path: root/doc/rfc/rfc4535.txt

Network Working Group                                          H. Harney
Request for Comments: 4535                                       U. Meth
Category: Standards Track                                   A. Colegrove
                                                            SPARTA, Inc.
                                                                G. Gross
                                                              IdentAware
                                                               June 2006


        GSAKMP: Group Secure Association Key Management Protocol

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

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


















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Table of Contents

   1. Introduction ....................................................7
      1.1. GSAKMP Overview ............................................7
      1.2. Document Organization ......................................9
   2. Terminology .....................................................9
   3. Security Considerations ........................................12
      3.1. Security Assumptions ......................................12
      3.2. Related Protocols .........................................13
           3.2.1. ISAKMP .............................................13
           3.2.2. FIPS Pub 196 .......................................13
           3.2.3. LKH ................................................13
           3.2.4. Diffie-Hellman .....................................14
      3.3. Denial of Service (DoS) Attack ............................14
      3.4. Rekey Availability ........................................14
      3.5. Proof of Trust Hierarchy ..................................15
   4. Architecture ...................................................15
      4.1. Trust Model ...............................................15
           4.1.1. Components .........................................15
           4.1.2. GO .................................................16
           4.1.3. GC/KS ..............................................16
           4.1.4. Subordinate GC/KS ..................................17
           4.1.5. GM .................................................17
           4.1.6. Assumptions ........................................18
      4.2. Rule-Based Security Policy ................................18
           4.2.1. Access Control .....................................19
           4.2.2. Authorizations for Security-Relevant Actions .......20
      4.3. Distributed Operation .....................................20
      4.4. Concept of Operation ......................................22
           4.4.1. Assumptions ........................................22
           4.4.2. Creation of a Policy Token .........................22
           4.4.3. Creation of a Group ................................23
           4.4.4. Discovery of GC/KS .................................24
           4.4.5. GC/KS Registration Policy Enforcement ..............24
           4.4.6. GM Registration Policy Enforcement .................24
           4.4.7. Autonomous Distributed GSAKMP Operations ...........24
   5. Group Life Cycle ...............................................27
      5.1. Group Definition ..........................................27
      5.2. Group Establishment .......................................27
           5.2.1. Standard Group Establishment .......................28
                  5.2.1.1. Request to Join ...........................30
                  5.2.1.2. Key Download ..............................31
                  5.2.1.3. Request to Join Error .....................33
                  5.2.1.4. Key Download - Ack/Failure ................34
                  5.2.1.5. Lack of Ack ...............................35
           5.2.2. Cookies: Group Establishment with Denial of
                  Service Protection .................................36
           5.2.3. Group Establishment for Receive-Only Members .......39



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      5.3. Group Maintenance .........................................39
           5.3.1. Group Management ...................................39
                  5.3.1.1. Rekey Events ..............................39
                  5.3.1.2. Policy Updates ............................40
                  5.3.1.3. Group Destruction .........................40
           5.3.2. Leaving a Group ....................................41
                  5.3.2.1. Eviction ..................................41
                  5.3.2.2. Voluntary Departure without Notice ........41
                  5.3.2.3. De-Registration ...........................41
                           5.3.2.3.1. Request to Depart ..............41
                           5.3.2.3.2. Departure_Response .............43
                           5.3.2.3.3. Departure_ACK ..................44
   6. Security Suite .................................................45
      6.1. Assumptions ...............................................45
      6.2. Definition Suite 1 ........................................45
   7. GSAKMP Payload Structure .......................................47
      7.1. GSAKMP Header .............................................47
           7.1.1. GSAKMP Header Structure ............................47
                  7.1.1.1. GroupID Structure .........................51
                           7.1.1.1.1. UTF-8 ..........................51
                           7.1.1.1.2. Octet String ...................52
                           7.1.1.1.3. IPv4 Group Identifier ..........52
                           7.1.1.1.4. IPv6 Group Identifier ..........53
           7.1.2. GSAKMP Header Processing ...........................53
      7.2. Generic Payload Header ....................................55
           7.2.1. Generic Payload Header Structure ...................55
           7.2.2. Generic Payload Header Processing ..................56
      7.3. Policy Token Payload ......................................56
           7.3.1. Policy Token Payload Structure .....................56
           7.3.2. Policy Token Payload Processing ....................57
      7.4. Key Download Payload ......................................58
           7.4.1. Key Download Payload Structure .....................58
                  7.4.1.1. Key Datum Structure .......................61
                  7.4.1.2. Rekey Array Structure .....................63
           7.4.2. Key Download Payload Processing ....................63
      7.5. Rekey Event Payload .......................................64
           7.5.1. Rekey Event Payload Structure ......................64
                  7.5.1.1.  Rekey Event Header Structure .............66
                  7.5.1.2.  Rekey Event Data Structure ...............67
                           7.5.1.2.1. Key Package Structure ..........68
           7.5.2. Rekey Event Payload Processing .....................69
      7.6. Identification Payload ....................................71
           7.6.1. Identification Payload Structure ...................71
                  7.6.1.1. ID_U_NAME Structure .......................74
           7.6.2. Identification Payload Processing ..................74
                  7.6.2.1. ID_U_NAME Processing ......................75
      7.7. Certificate Payload .......................................75
           7.7.1. Certificate Payload Structure ......................75



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           7.7.2. Certificate Payload Processing .....................77
      7.8. Signature Payload .........................................78
           7.8.1. Signature Payload Structure ........................78
           7.8.2. Signature Payload Processing .......................80
      7.9. Notification Payload ......................................81
           7.9.1. Notification Payload Structure .....................81
                  7.9.1.1. Notification Data - Acknowledgement
                           (ACK) Payload Type ........................83
                  7.9.1.2. Notification Data -
                           Cookie_Required and Cookie Payload Type ...83
                  7.9.1.3. Notification Data - Mechanism
                           Choices Payload Type ......................84
                  7.9.1.4. Notification Data - IPv4 and IPv6
                           Value Payload Types .......................85
           7.9.2. Notification Payload Processing ....................85
      7.10. Vendor ID Payload ........................................86
           7.10.1. Vendor ID Payload Structure .......................86
           7.10.2. Vendor ID Payload Processing ......................87
      7.11. Key Creation Payload .....................................88
           7.11.1. Key Creation Payload Structure ....................88
           7.11.2. Key Creation Payload Processing ...................89
      7.12. Nonce Payload ............................................90
           7.12.1. Nonce Payload Structure ...........................90
           7.12.2. Nonce Payload Processing ..........................91
   8. GSAKMP State Diagram ...........................................92
   9. IANA Considerations ............................................95
      9.1. IANA Port Number Assignment ...............................95
      9.2. Initial IANA Registry Contents ............................95
   10. Acknowledgements ..............................................96
   11. References ....................................................97
      11.1. Normative References .....................................97
      11.2. Informative References ...................................98
   Appendix A. LKH Information ......................................100
      A.1. LKH Overview .............................................100
      A.2. LKH and GSAKMP ...........................................101
      A.3. LKH Examples .............................................102
           A.3.1. LKH Key Download Example ..........................102
           A.3.2. LKH Rekey Event Example  ..........................103













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List of Figures

   1   GSAKMP Ladder Diagram .........................................28
   2   GSAKMP Ladder Diagram with Cookies ............................37
   3   GSAKMP Header Format ..........................................47
   4   GroupID UTF-8 Format ..........................................51
   5   GroupID Octet String Format ...................................52
   6   GroupID IPv4 Format ...........................................52
   7   GroupID IPv6 Format ...........................................53
   8   Generic Payload Header ........................................55
   9   Policy Token Payload Format ...................................56
   10  Key Download Payload Format ...................................58
   11  Key Download Data Item Format .................................59
   12  Key Datum Format ..............................................61
   13  Rekey Array Structure Format ..................................63
   14  Rekey Event Payload Format ....................................64
   15  Rekey Event Header Format .....................................66
   16  Rekey Event Data Format .......................................68
   17  Key Package Format ............................................68
   18  Identification Payload Format .................................72
   19  Unencoded Name (ID-U-NAME) Format .............................74
   20  Certificate Payload Format ....................................76
   21  Signature Payload Format ......................................78
   22  Notification Payload Format ...................................81
   23  Notification Data - Acknowledge Payload Type Format ...........83
   24  Notification Data - Mechanism Choices Payload Type Format......84
   25  Vendor ID Payload Format ......................................86
   26  Key Creation Payload Format ...................................88
   27  Nonce Payload Format ..........................................90
   28  GSAKMP State Diagram ..........................................92
   29  LKH Tree .....................................................100
   30  GSAKMP LKH Tree ..............................................101



















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List of Tables

   1   Request to Join (RTJ) Message Definition ......................30
   2   Key Download (KeyDL) Message Definition .......................31
   3   Request to Join Error (RTJ-Err) Message Definition ............33
   4   Key Download - Ack/Failure (KeyDL-A/F) Message Definition .....34
   5   Lack of Ack (LOA) Message Definition ..........................35
   6   Cookie Download Message Definition ............................37
   7   Rekey Event Message Definition ................................40
   8   Request_to_Depart (RTD) Message Definition ....................42
   9   Departure_Response (DR) Message Definition ....................43
   10  Departure_ACK (DA) Message Definition .........................44
   11  Group Identification Types ....................................48
   12  Payload Types .................................................49
   13  Exchange Types ................................................49
   14  Policy Token Types ............................................57
   15  Key Download Data Item Types ..................................60
   16  Cryptographic Key Types .......................................62
   17  Rekey Event Types .............................................66
   18  Identification Classification .................................72
   19  Identification Types ..........................................73
   20  Certificate Payload Types .....................................77
   21  Signature Types ...............................................79
   22  Notification Types ............................................82
   23  Acknowledgement Types .........................................83
   24  Mechanism Types ...............................................84
   25  Nonce Hash Types ..............................................85
   26  Types Of Key Creation Information .............................89
   27  Nonce Types ...................................................91
   28  GSAKMP States .................................................93
   29  State Transition Events .......................................94




















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1.  Introduction

   GSAKMP provides policy distribution, policy enforcement, key
   distribution, and key management for cryptographic groups.
   Cryptographic groups all share a common key (or set of keys) for data
   processing.  These keys all support a system-level security policy so
   that the cryptographic group can be trusted to perform security-
   relevant services.

   The ability of a group of entities to perform security services
   requires that a Group Secure Association (GSA) be established.  A GSA
   ensures that there is a common "group-level" definition of security
   policy and enforcement of that policy.  The distribution of
   cryptographic keys is a mechanism utilizing the group-level policy
   enforcements.

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 (GMs) 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).





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   The security features of the establishment protocol for the GSA
   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 [RFC3261] 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 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.  Transmission 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.








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RFC 4535                         GSAKMP                        June 2006


1.2.  Document Organization

   The remainder of this document is organized as follows:Section 2
   presents the terminology and concepts used to present the
   requirements of this protocol.  Section 3 outlines the security
   considerations with respect to GSAKMP.  Section 4 defines the
   architecture of 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 this document.

   Requirements Terminology: Keywords "MUST", "MUST NOT", "REQUIRED",
   "SHOULD", "SHOULD NOT" and "MAY" that appear in this document are to
   be interpreted as described in [RFC2119].

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




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

      -  Perform peer review of key management actions

      -  Manage 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 Protection Key (GTPK): The key or keys created for
      protecting the group data.

   Key Datum: A single key and its associated attributes for its usage.

   Key Encryption Key (KEK): Key used in an encryption mechanism for
      wrapping another key.

   Key Handle: The identifier of a particular instance or version of a
      key.

   Key ID: The identifier for a key that MUST stay static throughout the
      life cycle of this key.

   Key Package: Type/Length/Data format containing a Key Datum.

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

   Policy Token (PT): 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 Group Owner.
      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:




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         -  GSAKMP protocol version

         -  Key creation method

         -  Key dissemination policy

         -  Access control policy

         -  Group authorization policy

         -  Compromise recovery policy

         -  Data protection mechanisms

   Rekey: The act of changing keys within a group as defined by policy.

   Rekey Array: The construct that contains all the rekey information
      for a particular member.

   Rekey Key: The KEK used to encrypt keys for a subset of the group.

   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.

   Wrapping KeyID: The Key ID of the key used to wrap a Key Package.

   Wrapping Key Handle: The key handle of the key used to wrap the Key
      Package.

















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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.

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 [RFC4086].

   4.  The security of a group can be affected by the accuracy of the
       system clock.  Therefore, GSAKMP assumes that the system clock is
       close to correct time.  If a GSAKMP host relies on a network time
       service to set its local clock, then that protocol must be secure
       against attackers.  The maximum allowable clock skew across the
       group membership is policy configurable, with a default of 5
       minutes.

   5.  As described in the message processing section, the use of the
       nonce value used for freshness along with a signature is the
       mechanism used to foil replay attacks.  In any use of nonces, a
       core requirement is unpredictability of the nonce, from an
       attacker's viewpoint.  The utility of the nonce relies on the
       inability of an attacker either to reuse old nonces or to predict
       the nonce value.

   6.  GSAKMP does not provide identity protection.

   7.  The group's multicast routing infrastructure is not secured by
       GSAKMP, and therefore it may be possible to create a multicast
       flooding denial of service attack using the multicast
       application's data stream.  Either an insider (i.e., a rogue GM)
       or a non-member could direct the multicast routers to spray data
       at a victim system.




