with other than the current <SecretVersionNumber>.  The responder
GCKS in that case MAY reject the message by sending another response with
a new cookie or it MAY keep the old value of <secret> around for a short
time and accept cookies computed from either one.  The responder GCKS SHOULD
NOT accept cookies indefinitely after <secret> is changed, since that would
defeat part of the denial of service protection.  The responder GCKS SHOULD
change the value of <secret> frequently, especially if under attack.


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4.3 Group Maintenance


The Group Maintenance phase includes member joins and leaves, group rekey
activities, and the management of Rekey events.  These activities are
presented in the following sections.


4.3.1 Member Joins/Leaves


The addition of group members to a previously established group will closely
follow the processing presented in Sections 4.2.1.  With the exception of
the pure group establishment tasks (e.g., creation of policy token, GTEK,
and Rekey array), an entity becomes a GM using the same message exchanges
described in Sections 4.2.1.1 through 4.2.1.3.

A member who elects to voluntarily leave the group MUST destroy local copies
of the group key.


4.3.2 Rekey Events


A Rekey Event is any action, including compromise report or key expiration,
that requires the creation and dissemination of a new group key and/or Rekey
information.

Once an event has been identified (as defined in the group security policy
token), the GCKS MUST create and send a signed message containing the GTEK
and Rekey information to the group.

Each GM who receives this message MUST verify the signature on the message
to ensure its authenticity.  If the message signature does not verify,
the message MUST be discarded.  Upon verification the GM will find the
appropriate Rekey download packet and decrypt the information with a stored
Rekey key(s).  If a new Policy Token is distributed with the message, it
MUST be encrypted in the old GTEK.

The components of a Rekey Event message are shown in Table  5:



5 Security Suite


The Security Definition Suite 1 MUST be supported.  Other security suite
definitions MAY be defined in other internet specifications.





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                  Table 5:  Rekey Event Message Definition

    Message Name  : Rekey Event
    Dissection    : {HDR-GrpID, ([Policy Token])*, Rekey Array}SigC,
                    [Cert]
    Payload Types : GSAKMP Header, [Policy Token], Rekey Event,
                    Signature, [Certificate],

       SigC       : Signature of Group Controller Key Server
       Cert       : Necessary Certificates, zero or more
       {}SigX      :Indicates minimum fields used in Signature
       (data)*    : Indicates encrypted information
       []         : Indicate an optional data item

5.1 Assumptions


All petential GMS will hae enough information available to them to use the
correct Security Suite to join the group.  This can be accomplished by a
well known default suite 'Security Suite 1' or by announcing/posting another
suite.


5.2 Definition Suite 1


GSAKMP implementations MUST support the following suite of algorithms and
configurations.  The following definition of Suite 1 borrows heavily from
IKE's Oakley group 2 definition and Oakley itself.

The GSAKMP Suite 1 definition defines all the algorithm and cryptographic
definitions required to process group establishment messages.  It is
important to note that GSAKMP does not negotiate these cryptographic
mechanisms.  This definition is set by the Group Owner via the Policy Token
(passed during the GSAKMP exchange for member verification purposes).

The GSAKMP Suite definition is



Key download encryption algorithm definition:
Algorithm:  3DES
Mode:       CBC64
Key Length: 192 bits


Policy Token encryption algorithm definition:
Algorithm:  3DES
Mode:       CBC64
Key Length: 192 bits


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Policy Token digital signature algorithm is:
  DSS-ASN1-DER
  Hash algorithm is:
  SHA-1

Nonce Hash algorithm is:
  SHA-1

The Key Creation definition is:
Algorithm type is Diffie Hellman
MODP group definition
g:   2
p:   "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1"
     "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD"
     "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245"
     "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED"
     "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381"
     "FFFFFFFF FFFFFFFF"

NOTE: The p and g values comes from IKE [RFC 2409], section 6.2 Second
      Oakley Group, and p is 1024 bits long.


The digital signature algorithm is:
DSS-ASN1-DER
Hash algorithm is:
SHA-1
The digital signature ID type is:
U-NAME



6 GSAKMP Payload Structure


A GSAKMP Message is composed of a GSAKMP Header (Section  6.1) followed
by at least one GSAKMP Payload.  All GSAKMP Payloads are composed of the
Generic Payload Header (Section  6.2) followed by the specific payload data.
The message is chained by a preceeding payload defining its succeeding
payload.  The final payload in a message will point to no succeeding
payload.


6.1 GSAKMP Header


The GSAKMP Header fields are defined in Figure 3:


Group Identification Type (1 octet)  - Table 6 presents the group
    identification types.


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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !Group ID Type  !      Group ID Value                           ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~               ! Next Payload  !   Version     ! Exchange Type !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Sequence ID                                                   !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Length                                                        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                      Figure 3:  GSAKMP Header Format


                    Table 6:  Group Identification Types


                            Grp ID Type   Value
                           _____________________

                            IPv4            0
                            Other         1-255


Group Identification Value (variable length)  - Indicates the name/title
    of the group.  The specific format for this field is defined in
    Section A.1.

Next Payload (1 octet)  - Indicates the type of the first payload in the
    message.  The format for each payload is defined in the following
    sections.  Table 7 presents the payload types.

Version (1 octet)  - Indicates the version of the GSAKMP protocol in use.
    The current value is one (1).

Exchange Type (1 octet)  - Indicates the type of exchange (also known as
    the message type).  Table 8 presents the exchange type values.











