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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)
                                                        G Gross (IdentAware)
draft-ietf-msec-gsakmp-sec-04.txt     SPARTA, Inc., National Security Agency
                                  AT&T Labs, LogicaCMG, University of Surrey
                                                         IdentAware Security
Expires:  April 24, 2004                                        October 2003


                                   GSAKMP




                            Status of this memo



This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.  Internet-Drafts are working documents
of the Internet Engineering Task Force (IETF), its areas, and its working
groups.  Note that other groups may also distribute working documents as
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Internet-Drafts are draft documents valid for a maximum of six months and
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is inappropriate to use Internet-Drafts as reference material or to cite
them other than as ``work in progress''.

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

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


                                  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


INTERNET-DRAFT                      GSAKMP                      October 2003

    functions, and capabilities to destroy the group.  It also
    generates group keys.













































                              Copyright Notice

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



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Contents

1 Overview                                                                 8
  1.1 GSAKMP Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 8
  1.2 Protocol Considerations . . . . . . . . . . . . . . . . . . . . . . 9
  1.3 Document Organization . . . . . . . . . . . . . . . . . . . . . . . 9

2 Terminology                                                              9
3 Security Considerations                                                 11
  3.1 Security Assumptions  . . . . . . . . . . . . . . . . . . . . . . . 12
  3.2 GSAKMP Use of Other Protocols . . . . . . . . . . . . . . . . . . . 12
    3.2.1ISAKMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.2.2FIPS Pub 196 . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.2.3LKH  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.2.4Rekey Availability . . . . . . . . . . . . . . . . . . . . . . . 13
    3.2.5Diffie-Hellman . . . . . . . . . . . . . . . . . . . . . . . . . 13
  3.3 Denial of Service (DoS) Attack  . . . . . . . . . . . . . . . . . . 13
  3.4 Proof of Trust Hierarchy  . . . . . . . . . . . . . . . . . . . . . 14

4 Architecture                                                            14
  4.1 Trust Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
    4.1.1Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
    4.1.2GO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
    4.1.3GC/KS  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
    4.1.4Subordinate GC/KS  . . . . . . . . . . . . . . . . . . . . . . . 16
    4.1.5GM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
    4.1.6Assumptions  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
  4.2 Rule-Based Security Policy  . . . . . . . . . . . . . . . . . . . . 17
    4.2.1Access Control . . . . . . . . . . . . . . . . . . . . . . . . . 18
    4.2.2Authorizations for security relevant actions . . . . . . . . . . 19
  4.3 Distributed Operation . . . . . . . . . . . . . . . . . . . . . . . 19
  4.4 Concept of Operation  . . . . . . . . . . . . . . . . . . . . . . . 20
    4.4.1Assumptions  . . . . . . . . . . . . . . . . . . . . . . . . . . 21
    4.4.2Creation of a PT . . . . . . . . . . . . . . . . . . . . . . . . 21
    4.4.3Creation of a Group  . . . . . . . . . . . . . . . . . . . . . . 22
    4.4.4Discovery of GC/KS . . . . . . . . . . . . . . . . . . . . . . . 22
    4.4.5GC/KS registration policy enforcement  . . . . . . . . . . . . . 22
    4.4.6GM registration policy enforcement . . . . . . . . . . . . . . . 23
    4.4.7S-GC/KS operations . . . . . . . . . . . . . . . . . . . . . . . 23
  4.5 GSAKMP Interactions With NAT Traversal  . . . . . . . . . . . . . . 24
    4.5.1Non-Transparent Network Address Translation Behaviors  . . . . . 24
    4.5.2GSAKMP Avoidance of NAT Using an IP-v6 Over IP-v4 Network  . . . 25
    4.5.3GSAKMP Multicast IP-v4 NAT Architectural Assumptions . . . . . . 26
    4.5.4Representative Example GSAKMP Multi-Realm Configuration  . . . . 27
    4.5.5GSAKMP Registration Security Association NAT Traversal . . . . . 30
    4.5.6GSAKMP Re-key Security Association NAT Traversal . . . . . . . . 31
    4.5.7Multicast Application Security Association NAT Traversal . . . . 31
5 Group Life Cycle                                                        32
  5.1 Group Definition  . . . . . . . . . . . . . . . . . . . . . . . . . 32
  5.2 Group Establishment . . . . . . . . . . . . . . . . . . . . . . . . 33
    5.2.1Standard Group Establishment . . . . . . . . . . . . . . . . . . 33


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        5.2.1.1Request to Join . . . . . . . . . . . . . . . . . . . . . . 34
        5.2.1.2Key Download  . . . . . . . . . . . . . . . . . . . . . . . 35
        5.2.1.3Request to Join Error . . . . . . . . . . . . . . . . . . . 37
        5.2.1.4Key Download - Ack/Failure  . . . . . . . . . . . . . . . . 37
        5.2.1.5Lack of Ack . . . . . . . . . . . . . . . . . . . . . . . . 38
    5.2.2Cookies - Group Establishment with Denial of Service Protection  39
  5.3 Group Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 41
    5.3.1Rekey Events . . . . . . . . . . . . . . . . . . . . . . . . . . 42
    5.3.2Leaving a Group  . . . . . . . . . . . . . . . . . . . . . . . . 42
        5.3.2.1Eviction  . . . . . . . . . . . . . . . . . . . . . . . . . 42
        5.3.2.2Voluntary Departure without Notice  . . . . . . . . . . . . 43
        5.3.2.3De-Registration . . . . . . . . . . . . . . . . . . . . . . 43
           5.3.2.3.1Request to Depart - . . . . . . . . . . . . . . . . . . 43
           5.3.2.3.2Departure_Response -   . . . . . . . . . . . . . . . . . 44
           5.3.2.3.3Departure_ACK -  . . . . . . . . . . . . . . . . . . . . 45

6 Security Suite                                                          46
  6.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
  6.2 Definition Suite 1  . . . . . . . . . . . . . . . . . . . . . . . . 46
7 GSAKMP Payload Structure                                                47
  7.1 GSAKMP Header . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
    7.1.1GSAKMP Header Structure  . . . . . . . . . . . . . . . . . . . . 47
    7.1.2GSAKMP Header Processing . . . . . . . . . . . . . . . . . . . . 50
  7.2 Generic Payload Header  . . . . . . . . . . . . . . . . . . . . . . 51
    7.2.1Generic Payload Header Structure . . . . . . . . . . . . . . . . 51
    7.2.2Generic Payload Header Processing  . . . . . . . . . . . . . . . 51
  7.3 Policy Token Payload  . . . . . . . . . . . . . . . . . . . . . . . 52
  7.4 Key Download Payload  . . . . . . . . . . . . . . . . . . . . . . . 53
  7.5 Rekey Event Payload . . . . . . . . . . . . . . . . . . . . . . . . 54
  7.6 Identification Payload  . . . . . . . . . . . . . . . . . . . . . . 55
  7.7 Certificate Payload . . . . . . . . . . . . . . . . . . . . . . . . 56
  7.8 Signature Payload . . . . . . . . . . . . . . . . . . . . . . . . . 58
    7.8.1Signature Payload Structure  . . . . . . . . . . . . . . . . . . 58
    7.8.2Signature Payload Processing . . . . . . . . . . . . . . . . . . 59
  7.9 Notification Payload  . . . . . . . . . . . . . . . . . . . . . . . 60
    7.9.1Notification Data - Acknowledgement (ACK) Payload Type . . . . . 62
    7.9.2Notification Data - Cookie_Required and Cookie Payload Type  . . 62
    7.9.3Notification Data - Mechanism Choices Payload Type . . . . . . . 63
  7.10Key Creation Payload  . . . . . . . . . . . . . . . . . . . . . . . 64
    7.10.1Key Creation Payload Structure . . . . . . . . . . . . . . . . . 64
    7.10.2Key Creation Payload Processing  . . . . . . . . . . . . . . . . 65
  7.11Nonce Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
    7.11.1Nonce Payload Structure  . . . . . . . . . . . . . . . . . . . . 66
    7.11.2Nonce Payload Processing . . . . . . . . . . . . . . . . . . . . 67

8 GSAKMP State Diagram                                                    68
A APPENDIX A -- Variable Length Payload Field Definitions                 71
  A.1 Key Download Payload Fields . . . . . . . . . . . . . . . . . . . . 71
    A.1.1GTEK Key Packet Fields . . . . . . . . . . . . . . . . . . . . . 71
    A.1.2Rekey Key Packet Fields  . . . . . . . . . . . . . . . . . . . . 71
  A.2 Signature Payload Fields  . . . . . . . . . . . . . . . . . . . . . 72


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    A.2.1Signature ID Data Field Format . . . . . . . . . . . . . . . . . 72

B APPENDIX B -- LKH Variable Length Payload Field Definitions             72
  B.1 LKH Rekey Key Packet Fields . . . . . . . . . . . . . . . . . . . . 72
  B.2 LKH Rekey Packet Data Format Fields . . . . . . . . . . . . . . . . 73
    B.2.1Rekey Event Header . . . . . . . . . . . . . . . . . . . . . . . 73
    B.2.2Rekey Event Packet Data(s) . . . . . . . . . . . . . . . . . . . 74
    B.2.3Key Pack Data  . . . . . . . . . . . . . . . . . . . . . . . . . 75
    B.2.4Pack Data Formats  . . . . . . . . . . . . . . . . . . . . . . . 75
        B.2.4.1GTEK Pack Data  . . . . . . . . . . . . . . . . . . . . . . 76
        B.2.4.2LKH Pack Data . . . . . . . . . . . . . . . . . . . . . . . 76
    B.2.5Example  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
C APPENDIX C -- Change History                                            78
  C.1 Changes from GSAKMP-00 to GSAKMP-01 February 2003 . . . . . . . . . 78
  C.2 Changes from GSAKMP-01 to GSAKMP-02 June 2003 . . . . . . . . . . . 78
  C.3 Changes from GSAKMP-02 to GSAKMP-03 August 2003 . . . . . . . . . . 79
  C.4 Changes from GSAKMP-03 to GSAKMP-04 October 2003  . . . . . . . . . 79

D References, Authors Addesses, and Acknowledgements                      83
  D.1 References  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
  D.2 Authors Addresses . . . . . . . . . . . . . . . . . . . . . . . . . 84
  D.3 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . . . 86































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List of Figures

  1   GSAKMP NAT Example  . . . . . . . . . . . . . . . . . . . . . . . . 29
  2   GSAKMP Ladder Diagram . . . . . . . . . . . . . . . . . . . . . . . 34
  3   GSAKMP Ladder Diagram with Cookies  . . . . . . . . . . . . . . . . 40
  4   GSAKMP Header Format  . . . . . . . . . . . . . . . . . . . . . . . 48
  5   Generic Payload Header  . . . . . . . . . . . . . . . . . . . . . . 51
  6   Policy Token Payload Format . . . . . . . . . . . . . . . . . . . . 52
  7   Key Download Payload Format . . . . . . . . . . . . . . . . . . . . 53
  8   Rekey Event Payload Format  . . . . . . . . . . . . . . . . . . . . 55
  9   Identification Payload Format . . . . . . . . . . . . . . . . . . . 56
  10  Certificate Payload Format  . . . . . . . . . . . . . . . . . . . . 57
  11  Signature Payload Format  . . . . . . . . . . . . . . . . . . . . . 58
  12  Notification Payload Format . . . . . . . . . . . . . . . . . . . . 60
  13  Notification Data - Acknowledge Payload Type Format . . . . . . . . 62
  14  Notification Data - Mechanism Choices Payload Type Format . . . . . 63
  15  Key Creation Payload Format . . . . . . . . . . . . . . . . . . . . 64
  16  Nonce Payload Format  . . . . . . . . . . . . . . . . . . . . . . . 66
  17  GSAKMP State Diagram  . . . . . . . . . . . . . . . . . . . . . . . 68
  18   B. 1:  Rekey Event Header Format . . . . . . . . . . . . . . . . . 74
  19   B. 2:  Rekey Event Packet Data Format  . . . . . . . . . . . . . . 74
  20   B. 3:  Key Pack Data Format  . . . . . . . . . . . . . . . . . . . 75