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   8.  The compromise of a S-GC/KS forces the re-registration of all GMs
       under its control.  The GM recognizes this situation by finding
       the S-GC/KS's certificate on a CRL as supplied by a service such
       as LDAP.

   9.  The compromise of the GO forces termination of the group.  The GM
       recognizes this situation by finding the GO's certificate on a
       Certificate Revocation List (CRL) as supplied by a service such
       as LDAP.

3.2.  Related Protocols

   GSAKMP derives from two (2) existing protocols: ISAKMP [RFC2408] and
   FIPS Pub 196 [FIPS196].  In accordance with Security Suite 1, GSAKMP
   implementations MUST support the use of Diffie-Hellman key exchange
   [DH77] for two-party key creation and MAY use Logical Key Hierarchy
   (LKH) [RFC2627] for rekey capability.  The GSAKMP design was also
   influenced by the following protocols: [HHMCD01], [RFC2093],
   [RFC2094], [BMS], and [RFC2412].

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

   When group policy dictates that a recovery of the group security is
   necessary after the discovery of the compromise of a GM, then GSAKMP
   relies upon a rekey capability (i.e., LKH) to enable group recovery
   after a compromise [RFC2627].  This is optional since in many
   instances it may be better to destroy the compromised group and
   rebuild a secure group.











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3.2.4.  Diffie-Hellman

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

   The information in this section borrows heavily from [IKEv2], as this
   protocol has already worked through similar issues 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.  A strong random number generator
   combined with the recommendations from [RFC3526] on Diffie-Hellman
   exponent size is recommended as sufficient.  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 that prohibits using stronger
   values, nor is there anything that 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 such as 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: Group Establishment with Denial of Service
   Protection".

3.4.  Rekey Availability

   In addition to GSAKMP's capability to do rekey operations, GSAKMP
   MUST also have the capability to make this rekey information highly
   available to GMs.  The necessity of GMs receiving rekey messages
   requires the use of methods to increase the likelihood of receipt of
   rekey messages.  These methods MAY include multiple transmissions of
   the rekey message, posting of the rekey message on a bulletin board,
   etc.  Compliant GSAKMP implementations supporting the optional rekey
   capability MUST support retransmission of rekey messages.



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3.5.  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 [RFC3740].  GSAKMP uses the MSEC
   components to create a trust model for operations that implement the
   security principles of mutual suspicion and trusted policy creation
   authorities.

4.1.  Trust Model

4.1.1.  Components

   The trust model contains four key components:

   -  Group Owner (GO),

   -  Group Controller Key Server (GC/KS),

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

   -  Group Member (GM).

   The goal of the GSAKMP trust model is to derive trust from a common
   trusted policy creation authority for a group.  All security-relevant
   decisions and actions implemented by GSAKMP are based on information
   that ultimately is traceable to and verified by the trusted policy
   creation authority.  There are two trusted policy creation
   authorities for GSAKMP: the GO (policy creation authority) and the
   PKI root that allows us to verify the GO.




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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 the key creation authority, the GC/KS will create the set of keys
   for the group.  These keys include the Group Traffic Protection Keys
   (GTPKs) 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 GC/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 GTPK.  Change of the GTPK limits the exposure of data
   encrypted with any single GTPK.

   Finally, as the 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 a key tree approach, such
   as Logical Key Hierarchies (LKH), as an optional approach.










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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 GTPK.  It is assumed
   here that the group will transmit data with a single GTPK at any one
   time.  This GTPK 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 GC/KS, and during that process it has to verify the authority of
   the GC/KS.

4.1.5.  GM

   The GM has two jobs: to make sure all security-relevant actions are
   authorized and to use the group keys properly.  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 GMs
   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
      GMs 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 GMs to be group speakers.  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 GMs share a
      single GTPK and other SA state information.  Consequently, some SA
      security features such as sequence number checking for anti-replay



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      protection cannot be supported by this configuration.  GSAKMP
      implementations MUST support this group configuration.

   -  The GO authorizes a subset of the GMs to be group speakers (which
      may be the subset composed of all GMs).  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 number of speakers.  GSAKMP implementations
      MAY support this group configuration.

4.1.6.  Assumptions

   The assumptions for this trust model are that:

   -  the GCKS is never compromised,

   -  the GO is never compromised,

   -  the PKI, subject to certificate validation, is 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,

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



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   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 trusted
   policy creation authority (PKI root) that is authorized to identify
   someone as 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 that its supporting PKI implementations MUST be compliant to
   RFC 3280.

   If a GM's 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
   its 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.





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   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 [RFC4534].

4.2.2.  Authorizations for Security-Relevant Actions

   A critical aspect of the GSAKMP trust model is the authorization of
   security-relevant actions.  These 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/KSes.  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





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   application uses SAP [RFC2974] 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 (ERSes) of security infrastructure and ERSes
   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 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-known multicast address for GC/KSes that
   provide service for groups of interest.  If multiple GC/KSes 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 of the ERA.
   In this case, the GM is the announcing entity.  The (S-)GC/KSes
   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



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   security infrastructure discovery hub is needed.  The registration of
   S-GC/KSes 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 S-GC/KS.

4.4.1.  Assumptions

   The most basic assumption here is that there is one or more
   trustworthy PKIs 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 Policy Token

   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.




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   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.  For example, for IPsec,
      this could include SPD/SAD configuration data.

   -  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, 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.









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4.4.4.  Discovery of GC/KS

   Potential GMs will receive notice of the new group via some
   mechanism: announcement, Anycast, or 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 the DoS
   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.

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
   assign the authority to become a S-GC/KS in a manner that supports
   the overall group integrity and operations.

4.4.7.  Autonomous Distributed GSAKMP Operations

   In autonomous mode, each S-GC/KS operates a largely self-contained
   sub-group for which the Primary-GC/KS delegates the sub-group's
   membership management responsibility to the S-GC/KS.  In general, the
   S-GC/KS locally handles each Group Member's registration and
   de-registration without any interaction with the Primary-GC/KS.
   Periodically, the Primary-GC/KS multicasts a Rekey Event message
   addressed only to its one or more S-GC/KS.

   After a S-GC/KS successfully processes a Rekey Event message from the
   Primary-GC/KS, the S-GC/KS transmits to its sub-group its own Rekey



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   Event message containing a copy of the group's new GTPK and policy
   token.  The S-GC/KS encrypts its Rekey Event message's sub-group key
   management information using Logical Key Hierarchy or a comparable
   rekey protocol.  The S-GC/KS uses the rekey protocol to realize
   forward and backward secrecy, such that only the authorized sub-group
   members can decrypt and acquire access to the new GTPK and policy
   token.  The frequency at which the Primary-GC/KS transmits a Rekey
   Event message is a policy token parameter.

   For the special case of a S-GC/KS detecting an expelled or
   compromised group member, a mechanism is defined to trigger an
   immediate group rekey rather than wait for the group's rekey period
   to elapse.  See below for details.

   Each S-GC/KS will be registered by the GC/KS as a management node
   with responsibility for GTPK distribution, access control policy
   enforcement, LKH tree creation, and distribution of LKH key arrays.
   The S-GC/KS will be registered into the primary LKH tree as an
   endpoint.  Each S-GC/KS will hold an entire LKH key array for the
   GC's LKH key tree.

   For the purpose of clarity, the process of creating a distributed
   GSAKMP group will be explained in chronological order.

   First, the Group Owner will create a policy token that authorizes a
   subset of the group's membership to assume the role of S-GC/KS.

   The GO needs to ensure that the S-GC/KS rules in the policy token
   will be stringent enough to ensure trust in the S-GC/KSes.  This
   policy token is handed off to the primary GC.

   The GC will create the GTPK and initial LKH key tree.  The GC will
   then wait for a potential S-GC/KS to send a Request to Join (RTJ)
   message.

   A potential S-GC/KS will eventually send an RTJ.  The GC will enforce
   the access control policy as defined in the policy token.  The
   S-GC/KS will accept the role of S-GC/KS and create its own LKH key
   tree for its sub-group membership.

   The S-GC/KS will then offer registration services for the group.
   There are local management decisions that are optional to control the
   scope of group members that can be served by a S-GC/KS.  These are
   truly local management issues that allow the administrators of an
   S-GC/KS to restrict service to potential GMs.  These local controls
   do not affect the overall group security policy, as defined in the
   policy token.




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   A potential Group Member will send an RTJ to the S-GC/KS.  The
   S-GC/KS will enforce the entire access control policy as defined in
   the PT.  The GM will receive an LKH key array that corresponds to the
   LKH tree of the S-GC/KS.  The key tree generated by the S-GC/KS is
   independent of the key tree generated by the GC/KS; they share no
   common keys.

   The GM then has the keys it needs to receive group traffic and be
   subject to rekey from the S-GC/KS.  For the sake of this discussion,
   let's assume the GM is to be expelled from the group membership.

   The S-GC/KS will receive notification that the GM is to be expelled.
   This mechanism is outside the scope of this protocol.

   Upon notification that a GM that holds a key array within its LKH
   tree is to be expelled, the S-GC/KS does two things.  First, the
   S-GC/KS initiates a de-registration exchange with the GC/KS
   identifying the member to be expelled.  (The S-GC/KS proxies a Group
   Member's de-registration informing the GC/KS that the Group Member
   has been expelled from the group.)  Second, the S-GC/KS will wait for
   a rekey action by the GC/KS.  The immediacy of the rekey action by
   the GC/KS is a management decision at the GC/KS.  Security is best
   served by quick expulsion of untrusted members.

   Upon receipt of the de-registration notification from the S-GC/KS,
   the GC/KS will register the member to be expelled.  The GC/KS will
   then follow group procedure for initiating a rekey action (outside
   the scope of this protocol).  The GC/KS will communicate to the GO
   the expelled member's information (outside the scope of this
   protocol).  With this information, the GO will create a new PT for
   the group with the expelled GM identity added to the excluded list in
   the group's access control rules.  The GO provides this new PT to the
   GC/KS for distribution with the Rekey Event Message.

   The GC/KS will send out a rekey operation with a new PT.  The S-GC/KS
   will receive the rekey and process it.  At the same time, all other
   S-GC/KSes will receive the rekey and note the excluded GM identity.
   All S-GC/KSes will review local identities to ensure that the
   excluded GM is not a local member.  If it is, then the S-GC/KS will
   create a rekey message.  The S-GC/KSes must always create a rekey
   message, whether or not the expelled Group Member is a member of
   their subtrees.

   The S-GC/KS will then create a local rekey message.  The S-GC/KS will
   send the wrapped Group TPK to all members of its local LKH tree,
   except the excluded member(s).





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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, member deletions, and group destruction.  Each of these life
   cycle phases is discussed in the following sections.

   The use and processing of the optional Vendor ID payload for all
   messages can be found in Section 7.10.

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 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 Verbose Mode.  Group Establishment is discussed in
   Section 5.2.1.






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   A group is set in Terse or Verbose Mode by a policy token parameter.
   All (S-)GC/KSes in a Verbose Mode group MUST support Verbose Mode.
   GSAKMP allows Verbose Mode groups to have GMs that do not support
   Verbose Mode.  Candidate GMs that do not support Verbose Mode and
   receive a RTJ-Error or Lack-of-Ack message must handle these messages
   gracefully.  Additionally, a GM will not know ahead of time that it
   is interacting with the (S-)GC/KS in Verbose or Terse Mode until the
   policy token is received.

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

   Regardless of mode, any error message sent between component members
   indicates the first error encountered while processing the message.

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 1, illustrates 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 through
   5.2.1.5.

    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 Acknowledgement-------->!
              !                                         ! <Proc LOA>
              !<=======SHARED KEYED GROUP SESSION======>!

                  Figure 1: GSAKMP Ladder Diagram




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   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 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 possible values for this error condition are:
   Invalid-Payload-Type, Invalid-Version, Invalid-Group-ID, Invalid-
   Sequence-ID, Payload-Malformed, Invalid-ID-Information, Invalid-
   Certificate, Cert-Type-Unsupported, Invalid-Cert-Authority,
   Authentication-Failed, Certificate-Unavailable, Unauthorized-Request,
   Prohibited-by-Group-Policy, and Prohibited-by-Locally-Configured-
   Policy.

   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.  Eviction means that the member will be
   excluded from the group after the next Rekey Event.  The policy of
   when a particular group needs to rekey itself is stated in the policy
   token.  Eviction is discussed further in Section 5.3.2.1.

   For the following message structure sections, details about payload
   format and processing can be found in Section 7.  Each message is
   identified by its exchange type in the header of the message.  Nonces
   MUST be present in the messages unless synchronization time is
   available to the system.



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5.2.1.1.  Request to Join

   The exchange type for Request to Join is eight (8).

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

              Table 1: Request to Join (RTJ) Message Definition

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

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


   As shown by Figure 1, a potential GM MUST generate and send an RTJ
   message to request permission to join the group.  At a minimum, the
   GM MUST be able to manually configure the destination for the RTJ.
   As defined in the dissection of the RTJ message, this message MUST
   contain a Key Creation payload for KEK determination.  A Nonce
   payload MUST be included for freshness and the Nonce_I value MUST be
   saved for potential later use.  The GC/KS will use this supplied
   nonce only if the policy token for this group defines the use of
   nonces versus synchronization time.  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 default policy-token-specified mechanisms for the
   Key Download.