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                          Table 7:  Payload Types


                     Next_Payload_Type        Value

                    ___________________________________
                     None                       0
                     Policy Token               1
                     Key Download Packet        2
                     Rekey event                3
                     Identification             4
                     Reserved                   5
                     Certificate                6
                     Reserved                   7
                     Signature                  8
                     Notification               9
                     Reserved                  10
                     Key Creation              11
                     Nonce                     12
                     Reserved               13 - 127
                     Private Use           128 -- 255








                          Table 8:  Exchange Types


                         Exchange_Type      Value

                        __________________________
                         Reserved           0 - 3
                         Notification         4
                         Rekey Event          5
                         Reserved             6
                         No Message           7
                         Request to Join      8
                         Key Download         9
                         Cookie Download     10
                         Other             11-255





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Sequence ID (4 octets)  - Group Management replay protection field.
    Sequence ID for group management messages.  If not a group management
    message, this value is set to zero (0).  When a GCKS/SGCKS is initiated,
    it MUST generate/select an initial value, not zero (0).  For each
    distinct group management message that this GCKS/SGCKS transmits, this
    value MUST be incremented.  Receivers of this group management message
    MUST confirm that the value received is greater that the value of the
    sequence ID received with the last group management message from this
    GCKS/SGCKS. GCKS/SGCKS MUST also garantee that this value does not
    suffer from rollover problems.

Length (4 octets)  - Length of total message (header + payloads) in octets.



6.2 Generic Payload Header


Each GSAKMP payload defined in the following sections begins with a generic
header, shown in Figure 4, which provides a payload ``chaining`` capability
and clearly defines the boundaries of a payload.  The Generic Payload Header
fields are defined as follows:
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                     Figure 4:  Generic Payload Header


Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in
    the message, then this field will be 0.  This field provides the
    ``chaining`` capability.  Table 7 identifies the payload types.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.



6.3 Policy Token Payload


The Policy Token Payload contains group specific information that describes
the group security relevant behaviors, access control parameters, and
security mechanisms.  This information may contain a digital signature(s) to
prove authority and integrity of the information.  Figure 5 shows the format

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of the payload.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !   ID Type     !              Policy Token Data                ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 5:  Policy Token Payload Format

The Policy Token Payload fields are defined as follows:


Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

ID Type (1 octet)  - Specifies the type of Policy Token being used.
    Table 9 identifies the types of policy tokens.


                        Table 9:  Policy Token Types

                           ID_Type       Value
                          ______________________

                           Group           0
                           Auxiliary       1
                           Reserved       2-63
                           Unassigned   64-255

Policy Token Data (variable length)  - Contains Policy Token information.
    The values for this field are group specific and the format is specified
    by the ID Type field.  The Policy Token format is specified in [HCLM00].


If this payload is encrypted, only the Policy Token Data field is encrypted.

The payload type for the Policy Token Payload is one (1).





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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !                    Key Download Data                          ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 6:  Key Download Payload Format


6.4 Key Download Payload


The Key Download Payload contains group keys (eg., group keys, initial
rekey keys, etc.).  These key download payloads can have several security
attributes applied to them based upon the security policy of the group.
Figure 6 shows the format of the payload.

The security policy of the group dictates that the key download payload MUST
be encrypted with a key exchange key (KEK). The type of encryption used is
specified in the Policy Token.  The group members MUST create the KEK using
the key creation method identified in the Key Creation Payload.

The Key Download Payload fields are defined as follows:


Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

Key Download Data (variable length)  - Contains Key Download information.


    Number of Key Packets (2 octets)  -- Contains the total number of both
        GTEK and Rekey arrays being passed in this data block.

        For each Key Packet, the data format is as follows:


        Key Download Data (KDD) Type (1 octet)  -- Identifier for the Key
            Data field of this Key Packet.  See Table 10 for the possible
            values of this field.



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                     Table 10:  Key Download Data Types

                      Key Download Data Type   Value
                     ________________________________

                      GTEK                       0
                      Rekey - LKH                1
                      Unassigned               2-255


        Key Download Length (2 octets)  -- Length in octets of the Key
            Packet data following this field.

        Key Packet Data (variable length)  -- Contains Key information.
            The format of this field is specific depending on the value of
            the Key Download Data field.


If this payload is encrypted, only the Key Download Data field is encrypted.

For a Key Download Data value of GTEK, the Key Packet Data field format is
defined in Section A.2.1.

For a Key Download Data value of Rekey, the Key Packet Data field format is
defined in Section A.2.2.

The payload type for the Key Download Packet is two (2).


6.5 Rekey Event Payload


The Rekey Event Payload contains multiple keys encrypted in Rekey keys.
These Rekey Event payloads can have several security attributes applied to
them based upon the security policy of the group.  Figure 7 shows the format
of the payload.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !   ID Type     !           Rekey Event Data                    ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 7:  Rekey Event Payload Format

The Rekey Event Payload fields are defined as follows:


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Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

ID Type (1 octet)  - Specifies the type of Rekey Event being used.
    Table 11 presents the types of Rekey events.


                        Table 11:  Rekey Event Types

                       ID_Type                Value
                      ______________________________

                       None                     0
                       Group Recovery           1
                       Individual Recovery      2
                       Maintenance              3
                       Delete Group Key         4
                       Unassigned            5-255

Rekey Event Data (variable length)  - Contains Rekey Event information.
    The values for this field are group specific and the format is
    specified by the ID Type field.  The format for this field is defined in
    Section A.3


The Rekey Event payload type is three (3).