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List of Tables

  1   Request to Join (RTJ) Message Definition  . . . . . . . . . . . . . 35
  2   Key Download (KeyDL) Message Definition . . . . . . . . . . . . . . 36
  3   Request to Join Error (RTJ-Err) Message Definition  . . . . . . . . 37
  4   Key Download - Ack/Failure (KeyDL-A/F) Message Definition . . . . . 38
  5   Lack of Ack (LOA) Message Definition  . . . . . . . . . . . . . . . 39
  6   Cookie Download Message Definition  . . . . . . . . . . . . . . . . 40
  7   Rekey Event Message Definition  . . . . . . . . . . . . . . . . . . 42
  8   Request_to_Depart (RTD) Message Definition . . . . . . . . . . . . . 43
  9   Departure_Response (DR) Message Definition  . . . . . . . . . . . . 44
  10  Departure_ACK (DA) Message Definition . . . . . . . . . . . . . . . 45
  11  Group Identification Types  . . . . . . . . . . . . . . . . . . . . 48
  12  Payload Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
  13  Exchange Types  . . . . . . . . . . . . . . . . . . . . . . . . . . 49
  14  Policy Token Types  . . . . . . . . . . . . . . . . . . . . . . . . 52
  15  Key Download Data Types . . . . . . . . . . . . . . . . . . . . . . 54
  16  Rekey Event Types . . . . . . . . . . . . . . . . . . . . . . . . . 55
  17  Identification Types  . . . . . . . . . . . . . . . . . . . . . . . 56
  18  Certificate Payload Types . . . . . . . . . . . . . . . . . . . . . 57
  19  Signature Types . . . . . . . . . . . . . . . . . . . . . . . . . . 59
  20  Signature Types . . . . . . . . . . . . . . . . . . . . . . . . . . 59
  21  Notify Payload Types  . . . . . . . . . . . . . . . . . . . . . . . 61
  22  Acknowledgement Types . . . . . . . . . . . . . . . . . . . . . . . 62
  23  Mechanism Types . . . . . . . . . . . . . . . . . . . . . . . . . . 63
  24  Encryption Types  . . . . . . . . . . . . . . . . . . . . . . . . . 64
  25  Nonce Hash Types  . . . . . . . . . . . . . . . . . . . . . . . . . 64
  26  Types Of Key Creation Information . . . . . . . . . . . . . . . . . 65
  27  Nonce Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
  28  GSAKMP States . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
  29  State Transition Events . . . . . . . . . . . . . . . . . . . . . . 70






















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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 (GC/KS) 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 GC/KS).

The security features of the establishment protocol for the SA include


 -  Group policy identification

 -  Group policy dissemination

 -  GM to GC/KS 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 5.2.1.5
presents the terminology and concepts used to present the requirements of
this protocol.  Section 3 outlines the security considerations with respect
to GSAKMP. Section 5 describes the group management life-cycle.  Section 6
describes the Security Suite Definition.  Section 7 presents the message
types and formats used during each phase of the life-cycle.  Section 8
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 (GC/KS):  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 GC/KS

     -  Request group keys from the GC/KS

     -  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 GC/KS 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 as defined by policy.

Subordinate Group Controller Key Server (S-GC/KS):  Any group member having
    the appropriate processing and trust characteristics as defined in the
    group policy that has the potential to act as a S-GC/KS. 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 builds 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 Rekey Availability


In addition to GSAKMP having the capability to do rekey operations, GSAKMP
MUST aslo have the capability to make this rekey information available to
GMs.  The necessity of GMs receiving rekey messages, requires the use of
methods to increase the likelyhood of receipt of Rekey Messages.  These
methods MAY include multiple transmissions of the rekey message, posting of
the rekey message on a bulliten board, etc.


3.2.5 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 6, 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  5.2.2,
Cookies.



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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 GC/KS 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 GC/KS is an authorized disseminator, and 3) the
group mechanisms are acceptable for protecting the GMs data.



4 Architecture


This architecture presents a trust model for GSAKMP and a concept of
operations for establishing a trusted distributed infrastructure for group
key and policy distribution.

GSAKMP conforms to the IETF MSEC architectural concepts as specified in the
MSEC Architecture document [RFC xxxx].  GSAKMP uses the MSEC components to
create a trust model for operations that implement the security principles
of mutual suspicion and trust anchors.


4.1 Trust Model


4.1.1 Components


The trust model contains four key components:


 -  Group Owners (GO),

 -  Group Controllers / Key Servers (GC/KS),

 -  Subordinate GC/KS (S-GC/KS), and

 -  Group Members (GM).


The goal of the GSAKMP trust model is to derive trust from a common trust
anchor for a group.  All security relevant decisions and actions implemented
by GSAKMP are based on information that ultimately is traceable to and
verified by a core trust anchor.  There are two pieces of the trust anchors
for GSAKMP, the GO (policy creation authority) and the PKI root that allows


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us to verify the GO.


4.1.2 GO


The GO is the policy creation authority for the group.  The GO has a well
defined identity that is relevant to the group.  That identity can be of a
person or of a group trusted component.  All potential entities in the group
have to recognize the GO as the individual with authority to specify policy
for the group.

The policy reflects the protection requirements of the data in a group.
Ultimately, the data and the application environment drives the security
policy for the group.

The GO has to determine the security rules and mechanisms that are
appropriate for the data being protected by the group keys.  All this
information is captured in a policy token (PT). The GO creates the PT and
signs it.


4.1.3 GC/KS


The GC/KS is authorized to perform several functions:  key creation, key
distribution, rekey, and group membership management.

As key creation authority, the GC/KS will create the set of keys for the
group.  These keys include the Traffic Protection Keys (TPK) and first tier
rekey keys.  There may be second tier rekey trees if a distributed rekey
management structure is required for the group.

As the key distribution (registration) authority, it has to notify the
group of its location for registration services.  The GS/KS will have to
enforce key access control as part of the key distribution and registration
processes.

As the group rekey authority, it performs rekey in order to change the
group's TPK. Change of the TPK limits the exposure of data encrypted with
any single TPK.

Finally, as group membership management authority, the GC/KS can manage the
group membership (registration, eviction, de-registration, etc.).  This may
be done in part by using key tree approaches such as Logical Key Hierarchies
(LKH).







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4.1.4 Subordinate GC/KS


A subordinate GC/KS is used to distribute the GC/KS functionality across
multiple entities.  The S-GC/KS will have all the authorities of the GC/KS
except one:  it will not create the TPK. It is assumed here that the group
will transmit data with a single TPK at any one time.  This TPK comes from
the GC/KS.

Note that relative to the GC/KS, the S-GC/KS is responsible for an
additional security check:  the S-GC/KS must register as a member with the
GCKS, and during that process it has to verify the authority of the GC/KS.


4.1.5 GM


The GM has two jobs - make sure all security relevant actions are authorized
and properly use the group keys.  During the registration process, the GM
will verify that the PT is signed by a recognized GO. In addition, it will
verify that the GC/KS or S-GC/KS engaged in the registration process is
authorized, as specified in the PT. If rekey and new PTs are distributed
to the group, the GM will verify that they are proper and all actions are
authorized.

The GM is granted access to group data through receipt of the group keys
This carries along with it a responsibility to protect the key from
unauthorized disclosure.

GSAKMP does not offer any enforcement mechanisms to control which GM are
multicast speakers at a given moment.  This policy and its enforcement
depend on the multicast application and its protocols.  However, GSAKMP
does allow a group to have one of three Group Security Association multicast
speaker configurations:



 -  There is a single GM authorized to be the group's speaker.  There
    is one multicast application SA allocated by the GO in support of
    that speaker.  The PT initializes this multicast application SA and
    identifies the GM that has been authorized to be speaker.  All GM
    share a single TPK with that GM speaker.  Sequence number checking for
    anti-replay protection is feasible and enabled by default.  This is the
    default group configuration.  GSAKMP implementations MUST support this
    configuration.

 -  The GO authorizes all of the GM to be a group speaker.  The GO allocates
    one multicast application SA in support of these speakers.  The PT
    initializes this multicast application SA and indicates that any GM
    can be a speaker.  All of the GM share a single TPK and other SA state
    information.  Consequently, some SA security features such as sequence
    number checking for anti-replay protection can not be supported by

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    this configuration.  GSAKMP implementations MUST support this group
    configuration.

 -  The GO authorizes a subset of the GM to be a group speaker (which may be
    the subset comprised of all GM). The GO allocates a distinct multicast
    application SA for each of these speakers.  The PT identifies the
    authorized speakers, and initializes each of their multicast application
    Security Associations.  The speakers still share a common TPK across
    their SA, but each speaker has a separate SA state information instance
    at every peer GM. Consequently, this configuration supports SA security
    features such as sequence number checking for anti-replay protection or
    source authentication mechanisms that require per speaker state at the
    receiver.  The drawback of this configuration is that it does not scale
    to a large numbers of speakers.  GSAKMP implementations MAY support this
    group configuration.



4.1.6 Assumptions


The assumptions for this trust model are:


 -  the GCKS is assumed to be never compromised,

 -  the GO is assumed to be never compromised,

 -  the PKI, subject to certificate validation, is assumed to be
    trustworthy,,

 -  The GO is capable of creating a security policy to meet the demands of
    the group,

 -  the compromises of a group member will be detectable and reported to the
    GO in a trusted manner,

 -  the subsequent recovery from a compromise will deny inappropriate access
    to protected data to the compromised member,

 -  no security relevant actions depend on a precise network time,

 -  that there is confidentiality, integrity, multicast source authentication
    and anti-replay protection mechanisms for all GSAKMP control messages,


4.2 Rule-Based Security Policy


The trust model for GSAKMP revolves around the definition and enforcement
of the security policy.  In fact, the use of the key is only relevant, in


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a security sense, if it represents the successful enforcement of the group
security policy.

Group operations lend themselves to rule-based security policy.  The need
for distribution of data to many endpoints often leads to the defining of
those authorized endpoints based on rules.  For example, all IETF attendees
at a given conference could be defined as a single group.

If the security policy rules are to be relevant, they must be coupled with
validation mechanisms.  The core principle here is that the level of trust
one can afford a security policy is exactly equal to the level of trust one
has in the validation mechanism used to prove that policy.  For example, if
all IETF attendees are allowed in then they could register their identity
from their certificate upon check in to the meetings.  That certificate is
issued by a trust anchor (PKI root) that is authorized to identify someone
as being an IETF attendee.  The GO could make admittance rules to the IETF
group based on the identity certificates issued from trusted PKIs.

In GSAKMP, every security policy rule is coupled with an explicit validation
mechanism.  For interoperability considerations, GSAKMP requires its
supporting PKI implementations MUST be compliant to RFC 2459.