   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 and find
   the GMs credentials (e.g., certificate) for message verification.  It
   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



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   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.

   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.

   NOTE: At any one time, a GC/KS MUST process no more than one (1)
   valid RTJ message from a given GM per group until its pending
   registration protocol exchange concludes.

   If any error occurs during RTJ message processing, and the GC/KS is
   running in Terse Mode, the registration 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.

   The OPTIONAL Notification payload of type IPValue may be used for the
   GM to convey a specific IP value to the GC/KS.

5.2.1.2.  Key Download

   The exchange type for Key Download is nine (9).

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

               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)*,
                      [VendorID]} SigC, [Cert]
      Payload Types : GSAKMP Header, Identification, [Nonce], Key
                      Creation, Policy Token, Key Download, [Vendor
                      ID], Signature, [Certificate]

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





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   In response to a properly formed and verified 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, Key Creation material, encrypted
   policy token, encrypted key information, and signature information.
   If synchronized time is not available, the Nonce payloads MUST be
   included in the message for freshness.

   If present, the nonce values transmitted MUST be the GC/KS's
   generated Nonce_R value and the combined Nonce_C value that was
   generated by using the GC/KS's Nonce_R value and the Nonce_I value
   received from the GM in the RTJ.

   If two-party key determination is used, the key creation material
   supplied by the GM and/or the GC/KS will be used to generate the key.
   Generation of this key is dependent on the key exchange, as defined
   in Section 7.11, "Key Creation Payload".  The policy token and key
   material are encrypted in the generated key.

   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.
   If using nonces, the GM MUST use its saved Nonce_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.  If not using nonces, the
   GM MUST check the timestamp in the Signature payload to determine if
   the message is new.

   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





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   decrypt and process the key material from 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 announcement.  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, regardless of
   whether the GM is in Terse or Verbose Mode, the registration session
   MUST be terminated, the GM MUST send a Key Download - Ack/Failure
   message, and all saved state information MUST be cleared.  If in
   Terse Mode, the Notification Payload will be of type NACK to indicate
   termination.  If in Verbose Mode, the Notification Payload will
   contain the type of error encountered.

5.2.1.3.  Request to Join Error

   The exchange type for Request to Join Error is eleven (11).

   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, [VendorID]}
      Payload Types : GSAKMP Header, [Nonce] Notification, [Vendor ID]

   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 message 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 terminate 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, if present, 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





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   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 exchange type for Key Download - Ack/Failure is four (4).

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

      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, [VendorID]}SigM
      Payload Types : GSAKMP Header, [Nonce], Notification, [Vendor
                      ID], Signature
        SigM        : Signature of Group Member
        {}SigX      : Indicates fields used in Signature

   In response to a properly processed KeyDL message, the GM creates and
   sends the KeyDL-A/F message.  As defined in the dissection of the
   message, this message MUST contain payloads to hold the following
   information: Notification payload of type Acknowledgement (ACK) and
   signature information.  If synchronized time is not available, the
   Nonce payload MUST be present for freshness, and the nonce value
   transmitted MUST be the GM's generated Nonce_C value.  If the GM does
   not receive a KeyDL message within a locally configured amount of
   time, the GM MAY send a new RTJ.  If the GM receives a valid LOA (see
   Section 5.2.1.5) message from the GC/KS before receipt of a KeyDL
   message, the GM SHOULD send a KeyDL-A/F message of type NACK followed
   by a new RTJ.

   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.  If using nonces, the
   GC/KS MUST use its saved Nonce_C value and compare it for equality
   with the received Nonce_C value.  If not using nonces, the GC/KS MUST
   check the timestamp in the Signature payload to determine if the
   message is new.  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



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   signature verifies, the GC/KS processes the Notification payload.  If
   the notification type is of type ACK, then the registration has
   completed successfully, and both parties SHOULD remove state
   information associated with this GM's registration.

   If the GC/KS does not receive a KeyDL-A/F message of proper form or
   is unable to correctly process the KeyDL-A/F message, the
   Notification payload type is any value except ACK; or if no KeyDL-A/F
   message is received within the locally configured timeout, the GC/KS
   MUST evict this GM from the group in the next policy-defined Rekey
   Event.  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 exchange type for Lack of Ack is twelve (12).

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

                Table 5: Lack of Ack (LOA) Message Definition

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

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

   If the GC/KS's 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, Notification of error, and signature information.

   If synchronized time is not available, the Nonce payloads MUST be
   present for freshness, and the nonce values transmitted MUST be the
   GC/KS's generated Nonce_R value and the combined Nonce_C value which
   was generated by using the GC/KS's 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.






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   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.  If
   using nonces, the GM MUST use its save Nonce_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.  If not using nonces, the
   GM MUST check the timestamp in the Signature payload to determine if
   the message is new.  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 borrows heavily from [IKEv2] as this protocol has already
   worked through this issue and GSAKMP is copying this concept.  This
   section will contain paraphrased sections of [IKEv2] modified for
   GSAKMP to define the purpose of Cookies.

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

   The term "cookies" originates with Karn and Simpson [RFC2522] 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, in
   GSAKMP 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



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   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 in Section 5.2.1.1.  This initial exchange will
   then be as shown in Figure 2 with the components of the new message
   Cookie Download shown in Table 6.  The exchange type for Cookie
   Download is ten (10).

     CONTROLLER                  MESSAGE                  MEMBER
     in Cookie Mode
               !<--Request to Join without Cookie Info---!
   <Gen Cookie>!                                         !
   <Response  >!                                         !
               !----------Cookie Download--------------->!
               !                                         ! <Process CD>
               !<----Request to Join with Cookie Info----!
     <Process> !                                         !
     <RTJ    > !                                         !
               !-------------Key Download--------------->!
               !                                         ! <Proc KeyDL>
               !<-----Key Download -  Ack/Failure--------!
    <Process  >!                                         !
    <KeyDL-A/F>!                                         !
               !<=======SHARED KEYED GROUP SESSION======>!

               Figure 2: GSAKMP Ladder Diagram with Cookies


                 Table 6: Cookie Download Message Definition

      Message Name  : Cookie Download
      Dissection    : {HDR-GrpID, Notif_COOKIE_REQUIRED, [VendorID]}
      Payload Types : GSAKMP Header, Notification, [Vendor ID]


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

   A GSAKMP implementation SHOULD implement its GC/KS cookie generation
   in such a way as not to 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.



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   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, and IPi is the asserted IP address
   of the candidate GM.  The IP address is either the IP header's source
   IP address or else the IP address contained in the optional
   Notification "IPvalue" payload (if it is present).
   <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 connections are in the
   process of being initialized, a "Request to Join with Cookie Info"
   might be returned with a <SecretVersionNumber> other than the current
   one.  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.

   An alternative example for Cookie value generation in a NAT
   environment is to substitute the IPi value with the IPValue received
   in the Notification payload in the RTJ message.  This scenario is
   indicated by the presence of the Notification payload of type
   IPValue.  With this substitution, a calculation similar to that
   described above can be used.









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5.2.3.  Group Establishment for Receive-Only Members

   This section describes an OPTIONAL capability that may be implemented
   in a structured system where the authorized (S-)GC/KS is known in
   advance through out-of-band means and where synchronized time is
   available.

   Unlike Standard Group Establishment, in the Receive-Only system, the
   GMs and (S-)GC/KSes operate in Terse Mode and exchange one message
   only: the Key Download.  Potential new GMs do not send an RTJ.
   (S-)GC/KSes do not expect Key Download - ACK/Failure messages and do
   not remove GMs for lack or receipt of the message.

   Operation is as follows: upon notification via an authorized out-of-
   band event, the (S-)GC/KS forms and sends a Key Download message to
   the new member with the Nonce payloads ABSENT.  The GM verifies

   -  the ID payload identifies that GM

   -  the timestamp in the message is fresh

   -  the message is signed by an authorized (S-)GC/KS

   -  the signature on the message verifies

   When using a Diffie-Hellman Key Creation Type for receive-only
   members, a static-ephemeral model is assumed: the Key Creation
   payload in the Key Download message contains the (S-)GC/KS's public
   component.  The member's public component is assumed to be obtained
   through secure out-of-band means.

5.3.  Group Maintenance

   The Group Maintenance phase includes member joins and leaves, group
   rekey activities, policy updates, and group destruction.  These
   activities are presented in the following sections.

5.3.1.  Group Management

5.3.1.1.  Rekey Events

   A Rekey Event is any action, including a 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 GTPK and rekey information to the group.



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   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 GTPK.

   The exchange type for Rekey Event is five (5).

   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,
                      [VendorID]}SigC, [Cert]
      Payload Types : GSAKMP Header, [Policy Token], Rekey Event,
                      [Vendor ID], Signature, [Certificate],

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

5.3.1.2.  Policy Updates

   New policy tokens are sent via the Rekey Event message.  These policy
   updates may be coupled with an existing rekey event or may be sent in
   a message with the Rekey Event Type of the Rekey Event Payload set to
   None(0) (see Section 7.5.1).

   A policy token MUST NOT be processed if the processing of the Rekey
   Event message carrying it fails.  Policy token processing is type
   dependent and is beyond the scope of this document.

5.3.1.3.  Group Destruction

   Group destruction is also accomplished via the Rekey Event message.
   In a Rekey Event message for group destruction, the Sequence ID is
   set to 0xFFFFFFFF.  Upon receipt of this authenticated Rekey Event
   message, group components MUST terminate processing of information
   associated with the indicated group.








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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 (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 desirable 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 5.3.1.1.
   If future access to the group is also to be denied, the members MUST
   be added to a denied access control list, and the policy token's
   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 when that member wishes to leave.  De-registration consists of
   a three-message exchange between the GM and the member's GC/KS:  the
   Request_to_Depart, Departure_Response, and the Departure_Ack.
   Compliant GSAKMP implementations for GMs SHOULD support the de-
   registration messages.  Compliant GSAKMP implementations for GC/KSes
   MUST support the de-registration messages.

5.3.2.3.1.  Request to Depart

   The Exchange Type for a Request_to_Depart Message is thirteen (13).
   The components of a Request_to_Depart Message are shown in Table 8.

   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 dissection of the RTD message, this message MUST
   contain payloads to hold the following information: the GC/KS
   identification and Notification of the desire to leave the group.



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   When synchronization time is not available to the system as defined
   by the Policy Token, a Nonce payload MUST be included for freshness,
   and the Nonce_I value MUST be saved for later use.  This message MUST
   then be signed by the GM.

             Table 8: Request_to_Depart (RTD) Message Definition

     Message Name  : Request_to_Depart (RTD)
     Dissection    : {HDR-GrpID, GC/KS_ID, [Nonce_I], Notif_Leave_Group,
                     [VendorID]} SigM, [Cert]
     Payload Types : GSAKMP Header, Identification, [Nonce],
                     Notification, [Vendor ID], Signature,
                     [Certificate]

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

   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 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/KS's 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, then
   the GC/KS MUST form a Departure_Response message as defined in
   Section 5.3.2.3.2.

   If the processing of the message fails, the de-registration session
   MUST be terminated, and all state associated with this session is
   removed.  If the GC/KS is operating in Terse Mode, then no error
   message is sent to the GM.  If the GC/KS is operating in Verbose
   Mode, then the GC/KS sends a Departure_Response Message with a
   Notification Payload of type Request_to_Depart_Error.









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5.3.2.3.2.  Departure_Response

   The Exchange Type for a Departure_Response Message is fourteen (14).
   The components of a Departure_Response Message are shown in Table 9.

   In response to a properly formed and verified 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, Notification for acceptance of
   departure, and signature information.  If synchronization time is not
   available, the Nonce payloads MUST be included in the message for
   freshness.

             Table 9: Departure_Response (DR) Message Definition

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

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

   If present, the nonce values transmitted MUST be the GC/KS's
   generated Nonce_R value and the combined Nonce_C value that was
   generated by using the GC/KS's 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 GM's 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 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.  If using nonces, the
   GM MUST use its saved Nonce_I value, extract the received GC/KS
   Nonce_R value, compute the combined Nonce_C value, and compare it for
   equality with the received Nonce_C value.  If not using nonces, the
   GM MUST check the timestamp in the signature payload to determine if
   the message is new.  After freshness is confirmed, confirmation of
   the identity of the signer of the DR message is the GMs authorized



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   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 de-registration session.  If the member still desires to
   De-Register from the group, the member MUST restart the de-
   registration process.

   If the processing of the message fails, the de-registration session
   MUST be terminated, and all state associated with this session is
   removed.  If the GM is operating in Terse Mode, then a Departure_Ack
   Message with Notification Payload of type NACK is sent to the GC/KS.
   If the GM is operating in Verbose Mode, then the GM sends a
   Departure_Ack Message with a Notification Payload of the appropriate
   failure type.

5.3.2.3.3.  Departure_ACK

   The Exchange Type for a Departure_ACK Message is fifteen (15).  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, [VendorID]}SigM
      Payload Types : GSAKMP Header, [Nonce], Notification, [Vendor
                      ID], Signature
        SigM        : Signature of Group Member
        {}SigX      : Indicates 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: Notification payload of type
   Acknowledgement (ACK) and signature information.  If synchronization
   time is not available, the Nonce payload MUST be present for
   freshness, and the nonce value transmitted MUST be the GM's generated
   Nonce_C value.