6.6 Identification Payload


The Identification Payload contains entity-specific data used to exchange
identification information.  This information is used to verify the
identities of members.  Figure 8 shows the format of the Identification
Payload.

The Identification Payload fields are defined as follows:


Next Payload (1 octet) - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.


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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !   ID Type     !            Identification Data                ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                  Figure 8:  Identification Payload Format


Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

ID Type (1 octet)  - Specifies the type of Identification being used.
    Table 12 identifies possible values for this type.

                      Table 12:  Identification Types

                ID_Type                              Value

               ____________________________________________
                Sender Unencoded Name (S-U-NAME)       0
                Receiver Unencoded Name (R-U-NAME)     1
                Unassigned                           2-255

Identification Data (variable length)  - Contains identity information.
    The values for this field are group-specific and the format is
    specified by the ID Type field.  The format for this field is defined in
    Section A.4.1


The payload type for the Identification Payload is four (4).



6.7 Certificate Payload


The Certificate Payload provides a means to transport certificates or other
certificate-related information via GSAKMP and can appear in any GSAKMP
message.  Certificate payloads SHOULD be included in an exchange whenever an
appropriate directory service (e.g.  Secure DNS [DNSSEC]) is not available
to distribute certificates.  Figure 9 shows the format of the Certificate
Payload.

The Certificate Payload fields are defined as follows:


Next Payload (1 octet)  - Identifier for the payload type of the next

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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Cert Type                     !    Certificate Data           ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 9:  Certificate Payload Format


    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

Certificate Type (2 octets)  - This field indicates the type of certificate
    or certificate-related information contained in the Certificate Data
    field.  Table 13 presents the types of certificate payloads.


                    Table 13:  Certificate Payload Types

        Certificate_Type                                   Value
       ____________________________________________________________

        None                                                 0
        Reserved                                           1 - 3
        X.509 Certificate -- Signature - DER Encoding        4
        Reserved                                        5 -- 65534

Certificate Data (variable length)  - Actual encoding of certificate data.
    The type of certificate is indicated by the Certificate Type/Encoding
    field.


The payload type for the Certificate Payload is six (6).


6.8 Signature Payload


The Signature Payload contains data generated by the digital signature
function.  The digital signature covers the Signature Payload Span and
the Signature Payload up to but not including the Signature Data Length.
Figure 10 shows the format of the Signature Payload.


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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Signature Type! Sig ID Type   !   Signature Payload Span      ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                               ! Sig ID Role   !               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~   Signature Timestamp                         ! Signer ID Len ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~               !    Signer ID Data                             ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !     Signature Length          !     Signature Data            ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                    Figure 10:  Signature Payload Format


The Signature Payload fields are defined as follows:


Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

Signature Type (1 octet)  -- Indicates the type of signature.  Table 14
    presents the allowable signature types.


                         Table 14:  Signature Types

            Signature Type                               Value
           ____________________________________________________

            DSS with ASN.1/DER encoding (DSS-ASN1-DER)     0
            Other                                        1-255

Signature ID Type (1 octet)  -- Indicates the format for the Signature ID
    Data.  Table 15 presents the allowable signature ID types.  The formats
    for these types are defined in Section A.4.1

Signature Payload Span (4 octets)  - Identifies the information included in

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                         Table 15:  Signature Types

                      Signature ID Type         Value
                     _________________________________

                      Unencoded Name (U-NAME)     0
                      Other                     1-255


    the signature.  The first two octets define the first signature payload.
    The third and fourth octet define the last payload.  The payloads in the
    message are an ordered sequence beginning at the header, with a value of
    zero (0).  If the signature payload itself is not in the signature span,
    you MUST still sign over the signature payload up to the signature data.

Signature ID Role (1 octet)  -- Specifies the type of Authorization (Role)
    being used.  Refer to Table 16 for the types of authorization (role).


                       Table 16:  Authorization Types

              Auth_Type                                 Value
             _________________________________________________

              Group Controller Key Server                 0
              Group and Rekey Controller                  1
              Rekey Controller                            2
              Subordinate Group Controller Key Server     3
              Subordinate Group and Rekey Controller      4
              Subordinate Rekey Controller                5
              Member ID                                   6
              Unassigned                                7-255

Signature Timestamp (4 octets)  -- Date and time that the digital signature
    was applied.  This field contains the time in seconds from the epoch
    00:00 GMT 1 January 1970.

Signer ID Length (2 octets)  - Length in octets of the Signer' ID.

Signer ID Data (variable length)  -- Data identifying the Signer's ID
    (e.g., DN). The format for this field is based on the Signature ID Type
    field and is shown where that type is defined.

Signature Length (2 octets)  -- Length in octets of the Signature Data.

Signature Data (variable length)  - Data that results from applying the
    digital signature function to the GSAKMP message and/or payload.


The payload type for the Signature Payload is eight (8).


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6.9 Notification Payload


The Notification Payload can contain both GSAKMP and group specific data
and is used to transmit informational data, such as error conditions, to
a GSAKMP peer.  It is possible to send multiple independant Notification
payloads in a single GSAKMP message.  Figure 11 shows the format of the
Notification Payload.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !        Payload Length         !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !     Notify Payload Type       !  STATUS TYPE  !               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                       Notification Data                       ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                  Figure 11:  Notification Payload Format

The Notification Payload fields are defined as follows:


Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

Notify Payload Type (2 octets)  - Specifies the type of notification
    message.  Table 17 presents the Notify Payload Types.