If a GM public key certificate is revoked, then the entity that issues
that revocation SHOULD signal the GO, so that the GO can expel that GM.
The method that signals this event to the GO is not standardized by this
specification.

A direct mapping of rule to validation mechanism allows the use of multiple
rules and PKIs to create groups.  This allows a GO to define a group
security policy that spans multiple PKI domains, each with their own
Certificate Authority public key certificate.


4.2.1 Access Control


The access control policy for the group keys is equivalent to the access
control policy for the multicast application data the keys are protecting.

In a group, each data source is responsible for ensuring that the access
to the source's data is appropriate.  This implies that every data source
should have knowledge of the access control policy for the group keys.

In the general case, GSAKMP offers a suite of security services to its
applications, and does not prescribe how they use those services.

GSAKMP supports the creation of GSAs with multiple data sources.  It also
supports architectures where the GC/KS is not itself a data source.  In
the multiple data source architectures GSAKMP requires that the access
control policy is precisely defined and distributed to each data source.
The reference for this data structure is the GSAKMP Policy Token [ref TBD].


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4.2.2 Authorizations for security relevant actions


A critical aspect of the GSAKMP trust model is the authorization of security
relevant actions.  Security relevant actions include - download of group
key, rekey, and PT creation and updates.  These actions could be used to
disrupt the secure group and all entities in the group must verify that they
were instigated by authorized entities within the group.



4.3 Distributed Operation


Scalability is a core feature of GSAKMP. GSAKMP's approach to scalable
operations is the establishment of S-GC/KSs.  This allows the GSAKMP systems
to distribute the workload of setting up and managing very large groups.

Another aspect of distributed S-GC/KS operations is the enabling of local
management authorities.  In very large groups, subordinate enclaves may be
best suited to provide local management of the enclaves' group membership,
due to a direct knowledge of the group members.

One of the critical issues involved with distributed operation is the
discovery of the security infrastructure location and security suite.  Many
group applications that have dynamic interactions must "find" each other
to operate.  The discovery of the security infrastructure is just another
piece of information that has to be known by the group in order to operate
securely.

There are several methods for infrastructure discovery:


 -  Announcements

 -  Anycast

 -  Rendezvous points / Registration


One method for distributing the security infrastructure location is to use
announcements.  The SAP is commonly used to announce the existence of a
new multicast application or service.  If an application uses SAP[Ref RFC
2974] to announce the existence of a service on a multicast channel, that
service could be extended to include the security infrastructure location
for a particular group.

Announcements can also be used by GSAKMP in one of two modes - Expanding
Ring Searches (ERS) of security infrastructure and expanding ring searches
for infrastructure discovery.  In either case, the GSAKMP would use a
multicast broadcast that would slowly increase in its range by incremental
multicast hops.  The multicast source controls the packet's multicast range

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by explicitly setting its Time To Live count.

An expanding ring announcement operates by the GC/KS announcing its
existence for a particular group.  The number of hops this announcement
would travel would be a locally configured number.  The GMs would listen
on a well know multicast address for GC/KSs that provide service for groups
of interest.  If multiple GC/KSs are found that provide service, then the
GM would pick the closest one (in terms of multicast hops).  The GM would
then send a GSAKMP Request to Join message (RTJ) to the announced GC/KS.
If the announcement is found to be spurious then that is reported to the
appropriate management authorities.  The ERA concept is slightly different
from SAP in that it could occur over the data channel multicast address,
instead of a special multicast address dedicated for the SAP service.

An expanding ring search operates in the reverse order than the ERA. In
this case, the GM is the announcing entity.  The (S-)GC/KSs listen for the
requests for service, specifically the RTJ. The (S-)GC/KS responds to the
RTJ. .  If the GM receives more than one response, it would either ignore
the responses or send NACKs based on local configuration.

Anycast is a service that is very similar to ERS. It also can be used to
provide connection to the security infrastructure.  In this case, the GM
would send the RTJ to a well-known service request address.  This anycast
service would route the RTJ to an appropriate GC/KS. The anycast service
would have security infrastructure and network connectivity knowledge to
facilitate this connection.

Registration points can be used to distribute many group relevant data,
including security infrastructure.  Many group applications rely on well
known registration points to advertise the availability of groups.  There
is no reason that GSAKMP could not use the same approach for advertising
the existence and location of the security infrastructure.  This is a simple
process if the application being supported already supports registration.
The GSAKMP infrastructure can always provide a registration site if the
existence of this security infrastructure discovery hub is needed.  The
registration of S-GC/KSs at this site could be an efficient way to allow GM
registration.

GSAKMP infrastructure discovery can use whatever mechanism suits a
particular multicast application's requirements, including mechanisms
that have not been discussed by this architecture.  However, GSAKMP
infrastructure discovery is not standardized by this version of the GSAKMP
specification.



4.4 Concept of Operation


This concept of operation shows how the different roles in GSAKMP interact
to set up a secure group.  This particular concept of operation focuses on a
secure group that utilizes the distributed key dissemination services of the

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S-GC/KS.


4.4.1 Assumptions


The most basic assumption here is one or more trustworthy PKI for the group.
That trusted PKI will be used to create and verify security policy rules.

There is a GO that all GMs recognize as having group policy creation
authority.  All GM must be securely pre-configured to know the GO public
key.

All GMs have access to the GO PKI information, both the trusted anchor
public keys and the certificate path validation rules.

There is sufficient connectivity between the GSAKMP entities.



 -  The registration SA requires that GM can connect to the GC/KS or S-GC/KS
    using either TCP or UDP.

 -  The rekey SA requires that the data layer multicast communication
    service be available.  This can be multicast IP, overlay networks using
    TCP, or NAT tunnels.

 -  GSAKMP can support many different data layer secure applications each
    with unique connectivity requirements.


4.4.2 Creation of a PT


The GO creates and signs the Policy Token for a group.  The policy token
contains the rules for access control and authorizations for a particular
group.

The PT consists of the following information:


 -  Identification - this allows an unambiguous identification of the PT and
    the group,

 -  Access Control Rules - these rules specify who can have access to the
    group keys,

 -  Authorization Rules - these rules specify who can be a S-GC/KS,

 -  Mechanisms - these rules specify the security mechanisms that will be
    used by the group, this is necessary to ensure there is no weak link in
    the group security profile

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 -  Source authentication of the PT to the GO - the PT is a CMS signed
    object and this allows all GMs to verify the PT



4.4.3 Creation of a Group


The PT is sent to a potential GC/KS. This can occur in several ways, and
the method of transmittal is outside the scope of GSAKMP. The potential
GC/KS will verify the GO signature on the PT to ensure that it comes from a
trusted GO. Next, the GC/KS will verify that it is authorized to become the
GC/KS, based on the authorization rules in the PT. Assuming that the GC/KS
trusts the PT, is authorized to be a GC/KS, and is locally configured to
become a GC/KS for a given group and the GO, then the GC/KS will create the
keys necessary to start the group.  The GC/KS will take whatever action is
necessary (if any) to advertise its ability to distribute key for the group.
The GC/KS will then listen for RTJs.

The PT has a sequence number.  Every time a PT is distributed to the group
the group members verify that the sequence number on the PT is increasing.
The PT lifetime is not limited to a particular time interval, other than
by the lifetimes imposed by some of its attributes (e.g.  signature key
lifetime).  The current PT sequence number is downloaded to the GM in the
"Key Download" message.  Also, to avoid replay attacks, you should indicate
that this sequence number is never reset to a lower value (i.e.  rollover to
zero) as long as the group identifier remains valid and in use.  The GO must
preserve this sequence number across re-boots.


4.4.4 Discovery of GC/KS


Potential GMs will receive notice of the new group via some mechanism:
announcement, Anycast, registration look-up.  The GM will send an RTJ to the
GC/KS.


4.4.5 GC/KS registration policy enforcement


The GC/KS may or may not require cookies, depending on Denial of Service
environment and the local configuration.

Once the RTJ has been received, the GC/KS will verify that the GM is allowed
to have access to the group keys.  The GC/KS will then verify the signature
on the RTJ to ensure it was sent by the claimed identity.  If the checks
succeed, the GC/KS will ready a Key Download message for the GM. If not the
GC/KS can notify the GM of a non-security relevant problem.




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4.4.6 GM registration policy enforcement


Upon receipt of the Key Download message, the GM will verify the signature
on the message.  Then the GM will retrieve the PT from the Key Download
message and verify that the GO created and signed the PT. Once the PT is
verified as valid, the GM will verify that the GC/KS is authorized to
distribute key for this group.  Then the GM will verify that the mechanisms
used in the group are available and acceptable for protection of the GMs
data (assuming the GM is a data source).  The GM will then accept membership
in this group.

The GM will then check to see if it is allowed to be a S-GC/KS for this
group.  If the GM is allowed to be a S-GC/KS AND the local GM configuration
allows the GM to act as a S-GC/KS for this group, then the GM changes its
operating state to S-GC/KS. The GO needs to take care when assigning the
authority to become an S-GC/KS.


4.4.7 S-GC/KS operations


As a S-GC/KS, the host will now distribute keys and the PT. The first action
is to notify the potential GMs of its ability to distribute key for the
group.  This can be accomplished in exactly the same manner as the GC/KS
notifications.

The S-GC/KS may be authorized to be a local management GC and as such, it
can be authorized to create its own rekey trees.  There are several ways
to architect S-GC/KS operations that include rekey trees.  Rekey operations
with S-GC/KSs can use:



 -  the S-GC/KS to distribute the rekey arrays generated at the GC/KS,

 -  the S-GC/KS can create and distribute it's sub tree and report those
    keys back to the GC/KS, The GSAKMP message that sends those keys from
    the S-GC/KS to the GC/KS is not standardized in this version of the
    specification.  or

 -  the S-GC/KS can act as an independent rekey authority passing on the
    group keys to its subscribers.


In the independent mode of operation, the S-GC/KS holds the rekey key it
received upon group registration.  It will then create rekey messages for
its subscribers using the rekey key it creates.

Once the notification mechanisms have been activated and key trees created,
the S-GC/KS waits for RTJs.  GMs will join the group via the S-GC/KS. The
S-GC/KS will then manage its rekey group based on notification of local

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rekey needs.



4.5 GSAKMP Interactions With NAT Traversal


GSAKMP security association endpoints services that may straddle any
combination of IP-v4 public addresses and private addresses [RFC1918].
In such cases, GSAKMP endpoint identifiers may be embedded within the
GSAKMP policy token's security association Security Policy Database (SPD)
traffic selector rules.  These GSAKMP endpoint identifiers when resolved
to their equivalent private or public IP-v4 addresses entangle the GSAKMP
protocol with Network Address Translation (NAT) [RFC2663] [RFC3022] gateway
behaviors.  In addition, the NAT translation of IP-v4 header addresses also
impacts the GSAKMP registration SA, the GSAKMP re-key SA, and the multicast
application SA.

This section defines the GSAKMP mechanisms that partially mitigate
the inherent complexity spawned by IP-v4 NAT and Network Address Port
Translation (NAPT) traversal.  However, given the large number of
documented NAT problems and its erosion of end-to-end security, [reference
okazaki-v6ops-natpt-security-00.txt] new GSAKMP applications and deployments
SHOULD strongly prefer the use of IP-v6.  This specification offers IP-v4 to
IP-v6 transitional guidance in support of that objective.