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   Upon receipt of the Departure_ACK, the GC/KS MUST perform the
   following checks.  These 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, the
   GC/KS MUST check the message for freshness.  If using nonces, the
   GC/KS MUST use its saved Nonce_C value and compare it to the received
   Nonce_C value.  If not using nonces, the GC/KS MUST check the
   timestamp in the signature payload to determine if the message is
   new.  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 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 gives all the algorithm and
   cryptographic definitions required to process group establishment
   messages.  It is important to note that GSAKMP does not negotiate





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   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:  AES
     Mode:       CBC
     Key Length: 128 bits

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

     Nonce Hash algorithm is:
       SHA-1

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

     NOTE: The p and g values come from IKE [RFC2409], Section 6.2,
           "Second Oakley Group", and p is 1024 bits long.


     The GSAKMP message digital signature algorithm is:
     DSS-SHA1-ASN1-DER

     The digital signature ID type is:
     ID-DN-STRING












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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 preceding payload
   defining its succeeding payload.  Payloads are not required to be in
   the exact order shown in the message dissection in Section 5,
   provided that all required payloads are present.  Unless it is
   explicitly stated in a dissection that multiple payloads of a single
   type may be present, no more than one payload of each type allowed by
   the message may appear.  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.

   Padding of fields MUST NOT be done as this leads to processing
   errors.

   When a message contains a Vendor ID payload, the processing of the
   payloads of that message is modified as defined in Section 7.10.

7.1.  GSAKMP Header

7.1.1.  GSAKMP Header Structure

   The GSAKMP Header fields are shown in Figure 3 and defined as:

    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 3: GSAKMP Header Format






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   Group Identification Type (1 octet) - Table 11 presents the group
       identification types.  This field is treated as an unsigned
       value.

                     Table 11:  Group Identification Types

   Grp ID Type          Value       Description
   _____________________________________________________________________

   Reserved               0
   UTF-8                  1         Format defined in Section 7.1.1.1.1.
   Octet String           2         This type MUST be implemented.
                                    Format defined in Section 7.1.1.1.2.
   IPv4                   3         Format defined in Section 7.1.1.1.3.
   IPv6                   4         Format defined in Section 7.1.1.1.4.
   Reserved to IANA    5 - 192
   Private Use        193 - 255

   Group Identification Length (1 octet)  - Length of the Group
       Identification Value field in octets.  This value MUST NOT be
       zero (0).  This field is treated as an unsigned value.

   Group Identification Value (variable length)  - Indicates the
       name/title of the group.  All GroupID types should provide unique
       naming across groups.  GroupID types SHOULD provide this
       capability by including a random element generated by the creator
       (owner) of the group of at least eight (8) octets, providing
       extremely low probability of collision in group names.  The
       GroupID value is static throughout the life of the group.

   Next Payload (1 octet)  - Indicates the type of the next payload in
       the message.  The format for each payload is defined in the
       following sections.  Table 12 presents the payload types.  This
       field is treated as an unsigned value.

















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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
                      Vendor ID                  10
                      Key Creation               11
                      Nonce                      12
                      Reserved to IANA        13 - 192
                      Private Use            193 - 255

   Version (1 octet) - Indicates the version of the GSAKMP protocol in
       use.  The current value is one (1).  This field is treated as an
       unsigned value.

   Exchange Type (1 octet) - Indicates the type of exchange (also known
       as the message type).  Table 13 presents the exchange type
       values.  This field is treated as an unsigned value.

                           Table 13: Exchange Types

                    Exchange_Type                 Value
                   ________________________________________

                    Reserved                      0 - 3
                    Key Download Ack/Failure        4
                    Rekey Event                     5
                    Reserved                      6 - 7
                    Request to Join                 8
                    Key Download                    9
                    Cookie Download                10
                    Request to Join Error          11
                    Lack of Ack                    12
                    Request to Depart              13
                    Departure Response             14
                    Departure Ack                  15
                    Reserved to IANA            16 - 192
                    Private Use                193 - 255



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   Sequence ID (4 octets) - The Sequence ID is used for replay
       protection of group management messages.  If the message is not a
       group management message, this value MUST be set to zero (0).
       The first value used by a (S-)GC/KS MUST be 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 than the value of the sequence ID received with the last
       group management message from this (S-)GC/KS.  Group Components
       (e.g., GMs, S-GC/KSes) MUST terminate processing upon receipt of
       an authenticated group management message containing a Sequence
       ID of 0xFFFFFFFF.  This field is treated as an unsigned integer
       in network byte order.

   Length (4 octets) - Length of total message (header + payloads) in
       octets.  This field is treated as an unsigned integer in network
       byte order.


































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7.1.1.1.  GroupID Structure

   This section defines the formats for the defined GroupID types.

7.1.1.1.1.  UTF-8

   The format for type UTF-8 [RFC3629] is shown in Figure 4.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Random Value                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! UTF-8 String                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 4: GroupID UTF-8 Format

   Random Value (16 octets) - For the UTF-8 GroupID type, the Random
       Value is represented as a string of exactly 16 hexadecimal digits
       converted from its octet values in network-byte order.  The
       leading zero hexadecimal digits and the trailing zero hexadecimal
       digits are always included in the string, rather than being
       truncated.

   UTF-8 String (variable length) - This field contains the human
       readable portion of the GroupID in UTF-8 format.  Its length is
       calculated as the (GroupID Length - 16) for the Random Value
       field.  The minimum length for this field is one (1) octet.
















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7.1.1.1.2.  Octet String

   The format for type Octet String is shown in Figure 5.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Random Value                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Octet String                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 5:  GroupID Octet String Format

   Random Value (8 octets) - The 8-octet unsigned random value in
       network byte order format.

   Octet String (variable length) - This field contains the Octet String
       portion of the GroupID.  Its length is calculated as the (GroupID
       Length - 8) for the Random Value field.  The minimum length for
       this field is one (1) octet.

7.1.1.1.3.  IPv4 Group Identifier

   The format for type IPv4 Group Identifier is shown in Figure 6.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Random Value                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! IPv4 Value                                                    !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 6: GroupID IPv4 Format

   Random Value (8 octets) - The 8-octet unsigned random value in
       network byte order format.

   IPv4 Value (4 octets) - The IPv4 value in network byte order format.
       This value MAY contain the multicast address of the group.






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7.1.1.1.4.  IPv6 Group Identifier

   The format for type IPv6 Group Identifier is shown in Figure 7.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Random Value                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! IPv6 Value                                                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 7: GroupID IPv6 Format

   Random Value (8 octets) - The 8-octet unsigned random value in
       network byte order format.

   IPv6 Value (16 octets) - The IPv6 value in network byte order format.
       This value MAY contain the multicast address of the group.

7.1.2.  GSAKMP Header Processing

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

   1.  Group ID Type - The Group ID Type value MUST be checked to be a
       valid group identification payload type as defined by Table 11.
       If the value is not valid, then an error is logged.  If in
       Verbose Mode, an appropriate message containing notification
       value Payload-Malformed will be sent.

   2.  GroupID - The GroupID of the received message MUST be checked
       against the valid GroupIDs of the Group Component.  If no match
       is found, then an error is logged; in addition, if in Verbose
       Mode, an appropriate message containing notification value
       Invalid-Group-ID will be sent.







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   3.  Next Payload - The Next Payload value MUST be checked to be a
       valid payload type as defined by Table 12.  If the value is not
       valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Invalid-
       Payload-Type will be sent.

   4.  Version - The GSAKMP version number MUST be checked that its
       value is one (1).  For other values, see below for processing.
       The GSAKMP version number MUST be checked that it is consistent
       with the group's policy as specified in its Policy Token.  If the
       version is not supported or authorized, then an error is logged.
       If in Verbose Mode, an appropriate message containing
       notification value Invalid-Version will be sent.

   5.  Exchange Type - The Exchange Type MUST be checked to be a valid
       exchange type as defined by Table 13 and MUST be of the type
       expected to be received by the GSAKMP state machine.  If the
       exchange type is not valid, then an error is logged.  If in
       Verbose Mode, an appropriate message containing notification
       value Invalid-Exchange-Type will be sent.

   6.  Sequence ID - The Sequence ID value MUST be checked for
       correctness.  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.  Receipt
       of incorrect Sequence ID on group management messages MUST NOT
       cause a reply message to be generated.  Upon receipt of incorrect
       Sequence ID on non-group management messages, an error is logged.
       If in Verbose Mode, an appropriate message containing
       notification value Invalid-Sequence-ID will be sent.

   The length fields in the GSAKMP Header (Group ID Length and Length)
   are used to help process the message.  If any field is found to be
   incorrect, then an error is logged.  If in Verbose Mode, an
   appropriate message containing notification value Payload-Malformed
   will be sent.

   In order to allow a GSAKMP version one (v1) implementation to
   interoperate with future versions of the protocol, some ideas will be
   discussed here to this effect.

   A (S-)GC/KS that is operating in a multi-versioned group as defined
   by the Policy Token can take many approaches on how to interact with
   the GMs in this group for a rekey message.







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   One possible solution is for the (S-)GC/KS to send out multiple rekey
   messages, one per version level that it supports.  Then each GM would
   only process the message that has the version at which it is
   operating.

   An alternative approach that all GM v1 implementations MUST support
   is the embedding of a v1 message inside a version two (v2) message.
   If a GM running at v1 receives a GSAKMP message that has a version
   value greater than one (1), the GM will attempt to process the
   information immediately after the Group Header as a Group Header for
   v1 of the protocol.  If this is in fact a v1 Group Header, then the
   remainder of this v1 message will be processed in place.  After
   processing this v1 embedded message, the data following the v1
   message should be the payload as identified by the Next Payload field
   in the original header of the message and will be ignored by the v1
   member.  However, if the payload following the initial header is not
   a v1 Group Header, then the GM will gracefully handle the
   unrecognized message.

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 8, that 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 8: 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.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.




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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 checked to be a
       valid payload type as defined by Table 12.  If the payload type
       is not valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Invalid-
       Payload-Type will be sent.

   2.  RESERVED - This field MUST contain the value zero (0).  If the
       value of this field is not zero (0), then an error is logged.  If
       in Verbose Mode, an appropriate message containing notification
       value Payload-Malformed will be sent.

   The length field in the Generic Payload Header is used to process the
   remainder of the payload.  If this field is found to be incorrect,
   then an error is logged.  If in Verbose Mode, an appropriate message
   containing notification value Payload-Malformed will be sent.

7.3.  Policy Token Payload

7.3.1.  Policy Token Payload Structure

   The Policy Token Payload contains authenticatable group-specific
   information that describes the group security-relevant behaviors,
   access control parameters, and security mechanisms.  Figure 9 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        !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Policy Token Type             ! Policy Token Data             ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 9: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.




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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Policy Token Type (2 octets) - Specifies the type of Policy Token
       being used.  Table 14 identifies the types of policy tokens.
       This field is treated as an unsigned integer in network byte
       order format.

                       Table 14: Policy Token Types

    Policy_Token_Type      Value         Definition/Defined In
   ____________________________________________________________________

   Reserved                  0
   GSAKMP_ASN.1_PT_V1        1          All implementations of GSAKMP
                                        MUST support this PT format.
                                        Format specified in [RFC4534].
   Reserved to IANA      2 - 49152
   Private Use         49153 - 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.

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

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

7.3.2.  Policy Token Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Policy Token Type - The Policy Token Type value MUST be checked
       to be a valid policy token type as defined by Table 14.  If the
       value is not valid, then an error is logged.  If in Verbose Mode,
       an appropriate message containing notification value Payload-
       Malformed will be sent.





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   3.  Policy Token Data - This Policy Token Data MUST be processed
       according to the Policy Token Type specified.  The type will
       define the format of the data.

7.4.  Key Download Payload

   Refer to the terminology section for the different terms relating to
   keys used within this section.

7.4.1.  Key Download Payload Structure

   The Key Download Payload contains group keys (e.g., 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 10 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
   encryption mechanism 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.

    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        !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Number of Items               ! Key Download Data Items       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 10: Key Download Payload Format

   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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.






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   Number of Items (2 octets) - Contains the total number of group
       traffic protection keys and Rekey Arrays being passed in this
       data block.  This field is treated as an unsigned integer in
       network byte order format.

   Key Download Data Items (variable length) - Contains Key Download
       information.  The Key Download Data is a sequence of
       Type/Length/Data of the Number of Items.  The format for each
       item is defined in Figure 11.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! KDD Item Type !  Key Download Data Item Length!               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~ Data for Key Download Data Item (Key Datum/Rekey Array)       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 11: Key Download Data Item Format

   For each Key Download Data Item, the data format is as follows:

       Key Download Data (KDD) Item Type (1 octet) - Identifier for the
           type of data contained in this Key Download Data Item.  See
           Table 15 for the possible values of this field.  This field
           is treated as an unsigned value.

       Key Download Data Item Length (2 octets) - Length in octets of
           the Data for the Key Download Data Item following this field.
           This field is treated as an unsigned integer in network byte
           order format.