Status Type (1 octet)  - Specifies the status of group with respect to
    originator of notification.  Notification information specifies status
    data and can be used by a process managing a SA database to communicate
    with a peer process.  For example, a secure front end or security
    gateway may use the Notify message to synchronize SA communication.
    Table 18 presents the Notification Payload Status Types.

Notification Data (variable length)  - Informational or error data
    transmitted in addition to the Notify Payload Type.  Values for this
    field are Domain of Interpretation (DOI)-specific.



The payload type for the Notification Payload is nine (9).

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                      Table 17:  Notify Payload Types

               Information                         Value
              _______________________________________________

               None                                  0
               Invalid-Payload-Type                  1
               Situation-Not-Supported               2
               Invalid-Major-Version                 3
               Invalid-Version                       4
               Invalid-Group-ID                      5
               Invalid-Sequence-ID                   6
               Payload-Malformed                     7
               Invalid-Key-Information               8
               Invalid-ID-Information                9
               Invalid-Cert-Encoding                10
               Invalid-Certificate                  11
               Cert-Type-Unsupported                12
               Invalid-Cert-Authority               13
               Authentication-Failed                14
               Invalid-Signature                    15
               Notify-GSA-Lifetime                  16
               Certificate-Unavailable              17
               Unequal-Payload-Lengths              18
               Unauthorized Request                 19
               Unable To Take Requested Role        20
               Reserved                           21 - 22
               Acknowledgement                      23
               Reserved                           24 - 25
               Nack                                 26
               Cookie Required                      27
               Cookie                               28
               Reserved (future use)             29 - 8191
               Private Use                     8192 -- 16383


6.9.1 Notification Data - Acknowledgement (ACK) Payload Type


The data portion of the Notification payload of type ACK serves either
for confirmation of correct receipt of the Key Download message, or, when
needed, can provide other receipt information when included in a signed
message.  Figure 12 shows the format of the Notification Data - Acknowledge
Payload Type.

The Notification Data - Acknowledgement Payload Type data fields are defined
as follows:


Ack Type (1 octet)  - Specifies the type of acknowledgement.  Table 19


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                 Table 18:  Notify Payload -- Status Types

                       Status                  Value
                      _______________________________

                       Not connected             0
                       Establishing group        1
                       Reserved (future use)   2-255

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Ack Type     !       Acknowledgement Data                     ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



      Figure 12:  Notification Data - Acknowledge Payload Type Format


    presents the Notify Acknowledgement Payload Types.

                      Table 19:  Acknowledgement Types

                            ACK_Type     Value

                           ____________________
                            Simple         0
                            Unassigned   1-255



    Simple - Data portion null.


6.9.2 Notification Data - Cookie Request and Cookie Payload Type


The data portion of the Notification payload of types Cookie_Request and
Cookie contain the Cookie value.  The value for this field will have been
computed by the reponder GCKS and sent to the GM. The GM will take the value
received and place AS IS into the Notification payload Notification Data
field of type Cookie that is transmitted in the "Request to Join with Cookie
Info" back to the GCKS. This value MUST NOT be modified.

The format for this is already described in the discussion on cookies in
section 4.2.2.





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6.10 Key Creation Payload


The Key Creation Payload contains information used to create key encryption
keys.  The security attributes for this payload are provided in the Policy
Token.  Figure 13 shows the format of the payload.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !   ID Type     !           Key Creation Data                   ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                  Figure 13:  Key Creation Payload Format

The Key Creation Payload fields are defined as follows:


Next Payload (1 octet)  - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

ID Type (1 octet)  - Specifies the type of Key Creation being used.
    Table 20 identifies the types of key download information.


                Table 20:  Types Of Key Creation Information

                          ID_Type          Value
                         ________________________

                          Reserved           0
                          Diffie-Hellman     1
                          other            2-255

Key Creation Data (variable length)  - Contains Key Creation information.
    The values for this field are group specific and the format is specified
    by the ID Type field.


The payload type for the Key Creation Packet is eleven (11).



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6.11 Nonce Payload


The Nonce Payload contains random data used to guarantee freshness during an
exchange and protect against replay attacks.  Figure 14 shows the format of
the Nonce Payload.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Next Payload  !   RESERVED    !         Payload Length        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Nonce Type    !            Nonce Data                         ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                      Figure 14:  Nonce Payload Format

The Nonce Payload fields are defined as follows:


Next Payload (1 octet) - Identifier for the payload type of the next
    payload in the message.  If the current payload is the last in the
    message, then this field will be 0.

RESERVED (1 octet)  - Unused, set to 0.

Payload Length (2 octets)  - Length in octets of the current payload,
    including the generic payload header.

Nonce Type (1 octet)  - Specifies the type of Nonce being used.  Table 21
    identifies the types of nonces.


                           Table 21:  Nonce Types

Nonce_Type   Value     Definition
________________________________________________________________________________

None           0
Initiator      1
Responder      2
Combined       3       Hash ( Append (Initiator_Value, Responder_Value) )
                       The hash type comes from the Security Suite Definition.
Unassigned   4-255

Nonce Data (variable length)  - Contains the nonce information.  The values
    for this field are group-specific and the format is specified by the
    Nonce Type field.  If no group-specific information is provided, the
    minimum length for this field is 4 bytes.


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The payload type for the Nonce Payload is twelve (12).




















































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7 GSAKMP State Diagram


Figure 15 presents the states encountered in the use of this protocol.
Table 22 defines the states.  Table 23 defines the transitions.