4.5.1 Non-Transparent Network Address Translation Behaviors


The following NAT side effects are known to interact with the GSAKMP
protocol and its three security association types (Registration, Rekey, and
Data Layer (specifically IPSec in this example):

The following NAT behavior adversely impacts source-specific secure
multicast IPSec groups.  When a NAT gateway is on the path between a
multicast source endpoint residing behind a NAT and a public IP-v4 multicast
destination, the NAT alters the private source address to a public IP-v4
address.  This translation must be coordinated with every GSAKMP IPSec
receiver's inbound Security Policy Database (SPD) multicast entries that
uses that source address as a traffic selector [RFC2401bis].  In addition
to its impact on the inbound SPD, this NAT behavior also impacts the
source-specific multicast routing.  The GCKS must set up the GSAKMP receiver
with a SPD entry that anticipates the value(s) that the NAT translates the
packet's source address.  However, there are known cases where this address
translation can change without warning:

NAT gateways may re-boot and lose their address translation state
information.

The NAT gateway may de-allocate its address translation state after an
inactivity timer expires.  The address translation used by the NAT gateway

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after the resumption of data flow may differ than that known to the SPD
selectors at the GSAKMP endpoints.

The GCKS may not have global consistent knowledge of a GSAKMP endpoint's
current public and private address mappings due to network errors or race
conditions.  For example, an endpoint's address may change due to a DHCP
assigned address lease expiration.

Alternate paths may exist between a given pair of GSAKMP endpoints.  If
there are parallel NAT gateways along those paths, then the address
translation state information at each NAT gateway may produce different
translations on a per packet basis.

When multiple multicast source endpoints reside behind a NAT with a single
public IP-v4 address, the NAT gateway can not do UDP or TCP port translation
(i.e.  NAPT) because the ESP encryption conceals the transport layer
protocol headers.  The use of UDP encapsulated ESP [ref XXXXX] avoids this
problem.  However, this capability must be configured at the GCKS as a group
policy, and it must be supported in unison by all of the GSAKMP endpoints
within the group, even those that reside in the public Internet.  Note that
at the time of this writing this solution has IPR.

In a transport mode multicast application SA, the UDP checksum operation
may require the origin endpoint's IP address to complete successfully.  In
IKE-v2 [IKE-v2], this information is exchanged between the endpoints by
a NAT-OA payload (NAT original address).  See section X.Y of reference
[ipsec-nat-t-v03.txt].  A comparable facility must exist in a GSAKMP PT
payload that defines the multicast application SA attributes for each
multicast source endpoint.

The GSAKMP receiver endpoints must authenticate the source of all key
management packets and they must not trust a packet's IP addresses or port
numbers.

The presence of a NAT gateway makes it impossible to use an Authentication
Header, keyed by a group-wide key, to protect the integrity of the IP
header, from individuals within the cryptographic group.


4.5.2 GSAKMP Avoidance of NAT Using an IP-v6 Over IP-v4 Network


A straight forward and standards-based architecture that effectively
avoids the GSAKMP use of NAT gateways is the IP-v6 over IP-v4 transition
mechanism [RFC2529].  In IP-v6 over IP-v4 (a.k.a.  "6over4"), the underlying
IP-v4 network is treated as a virtual multicast-capable Local Area
Network.  The IP-v6 traffic tunnels over that IP-v4 virtual link layer.
Applying GSAKMP in a 6over4 architecture leverages the fact that an
administrative domain deploying GSAKMP would already be planning to deploy
IP-v4 multicast router(s).  The GSAKMP group's IP-v6 multicast routing
can execute in parallel to IP-v4 multicast routing on that same physical


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router infrastructure.  In particular, the NAT gateways at administrative
domain public/private boundaries are replaced by IP-v6 multicast routers
operating with 6over4 mode enabled on their network interfaces.  This
yields a substantial reduction in complexity and error cases over the
NAT-based approaches.  This reduction in complexity can translate into
better security.  The following factors may effect the decision to deploy
GSAKMP 6over4 rather than GSAKMP with IP-v4 NAT:

When traversing NAT, application layer protocols that contain IP-v4
addresses in their payload need the intervention of an Application Layer
Gateway (ALG) that understands that application layer protocol [RFC3027]
[RFC3235].  The ALG massages the payload's private IP-v4 addresses into
equivalent public IP-v4 addresses.  However, when encrypted by end-to-end
ESP such payloads are opaque to application layer gateways.

The primary drawback of the GSAKMP 6over4 approach is that the secure
multicast application must be (re-)written to an IP-v6 multicast socket API
or equivalent, and it must interact with the Multicast Listener Discovery
(MLD) API [reference vida-mld-v2-07.txt] [reference magma-msf-api-05.txt]
rather than IGMP. For new applications, this may not be of consequence; it
usually only becomes an issue if the application has an embedded base.  An
embedded base of GSAKMP multicast IP-v4 applications that are only available
in binary form will not be able to migrate to these transitional IP-v6
mechanisms.

The secondary drawbacks of GSAKMP 6over4 are that the IP hosts must be
upgraded to dual-stack, the attendant overlay IP-v6 multicast network
operational costs, and the difficulty of finding commercial wide-area IP-v6
multicast services.

Reliable scalable GSAKMP 6over4 deployment is far more practical than
GSAKMP/NAT. In particular, new GSAKMP multicast applications should prefer
GSAKMP 6over4.  However, GSAKMP supports either choice.


4.5.3 GSAKMP Multicast IP-v4 NAT Architectural Assumptions


To make the GSAKMP NAT interaction problem tractable to a solution, this
specification makes the following simplifying assumptions:

The secure multicast group destination address is a statically allocated
public IP-v4 multicast address known to all GSAKMP endpoints.

Wherever they are present in the GSAKMP policy token, GSAKMP IPSec endpoint
identifiers are expressed as permanent IP-v6 "6to4" addresses [RFC3056] to
assure that the GSAKMP endpoints that refer to hosts assigned private IP-v4
addresses are globally unique.

The GCKS resides within one of the private networks, but it also has a
permanent public IP-v4 address on at least one of its network interfaces.


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The GCKS domain name RR record should point to that public IP-v4 address,
and it should be protected by DNS-SEC.

Each private address space has one or more NAT gateways directly connected
to the IP-v4 public Internet, and a packet does not have to traverse
multiple private networks to reach the public Internet.  This can be thought
of as a "spoke and hub" configuration wherein the public Internet is the
hub.

Each of an administrative domain's NAT gateways are explicitly configured
with static private/public address translation mappings for the GCKS's
GSAKMP re-key multicast UDP packets inbound from the public Internet
[RFC2588].

The NAT gateways/firewalls are explicitly configured with stateless filter
rules that simply pass through without any address translation the group's
inbound multicast application packets arriving from the public Internet.
The NAT gateway does not translate the multicast application packet's public
multicast IP destination address into a private IP multicast address.

In the outbound direction, NAT gateways generally translate the multicast
application packet's private source IP address into a dynamically selected
public IP address.  Exceptions to this policy for source specific multicast
are noted in subsequent sections.

Within each administrative domain, a multicast routing protocol domain
routes packets based on the group's destination multicast public IP-v4
address.  The multicast routers will distribute the group's packets to all
of the group's GSAKMP endpoints residing in that administrative domain.  The
border routers of each of the administrative domains spanned by the group do
cross-realm multicast routing and distribution on behalf of the group.  The
IP-v4 multicast routers that exchange reachability information regarding the
group across trust boundaries authenticate that information.

GSAKMP IPSec group security associations are end-to-end transport mode,
rather than tunnels terminated at a combined NAT/security gateway [RFC2709].


4.5.4 Representative Example GSAKMP Multi-Realm Configuration


Figure 1 illustrates a representative group "Z" wherein a GSAKMP group
security association spans two private IP-v4 networks and the public IP-v4
Internet.  The Group "Z" GCKS has two network interfaces, one attached to
the public Internet and the other interface attached to the administrative
domain "B" private network.

The group members GM1 and GM2 reside within the administrative domain "A"
private network.  They communicate with the GCKS and the group Z multicast
source endpoint(s) through the administrative domain "A" NAT gateway.  When
GM1 or GM2 send multicast application SA traffic to the group Z public


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multicast address, the Group Z peer members (i.e.  GM3, GM4, GM5, and GM6)
receive that multicast with the source address translated by NAT gateway
"A" processing.  In the inverse direction, the administrative domain "A" NAT
gateway/firewall must be configured to allow Group Z multicast application
SA and re-key SA traffic to enter the private network "A" from the public
Internet (e.g.  a multicast originating from GM6).

The group members GM5 and GM6 reside within the administrative domain "B"
private network.  Their interactions with Group Z are very similar to those
discussed for members GM1 and GM2.  The only difference is that they use
private addresses when communicating with the GCKS, as they are both in
private network "B".

The group members GM3 and GM4 are in a public Internet administrative domain
operated by an ISP. They communicate with the GCKS using public IP-v4
addresses without passage through a NAT gateway.  When GM3 or GM4 send
multicast application SA traffic to the group Z public multicast address,
the Group Z peer members behind NAT gateways receive that multicast with the
source address unchanged by NAT processing.

Each administrative domain operates an IP-v4 multicast routing domain
instance.  The multicast routers distribute both GSAKMP re-key event
messages and multicast application SA data traffic.  The multicast routing
for group "Z" peers between these three multicast routing domains.





























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                    .                     .
"A" Admin Domain    .  ISP Admin Domain   . "B" Administrative domain
+-------------------.---------------------.-----------------------------+
!                   .                     .
!
!            P U B L.I C        I P - v 4 .   I N T E R N E T
!
!                   .                     .
!
+-------/\\----------.-----A-------A----A--.---------/\\--------------/\\--+

        !! public   .     !       !    !  .         !! public       !!
        !! IP-v4    .     !       !    !  .         !! IP-v4        !!
+-------\\/--------+ .    !       !    !  . +-------\\/--------+
+---\\/--+
!   NAT gateway   ! .     !       !    !  . !    Group "Z"    ! !NAT
"B"!
!    domain A     ! .     !       !    !  . !   GSAKMP GCKS   !
!gateway!
+---A------A----A-+ .     !       !    !  . +-A------A------A-+
+---A---+
    !      !    !   .     !       !    !  .   !      !      !       !
 registration SA!   .  registration SA !  . registration SA !       !
    !      !    !   .     !       !    !  .   !      !      !       !
  +-V-+  +-V-+  !   .   +-V-+   +-V-+  !  . +-V-+  +-V-+    !       !
  !GM1!  !GM2!  !   .   !GM3!   !GM4!  !  . !GM5!  !GM6!    !       !
  +-A-+  +-A-+  !   .   +-A-+   +-A-+  !  . +-A-+  +-A-+    !       !
    !      !    !   .     !       !    !  .   !      !      !       !
Group data/rekey SA . Group data/rekey SA . Group data/rekey Sec. Assoc.
    !      !    !   .     !       !    !  .   !      !      !       !
  +-V------V----V-+ . +---V-------V----V+ . +-V------V------V-------V--+
  !  Group "Z"    ! . !    Group "Z"    ! . !        Group "Z"         !
  !  multicast    ! . !    multicast    ! . !        multicast         !
  !routing domain ! . ! routing domain  ! . !     routing domain       !
  +---------------+ . +-----------------+ . +--------------------------+
                    .                     .
                    .                     .



