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rfc:rfc4535

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.

Harney, et al. Standards Track [Page 1] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 2] RFC 4535 GSAKMP June 2006

    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

Harney, et al. Standards Track [Page 3] RFC 4535 GSAKMP June 2006

         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

Harney, et al. Standards Track [Page 4] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 5] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 6] RFC 4535 GSAKMP June 2006

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).

Harney, et al. Standards Track [Page 7] RFC 4535 GSAKMP June 2006

 The security features of the establishment protocol for the GSA
 include
  1. Group policy identification
  1. Group policy dissemination
  1. GM to GC/KS SA establishment to protect data
  1. 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.

Harney, et al. Standards Track [Page 8] 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:
  1. Authenticate and validate the identities and the authorizations

of entities performing security-relevant actions

  1. Accept group keys from the GC/KS
  1. Request group keys from the GC/KS

Harney, et al. Standards Track [Page 9] RFC 4535 GSAKMP June 2006

  1. Enforce the cooperative group policies as stated in the group

policy token

  1. Perform peer review of key management actions
  1. 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:

Harney, et al. Standards Track [Page 10] RFC 4535 GSAKMP June 2006

  1. GSAKMP protocol version
  1. Key creation method
  1. Key dissemination policy
  1. Access control policy
  1. Group authorization policy
  1. Compromise recovery policy
  1. 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.

Harney, et al. Standards Track [Page 11] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 12] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 13] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 14] RFC 4535 GSAKMP June 2006

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:
  1. Group Owner (GO),
  1. Group Controller Key Server (GC/KS),
  1. Subordinate GC/KS (S-GC/KS), and
  1. 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.

Harney, et al. Standards Track [Page 15] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 16] RFC 4535 GSAKMP June 2006

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:
  1. 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.
  1. 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

Harney, et al. Standards Track [Page 17] RFC 4535 GSAKMP June 2006

    protection cannot be supported by this configuration.  GSAKMP
    implementations MUST support this group configuration.
  1. 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:
  1. the GCKS is never compromised,
  1. the GO is never compromised,
  1. the PKI, subject to certificate validation, is trustworthy,
  1. The GO is capable of creating a security policy to meet the

demands of the group,

  1. the compromises of a group member will be detectable and reported

to the GO in a trusted manner,

  1. the subsequent recovery from a compromise will deny inappropriate

access to protected data to the compromised member,

  1. no security-relevant actions depend on a precise network time,
  1. 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.

Harney, et al. Standards Track [Page 18] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 19] RFC 4535 GSAKMP June 2006

 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:
  1. Announcements
  1. Anycast
  1. 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

Harney, et al. Standards Track [Page 20] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 21] RFC 4535 GSAKMP June 2006

 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.
  1. The registration SA requires that GM can connect to the GC/KS or

S-GC/KS using either TCP or UDP.

  1. 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.
  1. 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.

Harney, et al. Standards Track [Page 22] RFC 4535 GSAKMP June 2006

 The PT consists of the following information:
  1. Identification: This allows an unambiguous identification of the

PT and the group.

  1. Access Control Rules: These rules specify who can have access to

the group keys.

  1. Authorization Rules: These rules specify who can be a S-GC/KS.
  1. 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.
  1. 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.

Harney, et al. Standards Track [Page 23] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 24] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 25] RFC 4535 GSAKMP June 2006

 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).

Harney, et al. Standards Track [Page 26] RFC 4535 GSAKMP June 2006

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:
  1. Determine Access Policy: identify the entities that are authorized

to receive the group key.

  1. Determine Authorization Policy: identify which entities are

authorized to perform security-relevant actions, including key

    dissemination, policy creation, and initiation of security-
    management actions.
  1. Determine Mechanisms: define the algorithms and protocols used by

GSAKMP to secure the group.

  1. 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.

Harney, et al. Standards Track [Page 27] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 28] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 29] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 30] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 31] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 32] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 33] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 34] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 35] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 36] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 37] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 38] RFC 4535 GSAKMP June 2006

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
  1. the ID payload identifies that GM
  1. the timestamp in the message is fresh
  1. the message is signed by an authorized (S-)GC/KS
  1. 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.

Harney, et al. Standards Track [Page 39] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 40] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 41] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 42] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 43] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 44] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 45] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 46] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 47] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 48] RFC 4535 GSAKMP June 2006

                         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

Harney, et al. Standards Track [Page 49] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 50] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 51] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 52] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 53] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 54] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 55] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 56] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 57] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 58] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 59] RFC 4535 GSAKMP June 2006

               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).

Harney, et al. Standards Track [Page 60] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 61] RFC 4535 GSAKMP June 2006

                  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.

Harney, et al. Standards Track [Page 62] RFC 4535 GSAKMP June 2006

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:

Harney, et al. Standards Track [Page 63] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 64] RFC 4535 GSAKMP June 2006

  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).

Harney, et al. Standards Track [Page 65] RFC 4535 GSAKMP June 2006

                     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

Harney, et al. Standards Track [Page 66] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 67] RFC 4535 GSAKMP June 2006

  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

Harney, et al. Standards Track [Page 68] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 69] RFC 4535 GSAKMP June 2006

     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.

Harney, et al. Standards Track [Page 70] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 71] RFC 4535 GSAKMP June 2006

  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.

Harney, et al. Standards Track [Page 72] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 73] RFC 4535 GSAKMP June 2006

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".

Harney, et al. Standards Track [Page 74] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 75] RFC 4535 GSAKMP June 2006

 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).

Harney, et al. Standards Track [Page 76] RFC 4535 GSAKMP June 2006

                 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

Harney, et al. Standards Track [Page 77] RFC 4535 GSAKMP June 2006

     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.

Harney, et al. Standards Track [Page 78] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 79] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 80] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 81] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 82] RFC 4535 GSAKMP June 2006

    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.

Harney, et al. Standards Track [Page 83] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 84] RFC 4535 GSAKMP June 2006

                     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.

Harney, et al. Standards Track [Page 85] RFC 4535 GSAKMP June 2006

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:

Harney, et al. Standards Track [Page 86] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 87] RFC 4535 GSAKMP June 2006

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).

Harney, et al. Standards Track [Page 88] RFC 4535 GSAKMP June 2006

             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.

Harney, et al. Standards Track [Page 89] RFC 4535 GSAKMP June 2006

 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.

Harney, et al. Standards Track [Page 90] RFC 4535 GSAKMP June 2006

                        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.

Harney, et al. Standards Track [Page 91] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 92] RFC 4535 GSAKMP June 2006

                      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.
______________________________________________________________________

Harney, et al. Standards Track [Page 93] RFC 4535 GSAKMP June 2006

                 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
              :
____________________________________________________________________

Harney, et al. Standards Track [Page 94] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 95] RFC 4535 GSAKMP June 2006

 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".

Harney, et al. Standards Track [Page 96] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 97] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 98] RFC 4535 GSAKMP June 2006

 [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.

Harney, et al. Standards Track [Page 99] RFC 4535 GSAKMP June 2006

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.

Harney, et al. Standards Track [Page 100] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 101] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 102] RFC 4535 GSAKMP June 2006

     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).

Harney, et al. Standards Track [Page 103] RFC 4535 GSAKMP June 2006

 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

Harney, et al. Standards Track [Page 104] RFC 4535 GSAKMP June 2006

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

Harney, et al. Standards Track [Page 105] RFC 4535 GSAKMP June 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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Harney, et al. Standards Track [Page 106]

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