       !-----------------> (                  )
       !   !-------------> (       Idle       ) <------------------!
       !   !               (                  )                    !
       !   !                !                !                     !
       !   !                !                !                     !
       !   !               (1a)             (1)                    !
       !   !                !                !                     !
       !   !                !                !                     !
       !   !                V                V                     !
       !   !---(5a)--- (Wait for  )       (Wait for  ) ----(5)-----!
       !               (Group     )       (GCKS Event) <---
       !               (Membership)        ^  !   \        \
       !                    !              !  !    \        \
       !                    !              !  !     \--(2)---\
       !                   (2a)           (4)(3)
       !                    !              !  !
       !                    !              !  !
       !                    V              !  V
       !-------(4a)--- (Wait for  )       (Wait for  )
                       (Group     )       (Response  )
                       (Membership)       (from Key  )
                  /--> (Event     )       (Download  )
                 /         /
                /         /
               /--(3a)---/


                      Figure 15:  GSAKMP State Diagram



















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                          Table 22:  GSAKMP States
__________________________________________________________________________

 Idle                : GSAKMP Application waiting for input
_____________________:____________________________________________________
                     :
 Wait for GCKS Event : GCKS up and running, waiting for events
_____________________:____________________________________________________
                     :
 Wait for Response   : GCKS has sent Key Download,
  from Key Download  :  waiting for response from GM
_____________________:____________________________________________________
                     :
 Wait for Group      : GM in process of joining group
  Membership         :
_____________________:____________________________________________________
                     :
 Wait for Group      : GM has group key, waiting for
  Membership Event   :  group management messages.
                     :

__________________________________________________________________________
















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                     Table 23:  State Transition Events
   ____________________________________________________________________

    Transition 1  : Create group command
   _______________:____________________________________________________
                  :
    Transition 2  : Receive bad RTJ
                  : Receive valid command to change group membership
                  : Send Compromise message x times
   _______________:____________________________________________________
                  :
    Transition 3  : Receive valid RTJ
   _______________:____________________________________________________
                  :
    Transition 4  : Timeout
                  : Receive Ack
                  : Receive Nack
   _______________:____________________________________________________
                  :
    Transition 5  : Delete group command
   _______________:____________________________________________________
                  :
    Transition 1a : Join group command
   _______________:____________________________________________________
                  :
    Transition 2a : Send Ack
   _______________:____________________________________________________
                  :
    Transition 3a : Receipt of group management messages
   _______________:____________________________________________________
                  :
    Transition 4a : Delete group command
   _______________:____________________________________________________
                  :
    Transition 5a : Time out
                  : Msg failure
                  : errors
                  :

   ____________________________________________________________________







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A APPENDIX A -- Variable Length Payload Field Definitions


This appendix defines the format of all variable length fields that contain
multiple items of information.



A.1 GSAKMP Header Fields


Group Identification Value Format  - For IPv4, this field is 8 octets long,
    4 octets for IPv4 internet address in network byte order, and 4 octets
    for serial number in network byte order.


A.2 Key Download Payload Fields


A.2.1 GTEK Key Packet Fields


For a Key Download Data value of GTEK, the Key Packet Data field is
formatted as follows:


Key Type (1 octet)  -- This is the encryption algorithm for which this key
    data is to be used.  This value is specified in the Policy Token.

Key Creation Date (4 octets)  -- This is the time value of when this key
    data was originally generated.  This field contains the time in seconds
    from the epoch 00:00 GMT 1 January 1970.

Key Expiration Date (4 octets)  -- This is the time value of when this key
    is no longer valid for use.  This field contains the time in seconds
    from the epoch 00:00 GMT 1 January 1970.

Key Handle (4 octets)  -- This is the randomly generated value to uniquely
    identify a key.

Key Data (variable length)  -- This is the actual encryption key data,
    which is dependent on the Key Type algorithm for its format.


A.2.2 Rekey Key Packet Fields


This field is defined within the specific type of rekey scheme used by the
group.

For LKH, the format of the this field is defined in Section B.1.


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A.3 Rekey Event Payload Fields


This field is defined within the specific type of rekey event scheme used by
the group.

For LKH, the format of the this field is defined in Section B.2.



A.4 Signature Payload Fields


A.4.1 Signature ID Data Field Format


Identification Data  - For type Unencoded Name (U-NAME) the format is:


    Serial Number (4 octets)  -- The certificate serial number in network
        byte order.

    Length (4 octets)  -- Length in octets of the DN Data field.

    DN Data (variable length)  -- The actual ascii DN value using the
        slash (/) character for field delimiters.  (e.g.  "/C=US/ST=MD/
        L=Somewhere/O=ACME, Inc./OU=DIV1/CN=user1/Email=user1@acme.com"
        without the surrounding quotes)


B APPENDIX B -- LKH Variable Length Payload Field Definitions


This appendix defines the format of all LKH specific variable length fields
that contain multiple items of information.



B.1 LKH Rekey Key Packet Fields


When using the Logical Key Hierarchy (LKH) protocol for Rekey operations,
the Key Packet Data is assumed to contain LKH Array data of the following
format:


LKH Version (1 octet)  -- Contains the version of the LKH protocol in which
    the data is formatted.  The current value for this field is one (1).

Leaf ID (2 octets)  -- This is the Leaf Node ID of the LKH sequence
    contained in this Key Packet Data block.  The leftmost leaf node ID
    value is one (1).