                       Figure 1:  GSAKMP NAT Example







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4.5.5 GSAKMP Registration Security Association NAT Traversal


This class of GSAKMP unicast messages are exchanged between a GCKS in
the public IP-v4 Internet and a group member that may be in a private
network.  The following GSAKMP message types are sent and received over
the registration security association as UDP packets with an authenticated
payload:



 -  Request-To-Join

 -  Key Download - This message contains a Policy Token that includes a
    multicast application SA initialization payload, including IPSec SPD
    traffic selector rules that refer to GSAKMP endpoint identifiers.  It
    also contains the re-key SA initialization payload, which also refers to
    GSAKMP IPSec endpoint identifiers.

 -  Notification - Request To Join Acknowledge/Negative Acknowledge

 -  Request-To-Depart

 -  Departure-Response

 -  Notification - Departure Acknowledgement


A group member sends a registration SA GSAKMP message to the GCKS public
IP-v4 address and the GSAKMP reserved port number.  The group member assigns
a unique GSAKMP UDP source port number for each GSAKMP registration SA
that it participates in.  The group member MUST send the GSAKMP UDP packet
without a checksum to avoid NAT alterations to that field.  The UDP packet's
transmission error detection depends on the GSAKMP signature payload.  A
NAT gateway on the path leading to the GCKS translates the private source IP
address and source UDP port number into a public address and a temporary UDP
port number (assuming NAPT), then forwards the packet to the GCKS. The NAT
gateway creates state information for that public/private address mapping so
it can do the inverse translation on the GSAKMP messages sent from the GCKS
to that group member.

The GCKS must process the GSAKMP messages that it receives from group
members originating from any source IP address or source port number, even
if those two values have changed since the last time that the GCKS had
interacted with a given group member.  This could cause problems if the
GC/KS is operating in the mandatory cookie exchange mode.  To identify the
group member, the GCKS MUST use the GSAKMP signature payload's identifying
information and validate the message's digital signature.

After processing a message from a group member that requires a GCKS
response, the GCKS creates the GSAKMP UDP message destined for the same
IP-v4 address and UDP port that the GCKS found in the group member message's

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source IP address and UDP source port.


4.5.6 GSAKMP Re-key Security Association NAT Traversal


The GCKS multicasts the GSAKMP Re-key Event message to the re-key SA in a
UDP packet addressed to group's destination public IP-v4 multicast address.
Both the UDP source port and the UDP destination port are set to the GSAKMP
reserved port number.  The UDP checksum is optional.  The GCKS sends two
copies of the GSAKMP Re-key Event message, one originating from its public
Internet interface, and the other copy originating from one of its private
network interfaces.  Group members behind a NAT gateway will receive the
Re-key Event message unchanged provided that the intervening NAT gateway has
been configured correctly to allow the packet through without translation.


4.5.7 Multicast Application Security Association NAT Traversal


Each such SA has a group-wide unique SPI, its own sequence number, and
associated group keying material.  Unlike the Re-key Event message multicast
to the re-key SA, a multicast application message sent to the group may
originate from a GSAKMP endpoint located behind a NAT gateway.  Since the
application's message is encrypted within an ESP payload, the transport
layer protocol header port fields are concealed from NAT gateways and
they can not participate in NAPT. The multicast application IPSec SA
must be handled differently depending on whether the application requires
source-specific multicast.

If the application requires IPSec source-specific multicast routing, then
there must be a separate public IP-v4 address statically reserved at the NAT
gateway for each multicast source endpoint private/public address mapping.
This constraint allows the GCKS to specify at every group member the inbound
SPD traffic selector with a pre-determined public source address for each
multicast source GSAKMP endpoint in the group.  The traffic selector's
public source address in combination with the group's destination multicast
address and SPI selects the inbound SA. Keeping the NAT gateway's source
address mapping static rather than dynamic also allows the multicast
routers along the packet's path to apply source-specific routing policies.
Note that the use of a static source address mapping NAT avoids the need
for the group policy token to specify UDP encapsulated ESP. The GCKS SPD
configuration database must be kept synchronized with the group's NAT
gateway address mapping configurations.

If source-specific multicast routing is not required by the application,
then the NAT gateway's source address translation can use dynamically
allocated public IP-v4 addresses rather than statically allocated IP-v4
addresses.  However, unless the group uses UDP encapsulated ESP, then
the NAT gateway must have a pool of public IP-v4 addresses reserved that
is at least as large as the number of multicast source GSAKMP endpoints


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within its private network.  This allows the NAT gateway to do a one-to-one
mapping from every GSAKMP endpoint's private source address to a dynamically
allocated public source address.  The GCKS specifies the SPD inbound traffic
selector as the combination of the group's destination multicast address and
the SPI.

In some deployments, the number of public IP-v4 addresses assigned to a NAT
gateway is very limited (e.g.  only one public address).  Also, it may be
difficult to predict how many multicast source endpoints will reside within
the private network before the group begins its operation.  For these cases,
the group MAY use UDP encapsulated ESP. The NAT gateway applies NAPT to the
UDP header's source port field, sidestepping the constraint of its limited
public address pool.  The GCKS modifies the group policy token to specify
that the outbound SPD processing must pre-append a UDP header in front of
the ESP header.  When a GSAKMP endpoint originates a multicast application
packet, it inserts a UDP header in front of the ESP header, as per reference
[XXXXX].



5 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.


5.1 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


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    Policy Token and apply the GO signature.



5.2 Group Establishment


GSAKMP Group Establishment consists of three mandatory-to-implement
messages, the Request to Join, the Key Download, and the Key Download
Ack/Failure.  The exchange may also include two OPTIONAL error messages,
the Request to Join Error and the Lack_of_Ack messages.  Operation using
the mandatory messages only is referred to as "Terse Mode", while
inclusion of the error messaging is referred to as "Verbose Mode".  GSAKMP
implementations MUST support Terse Mode and MAY support Versbose Mode.
Group Establishment is discussed in Section 5.2.1.

For Denial of Service protection, a Cookie Exchange MAY precede the Group
Establishment exchange.  The Cookie Exchange is described in Section 5.2.2.


5.2.1 Standard Group Establishment


After the out-of-band receipt of a Policy Token, a potential Group
Controller Key Server (GC/KS) verifies the token and its eligibility to
perform GC/KS functionality.  It is then permitted to create any needed
group keys and begin to establish the group.

The GSAKMP Ladder Diagram, Figure 2, is presented to illustrate the
process of establishing a cryptographic group.  The left side of the
diagram represents the actions of the GC/KS. 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 5.2.1.1 -  5.2.1.5.

The Request to Join message is sent from a potential GM to the GC/KS to
request admission to the cryptographic group.  The message contains key
creation material, freshness data, an optional selection of mechanisms, and
the signature of the GM.

The Key Download message is sent from the GC/KS to the GM in response
to an accepted Request to Join.  This GC/KS-signed message contains the
identifier of the GM, freshness data, key creation material, encrypted keys,
and the encrypted Policy Token.  The Policy Token is used to facilitate
well-ordered group creation and MUST include the group's identification,
group permissions, group join policy, group controller key server identity,
group management information, and digital signature of the GO. This will
allow the GM to determine whether group policy is compatible with local
policy.

The Request to Join Error message is sent from the GC/KS to the GM in
response to an unaccepted Request to Join.  This message is not signed
by the GC/KS for two reasons:  1) The GM, at this point, has no knowledge

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          CONTROLLER   Mandatory/     MESSAGE                  MEMBER
                       Optional
                    !<-M----------Request to Join-------------!
      <Process RTJ> !                                         !
                    !--M----------Key Download--------------->!
                    !                                         ! <Process KeyDL>
                    !--O-------Request to Join Error--------->! or
                    !                                         ! <Proc RTJ-Err>
                    !<-M----Key Download - Ack/Failure--------!
 <Process KeyDL-A/F>!                                         !
                    !--O------Lack of Ackknowledgement------->!
                    !                                         ! <Proc LOA>
                    !<=======SHARED KEYED GROUP SESSION======>!




                      Figure 2:  GSAKMP Ladder Diagram


of who is authorized to act as a GC/KS and so the signature would thus be
meaningless to the GM, and 2) Signing responses to denied join requests
would provide a denial of service potential.  The message contains an
indication of the error condition.

The Key Download Ack/Failure message indicates Key Download receipt status
at the GM. It is a GM-signed message containing freshness data and status.

The Lack_of_Ack message is sent from the GC/KS to the GM in response to an
invalid or absent Key Download Ack/Failure message.  The signed message
contains freshness and status data and is used to warn the GM of impending
eviction from the group if a valid Key Download Ack/Failure is not sent.

For the following message structure sections, details about payload format
and processing can be found in Section 7.


5.2.1.1 Request to Join


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

As shown by Figure 2, a potential GM MUST generate and send an RTJ message
to request permission to join the group.  As defined in the disection of
the RTJ message, this message MUST contain payloads to hold the following
information:  Key Creation payload for KEK generation and Nonce payload
for freshness.  The Nonce_I value MUST be saved for later use.  An OPTIONAL
Notification payload of type Mechanism Choices MAY be included to identify
the mechanisms the GM wants to use.  Absence of this payload will cause the
GC/KS to select appropriate mechanisms for the Key Download.



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             Table 1:  Request to Join (RTJ) Message Definition

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

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

In response, the GC/KS accepts or denies the request based on local
configuration.  <Process RTJ> indicates the GC/KS actions that will
determine if the RTJ will be acted upon.  The following checks SHOULD be
performed in the order presented.

In this procedure, the GC/KS MUST verify that the message header is properly
formed and confirm that this message is for this group by checking the value
of the GroupID. If the header checks pass, then the identity of the sender
is extracted from the Signature payload.  This identity MUST be used to
perform access control checks, find the GMs credentials (e.g.  certificate)
for message verification, and MUST also be used in the Key Download message.
Then the GC/KS will verify the signature on the message to ensure its
authenticity.  The GC/KS MUST use verified and trusted authentication
material from a known root.  If the message signature verifies, the GC/KS
then confirms that all required payloads are present and properly formatted
based upon the mechanisms announced and/or requested.  If all checks pass,
the GC/KS will create and send the Key Download message as described in
section  5.2.1.2.

NOTE: At any one time, a GC/KS MUST process no more that one (1) valid RTJ
message from a single GM per group.

If the GM receives no response to the RTJ within the GM's locally configured
timeout value, the GM SHOULD resend the RTJ message up to three (3) times.

If any error occurs during RTJ message processing, and the GC/KS is
running in Terse mode, the session MUST be terminated and all saved state
information MUST be cleared.

The OPTIONAL Notification payload of type Cookie is discussed in section
5.2.2.


5.2.1.2 Key Download


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


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             Table 2:  Key Download (KeyDL) Message Definition

    Message Name  : Key Download (KeyDL)
    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

In response to a properly formed and verfied RTJ message, the GC/KS creates
and sends the KeyDL message.  As defined in the dissection of the message,
this message MUST contain payloads to hold the following information:
GM identification, Nonce payloads for freshness, Key Creation material,
encrypted Policy Token, enctyped key information, and signature information.

The nonce values transmitted MUST be the GC/KSs generated Nonce_R value
and the conbined Nonce_C value which was generated by using the GS/KSs
Nonce_R value and the Nonce_I value received from the GM in the RTJ. The
key creation material supplied by the GM and/or the GC/KS will be used to
generate the KEK. Generation of this KEK is defined by policy.  The Policy
Token and Key material are encrypted in the generated KEK.