       Data for Key Download Data Item (variable length) - Contains Keys
           and related information.  The format of this field is
           specific depending on the value of the Key Download Data Item
           Type field.  For KDD Item Type of GTPK, this field will
           contain a Key Datum as defined in Section 7.4.1.1.  For KDD
           Item Type Rekey - LKH, this field will contain a Rekey Array
           as defined in Section 7.4.1.2.












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                 Table 15: Key Download Data Item Types

   Key Download Data     Value      Definition
   Item Type
   _________________________________________________________________

   GTPK                    0        This type MUST be implemented.
                                    This type identifies that the
                                    data contains group traffic
                                    protection key information.
   Rekey - LKH             1        Optional
   Reserved to IANA     2 - 192
   Private Use         193 - 255

   The encryption of this payload only covers the data subsequent to the
   Generic Payload header (Number of Items and Key Download Data Items
   fields).

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
































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7.4.1.1.  Key Datum Structure

   A Key Datum contains all the information for a key.  Figure 12 shows
   the format for this structure.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Key Type                      ! Key ID                        ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                               ! Key Handle                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                               ! Key Creation Date             ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !               ! Key Expiration Date                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                               !               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~ Key Data                                                      ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 12: Key Datum Format

   Key Type (2 octets) - This is the cryptographic algorithm for which
       this key data is to be used.  This value is specified in the
       Policy Token.  See Table 16 for the possible values of this
       field.  This field is treated as an unsigned value.














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                    Table 16: Cryptographic Key Types

    Cryptographic_Key_Types     Value         Description/Defined In
   ____________________________________________________________________

   Reserved                     0 - 2
   3DES_CBC64_192                 3           See [RFC2451].
   Reserved                     4 - 11
   AES_CBC_128                    12          This type MUST be
                                              supported.  See [IKEv2].
   AES_CTR                        13          See [IKEv2].
   Reserved to IANA           14 - 49152
   Private Use              49153 - 65535

   Key ID (4 octets) - This is the permanent ID of all versions of the
       key.  This value MAY be defined by the Policy Token.  This field
       is treated as an octet string.

   Key Handle (4 octets) - This is the value to uniquely identify a
       version (particular instance) of a key.  This field is treated as
       an octet string.

   Key Creation Date (15 octets) - This is the time value of when this
       key data was originally generated.  This field contains the
       timestamp in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year
       (0000 - 9999), MM is the numerical value of the month (01 - 12),
       DD is the day of the month (01 - 31), HH is the hour of the day
       (00 - 23), MM is the minute within the hour (00 - 59), SS is the
       seconds within the minute (00 - 59), and the letter Z indicates
       that this is Zulu time.  This format is loosely based on
       [RFC3161].

   Key Expiration Date (15 octets) - This is the time value of when this
       key is no longer valid for use.  This field contains the
       timestamp in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year
       (0000 - 9999), MM is the numerical value of the month (01 - 12),
       DD is the day of the month (01 - 31), HH is the hour of the day
       (00 - 23), MM is the minute within the hour (00 - 59), SS is the
       seconds within the minute (00 - 59), and the letter Z indicates
       that this is Zulu time.  This format is loosely based on
       [RFC3161].

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

   NOTE: The combination of the Key ID and the Key Handle MUST be unique
   within the group.  This combination will be used to uniquely identify
   a key.



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7.4.1.2.  Rekey Array Structure

   A Rekey Array contains the information for the set of KEKs that is
   associated with a Group Member.  Figure 13 shows the format for this
   structure.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Rekey Version#! Member ID                                     ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~               ! Number of KEK Keys            !               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~ Key Datum(s)                                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 13: Rekey Array Structure Format

   Rekey Version (1 octet) - Contains the version of the Rekey protocol
       in which the data is formatted.  For Key Download Data Item Type
       of Rekey - LKH, refer to Section A.2 for a description of this
       value.  This field is treated as an unsigned value.

   Member ID (4 octets) - This is the Member ID of the Rekey sequence
       contained in this Rekey Array.  This field is treated as an octet
       string.  For Key Download Data Item Type of Rekey - LKH, refer to
       Section A.2 for a description of this value.

   Number of KEK Keys (2 octets) - This value is the number of distinct
       KEK keys in this sequence.  This value is treated as an unsigned
       integer in network byte order format.

   Key Datum(s) (variable length) - The sequence of KEKs in Key Datum
       format.  The format for each Key Datum in this sequence is
       defined in section 7.4.1.1.

   Key ID (for Key ID within the Rekey) - LKH space, refer to Section
       A.2 for a description of this value.

7.4.2.  Key Download Payload Processing

   Prior to processing its data, the payload contents MUST be decrypted.

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






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   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  KDD Item Type - All KDD Item Type fields MUST be checked to be a
       valid Key Download Data Item type as defined by Table 15.  If the
       value is not valid, then an error is logged.  If in Verbose Mode,
       an appropriate message containing notification value Payload-
       Malformed will be sent.

   3.  Key Type - All Key Type fields MUST be checked to be a valid
       encryption type as defined by Table 16.  If the value is not
       valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Invalid-Key-
       Information will be sent.

   4.  Key Expiration Date - All Key Expiration Date fields MUST be
       checked confirm that their values represent a future and not a
       past time value.  If the value is not valid, then an error is
       logged.  If in Verbose Mode, an appropriate message containing
       notification value Invalid-Key-Information will be sent.

   The length and counter fields in the payload are used to help process
   the payload.  If any field is found to be incorrect, then an error is
   logged.  If in Verbose Mode, an appropriate message containing
   notification value Payload-Malformed will be sent.

7.5.  Rekey Event Payload

   Refer to the terminology section for the different terms relating to
   keys used within this section.

7.5.1.  Rekey Event Payload Structure

   The Rekey Event Payload MAY contain multiple keys encrypted in
   Wrapping KEKs.  Figure 14 shows the format of the payload.  If the
   data to be contained within a Rekey Event Payload is too large for
   the payload, the sequence can be split across multiple Rekey Event
   Payloads at a Rekey Event Data boundary.












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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        !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! RekeyEvnt Type!  Rekey Event Header                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~ Rekey Event Data(s)                                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 14: Rekey Event Payload Format

   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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Rekey Event Type (1 octet) - Specifies the type of Rekey Event being
       used.  Table 17 presents the types of Rekey events.  This field
       is treated as an unsigned value.

   Rekey Event Header (variable length) - This is the header information
       for the Rekey Event.  The format for this is defined in Section
       7.5.1.1, "Rekey Event Header Structure".

   Rekey Event Data(s) (variable length) - This is the rekey information
       for the Rekey Event.  The format for this is defined in Section
       7.5.1.2, "Rekey Event Data Structure".

   The Rekey Event payload type is three (3).












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                       Table 17: Rekey Event Types

   Rekey_Event_Type     Value       Definition/Defined In
   _____________________________________________________________________

   None                   0         This type MUST be implemented.
                                    In this case, the size of the Rekey
                                    Event Data field will be zero bytes
                                    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.  GSAKMP
                                    rekey msg requires a Rekey Event
                                    Payload, and in this instance it
                                    would have rekey data of type None.
   GSAKMP_LKH             1         The rekey data will be of
                                    type LKH formatted according to
                                    GSAKMP.  The format for this field
                                    is defined in Section 7.5.1.2.
   Reserved to IANA    2 - 192
   Private Use        193 - 255

7.5.1.1.  Rekey Event Header Structure

   The format for the Rekey Event Header is shown in Figure 15.

    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                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                               ! RekeyEnt Type ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Algorithm Ver ! # of Rekey Event Data(s)      !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 15: Rekey Event Header Format






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   Group Identification Value (variable length) - Indicates the
       name/title of the group to be rekeyed.  This is the same format,
       length, and value as the Group Identification Value in Section
       7.1, "GSAKMP Header".

   Time/Date Stamp (15 octets) - This is the time value when the Rekey
       Event Data was generated.  This field contains the timestamp in
       UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year (0000 -
       9999), MM is the numerical value of the month (01 - 12), DD is
       the day of the month (01 - 31), HH is the hour of the day (00 -
       23), MM is the minute within the hour (00 - 59), SS is the
       seconds within the minute (00 - 59), and the letter Z indicates
       that this is Zulu time.  This format is loosely based on
       [RFC3161].

   Rekey Event Type (1 octet) - This is the Rekey algorithm being used
       for this group.  The values for this field can be found in Table
       17.  This field is treated as an unsigned value.

   Algorithm Version (1 octet) - Indicates the version of the Rekey Type
       being used.  For Rekey Event Type of GSAKMP_LKH, refer to Section
       A.2 for a description of this value.  This field is treated as an
       unsigned value.

   # of Rekey Event Data(s) (2 octets) - The number of Rekey Event
       Data(s) contained in the Rekey Data.  This value is treated as an
       unsigned integer in network byte order.

7.5.1.2.  Rekey Event Data Structure

   As defined in the Rekey Event Header, # of Rekey Data(s) field,
   multiple pieces of information are sent in a Rekey Event Data.  Each
   end user, will be interested in only one Rekey Event Data among all
   of the information sent.  Each Rekey Event Data will contain all the
   Key Packages that a user requires.  For each Rekey Event Data, the
   data following the Wrapping fields is encrypted with the key
   identified in the Wrapping Header.  Figure 16 shows the format of
   each Rekey Event Data.













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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Packet Length                 ! Wrapping KeyID                ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                               ! Wrapping Key Handle           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                               ! # of Key Packages             !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Key Packages(s)                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 16: Rekey Event Data Format

   Packet Length (2 octets) - Length in octets of the Rekey Event Data,
       which consists of the # of Key Packages and the Key Packages(s).
       This value is treated as an unsigned integer in network byte
       order.

   Wrapping KeyID (4 octets) - This is the Key ID of the KEK that is
       being used for encryption/decryption of the new (rekeyed) keys.
       For Rekey Event Type of Rekey - LKH, refer to Section A.2 for a
       description of this value.

   Wrapping Key Handle (4 octets) - This is a Key Handle of the KEK that
       is being used for encryption/decryption of the new (rekeyed)
       keys.  Refer to Section 7.4.1.1 for the values of this field.

   # of Key Packages (2 octets) - The number of key packages contained
       in this Rekey Event Data.  This value is treated as an unsigned
       integer in network byte order.

   Key Package(s) (variable length) - The type/length/value format of a
       Key Datum.  The format for this is defined in Section 7.5.1.2.1.

7.5.1.2.1.  Key Package Structure

   Each Key Package contains all the information about the key.  Figure
   17 shows the format for a Key Package.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! KeyPkg Type   ! Key Package Length            ! Key Datum     ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 17: Key Package Format




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   Key Package Type (1 octet) - The type of key in this key package.
       Legal values for this field are defined in Table 15, Key Download
       Data Types.  This field is treated as an unsigned value.

   Key Package Length (2 octets) - The length of the Key Datum.  This
       field is treated as an unsigned integer in network byte order
       format.

   Key Datum (variable length) - The actual data of the key.  The format
       for this field is defined in Section 7.4.1.1, "Key Datum
       Structure".

7.5.2.  Rekey Event Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Rekey Event Type field within "Rekey Event" payload header - The
       Rekey Event Type MUST be checked to be a valid rekey event type
       as defined by Table 17.  If the Rekey Event Type is not valid,
       then regardless of mode (e.g., Terse or Verbose) an error is
       logged.  No response error message is generated for receipt of a
       Group Management Message.

   3.  Group ID Value - The Group ID value of the Rekey Event Header
       received message MUST be checked against the GroupID of the Group
       Component.  If no match is found, the payload is discarded, then
       regardless of mode (e.g., Terse or Verbose) an error is logged.
       No response error message is generated for receipt of a Group
       Management Message.

   4.  Date/Time Stamp - The Date/Time Stamp value of the Rekey Event
       Header MAY be checked to determine if the Rekey Event generation
       time is recent relative to network delay and processing times.
       If the TimeStamp is judged not to be recent, an error is logged.
       No response error message is generated for receipt of a Group
       Management Message.

   5.  Rekey Event Type field within the "Rekey Event Header" - The
       Rekey Event Type of the Rekey Event Header received message MUST
       be checked to be a valid rekey event type, as defined by Table
       17, and the same value of the Rekey Event Type earlier in this
       payload.  If the Rekey Event Type is not valid or not equal to
       the previous value of the Rekey Event Type, then regardless of



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       mode (e.g., Terse or Verbose) an error is logged.  No response
       error message is generated for receipt of a Group Management
       Message.

   6.  Algorithm Version - The Rekey Algorithm Version number MUST be
       checked to ensure that the version indicated is supported.  If it
       is not supported, then regardless of mode (e.g., Terse or
       Verbose) an error is logged.  No response error message is
       generated for receipt of a Group Management Message.

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

   A GM MUST process all the Rekey Event Datas as based on the rekey
   method used there is a potential that multiple Rekey Event Datas are
   for this GM.  The Rekey Event Datas are processed in order until all
   Rekey Event Datas are consumed.

   1.  Wrapping KeyID - The Wrapping KeyID MUST be checked against the
       list of stored KEKs that this GM holds.  If a match is found,
       then continue processing this Rekey Event Data.  Otherwise, skip
       to the next Rekey Event Data.

   2.  Wrapping Handle - If a matching Wrapping KeyID was found, then
       the Wrapping Handle MUST be checked against the handle of the KEK
       for which the KeyID was a match.  If the handles match, then the
       GM will process the Key Packages associated with this Rekey Event
       Data.  Otherwise, skip to the next Rekey Event Data.