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Number of LKH Keys (2 octets)  -- This value is the number of distinct LKH
    keys in this sequence.

    For each LKH key in the sequence, the data format is as follows:



    LKH ID (2 octets)  -- This is the position of this key in the binary
        tree structure used by LKH. The base node of the binary tree has a
        value of one (1).

    Key Type (1 octet)  -- This is the encryption algorithm for which this
        key data is to be used.  This value is specified in the Policy
        Token.

    Key Creation Date (4 octets)  -- This is the time value of when this
        key data was originally generated.  This field contains the time in
        seconds from the epoch 00:00 GMT 1 January 1970.

    Key Expiration Date (4 octets)  -- This is the time value of when this
        key is no longer valid for use.  This field contains the time in
        seconds from the epoch 00:00 GMT 1 January 1970.

    Key Handle (4 octets)  -- This is the randomly generated value to
        uniquely identify a key.

    Key Data (variable length)  -- This is the actual encryption key data,
        which is dependent on the Key Type algorithm for its format.


B.2 LKH Rekey Packet Data Format Fields


This section defines the format of the Rekey Event Data in the Rekey Event
Payload, when using Logical Key Hierarchy (LKH) as the rekeying mechanism.

The Rekey Event Data consists of Rekey Event Header and Rekey Event Packet
Data(s).  A Packet Data is a complete set of information that an end-user
requires to be Rekeyed.  Packet Datas are comprised of new Key Packs of
types GTEK and Rekey.


B.2.1 Rekey Event Header


The Rekey Event Data Header contains information about the rekey data being
transmitted to the group.  Figure 16 shows the format for the header.


Group Identification Value (variable length)  - Indicates the name/title
    of the group to be rekeyed.  This is the same format as the Group


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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !                    Group ID Value                             ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                    Group ID Value                             !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Time/Date Stamp                                               !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Rekey Type    ! Algorithm Ver ! # of Rekey Packets            !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Rekey Event Packet Data(s)                                    ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!


               Figure 16:   B. 1:  Rekey Event Header Format


    Identification Value in Section  6.1 GSAKMP Message Header.

Time/Date Stamp (4 octets)  - This is the time stamp when the Rekey Event
    Data was generated.  This field contains the time in seconds from the
    epoch 00:00 GMT 1 January 1970.

Rekey Type (1 octet)  - This is the Rekey algorithm being used for this
    group.  This value is token specific.  For this appendix, this value is
    LKH, which has a value of one (1).

Algorithm Version (1 octet)  - Indicates the version of the Rekey Type
    being used.  The value at this time is one (1).

# of Rekey Packets (2 octets)  - The number of Rekey Packets contained in
    the Rekey Data.

Rekey Event Packet Data(s) (variable length)  - Contains the packets of
    rekey event information being transmitted.


B.2.2 Rekey Event Packet Data(s)


As defined in the Rekey Event Header, # of Rekey Packets field, multiple
pieces of information are sent in a Rekey Event Data.  Each end user, will
be interested in only one packet of the information sent.  Each Packet, will
contain all the Key Packs that a user requires.  For each Packet, the data
following the Security Header fields is encrypted with the key identified in
the Security Header.  Figure 17 shows the format of each Rekey Event Packet
with respect to LKH.


Packet Length (2 octets)  - Length in octets of the Rekey Packet, which


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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Packet Length                 ! Security Header: LKH ID       !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Security Header: Key Handle                                   !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! # of Key Packs                ! Key Pack Data(s)              !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!


             Figure 17:   B. 2:  Rekey Event Packet Data Format


    consists of the # of Key Packs and the Key Pack Data(s).

Security Header:  LKH ID (2 octets)  - This is the LKH ID of the Rekey Pack
    that is being used for encryption/decryption.  Refer to Section B.1 for
    the values of this field.

Security Header:  Key Handle (4 octets)  - This is a randomly generated
    value to uniquely identify the key defined by the LKH ID.

# of Key Packs (2 octets)  - The number of key packs contained in this
    Packet Data.

Key Pack Data(s) (variable length)  - Contains all the key pack data for
    this packet.


B.2.3 Key Pack Data


Each Key Pack contains all the information about the key.  Figure 18 shows
the format for each type of key pack.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Pack Type     ! Pack Length                   ! Pack Data     ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!


                  Figure 18:   B. 3:  Key Pack Data Format


Pack Type (1 octet)  - The type of key in this key pack.  Legal values are
    GTEK (0) and LKH (1).

Pack Length (2 octets)  - The length of the Pack Data.

Pack Data (variable length)  - The actual data of the key, defined by the

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    key type.



B.2.4 Pack Data Formats


There are 2 legal values for the Pack Type, GTEK and LKH. The formats for
each Pack type are defined in this section.


B.2.4.1 GTEK Pack Data


This is data for the new GTEK being sent to the Rekeyed group.


Key Type (1 octet)  - This is the encryption algorithm for which this key
    data is to be used.  This value is specified in the Policy Token.

Key Creation Date (4 octets)  - This is the time value of when this key
    data was originally generated.  This field contains the time in seconds
    from the epoch 00:00 GMT 1 January 1970.

Key Expiration Date (4 octets)  - This is the time value of when this key
    is no longer valid for use.  This field contains the time in seconds
    from the epoch 00:00 GMT 1 January 1970.

Key Handle (4 octets)  - This is the randomly generated value to uniquely
    identify a key.