The GM MUST be able to process the Key Download message.  <Process KeyDL>
indicates the GM actions that will determine how the Key Download message
will be acted upon.  The following checks SHOULD be performed in the order
presented.

In this procedure, the GM will verify that the message header is properly
formed and confirm that this message is for this group by checking the
value of the GroupID. If the header checks pass, the GM MUST confirm that
this message was intended for itself by comparing the Member ID in the
Identification payload to its identity.  After identification confirmation,
the freshness values are checked.  The GM MUST use its save Nonve_I value,
extract the received GC/KS Nonce_R value, compute the combined Nonce_C value,
and compare it to the received Nonce_C value.  After freshness is confirmed,
the signature MUST be verified to ensure its authenticity, The GM MUST use
verified and trusted authentication material from a known root.  If the
message signature verifies, the key creation material is extracted from the
Key Creation payload to generate the KEK. This KEK is then used to decrypt
the Policy Token data.  The signature on the policy token MUST be verified.
Access control checks MUST be performed on both the GO and the GC/KS to
determine both their authorities within this group.  After all these checks
pass, the KEK can then be used to decrypt and process the key material from


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the Key Download payload.  If all is successful, the GM will create and send
the Key Download - Ack/Failure message as described in section 5.2.1.4.

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.

If any error occurs during KeyDL message processing, and the GM is running
in Terse mode, the session MUST be terminated, the GM MUST send a Key
Download - Ack/Failure message with a Notification Payload of type NACK to
indicate termination, and all saved state information MUST be cleared.


5.2.1.3 Request to Join Error


The components of the Request to Join Error Message are shown in Table 3:


        Table 3:  Request to Join Error (RTJ-Err) Message Definition

    Message Name  : Request to Join Error (RTJ-Err)
    Dissection    : {HDR-GrpID, Nonce_I, Notification}
    Payload Types : GSAKMP Header, Nonce, Notification


In response to an unacceptable RTJ, the GC/KS MAY send a Request to Join
Error (RTJ-Err) message containing an appropriate Notification payload.
Note that the RTJ-Err message is not a signed for the following reasons:
the lack of awareness on the GM's perspective of who is a valid GC/KS as
well as the need to protect the GC/KS from signing messages and using
valuable resources.  Following the sending of an RTJ-Err, the GC/KS MUST
terminated the session and all saved state information MUST be cleared.

Upon receipt of an RTJ-Err message, the GM will validate the following:
the GroupID in the header belongs to a group to which the GM has sent an
RTJ, and the Nonce_I matches a Nonce_I sent in an RTJ to that group.  If
the above checks are successful, the GM MAY terminate the state associated
with that GroupID and Nonce.  The GM SHOULD be capable of receiving a valid
KeyDownload message for that GroupID and Nonce after receiving an RTJ-Err
for a locally-configured amount of time.


5.2.1.4 Key Download - Ack/Failure


The components of the Key Download - Ack/Failure Message are shown in
Table 4:

In response to a properly processed KeyDL message, the GM creates and sends

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    Table 4:  Key Download - Ack/Failure (KeyDL-A/F) Message Definition

    Message Name  : Key Download - Ack/Failure (KeyDL-A/F)
    Dissection    : {HDR-GrpID, Nonce_C, Notif_Ack}SigM
    Payload Types : GSAKMP Header, Nonce, Notification, Signature

       SigM       : Signature of Group Member
       {}SigX      :Indicates minimum fields used in Signature

the KeyDL-A/F message.  As defined in the dissection of the message, this
message MUST contain payloads to hold the following information:  Nonce
payload for freshness, Notification payload of type Acknowledgment (ACK).
and signature information.  The nonce value transmitted MUST be the GMs
generated Nonce_C value.

The GC/KS MUST be able to process the KeyDL-A/F message.  <Process
KeyDL-A/F> indicates the GC/KS actions that will determine how the
KeyDL-A/F message will be acted upon.  The following checks SHOULD be
performed in the order presented.

In this procedure, the GC/KS will verify that the message header is properly
formed and confirm that this message is for this group by checking the value
of the GroupID. If the header checks pass, the GC/KS MUST check the message
for freshness.  The GC/KS MUST use its saved Nonve_C value, and compare it
to the received Nonce_C value.  After freshness is confirmed, the signature
MUST be verified to ensure its authenticity, The GC/KS MUST use verified and
trusted authentication material from a known root.  If the message signature
verifies, the GC/KS processes the Notification payload.  If the notification
type is of type ACK, then the GC/KS and GM have established a GSA.

If the GC/KS does not receive a KeyDL-A/F message of proper form, is unable
to correctly process the KeyDL-A/F message, the Notification payload type
is any value excpet ACK, or if no KeyDL-A/F message is received within the
locally configured timeout, the GC/KS MUST remove this GM from the group
and handle according to policy.  The GC/KS MAY send the OPTIONAL Lack_of_Ack
message if running in Verbose Mode as defined in section 5.2.1.5.


5.2.1.5 Lack of Ack


The components of a Lack of Ack Message are shown in Table 5:

If the GC/KSs local timeout value expires prior to receiving a KeyDL-A/F
from the GM, the GC/KS MAY create and send a LOA message to the GM. As
defined in the dissection of the message, this message MUST contain payloads
to hold the following information:  GM identification, Nonce payloads for
freshness, Notification of error, and signature information.

The nonce values transmitted MUST be the GC/KSs generated Nonce_R value and


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               Table 5:  Lack of Ack (LOA) Message Definition

    Message Name  : Lack of Ack (LOA)
    Dissection    : {HDR-GrpID, Member ID, Nonce_R, Nonce_C,
                    Notification} SigC, [Cert]
    Payload Types : GSAKMP Header, Identification, Nonce,
                    Notification, 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

the conbined Nonce_C value which was generated by using the GS/KSs Nonce_R
value and the Nonce_I value received from the GM in the RTJ. These values
were already generated during the Key Download message phase.

The GM MAY be able to process the LOA message based upon local
configuration.  <Process LOA> indicates the GM actions that will determine
how the LOA message will be acted upon.  The following checks SHOULD be
performed in the order presented.

In this procedure, the GM MUST verify that the message header is properly
formed and confirm that this message is for this group by checking the
value of the GroupID. If the header checks pass, the GM MUST confirm that
this message was intended for itself by comparing the Member ID in the
Identification payload to its identity.  After identification confirmation,
the freshness values are checked.  The GM MUST use its save Nonve_I value,
extract the received GC/KS Nonce_R value, compute the combined Nonce_C value,
and compare it to the received Nonce_C value.  After freshness is confirmed,
access control checks MUST be performed on the GC/KS to determine its
authority within this group.  Then signature MUST be verified to ensure its
authenticity, The GM MUST use verified and trusted authentication material
from a known root.

If the checks succeed, the GM SHOULD resend a KeyDL-A/F for that session.


5.2.2 Cookies - Group Establishment with Denial of Service Protection


This section defines an OPTIONAL capability that MAY be implemented into
GSAKMP when using IP based groups.  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.


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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 GC/KS is flooded with Request to Join requests from forged IP
addresses.  This attack can be made less effective if a GC/KS 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 GC/KS 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_Required.  Potential GMs who receive such
responses MUST retry the Request to Join message with the responder GC/KS
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 5.2.1.1.  This initial exchange will then be as shown in Figure 3
with the components of the new message Cookie Download shown in Table 6.

          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 KeyDL>
                    !<-----Key Download -  Ack/Failure--------!
  <Proc KeyDL-A/F>  !                                         !
                    !<=======SHARED KEYED GROUP SESSION======>!




               Figure 3:  GSAKMP Ladder Diagram with Cookies


                Table 6:  Cookie Download Message Definition

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

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



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A GSAKMP implementation SHOULD implement its GC/KS 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.

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
GC/KS 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 GC/KS 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
GC/KS 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 GC/KS SHOULD
NOT accept cookies indefinitely after <secret> is changed, since that would
defeat part of the denial of service protection.  The responder GC/KS SHOULD
change the value of <secret> frequently, especially if under attack.



5.3 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.






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5.3.1 Rekey Events


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

Once an event has been identified (as defined in the group security policy
token), the GC/KS MUST create and provide 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  7:


                  Table 7:  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


5.3.2 Leaving a Group


There are several conditions under which a member will leave a group:
eviction, voluntary departure without notice, and voluntary departure with
notice -- or De-Registration.  Each of these is discussed in this section.


5.3.2.1 Eviction


At some point in the group's lifetime, it may be desireable to evict one or
more members from a group.  From a key management viewpoint, this involves
revoking access to the group's protected data by "disabling" the departing
members' keys.  This is accomplished with a Rekey Event, which is discussed
in more detail in section 5.3.1.  If future access to the group is also to
be denied, the members MUST be added to a denied access control list, and

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the tokens authorization rules MUST be appropriately updated so that they
will exclude the expelled GM(s).  After receipt of a new PT, GMs SHOULD
evaluate the trustworthiness of any recent application data originating from
the expelled GM(s).


5.3.2.2 Voluntary Departure without Notice


If a member wishes to leave a group for which membership imposes no cost
or responsibility to that member, then the member MAY merely delete local
copies of group keys and cease group activities.


5.3.2.3 De-Registration


If the membership in the group does impose cost or responsibility to the
departing member, then the member SHOULD de-register from the group that
the member wishes to leave.  De-Registration consists of a three-message
exchange between the GM and the member's GCKS: the Request_to_Depart,
Departure_Reponse, and the Departure_Ack.  These messages SHOULD be done
under the protection of the GSA.


5.3.2.3.1 Request to Depart - The components of a Request_to_Depart Message
are shown in Table 8.


            Table 8:  Request_to_Depart (RTD) Message Definition

    Message Name  : Request_to_Depart (RTD)
    Dissection    : {HDR-GrpID, GS/KS_ID, Nonce_I, Notif_Leave_Group}
                    SigM, [Cert]
    Payload Types : GSAKMP Header, Identification, Nonce,
                    Notification, Signature, [Certificate]
       SigM       : Signature of Group Member
       Cert       : Necessary Certificates, zero or more
       {}SigX      :Indicates minimum fields used in Signature
       []         : Indicate an optional data item


Any GM desiring to initiate the De-Registration process MUST generate and
send an RTD message to notify the GC/KS of its intent.  As defined in the
disection of the RTD message, this message MUST contain payloads to hold
the following information:  the GC/KS identification, Nonce payload for
freshness, and Notification of the desire to leave the group.  The Nonce_I
value MUST be saved for later use.  This message MUST then by signed by the
GM.

Upon receipt of the RTD message, the GC/KS MUST verify that the message
header is properly formed and confirm that this message is for this group

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by checking the value of the GroupID. If the header checks pass, then
the identifier value in Identification payload is compared to its own,
the GC/KSs identity, to confirm that the GM intended to converse with
this GC/KS, the GC/KS who registered this member into the group.  Then
the identity of the sender is extracted from the Signature payload.  This
identity MUST be used to confirm that this GM is a member of the group
serviced by this GC/KS. Then the GC/KS will confirm from the Notification
payload that the GM is requesting to leave the group.  Then the GC/KS will
verify the signature on the message to ensure its authenticity.  The GC/KS
MUST use verified and trusted authentication material from a known root.  If
all checks pass and the message is successfully processed, and/or the GC/KS
is in Verbose Mode, then the GCKS MUST form a Departure_Response message as
defined in section 5.3.2.3.2.

If the processing of the message fails and/or the GC/KS is in Terse Mode,
then the session MUST be terminated and all state associated with this
session is removed.