   If a GM has found a matching Wrapping KeyID and Wrapping Handle, the
   GM decrypts the remaining data in this Rekey Event Data according to
   policy using the KEK defined by the Wrapping KeyID and Handle.  After
   decrypting the data, the GM extracts the # of Key Packages field to
   help process the subsequent Key Packages.  The Key Packages are
   processed as follows:

   1.  Key Package Type - The Key Package Type MUST be checked to be a
       valid key package type as defined by Table 15.  If the Key
       Package Type is not valid, then regardless of mode (e.g., Terse
       or Verbose) an error is logged.  No response error message is
       generated for receipt of a Group Management Message.

   2.  Key Package Length - The Key Package Length is used to process
       the subsequent Key Datum information.






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   3.  Key Type - The Key Type MUST be checked to be a valid key type as
       defined by Table 16.  If the Key Package Type is not valid, then
       regardless of mode (e.g., Terse or Verbose) an error is logged.
       No response error message is generated for receipt of a Group
       Management Message.

   4.  Key ID - The Key ID MUST be checked against the set of Key IDs
       that this user maintains for this Key Type.  If no match is
       found, then regardless of mode (e.g., Terse or Verbose) an error
       is logged.  No response error message is generated for receipt of
       a Group Management Message.

   5.  Key Handle - The Key Handle is extracted as is and is used to be
       the new Key Handle for the Key currently associated with the Key
       Package's Key ID.

   6.  Key Creation Date - The Key Creation Date MUST be checked that it
       is subsequent to the Key Creation Date for the currently held
       key.  If this date is prior to the currently held key, then
       regardless of mode (e.g., Terse or Verbose) an error is logged.
       No response error message is generated for receipt of a Group
       Management Message.

   7.  Key Expiration Date - The Key Expiration Date MUST be checked
       that it is subsequent to the Key Creation Date just received and
       that the time rules conform with policy.  If the expiration date
       is not subsequent to the creation date or does not conform with
       policy, then regardless of mode (e.g., Terse or Verbose) an error
       is logged.  No response error message is generated for receipt of
       a Group Management Message.

   8.  Key Data - The Key Data is extracted based on the length
       information in the key package.

   If there were no errors when processing the Key Package, the key
   represented by the KeyID will have all of its data updated based upon
   the received information.

7.6.  Identification Payload

7.6.1.  Identification Payload Structure

   The Identification Payload contains entity-specific data used to
   exchange identification information.  This information is used to
   verify the identities of members.  Figure 18 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 Classif    !  ID Type      !      Identification Data      ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 18: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Identification (ID) Classification (1 octet) - Classifies the
       ownership of the Identification Data.  Table 18 identifies
       possible values for this field.  This field is treated as an
       unsigned value.

                   Table 18: Identification Classification

                        ID_Classification     Value
                       _______________________________

                        Sender                  0
                        Receiver                1
                        Third Party             2
                        Reserved to IANA     3 - 192
                        Private Use         193 - 255

   Identification (ID) Type (1 octet) - Specifies the type of
       Identification being used.  Table 19 identifies possible values
       for this type.  This field is treated as an unsigned value.  All
       defined types are OPTIONAL unless otherwise stated.







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   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 stated in conjunction with the type in Table 19.

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

                      Table 19: Identification Types

   ID_Type              Value       PKIX Cert           Description
                                    Field               Defined In
   _____________________________________________________________________

   Reserved               0
   ID_IPV4_ADDR           1         SubjAltName         See [IKEv2]
                                    iPAddress           Section 3.5.
   ID_FQDN                2         SubjAltName         See [IKEv2]
                                    dNSName             Section 3.5.
   ID_RFC822_ADDR         3         SubjAltName         See [IKEv2]
                                    rfc822Name          Section 3.5.
   Reserved               4
   ID_IPV6_ADDR           5         SubjAltName         See [IKEv2]
                                    iPAddress           Section 3.5.
   Reserved             6 - 8
   ID_DER_ASN1_DN         9         Entire Subject,     See [IKEv2]
                                    bitwise Compare     Section 3.5.
   Reserved               10
   ID_KEY_ID              11        N/A                 See [IKEv2]
   Reserved            12 - 29                          Section 3.5.
   Unencoded Name         30        Subject             The format for
    (ID_U_NAME)                                         this type is
                                                        defined in
                                                        Section 7.6.1.1.
   ID_DN_STRING           31        Subject             See [RFC4514].
                                                        This type MUST
                                                        be implemented.
   Reserved to IANA    32 - 192
   Private Use        193 - 255













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7.6.1.1.  ID_U_NAME Structure

   The format for type Unencoded Name (ID_U_NAME) is shown in Figure 19.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Serial Number                                                 ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Length                                                        !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! DN Data                                                       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 19: Unencoded Name (ID-U-NAME) Format

   Serial Number (20 octets) - The certificate serial number.  This
       field is treated as an unsigned integer in network byte order
       format.

   Length (4 octets) - Length in octets of the DN Data field.  This
       field is treated as an unsigned integer in network byte order
       format.

   DN Data (variable length) - The actual UTF-8 DN value (Subject field)
       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).

7.6.2.  Identification Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".






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   2.  Identification Classification - The Identification Classification
       value MUST be checked to be a valid identification classification
       type as defined by Table 18.  If the value is not valid, then an
       error is logged.  If in Verbose Mode, an appropriate message
       containing notification value Payload-Malformed will be sent.

   3.  Identification Type - The Identification Type value MUST be
       checked to be a valid identification type as defined by Table 19.
       If the value is not valid, then an error is logged.  If in
       Verbose Mode, an appropriate message containing notification
       value Payload-Malformed will be sent.

   4.  Identification Data - This Identification Data MUST be processed
       according to the identification type specified.  The type will
       define the format of the data.  If the identification data is
       being used to find a match and no match is found, then an error
       is logged.  If in Verbose Mode, an appropriate message containing
       notification value Invalid-ID-Information will be sent.

7.6.2.1.  ID_U_NAME Processing

   When processing the Identification Data of type ID_U_NAME, the
   following fields MUST be checked for correct values:

   1.  Serial Number - The serial number MUST be a greater than or equal
       to one (1) to be a valid serial number from a conforming CA
       [RFC3280].  If the value is not valid, then an error is logged.
       If in Verbose Mode, an appropriate message containing
       notification value Payload-Malformed will be sent.

   2.  DN Data - The DN data is processed as a UTF-8 string.

   3.  The CA MUST be a valid trusted policy creation authority as
       defined by the Policy Token.

   These 2 pieces of information, Serial Number and DN Data, in
   conjunction, will then be used for party identification.  These
   values are also used to help identify the certificate when necessary.

7.7.  Certificate Payload

7.7.1.  Certificate Payload Structure

   The Certificate Payload provides a means to transport certificates or
   other certificate-related information via GSAKMP and can appear in
   any GSAKMP message.  Certificate payloads SHOULD be included in an
   exchange whenever an appropriate directory service (e.g., LDAP
   [RFC4523]) is not available to distribute certificates.  Multiple



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   certificate payloads MAY be sent to enable verification of
   certificate chains.  Conversely, zero (0) certificate payloads may be
   sent, and the receiving GSAKMP MUST rely on some other mechanism to
   retrieve certificates for verification purposes.  Figure 20 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 20: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Certificate Type (2 octets) - This field indicates the type of
       certificate or certificate-related information contained in the
       Certificate Data field.  Table 20 presents the types of
       certificate payloads.  This field is treated as an unsigned
       integer in network byte order format.

   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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                   Table 20: Certificate Payload Types

   Certificate_Type                   Value        Description/
                                                   Defined In
   _____________________________________________________________________

   None                                 0
   Reserved                           1 - 3
   X.509v3 Certificate                  4          This type MUST be
     -- Signature                                  implemented.
     -- DER Encoding                               Contains a DER
                                                   encoded X.509
                                                   certificate.
   Reserved                           5 - 6
   Certificate Revocation List          7          Contains a BER
     (CRL)                                         encoded X.509 CRL.
   Reserved                           8 - 9
   X.509 Certificate                   10          See [IKEv2], Sec 3.6.
     -- Attribute
   Raw RSA Key                         11          See [IKEv2], Sec 3.6.
   Hash and URL of X.509               12          See [IKEv2], Sec 3.6.
    Certificate
   Hash and URL of X.509               13          See [IKEv2], Sec 3.6.
    bundle
   Reserved to IANA                14 -- 49152
   Private Use                   49153 -- 65535

7.7.2.  Certificate Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Certificate Type - The Certificate Type value MUST be checked to
       be a valid certificate type as defined by Table 20.  If the value
       is not valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Cert-Type-
       Unsupported will be sent.

   3.  Certificate Data - This Certificate Data MUST be processed
       according to the certificate type specified.  The type will
       define the format of the data.  Receipt of a certificate of the
       trusted policy creation authority in a Certificate payload causes





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       the payload to be discarded.  This received certificate MUST NOT
       be used to verify the message.  The certificate of the trusted
       policy creation authority MUST be retrieved by other means.

7.8.  Signature Payload

7.8.1.  Signature Payload Structure

       The Signature Payload contains data generated by the digital
       signature function.  The digital signature, as defined by the
       dissection of each message, covers the message from the GSAKMP
       Message Header through the Signature Payload, up to but not
       including the Signature Data Length.  Figure 21 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 Timestamp                                           ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                               ! Signer ID Length              !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !                    Signer ID Data                             ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !     Signature Length          !     Signature Data            ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 21: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

   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.  This field is treated as
       an unsigned integer in network byte order format.

   Signature Type (2 octets) - Indicates the type of signature.  Table
       21 presents the allowable signature types.  This field is treated
       as an unsigned integer in network byte order format.

                        Table 21: Signature Types

   Signature Type                         Value         Description/
                                                        Defined In
   _____________________________________________________________________

   DSS/SHA1 with ASN.1/DER encoding         0           This type MUST
   (DSS-SHA1-ASN1-DER)                                  be supported.
   RSA1024-MD5                              1           See [RFC3447].
   ECDSA-P384-SHA3                          2           See [FIPS186-2].
   Reserved to IANA                       3 - 41952
   Private Use                        41953 - 65536

   Signature ID Type (1 octet) - Indicates the format for the Signature
       ID Data.  These values are the same as those defined for the
       Identification Payload Identification types, which can be found
       in Table 19.  This field is treated as an unsigned value.

   Signature Timestamp (15 octets) - This is the time value when the
       digital signature was applied.  This field contains the timestamp
       in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year (0000 -
       9999), MM is the numerical value of the month (01 - 12), DD is
       the day of the month (01 - 31), HH is the hour of the day (00 -
       23), MM is the minute within the hour (00 - 59), SS is the
       seconds within the minute (00 - 59), and the letter Z indicates
       that this is Zulu time.  This format is loosely based on
       [RFC3161].

   Signer ID Length (2 octets) - Length in octets of the Signer's ID.
       This field is treated as an unsigned integer in network byte
       order format.

   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.





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   Signature Length (2 octets) - Length in octets of the Signature Data.
       This field is treated as an unsigned integer in network byte
       order format.

   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:

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Signature Type - The Signature Type value MUST be checked to be a
       valid signature type as defined by Table 21.  If the value is not
       valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Payload-
       Malformed will be sent.

   3.  Signature ID Type - The Signature ID Type value MUST be checked
       to be a valid signature ID type as defined by Table 19.  If the
       value is not valid, then an error is logged.  If in Verbose Mode,
       an appropriate message containing notification value Payload-
       Malformed will be sent.

   4.  Signature Timestamp - This field MAY be checked to determine if
       the transaction signing time is fresh relative to expected
       network delays.  Such a check is appropriate for systems in which
       archived sequences of events are desired.

       NOTE: The maximum acceptable age of a signature timestamp
       relative to the local system clock is a locally configured
       parameter that can be tuned by its GSAKMP management interface.

   5.  Signature ID Data - This field will be used to identify the
       sending party.  This information MUST then be used to confirm
       that the correct party sent this information.  This field is also
       used to retrieve the appropriate public key of the certificate to
       verify the message.






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   6.  Signature Data - This value MUST be compared to the recomputed
       signature to verify the message.  Information on how to verify
       certificates used to ascertain the validity of the signature can
       be found in [RFC3280].  Only after the certificate identified by
       the Signature ID Data is verified can the signature be computed
       to compare to the signature data for signature verification.  A
       potential error that can occur during signature verification is
       Authentication-Failed.  Potential errors that can occur while
       processing certificates for signature verification are: Invalid-
       Certificate, Invalid-Cert-Authority, Cert-Type-Unsupported, and
       Certificate-Unavailable.

   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

7.9.1.  Notification Payload Structure

   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
   independent Notification payloads in a single GSAKMP message.  Figure
   22 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         !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Notification Type             !  Notification Data            ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 22: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

   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.  This field is treated as
       an unsigned integer in network byte order format.

   Notification Type (2 octets) - Specifies the type of notification
       message.  Table 22 presents the Notify Payload Types.  This field
       is treated as an unsigned integer in network byte order format.