Key Data (variable length)  - This is the actual encryption key data, which
    is dependent on the Key Type algorithm for its format.


B.2.4.2 LKH Pack Data


This is the data to fix an Group Member Rekey sequence to recover from a
compromise.


LKH ID (2 octets)  -- This is the position of this key in the binary tree
    structure used by LKH. Refer to Section B.1 for the values of this
    field.

Key Type (1 octet)  - This is the encryption algorithm for which this key
    data is to be used.  This value is specified in the Policy Token.

Key Creation Date (4 octets)  - This is the time value of when this key
    data was originally generated.  This field contains the time in seconds
    from the epoch 00:00 GMT 1 January 1970.

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Key Expiration Date (4 octets)  - This is the time value of when this key
    is no longer valid for use.  This field contains the time in seconds
    from the epoch 00:00 GMT 1 January 1970.

Key Handle (4 octets)  - This is the randomly generated value to uniquely
    identify a key.

Key Data (variable length)  - This is the actual encryption key data, which
    is dependent on the Key Type algorithm for its format.



B.2.5 Example


This section will give an example of the data.  The data to be transmitted
is:

| GroupID | Date/Time | Rekey Type | Algorithm Ver | # of Packets|
{ (GTEK)A, (GTEK, B, E)6, (GTEK, B)F }

This data shows that three packets are being transmitted.  Read each
packet as:
a) GTEK wrapped in LKH key A
b) GTEK, LKH keys B & E, all wrapped in LKH key 6
c) GTEK and LKH key B, all wrapped in LKH key F

We will show format for all header data, and packet (b).

Definition of values:
0xLLLL     - length value
0xHHHHHHH# - handle value
0xTTTTTTTC - creation time
0xTTTTTTTE - expiration time



GroupID        - 0xAABBCCDD
                 0x12345678
Date/Time      - 0x34574509
Rekey Type     - 0x01 (LKH)
Algorithm Vers - 0x01
# of Packets   - 0x0003
For Packet (b):
Packet Length      - 0xLLLL
Sec HDR:LKH ID     - 0x0006
Sec HDR:Key Handle - 0xHHHHHHH1
# of Key Packs     - 0x0003
  Key Pack 1:
    Pack Type   - 0x00 (GTEK)
    Pack Length - 0xLLLL
      Key Type            - 0x02 (DES3)

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      Key Creation Date   - 0xTTTTTTTC
      Key Expiration Date - 0xTTTTTTTE
      Key Handle          - 0xHHHHHHH2
      Key Data            - variable, based on key definition
  Key Pack 2:
    Pack Type   - 0x01 (LKH)
    Pack Length - 0xLLLL
      LKH ID              - 0x000B
      Key Type            - 0x02 (DES3)
      Key Creation Date   - 0xTTTTTTTC
      Key Expiration Date - 0xTTTTTTTE
      Key Handle          - 0xHHHHHHH3
      Key Data            - variable, based on key definition
  Key Pack 3:
    Pack Type   - 0x01 (LKH)
    Pack Length - 0xLLLL
      LKH ID              - 0x000E
      Key Type            - 0x02 (DES3)
      Key Creation Date   - 0xTTTTTTTC
      Key Expiration Date - 0xTTTTTTTE
      Key Handle          - 0xHHHHHHH4
      Key Data            - variable, based on key definition



C APPENDIX C -- Change History


C.1 Changes from GSAKMP-00 to GSAKMP-01 February 2003


This specification was based on two earlier versions of GSAKMP drafts,
referred to to GSAKMP and GSAKMP-Light.  These two specifications were
merged to incorporate all information necessary to allow the original
GSAKMP-Light specification to stand on its own.  The original GSAKMP
protocol no longer exists as a standard, it has been subsumed by
GSAKMP-Light.  GSAKMP-Light is now called GSAKMP.

Major modifications to the specification are


Removed Payloads:   Authorization, Certificate Request, Vendor ID, and
    Hash.

Removed Messages:   Group Removal/Destruction.

Signature Processing:   The signature processing has been modified.






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C.2 Changes from GSAKMP-01 to GSAKMP-02 June 2003


1.  The specification was modified to confirm that key words are used as
    defined by RFC2119.

2.  The Protocol Considerations section for IANA port number was added.

3.  The Cookie section for mitigation of DoS attacks was added.

4.  The Protocol State Diagram was added.



C.3 Changes from GSAKMP-02 to GSAKMP-03 August 2003


1.  Clarrified Nonce value in Request to Join With Cookie msg.

2.  Added Signature ID Type to Security Suite 1 definition.

3.  Clarrified format of Identification information used in Signature and
    Identification Payloads.

4.  Split Signature Type field into it's two appropriate fields.  This was
    not a change in the payload, just cleaning up the definition.


D References, Authors Addesses, and Acknowledgements


The following references were used in the preparation of this document.



D.1 References


[HHMCD01] , Thomas Hardjono, Hugh Harney, Pat McDaniel, Andrea Colgrove,
Pete Dinsmore, Group Security Policy Token:  Definition and Payloads',
draft-ietf-msec-gspt-00.txt, Work in progress.

[MSST98] Maughan, D., Schertler, M., Schneider, M., and J. Turner,
``Internet Security Association and Key Management Protocol (ISAKMP)'', RFC
2408, November 1998.

[FIPS 196], ``Entity Authentication Using Public Key Cryptography,'' Federal
Information Processing Standards Publication 196, NIST, February 1997.