5.3.2.3.2 Departure_Response -  The components of a Departure_Response
Message are shown in Table 9.


            Table 9:  Departure_Response (DR) Message Definition

    Message Name  : Departure_Response (DR)
    Dissection    : {HDR-GrpID, Member_ID, Nonce_R, Nonce_C,
                    Notification} SigC, [Cert]
    Payload Types : GSAKMP Header, Identification, Nonce,
                    Notification, Signature, [Certificate]

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

In response to a properly formed and verfied RTD message, the GC/KS
MUST create and send the DR message.  As defined in the dissection of
the message, this message MUST contain payloads to hold the following
information:  GM identification, Nonce payloads for freshness, Notification
for acceptance of departure, and signature information.

The nonce values transmitted MUST be the GC/KSs generated Nonce_R value and
the conbined Nonce_C value which was generated by using the GS/KSs Nonce_R
value and the Nonce_I value received from the GM in the RTD. This Nonce_C
value MUST be saved relative to this departing GMs ID.

The GM MUST be able to process the Departure_Response message.  The
following checks SHOULD be performed in the order presented.

The GM MUST verify that the message header is properly formed and confirm
that this message is for this group by checking the value of the GroupID. If

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the header checks pass, the GM MUST confirm that this message was intended
for itself by comparing the Member ID in the Identification payload to
its identity.  After identification confirmation, the freshness values are
checked.  The GM MUST use its saved Nonve_I value, extract the received
GC/KS Nonce_R value, compute the combined Nonce_C value, and compare it to
the received Nonce_C value.  After freshness is confirmed, confirmation of
the identity of the signer of the DR message is the GMs authorized GC/KS is
performed.  Then the signature MUST be verified to ensure its authenticity,
The GM MUST use verified and trusted authentication material from a known
root.  If the message signature verifies, then the GM MUST verify that the
Notification is of Type Departure_Accepted or Request_to_Depart_Error.

If the processing is successful, and the Notification payload is of type
Departure_Accepted, the member MUST form the Departure_ACK message as defined
in section 5.3.2.3.3.  If the processing is successful, and the Notification
payload is of type Request_to_Depart_Error, the member MUST remove all state
associated with the action.  If the member still desires to De-Register from
the group, the member MUST restart the De-Registration process.


5.3.2.3.3 Departure_ACK -  The components of the Departure_ACK Message are
shown in Table 10:


              Table 10:  Departure_ACK (DA) Message Definition

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


In response to a properly processed Departure_Response message, the
GM MUST create and send the Departure_ACK message.  As defined in the
dissection of the message, this message MUST contain payloads to hold the
following information:  Nonce payload for freshness, Notification payload
of type Acknowledgment (ACK), and signature information.  The nonce value
transmitted MUST be the GMs generated Nonce_C value.

Upon receipt of the Departure_ACK, the GCKS MUST perform the following
checks.  These checks SHOULD be performed in the order presented.

In this procedure, the GC/KS will verify that the message header is properly
formed and confirm that this message is for this group by checking the value
of the GroupID. If the header checks pass, the GC/KS MUST check the message
for freshness.  The GC/KS MUST use its saved Nonve_C value, and compare it
to the received Nonce_C value.  After freshness is confirmed, the signature
MUST be verified to ensure its authenticity, The GC/KS MUST use verified and
trusted authentication material from a known root.  If the message signature
verifies, the GC/KS processes the Notification payload.  If the notification
type is of type ACK, this is considered a successful processing of this

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message.

If the processing of the message is successful, the GC/KS MUST remove the
member from the group.  This MAY involve initiating a Rekey Event for the
group.

If the processing of the message fails or if no Departure_Ack is received,
the GC/KS MAY issue a LOA message.



6 Security Suite


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


6.1 Assumptions


All potential GMs will have 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.


6.2 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 1 definition is


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

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


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  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



7 GSAKMP Payload Structure


A GSAKMP Message is composed of a GSAKMP Header (Section  7.1) followed
by at least one GSAKMP Payload.  All GSAKMP Payloads are composed of the
Generic Payload Header (Section  7.2) 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.

All fields of type integer in the Header and Payload structure that are
larger than one octet, MUST be converted into Network Byte Order prior to
data transmission.


7.1 GSAKMP Header


7.1.1 GSAKMP Header Structure


The GSAKMP Header fields are defined in Figure 4:


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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! GroupID Type  ! GroupID Length!      Group ID Value           ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~               ! Next Payload  !   Version     ! Exchange Type !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Sequence ID                                                   !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Length                                                        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                      Figure 4:  GSAKMP Header Format


Group Identification Type (1 octet)  - Table 11 presents the group
    identification types.


                   Table 11:  Group Identification Types


                   Grp ID Type                    Value
                  ______________________________________

                   Network Byte Ordered Integer     0
                   Ascii                            1
                   Other                          2-255

Group Identification Length (1 octet)  - Length of Group ID field in
    octets.

Group Identification Value (variable length)  - Indicates the name/title of
    the group.

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 12 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 13 presents the exchange type values.





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                          Table 12:  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 13:  Exchange Types


                     Exchange_Type              Value
                    ___________________________________

                     Reserved                   0 - 3
                     Key Download Ack/Failure     4
                     Rekey Event                  5
                     Reserved                     6
                     No Message                   7
                     Request to Join              8
                     Key Download                 9
                     Cookie Download              10
                     Request to Join Error        11
                     Ack Error                    12
                     Other                      13-255




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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 MUST be set to zero (0).  When a (S-)GC/KS is
    initiated, it MUST set its initial sequence ID value to one (1).  For
    each distinct group management message that this (S-)GC/KS transmits,
    this value MUST be incremented by one (1).  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 (S-)GC/KS. GMs MUST also recognize receipt of a Group
    Management messages that suffer from rolloever and handle accordingly.

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



7.1.2 GSAKMP Header Processing


When processing the GSASKMP Header, the following fields MUST be checked for
correct values:


1.  GroupID - The GroupID of the received message MUST match the GroupID of
    the processing member.

2.  Next Payload - The Next Payload value MUST be a valid payload type as
    defined by Table 12.

3.  Version - The GSAKMP version numbers MUST match.

4.  Exchange Type - The Exchange Type MUST be a valid exchange type as
    defined by Table 13 and MUST be of the type expected to receive.

5.  Sequence ID - The Sequence ID value MUST be of the correct value.  For
    negotiation messages this value MUST be zero (0).  For group management
    messages, this value MUST be greater than the last sequence ID received
    from this (S-)GC/KS.


The length fields in the GSAKMP Header are used to help process the message.
If any field is found to be incorrect, then termination processing MUST be
initiated.











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7.2 Generic Payload Header


7.2.1 Generic Payload Header Structure


Each GSAKMP payload defined in the following sections begins with a generic
header, shown in Figure 5, 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 5:  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 12 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.



7.2.2 Generic Payload Header Processing


When processing the Generic Payload Header, the following fields MUST be
checked for correct values:


1.  Next Payload - The Next Payload value MUST be a valid payload type as
    defined by Table 12.

2.  RESERVED - This field MUST contain the value zero (0).


The length field in the Generic Payload Header is used to process the
remainder of the payload.  If any field is found to be incorrect, then
termination processing MUST be initiated.



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7.3 Policy Token Payload


The Policy Token Payload contains authenticatable group specific information
that describes the group security relevant behaviors, access control
parameters, and security mechanisms.  Figure 6 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        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !   PT Type     !              Policy Token Data                ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 6:  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.

Policy Token (PT) Type (2 octets)  - Specifies the type of Policy Token
    being used.  Table 14 identifies the types of policy tokens.


                       Table 14:  Policy Token Types

 PT_Type          Value      Definition
____________________________________________________________________________

GSAKMP_V1_PT        0        The format for this Policy Token is specified
                             in [HCLM00].
GSAKMP_ASN.1_PT     1        All implementations of GSAKMP MUST support
                             this Policy Token format.  This format is
                             specified in TBD.
Reserved         2-65535

Policy Token Data (variable length)  - Contains Policy Token information.
    The values for this field are token specific and the format is specified
    by the PT Type field.


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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 7:  Key Download Payload Format


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

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


7.4 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 7 shows the format of the payload.

The security policy of the group dictates that the key download payload MUST
be encrypted with a key encryption 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:



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        Key Download Data (KDD) Type (1 octet)  -- Identifier for the Key
            Data field of this Key Packet.  See Table 15 for the possible
            values of this field.


                     Table 15:  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.1.1.

For a Key Download Data value of Rekey, the Key Packet Data field format is
defined in Section A.1.2.

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



7.5 Rekey Event Payload


The Rekey Event Payload MAY contain 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 8 shows the format
of the payload.

The Rekey Event 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,

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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        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Rekey Type    !           Rekey Event Data                    ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 8:  Rekey Event Payload Format


    including the generic payload header.

Rekey Type (1 octet)  - Specifies the type of Rekey Event being used.
    Table 16 presents the types of Rekey events.


                        Table 16:  Rekey Event Types

Rekey_Type    Value     Definition
______________________________________________________________________________

None            0       This type MUST be implemented.  In this case, the
                        size of the Rekey Event Data field will be zero byes
                        long.  The purpose of a Rekey Event Payload with
                        type None is when it is necessary to send out a new
                        token with no rekey information.  GSAKMPekey Msg
                        requires a Rekey Event PL, and in this instance it
                        would have rekey data of type None.
GSAKMP_LKH      1       The rekey data will by of type LKH formatted
                        according to GSAKMP. The format for this field is
                        defined in Section B.2.
Unassigned   2-255

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


The Rekey Event payload type is three (3).


7.6 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 9 shows the format of the Identification
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        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !   ID Type     !            Identification Data                ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                  Figure 9:  Identification Payload Format


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.

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

Identification (ID) Type (1 octet)  - Specifies the type of Identification
    being used.  Table 17 identifies possible values for this type.

                      Table 17:  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.2.1



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


7.7 Certificate Payload


The Certificate Payload provides a means to transport certificates or other
certificate-related information via GSAKMP and can appear in any GSAKMP

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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 10 shows the format of the Certificate
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        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Cert Type                     !    Certificate Data           ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                   Figure 10:  Certificate Payload Format

The Certificate 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.

Certificate Type (2 octets)  - This field indicates the type of certificate
    or certificate-related information contained in the Certificate Data
    field.  Table 18 presents the types of certificate payloads.


                    Table 18:  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).



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7.8 Signature Payload


7.8.1 Signature Payload Structure


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 11 shows the format of the Signature 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        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Signature Type! Sig ID Type   !   Signature Payload Span      ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                               ! Signature Timestamp           ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                               ! Signer ID Lenth               !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !                    Signer ID Data                             ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    !     Signature Length          !     Signature Data            ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                    Figure 11:  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 19
    presents the allowable signature types.

Signature ID Type (1 octet)  -- Indicates the format for the Signature ID
    Data.  Table 20 presents the allowable signature ID types.  The formats
    for these types are defined in Section A.2.1


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                         Table 19:  Signature Types

            Signature Type                               Value
           ____________________________________________________

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


                         Table 20:  Signature Types

                      Signature ID Type         Value
                     _________________________________

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


Signature Payload Span (4 octets)  - Identifies the information included in
    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 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.  The contents of
    this field MUST be checked against the Policy Token to determine the
    authority and access of the Signer within the context of the group.

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).