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

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

                    Table 22: Notification Types

      Notification Type                             Value
     __________________________________________________________

      None                                            0
      Invalid-Payload-Type                            1
      Reserved                                      2 - 3
      Invalid-Version                                 4
      Invalid-Group-ID                                5
      Invalid-Sequence-ID                             6
      Payload-Malformed                               7
      Invalid-Key-Information                         8
      Invalid-ID-Information                          9
      Reserved                                     10 - 11
      Cert-Type-Unsupported                           12
      Invalid-Cert-Authority                          13
      Authentication-Failed                           14
      Reserved                                     15 - 16
      Certificate-Unavailable                         17
      Reserved                                        18
      Unauthorized-Request                            19
      Reserved                                     20 - 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
      Invalid Exchange Type                           33
      IPv4 Value                                      34



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      IPv6 Value                                      35
      Prohibited by Group Policy                      36
      Prohibited by Locally Configured Policy         37
      Reserved to IANA                            38 - 49152
      Private Use                               49153 -- 65535

7.9.1.1.  Notification Data - Acknowledgement (ACK) Payload Type

   The data portion of the Notification payload of type ACK either
   serves as confirmation of correct receipt of the Key Download message
   or, when needed, provides other receipt information when included in
   a signed message.  Figure 23 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 23: 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 23
       presents the Notify Acknowledgement Payload Types.  This field is
       treated as an unsigned value.

                        Table 23: Acknowledgement Types

             ACK_Type             Value       Definition
            _____________________________________________________

             Simple                 0         Data portion null.
             Reserved to IANA     1 - 192
             Private Use        193 - 255

7.9.1.2.  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.




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

7.9.1.3.  Notification Data - Mechanism Choices Payload Type

   The data portion of the Notification payload of type 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 24 shows the format of the Notification
   Data - Mechanism Choices Payload Type.  Multiple type|length|data
   choices are strung together in one notification payload to allow a
   user to transmit all relevant information within one Notification
   Payload.  The length of the payload will control 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     ! Mechanism Choice Data         !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..

   Figure 24: 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 24
       presents the Notify Mechanism Choices Mechanism Types.  This
       field is treated as an unsigned value.

                          Table 24: Mechanism Types

      Mechanism_Type             Value       Mechanism Choice
                                             Data Value Table Reference
     ___________________________________________________________________

      Key Creation Algorithm       0         Table 26
      Encryption Algorithm         1         Table 16
      Nonce Hash Algorithm         2         Table 25
      Reserved to IANA          3 - 192
      Private Use              193 - 255

   Mechanism Choice Data (2 octets) - 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.  This field is treated as an unsigned integer in
       network byte order format.



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                       Table 25: Nonce Hash Types

   Nonce_Hash_Type        Value         Description
   __________________________________________________________________

   Reserved                 0
   SHA-1                    1           This type MUST be supported.
   Reserved to IANA     2 - 49152
   Private Use        49153 - 65535

7.9.1.4.  Notification Data - IPv4 and IPv6 Value Payload Types

   The data portion of the Notification payload of type IPv4 and IPv6
   value contains the appropriate IP value in network byte order.  This
   value will be set by the creator of the message for consumption by
   the receiver of the message.

7.9.2.  Notification Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Notification Type - The Notification type value MUST be checked
       to be a notification type as defined by Table 22.  If the value
       is not valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Payload-
       Malformed will be sent.

   3.  Notification Data - This Notification Data MUST be processed
       according to the notification type specified.  The type will
       define the format of the data.  When processing this data, any
       type field MUST be checked against the appropriate table for
       correct values.  If the contents of the Notification Data are not
       valid, then an error is logged.  If in Verbose Mode, an
       appropriate message containing notification value Payload-
       Malformed will be sent.











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7.10.  Vendor ID Payload

7.10.1.  Vendor ID Payload Structure

       The Vendor ID Payload contains a vendor-defined constant.  The
       constant is used by vendors to identify and recognize remote
       instances of their implementations.  This mechanism allows a
       vendor to experiment with new features while maintaining
       backwards compatibility.  Figure 25 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        !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !                         Vendor ID (VID)                       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 25: Vendor ID Payload Format

   A Vendor ID payload MAY announce that the sender is capable of
   accepting certain extensions to the protocol, or it MAY simply
   identify the implementation as an aid in debugging.  A Vendor ID
   payload MUST NOT change the interpretation of any information defined
   in this specification.  Multiple Vendor ID payloads MAY be sent.  An
   implementation is NOT REQUIRED to send any Vendor ID payload at all.

   A Vendor ID payload may be sent as part of any message.  Receipt of a
   familiar Vendor ID payload allows an implementation to make use of
   Private Use numbers described throughout this specification --
   private payloads, private exchanges, private notifications, etc.
   This implies that all the processing rules defined for all the
   payloads are now modified to recognize all values defined by this
   Vendor ID for all fields of all payloads.  Unfamiliar Vendor IDs MUST
   be ignored.

   Writers of Internet-Drafts who wish to extend this protocol MUST
   define a Vendor ID payload to announce the ability to implement the
   extension in the Internet-Draft.  It is expected that Internet-Drafts
   that gain acceptance and are standardized will be given assigned
   values out of the Reserved to IANA range, and the requirement to use
   a Vendor ID payload will go away.

   The Vendor ID payload fields are defined as follows:






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   Next Payload (1 octet) - Identifier for the payload type of the next
       payload in the message.  If the current payload is the last in
       the message, then this field will be 0.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Vendor ID (variable length) - The Vendor ID value.  The minimum
       length for this field is four (4) octets.  It is the
       responsibility of the person choosing the Vendor ID to assure its
       uniqueness in spite of the absence of any central registry for
       IDs.  Good practice is to include a company name, a person name,
       or similar type data.  A message digest of a long unique string
       is preferable to the long unique string itself.

   The payload type for the Vendor ID Payload is ten (10).

7.10.2.  Vendor ID Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Vendor ID - The Vendor ID Data MUST be processed to determine if
       the Vendor ID value is recognized by the implementation.  If the
       Vendor ID value is not recognized, then regardless of mode (e.g.,
       Terse or Verbose) this information is logged.  Processing of the
       message MUST continue regardless of recognition of this value.

   It is recommended that implementations that want to use Vendor-ID-
   specific information attempt to process the Vendor ID payloads of an
   incoming message prior to the remainder of the message processing.
   This will allow the implementation to recognize that when processing
   other payloads it can use the larger set of values for payload fields
   (Private Use values, etc.) as defined by the recognized Vendor IDs.








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7.11.  Key Creation Payload

7.11.1.  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 26 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 Creation Type             ! Key Creation Data             ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 26: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Key Creation Type (2 octets) - Specifies the type of Key Creation
       being used.  Table 26 identifies the types of key creation
       information.  This field is treated as an unsigned integer in
       network byte order format.

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

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








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               Table 26: Types of Key Creation Information

   Key Creation Type           Value        Definition/Defined In
   _____________________________________________________________________

   Reserved                    0 - 1
   Diffie-Hellman                2          This type MUST be supported.
     1024-bit MODP Group                    Defined in [IKEv2] B.2.
     Truncated                              If the output of the process
                                            is longer than needed for
                                            the defined mechanism, use
                                            the first X low order bits
                                            and truncate the remainder.
   Reserved                   3 - 13
   Diffie-Hellman               14          Defined in [RFC3526].
     2048-bit MODP Group                    If the output of the process
     Truncated                              is longer than needed for
                                            the defined mechanism, use
                                            the first X low order bits
                                            and truncate the remainder.
   Reserved to IANA         15 - 49152
   Private Use             49153 - 65535

7.11.2.  Key Creation Payload Processing

   The specifics of the Key Creation Payload are defined in Section
   7.11.

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Key Creation Type - The Key Creation Type value MUST be checked
       to be a valid key creation type as defined by Table 26.  If the
       value is not valid, then an error is logged.  If in Verbose Mode,
       an appropriate message containing notification value Payload-
       Malformed will be sent.

   3.  Key Creation Data - This Key Creation Data MUST be processed
       according to the key creation type specified to generate the KEK
       to protect the information to be sent in the appropriate message.
       The type will define the format of the data.






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   Implementations that want to derive other keys from the initial Key
   Creation keying material (for example, DH Secret keying material)
   MUST define a Key Creation Type other than one of those shown in
   Table 26.  The new Key Creation Type must specify that derivation's
   algorithm, for which the KEK MAY be one of the keys derived.

7.12.  Nonce Payload

7.12.1.  Nonce Payload Structure

   The Nonce Payload contains random data used to guarantee freshness
   during an exchange and protect against replay attacks.  Figure 27
   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 27: 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.  This field provides the
       "chaining" capability.  Table 12 identifies the payload types.
       This field is treated as an unsigned value.

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

   Payload Length (2 octets) - Length in octets of the current payload,
       including the generic payload header.  This field is treated as
       an unsigned integer in network byte order format.

   Nonce Type (1 octet) - Specifies the type of nonce being used.  Table
       27 identifies the types of nonces.  This field is treated as an
       unsigned value.










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                          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
                                      Policy (e.g., Security Suite
                                      Definition of Policy Token).
   Reserved to IANA       4 - 192
   Private Use           192 - 255

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

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

7.12.2.  Nonce Payload Processing

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

   1.  Next Payload, RESERVED, Payload Length - These fields are
       processed as defined in Section 7.2.2, "Generic Payload Header
       Processing".

   2.  Nonce Type - The Nonce Type value MUST be checked to be a valid
       nonce type as defined by Table 27.  If the value is not valid,
       then an error is logged.  If in Verbose Mode, an appropriate
       message containing notification value Payload-Malformed will be
       sent.

   3.  Nonce Data - This is the nonce data and it must be checked
       according to its content.  The size of this field is defined in
       Section 7.12, "Nonce Payload".  Refer to Section 5.2, "Group
       Establishment", for interpretation of this field.








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8.  GSAKMP State Diagram

   Figure 28 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 28: 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
                : Member Deregistration
  ______________:_____________________________________________________
                :
  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
                : Deregistration command
  ______________:_____________________________________________________
                :
  Transition 5a : Time out
                : Msg failure
                : errors
                :
  ____________________________________________________________________










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9.  IANA Considerations

9.1.  IANA Port Number Assignment

   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.

9.2.  Initial IANA Registry Contents

   The following registry entries have been created:

   GSAKMP Group Identification Types (Section 7.1.1)
   GSAKMP Payload Types (Section 7.1.1)
   GSAKMP Exchange Types (Section 7.1.1)
   GSAKMP Policy Token Types (Section 7.3.1)
   GSAKMP Key Download Data Item Types (Section 7.4.1)
   GSAKMP Cryptographic Key Types (Section 7.4.1.1)
   GSAKMP Rekey Event Types (Section 7.5.1)
   GSAKMP Identification Classification (Section 7.6.1)
   GSAKMP Identification Types (Section 7.6.1)
   GSAKMP Certificate Types (Section 7.7.1)
   GSAKMP Signature Types (Section 7.8.1)
   GSAKMP Notification Types (Section 7.9.1)
   GSAKMP Acknowledgement Types (Section 7.9.1.1)
   GSAKMP Mechanism Types (Section 7.9.1.3)
   GSAKMP Nonce Hash Types (Section 7.9.1.3)
   GSAKMP Key Creation Types (Section 7.11.1)
   GSAKMP Nonce Types (Section 7.12.1)

   Changes and additions to the following registries are by IETF
   Standards Action:

   GSAKMP Group Identification Types
   GSAKMP Payload Types
   GSAKMP Exchange Types
   GSAKMP Policy Token Types
   GSAKMP Key Download Data Item Types
   GSAKMP Rekey Event Types
   GSAKMP Identification Classification
   GSAKMP Notification Types
   GSAKMP Acknowledgement Types
   GSAKMP Mechanism Types
   GSAKMP Nonce Types







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   Changes and additions to the following registries are by Expert
   Review:

   GSAKMP Cryptographic Key Types
   GSAKMP Identification Types
   GSAKMP Certificate Types
   GSAKMP Signature Types
   GSAKMP Nonce Hash Types
   GSAKMP Key Creation Types

10.  Acknowledgements

   This document is the collaborative effort of many individuals.  If
   there were no limit to the number of authors that could appear on an
   RFC, the following, in alphabetical order, would have been listed:
   Haitham S. Cruickshank of University of Surrey, Sunil Iyengar of
   University Of Surrey Gavin Kenny of LogicaCMG, Patrick McDaniel of
   AT&T Labs Research, and Angela Schuett of NSA.

   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".






















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11.  References

11.1.  Normative References

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

   [FIPS186-2] NIST, "Digital Signature Standard", FIPS PUB 186-2,
               National Institute of Standards and Technology, U.S.
               Department of Commerce, January 2000.

   [FIPS196]   "Entity Authentication Using Public Key Cryptography,"
               Federal Information Processing Standards Publication 196,
               NIST, February 1997.

   [IKEv2]     Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
               RFC 4306, December 2005.

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

   [RFC2409]   Harkins, D. and D. Carrel, "The Internet Key Exchange
               (IKE)", RFC 2409, November 1998.

   [RFC2412]   Orman, H., "The OAKLEY Key Determination Protocol", RFC
               2412, November 1998.

   [RFC2627]   Wallner, D., Harder, E., and R. Agee, "Key Management for
               Multicast: Issues and Architectures", RFC 2627, June
               1999.

   [RFC3280]   Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
               X.509 Public Key Infrastructure Certificate and
               Certificate Revocation List (CRL) Profile", RFC 3280,
               April 2002.