[DH77], Diffie, W., and M. Hellman, ``New Directions in Cryptography'', IEEE
Transactions on Information Theory, June 1977.


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INTERNET-DRAFT                        GSAKMP                        Aug 2003

[WHA98], Wallner, D., Harder E., and Agee R., ``Key Management for
Multicast:  Issues and Architectures'', Internet Draft, Informational,
September 1998.

[BMS], Balenson D., McGrew D., Sherman A., ``Key Management for Large
Dynamic Groups:  One-Way Function Trees and Amortized Initialization'',
Internet Draft, February 1999.

[RFC 2093] Harney H., Muckenhirn C., and Rivers T., ``Group Key, Management
Protocol Specification'', RFC 2093, Experimental, July 1997.

[RFC 2094] Harney H., Muckenhirn C., and Rivers T., ``Group Key Management
Protocol Architecture'', RFC 2094, Experimental, July 1997.

[RFC 2104] Krawczyk H., Bellare M., and Canetti R., ``HMAC: Keyed-Hashing
for Message Authentication'', RFC 2104, Informational, February

[RFC 2401] Kent S. and Atkinson, R., ``Security Architecture for the
Internet Protocol'', RFC 2401, November 1998, Proposed Standard.

[RFC 2402] Kent S. and Atkinson, R., ``IP Authentication Header'', RFC 2402,
November 1998, Proposed Standard.1997.

[RFC 2406] Kent S. and Atkinson, R., ``IP Encapsulating Security Payload
(ESP)'', RFC 2406, November 1998, Proposed Standard.

[RFC 2408] Maughan D., Schertler M., Schneider M., and Turner J., ``Internet
Security Association and Key Management Protocol (ISAKMP)'', RFC 2408,
Proposed Standard, November 1998.

[RFC 2409] Harkins D. and Carrel D., ``The Internet Key Exchange (IKE)'',
RFC 2409, Proposed Standard, November 1998.

[RFC 2412] Orman H. K., ``The OAKLEY Key Determination Protocol'', RFC 2412,
Informational, November 1998.

[RFC2543], M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg, SIP:
Session Initiation Protocol, March 99

[RFC2627] D. Wallner, E. Harder, R. Agee, Kay Management for Multicast:
Issues and Architectures, June 1999

[RFC2974], M. Handley, C. Perkins, E. Whelan, Session Announcement Protocol,
Oct 2000.

[IKEv2], C. Kaufman, ``Internet Key Exchange (IKEv2) Protocol'',
draft-ietf-ipsec-ikev2-o6.txt, March 2003

[HCM] H. Harney, A. Colegrove, P. McDaniel, "Principles of Policy in Secure
Groups", Proceedings of Network and Distributed Systems Security 2001
Internet Society, San Diego, CA, February 2001


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[HCLM00] H. Harney, A. Colegrove, P. Lough, U. Meth, ``GSAKMP Token
Specification'', draft-ietf-msec-tokenspec-sec-00.txt



D.2 Authors Addresses


Hugh Harney (point-of-contact)
SPARTA, Inc.
7075 Samuel Morse Drive
Columbia, MD 21046
(410) 872-1515 ext 203
FAX (410) 872-8079
hh@sparta.com

Uri Meth
SPARTA, Inc.
7075 Samuel Morse Drive
Columbia, MD 21046
(410) 872-1515 ext 233
FAX (410) 872-8079
umeth@sparta.com

Andrea Colegrove
SPARTA, Inc.
7075 Samuel Morse Drive
Columbia, MD 21046
(410) 872-1515 ext 232
FAX (410) 872-8079
acc@sparta.com

Angela Schuett
R231 NSA
9800 Savage Rd
Suite 6534
Fort Meade, MD 20755
(301) 688-0850
FAX (301) 688-0255
amschue@tycho.ncsc.mil

Patrick McDaniel
AT&T Labs - Research
A203, Bldg.  103
180 Park Ave.
Florham Park, NJ 07932
Office (973) 360-5721
pdmcdan@research.att.com

Gavin Kenny
LogicaCMG
Keats House

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The Office Park
Springfield Drive
Leatherhead, Surrey KT22 7LP, UK
+44 1372 838043
FAX +44 1372 759196
Gavin.IA.Kenny@LogicaCMG.com


Haitham S. Cruickshan
Centre for Communication Systems Research (CCSR)
University of Surrey
Guildford, Surrey GU2 7XH, UK
+44 1483 686007 (indirect 689844)
FAX +44 1483 686011
H.Cruickshank@surrey.ac.uk

Sunil Iyengar
Centre For Communication And Systems Research(CCSR)
School of Electronics, Computing and Mathematics
University Of Surrey, Guildford GU2 7XH
Surrey, England, United Kingdom
+44 (0)1483 876008
s.iyengar@eim.surrey.ac.uk



D.3 Acknowledgements


The following individuals deserve recognition and thanks for their
contributions which have greatly improved this protocol:  Eric Harder
is an author to the Tunneled-GSAKMP, whose concepts are found in GSAKMP
as well.  Rod Fleischer, also a Tunneled-GSAKMP author, and Peter Lough
were both instrumental in coding a prototype of the GSAKMP software and
helped define many areas of the protocol that were vague at best.  Andrew
McFarland and Gregory Bergren provided critical analysis of early versions
of the specification.  Ran Canetti analyzed the security of the protocol
and provided denial of service suggestions leading to optional "cookie
protection".

Document expiration:  February 4, 2004












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