7.8.2 Signature Payload Processing


When processing the Signature Payload, the following fields MUST be checked
for correct values:

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1.  Signature Type - The Signature Type value MUST be a valid signature type
    as defined by Table 19.

2.  Signature ID Type - The Signature ID Type value MUST be a valid
    signature ID type as defined by Table 20.

3.  Signature Span - The signature span values MUST encompass the payloads
    as defined by the message disection for this message type.

4.  Signature ID Data - This field will be used to identify the sending
    party.  This information MUST then be used, when applicable, to confirm
    that the correct party sent us this information.

5.  Signature Data - This value MUST be compared to the recomputed signature
    to verify the message.



The length fields in the Signature Payload are used to process the remainder
of the payload.  If any field is found to be incorrect, then termination
processing MUST be initiated.


7.9 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 12 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       !  Notification Data            ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                  Figure 12:  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.

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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 21 presents the Notify Payload Types.


                      Table 21:  Notify Payload Types

               Notification Type                   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
               Mechanism Choices                    29
               Leave Group                          30
               Departure Accepted                   31
               Request to Depart Error              32
               Reserved (future use)             33 - 8191
               Private Use                     8192 -- 16383

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.




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


7.9.1 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 13 shows the format of the Notification Data - Acknowledge
Payload Type.

     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 13:  Notification Data - Acknowledge Payload Type Format

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


Ack Type (1 octet)  - Specifies the type of acknowledgement.  Table 22
    presents the Notify Acknowledgement Payload Types.


                      Table 22:  Acknowledgement Types

                 ACK_Type     Value     Definition
                ___________________________________________

                 Simple         0       Data portion null.
                 Unassigned   1-255


7.9.2 Notification Data - Cookie_Required and Cookie Payload Type


The data portion of the Notification payload of types Cookie_Required and
Cookie contain the Cookie value.  The value for this field will have been
computed by the responder GC/KS and sent to the GM. The GM will take the
value received and copy it into the Notification payload Notification Data
field of type Cookie that is transmitted in the "Request to Join with Cookie
Info" back to the GC/KS. The cookie value MUST NOT be modified.

The format for this is already described in the discussion on cookies in
section 5.2.2.


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7.9.3 Notification Data - Mechanism Choices Payload Type


The data portion of the Notification payload of types Mechanism Choices
contains the mechanisms the GM is requesting to use for the negotiation with
the GC/KS. This information will be supplied by the GM in a RTJ message.
Figure 14 shows the format of the Notification Data - Mechanism Choices
Payload Type.  Multiple type!length!data choices are strung togther in one
notification payload to allow a user to transmit all relevant information
within one Notification Payload.  The length of the payload will contol the
parsing of the Notification Data Mechanism Choices field.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Mech Type     ! Length        ! Mechanism Choice Data         ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-! ...



   Figure 14:  Notification Data - Mechanism Choices Payload Type Format

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


Mechanism Type (1 octet)  - Specifies the type of mechanism.  Table 23
    presents the Notify Mechanism Choices Mechanism Types.


                         Table 23:  Mechanism Types

Mechanism_Type           Value     Mechanism Choice Data Value Table Reference
________________________________________________________________________________

Key Creation Algorithm     0       Table 26
Encryption Algorithm       1       Table 24
Nonce Hash Algorithm       2       Table 25
Unassigned               1-255

Length (1 octet)  -- Length in octets of the Mechanism Choice Data.

Mechanism Choice Data (variable length) - The data value for the mechanism
    type being selected.  The values are specific to each Mechanism Type
    defined.  All tables necessary to define the values that are not defined
    elsewhere (in this specification or others) are defined here.







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                        Table 24:  Encryption Types

                        Encryption_Types    Value
                       ____________________________

                        Reserved            0 - 2
                        3DES_CBC64_192        3
                        Unassigned         4 - 16k


                        Table 25:  Nonce Hash Types

                         Nonce_Hash_Type   Value
                        __________________________

                         Reserved            0
                         SHA-1               1
                         Unassigned       2 - 16k


7.10 Key Creation Payload


7.10.1 Key Creation Payload Structure


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 15 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        !
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
    ! Key Crtn Type !           Key Creation Data                   ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!



                  Figure 15:  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.


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

Key Creation (Crtn) Type (1 octet)  - Specifies the type of Key Creation
    being used.  Table 26 identifies the types of key download information.


                Table 26:  Types Of Key Creation Information

        Key Creation Type   Value     Definition
       ____________________________________________________________

        Reserved              0
        Diffie-Hellman        1       This type MUST be supported.
        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).


7.10.2 Key Creation Payload Processing


The specifics of the Key Creation Payload are defined in section 7.10.

When processing the Key Creation Payload, the following fields MUST be
checked for correct values:



1.  Key Creation Type - The Key Creation Type value MUST be a valid key
    creation type as defined by Table 26.

2.  Key Creation Data - This data will be used to compute the key encryption
    key (KEK).


If any field is found to be incorrect, then termination processing MUST be
initiated.










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7.11 Nonce Payload


7.11.1 Nonce Payload Structure


The Nonce Payload contains random data used to guarantee freshness during an
exchange and protect against replay attacks.  Figure 16 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 16:  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 27
    identifies the types of nonces.


                           Table 27:  Nonce Types

Nonce_Type            Value     Definition
______________________________________________________________________________

None                    0
Initiator (Nonce_I)     1
Responder (Nonce_R)     2
Combined (Nonce_C)      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

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    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.



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


7.11.2 Nonce Payload Processing


The specifics of the Nonce Payload are defined in section 7.11.

When processing the Nonce Payload, the following fields MUST be checked for
correct values:


1.  Nonce Type - The Nonce Type value MUST be a valid key creation type as
    defined by Table 27.

2.  Nonce Data - This is the nonce data and it must be checked according
    to its type.  The size of this field is defined in Nonce Payload
    section 7.11.


It any value is found to be incorrect, then termination processing MUST be
initiated.

























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8 GSAKMP State Diagram


Figure 17 presents the states encountered in the use of this protocol.
Table 28 defines the states.  Table 29 defines the transitions.

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


                      Figure 17:  GSAKMP State Diagram



















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                          Table 28:  GSAKMP States
___________________________________________________________________________

Idle                 : GSAKMP Application waiting for input
_____________________:_____________________________________________________
                     :
Wait for GC/KS Event : GC/KS up and running, waiting for events
_____________________:_____________________________________________________
                     :
Wait for Response    : GC/KS 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 29:  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 Key Download Payload Fields


A.1.1 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.1.2 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.2 Signature Payload Fields


A.2.1 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).

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

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        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 18 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
    Identification Value in Section  7.1 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).

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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 18:   B. 1:  Rekey Event Header Format


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 19 shows the format of each Rekey Event Packet
with respect to LKH.

     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 19:   B. 2:  Rekey Event Packet Data Format


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Packet Length (2 octets)  - Length in octets of the Rekey Packet, which
    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 20 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 20:   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
    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.





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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.

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.

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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)
      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


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      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.



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.



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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.



C.4 Changes from GSAKMP-03 to GSAKMP-04 October 2003


1.  Terminology Section


   (a)  Rekey definition was made more verbose.


2.  Securiry Considerations Section


   (a)  ISAKMP Section


        i.  Corrected GSAKMPs relationship definition to ISAKMP.


   (b)  Rekey Availability Section


        i.  Added this new section.


3.  Architecture Section


   (a)  This section in its entirety was added for this revision of the
        specification.


4.  Group Life Cycle Section


   (a)  Group Establishment Section



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        i.  Introduced Verbose and Terse concept.


   (b)  Standard Group Establishment Section


        i.  Added messages Request to Join Error and Lack_of_Ack to ladder
            diagram to show verbose error messaging.

       ii.  Modified definition of Ack message on ladder diagram to be
            consistant with new naming convention.

      iii.  Reworked all section wording to convey the new message
            trasmissions.


   (c)  Request to Join Section


        i.  Completly reworked to better define the process of building and
            processing the RTJ message by the GM and GC/KS.


   (d)  Key Download Section


        i.  Completly reworked to better define the process of building and
            processing the KeyDL message by the GC/KS and GM.


   (e)  Request to Join Error Section


        i.  New section added for this new verbose message.


   (f)  Key Download = Ack/Failure Section


        i.  Completly reworked to better define the process of building and
            processing the KeyDL-A/F message by the GM and GC/KS.


   (g)  Lack_of_Ack Section


        i.  New section added for this new verbose message.


   (h)  Added the following new Sub-sections to this section.



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        i.  Leaving Group

       ii.  Eviction

      iii.  Voluntary Departure without Notice

       iv.  Deregistration

        v.  Request to Depart Message

       vi.  Departure Response Message

      vii.  Departure Ack Message


5.  GSAKMP Payload Structure Section


   (a)  Added note that all all integer fields larger than one octet MUST
        be converted to Network Byte Order prior to trnasmission.

   (b)  GSAKMP Header Section



        i.  Existing section became the Structure subsection.

       ii.  Added the Processgin subsection.

      iii.  GroupID Type was modified to GroupID Length with the
            appropriate definitions.

       iv.  New Exchange Types added for verbose mode.

        v.  Sequence ID definition was modified for:


            A.  New initial value.

            B.  Rollover handling responsibility.


   (c)  GSAKMP Payload Header Section


        i.  Existing section became the Structure subsection.

       ii.  Added the Processgin subsection.


   (d)  Policy Token Payload Section


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        i.  The header paragraph was corrected to not levy any requirements
            from GSAKMP on the Policy Token.

       ii.  The PT Type field was expaned from one (1) to two (2) octets.

      iii.  The values of the PT Types were modified and defined to reflect
            the true purpose.


   (e)  Rekey Event Payload Section


        i.  Renamed Type field to be unique within specification.

       ii.  The values of the Rekey Type field were modified and defined to
            reflect thier true purpose.


   (f)  Signature Payload Section


        i.  Existing section became the Structure subsection.

       ii.  Added the Processgin subsection.

      iii.  Removed the one (1) octet field Signature ID Role from the
            payload, it contained irrelevant data.

       iv.  Expnaded the definition of Singer ID Data to inform the user
            how to intepret this field.


   (g)  Notification Payload Section


        i.  Removed the one (1) octet Status Type field from the payload.
            It was irrelevant information.  Additionally, all refereneces
            to Status Type were removed from the payload definition.

       ii.  Added new Notification Payload Type "Mechanism Choices".

      iii.  Added section "Notification Data - Mechanism Choices Payload
            Type" to define the format of a Notification Payload of type
            Mechanism Choices.


   (h)  Key Creation Payload Section


        i.  Existing section became the Structure subsection.



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       ii.  Added the Processgin subsection.

      iii.  Renamed Type field to be unique within specification.


   (i)  Nonce Payload Section


        i.  Existing section became the Structure subsection.

       ii.  Added the Processgin subsection.



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.

[DSS] NIST, "Digital Signature Standard", FIPS 186, National Institute of
Standards and Technology, U.S. Department of Commerce, May, 1994.

[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.



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[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

[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

Harney, etal.          draft-ietf-msec-gsakmp-sec-04.txt           [Page 84]

INTERNET-DRAFT                      GSAKMP                      October 2003

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
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)


Harney, etal.          draft-ietf-msec-gsakmp-sec-04.txt           [Page 85]

INTERNET-DRAFT                      GSAKMP                      October 2003

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

George Gross
IdentAware Security
82 Old Mountain Road
Lebanon, NJ 08833
(908) 268 - 1629
gmgross@nac.net



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:  April 24, 2004















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