   [RFC3629]   Yergeau, F., "UTF-8, a transformation format of ISO
               10646", STD 63, RFC 3629, November 2003.

   [RFC4514]   Zeilenga, K., Ed., "Lightweight Directory Access Protocol
               (LDAP): String Representation of Distinguished Names",
               RFC 4514, June 2006.

   [RFC4534]   Colegrove, A. and H. Harney, "Group Security Policy Token
               v1", RFC 4534, June 2006.





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11.2.  Informative References

   [BMS]       Balenson, D., McGrew, D., and A. Sherman, "Key Management
               for Large Dynamic Groups:  One-Way Function Trees and
               Amortized Initialization", Work in Progress, February
               1999.

   [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.

   [HHMCD01]   Hardjono, T., Harney, H., McDaniel, P., Colegrove, A.,
               and P. Dinsmore, "Group Security Policy Token:
               Definition and Payloads", Work in Progress, August 2003.

   [RFC2093]   Harney, H. and C. Muckenhirn, "Group Key Management
               Protocol (GKMP) Specification", RFC 2093, July 1997.

   [RFC2094]   Harney, H. and C. Muckenhirn, "Group Key Management
               Protocol (GKMP) Architecture", RFC 2094, July 1997.

   [RFC2408]   Maughan D., Schertler M., Schneider M., and Turner J.,
               "Internet Security Association and Key Management
               Protocol (ISAKMP)", RFC 2408, Proposed Standard, November
               1998

   [RFC2451]   Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
               Algorithms", RFC 2451, November 1998.

   [RFC2522]   Karn, P. and W. Simpson, "Photuris: Session-Key
               Management Protocol", RFC 2522, March 1999.

   [RFC4523]   Zeilenga, K., "Lightweight Directory Access Protocol
               (LDAP) Schema Definitions for X.509 Certificates", RFC
               4523, June 2006.

   [RFC2974]   Handley, M., Perkins, C., and E. Whelan, "Session
               Announcement Protocol", RFC 2974, October 2000.

   [RFC3161]   Adams, C., Cain, P., Pinkas, D., and R. Zuccherato,
               "Internet X.509 Public Key Infrastructure Time-Stamp
               Protocol (TSP)", RFC 3161, August 2001.

   [RFC3261]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
               A., Peterson, J., Sparks, R., Handley, M., and E.
               Schooler, "SIP: Session Initiation Protocol", RFC 3261,
               June 2002.



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   [RFC3447]   Jonsson, J. and B. Kaliski, "Public-Key Cryptography
               Standards (PKCS) #1: RSA Cryptography Specifications
               Version 2.1", RFC 3447, February 2003.

   [RFC3526]   Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
               Diffie-Hellman groups for Internet Key Exchange (IKE)",
               RFC 3526, May 2003.

   [RFC3740]   Hardjono, T. and B. Weis, "The Multicast Group Security
               Architecture", RFC 3740, March 2004.

   [RFC4086]   Eastlake, D., 3rd, Schiller, J., and S. Crocker,
               "Randomness Requirements for Security", BCP 106, RFC
               4086, June 2005.





































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Appendix A.  LKH Information

   This appendix will give an overview of LKH, define the values for
   fields within GSAKMP messages that are specific to LKH, and give an
   example of a Rekey Event Message using the LKH scheme.

A.1.  LKH Overview

   LKH provides a topology for handling key distribution for a group
   rekey.  It rekeys a group based upon a tree structure and subgroup
   keys.  In the LKH tree shown in Figure 29, members are represented by
   the leaf nodes on the tree, while intermediate tree nodes represent
   abstract key groups.  A member will possess multiple keys: the group
   traffic protection key (GTPK), subgroup keys for every node on its
   path to the root of the tree, and a personal key.  For example, the
   member labeled as #3 will have the GTPK, Key A, Key D, and Key 3.

                              root
                    /                      \
                   /                        \
                A                               B
            /      \                        /      \
           /        \                      /        \
        C               D               E               F
      /   \           /   \           /   \           /   \
     /     \         /     \         /     \         /     \
   1         2     3         4     5         6     7         8


                      Figure 29: LKH Tree

   This keying topology provides for a rapid rekey to all but a
   compromised member of the group.  If Member 3 were compromised, the
   new GTPK (GTPK') would need to be distributed to the group under a
   key not possessed by Member 3.  Additionally, new Keys A and D (Key
   A' and Key D') would also need to be securely distributed to the
   other members of those subtrees.  Encrypting the GTPK' with Key B
   would securely distribute that key to Members 5, 6, 7, and 8.  Key C
   can be used to encrypt both the GTPK' and Key A' for Members 1 and 2.
   Member 3's nearest neighbor, Member 4, can obtain GTPK', Key D', and
   Key A' encrypted under its personal key, Key 4.  At the end of this
   process, the group is securely rekeyed with Member 3 fully excluded.









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A.2.  LKH and GSAKMP

   When using LKH with GSAKMP, the following issues require attention:

   1.  Rekey Version # - The Rekey Version # in the Rekey Array of the
       Key Download Payload MUST contain the value one (1).

   2.  Algorithm Version - The Algorithm Version in the Rekey Event
       Payload MUST contain the value one (1).

   3.  Degree of Tree - The LKH tree used can be of any degree; it need
       not be binary.

   4.  Node Identification - Each node in the tree is treated as a KEK.
       A KEK is just a special key.  As the rule stated for all keys in
       GSAKMP, the set of the KeyID and the KeyHandle MUST be unique.  A
       suggestion on how to do this will be given in this section.

   5.  Wrapping KeyID and Handle - This is the KeyID and Handle of the
       LKH node used to wrap/encrypt the data in a Rekey Event Data.

   For the following discussion, refer to Figure 30.

   Key:
   o: a node in the LKH tree
   N: this line contains the KeyID node number
   L: this line contains the MemberID number for all leaves ONLY

       LEVEL
       ----
       root                          o
   N:                         /      1     \
                             /              \
       1              o                             o
   N:              /  2  \                       /  3  \
                  /       \                     /       \
       2      o               o             o               o
   N:        /4\             /5\           /6\             /7\
            /   \           /   \         /   \           /   \
       3  o       o       o       o     o       o       o       o
   N:     8       9      10      11    12      13      14      15
   L:     1       2       3       4     5       6       7       8

                        Figure 30: GSAKMP LKH Tree







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   To guarantee uniqueness of KeyID, the Rekey Controller SHOULD build a
   virtual tree and label the KeyID of each node, doing a breadth-first
   search of a fully populated tree regardless of whether or not the
   tree is actually full.  For simplicity of this example, the root of
   the tree was given KeyID value of one (1).  These KeyID values will
   be static throughout the life of this tree.  Additionally, the rekey
   arrays distributed to GMs requires a MemberID value associated with
   them to be distributed with the KeyDownload Payload.  These MemberID
   values MUST be unique.  Therefore, the set associated with each leaf
   node (the nodes from that leaf back to the root) are given a
   MemberID.  In this example, the leftmost leaf node is given MemberID
   value of one (1).  These 2 sets of values, the KeyIDs (represented on
   lines N) and the MemberIDs (represented on line L), will give
   sufficient information in the KeyDownload and RekeyEvent Payloads to
   disseminate information.  The KeyHandle associated with these keys is
   regenerated each time the key is replaced in the tree due to
   compromise.

A.3.  LKH Examples

   Definition of values:
   0xLLLL          - length value
   0xHHHHHHH#      - handle value
   YYYYMMDDHHMMSSZ - time value

A.3.1.  LKH Key Download Example

   This section will give an example of the data for the Key Download
   payload.  The GM will be given MemberID 1 and its associated keys.
   The data shown will be subsequent to the Generic Payload Header.

   | GTPK | MemberID 1 | KeyID 2 | KeyID 4 | KeyID 8

   Number of Items                   - 0x0002
     Item #1:
       Key Download Data Item Type   - 0x00 (GTPK)
       Key Download Data Item Length - 0xLLLL
         Key Type                    - 0x03 (3DES`CBC64`192)
         Key ID                      - KEY1
         Key Handle                  - 0xHHHHHHH0
         Key Creation Date           - YYYYMMDDHHMMSSZ
         Key Expiration Date         - YYYYMMDDHHMMSSZ
         Key Data                    - variable, based on key definition
     Item #2:
       Key Download Data Item Type   - 0x01 (Rekey - LKH)
       Key Download Data Item Length - 0xLLLL
       Rekey Version Number          - 0x01
       Member ID                     - 0x00000001



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       Number of KEK Keys            - 0x0003
         KEK #1:
           Key Type                  - 0x03 (3DES`CBC64`192)
           Key ID                    - 0x00000002
           Key Handle                - 0xHHHHHHH2
           Key Creation Date         - YYYYMMDDHHMMSSZ
           Key Expiration Date       - YYYYMMDDHHMMSSZ
           Key Data                  - variable, based on key definition
         KEK #2:
           Key Type                  - 0x03 (3DES`CBC64`192)
           Key ID                    - 0x00000004
           Key Handle                - 0xHHHHHHH4
           Key Creation Date         - YYYYMMDDHHMMSSZ
           Key Expiration Date       - YYYYMMDDHHMMSSZ
           Key Data                  - variable, based on key definition
         KEK #3:
           Key Type                  - 0x03 (3DES`CBC64`192)
           Key ID                    - 0x00000008
           Key Handle                - 0xHHHHHHH8
           Key Creation Date         - YYYYMMDDHHMMSSZ
           Key Expiration Date       - YYYYMMDDHHMMSSZ
           Key Data                  - variable, based on key definition

A.3.2.  LKH Rekey Event Example

   This section will give an example of the data for the Rekey Event
   payload.  The GM with MemberID 6 will be keyed out of the group.  The
   data shown will be subsequent to the Generic Payload Header.

   | Rekey Event Type | GroupID | Date/Time | Rekey Type |
   Algorithm Ver | # of Packets |
   { (GTPK)2, (GTPK, 3', 6')12, (GTPK, 3')7 }

   This data shows that three packets are being transmitted.  Read each
   packet as:

   a) GTPK wrapped in LKH KeyID 2
   b) GTPK, LKH KeyIDs 3' & 6', all wrapped in LKH KeyID 12
   c) GTPK and LKH KeyID 3', all wrapped in LKH KeyID 7

   NOTE: Although in this example multiple keys are encrypted under one
   key, alternative pairings are legal (e.g., (GTPK)2, (GTPK)3', (3')6',
   (3')7', (6')12).

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






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   Rekey Event Type  - 0x01 (GSAKMP`LKH)
   GroupID           - 0xAABBCCDD
                       0x12345678
   Time/Date Stamp   - YYYYMMDDHHMMSSZ
   Rekey Event Type  - 0x01 (GSAKMP`LKH)
   Algorithm Vers    - 0x01
   # of RkyEvt Pkts  - 0x0003
   For Packet (b):
   Packet Length       - 0xLLLL
   Wrapping KeyID      - 0x000C
   Wrapping Key Handle - 0xHHHHHHHD
   # of Key Packages   - 0x0003
     Key Package 1:
       Key Pkg Type  - 0x00 (GTPK)
       Pack Length   - 0xLLLL
         Key Type            - 0x03 (3DES`CBC64`192)
         Key ID              - KEY1
         Key Handle          - 0xHHHHHHH0
         Key Creation Date   - YYYYMMDDHHMMSSZ
         Key Expiration Date - YYYYMMDDHHMMSSZ
         Key Data            - variable, based on key definition
     Key Package 2:
       Key Pkg Type  - 0x01 (Rekey  - LKH)
       Pack Length   - 0xLLLL
         Key Type            - 0x03 (3DES`CBC64`192)
         Key ID              - 0x00000003
         Key Handle          - 0xHHHHHHH3
         Key Creation Date   - YYYYMMDDHHMMSSZ
         Key Expiration Date - YYYYMMDDHHMMSSZ
         Key Data            - variable, based on key definition
     Key Package 3:
       Key Pkg Type  - 0x01 (Rekey  - LKH)
       Pack Length   - 0xLLLL
         Key Type            - 0x03 (3DES`CBC64`192)
         Key ID              - 0x00000006
         Key Handle          - 0xHHHHHHH6
         Key Creation Date   - YYYYMMDDHHMMSSZ
         Key Expiration Date - YYYYMMDDHHMMSSZ
         Key Data            - variable, based on key definition












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Authors' Addresses

   Hugh Harney (point-of-contact)
   SPARTA, Inc.
   7110 Samuel Morse Drive
   Columbia, MD 21046

   Phone: (443) 430-8032
   Fax:   (443) 430-8181
   EMail: hh@sparta.com


   Uri Meth
   SPARTA, Inc.
   7110 Samuel Morse Drive
   Columbia, MD 21046

   Phone: (443) 430-8058
   Fax:   (443) 430-8207
   EMail: umeth@sparta.com


   Andrea Colegrove
   SPARTA, Inc.
   7110 Samuel Morse Drive
   Columbia, MD 21046

   Phone: (443) 430-8014
   Fax:   (443) 430-8163
   EMail: acc@sparta.com


   George Gross
   IdentAware Security
   82 Old Mountain Road
   Lebanon, NJ 08833

   Phone: (908) 268-1629
   EMail: gmgross@identaware.com












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Full Copyright Statement

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