[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-weis-gdoi-update) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 6407

MSEC Working Group                                               B. Weis
Internet-Draft                                                 S. Rowles
Intended status: Standards Track                           Cisco Systems
Expires: January 13, 2011                                    T. Hardjono
                                                                     MIT
                                                           July 12, 2010


                   The Group Domain of Interpretation
                     draft-ietf-msec-gdoi-update-06

Abstract

   This document describes an updated version of the Group Domain of
   Interpretation (GDOI) protocol specified in RFC 3547.  The GDOI
   provides group key management to support secure group communications
   according to the architecture specified in RFC 4046.  The GDOI
   manages group security associations, which are used by IPsec and
   potentially other data security protocols.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 13, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



Weis, et al.            Expires January 13, 2011                [Page 1]

Internet-Draft                    GDOI                         July 2010


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements notation  . . . . . . . . . . . . . . . . . .  5
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  6
     1.3.  GDOI Applications  . . . . . . . . . . . . . . . . . . . .  6
     1.4.  Extending GDOI . . . . . . . . . . . . . . . . . . . . . .  6
     1.5.  Forward and Backward Access Control  . . . . . . . . . . .  7

   2.  GDOI Phase 1 protocol  . . . . . . . . . . . . . . . . . . . .  9
     2.1.  ISAKMP Phase 1 protocol  . . . . . . . . . . . . . . . . .  9

   3.  GROUPKEY-PULL Exchange . . . . . . . . . . . . . . . . . . . . 10
     3.1.  Authorization  . . . . . . . . . . . . . . . . . . . . . . 10
     3.2.  Messages . . . . . . . . . . . . . . . . . . . . . . . . . 10
     3.3.  Initiator Operations . . . . . . . . . . . . . . . . . . . 12
     3.4.  Receiver Operations  . . . . . . . . . . . . . . . . . . . 13

   4.  GROUPKEY-PUSH Message  . . . . . . . . . . . . . . . . . . . . 15
     4.1.  Use of signature keys  . . . . . . . . . . . . . . . . . . 16
     4.2.  ISAKMP Header Initialization . . . . . . . . . . . . . . . 16
     4.3.  Deletion of SAs  . . . . . . . . . . . . . . . . . . . . . 16
     4.4.  GCKS Operations  . . . . . . . . . . . . . . . . . . . . . 17
     4.5.  Group Member Operations  . . . . . . . . . . . . . . . . . 18

   5.  Payloads and Defined Values  . . . . . . . . . . . . . . . . . 19
     5.1.  Identification Payload . . . . . . . . . . . . . . . . . . 19
     5.2.  Security Association Payload . . . . . . . . . . . . . . . 19
     5.3.  SA KEK payload . . . . . . . . . . . . . . . . . . . . . . 21
     5.4.  Group Associated Policy  . . . . . . . . . . . . . . . . . 27
     5.5.  SA TEK Payload . . . . . . . . . . . . . . . . . . . . . . 30



Weis, et al.            Expires January 13, 2011                [Page 2]

Internet-Draft                    GDOI                         July 2010


     5.6.  Key Download Payload . . . . . . . . . . . . . . . . . . . 34
     5.7.  Sequence Number Payload  . . . . . . . . . . . . . . . . . 42
     5.8.  Nonce  . . . . . . . . . . . . . . . . . . . . . . . . . . 43

   6.  Algorithm Selection  . . . . . . . . . . . . . . . . . . . . . 44
     6.1.  KEK  . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
     6.2.  TEK  . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 46
     7.1.  ISAKMP Phase 1 . . . . . . . . . . . . . . . . . . . . . . 46
     7.2.  GROUPKEY-PULL Exchange . . . . . . . . . . . . . . . . . . 47
     7.3.  GROUPKEY-PUSH Exchange . . . . . . . . . . . . . . . . . . 49

   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 51
     8.1.  Additions to current registries  . . . . . . . . . . . . . 51
     8.2.  New registries . . . . . . . . . . . . . . . . . . . . . . 51

   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 53

   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 54
     10.2. Informative References . . . . . . . . . . . . . . . . . . 54

   Appendix A.  Alternate GDOI Phase 1 protocols  . . . . . . . . . . 58
     A.1.  IKEv2 Exchange . . . . . . . . . . . . . . . . . . . . . . 58
     A.2.  KINK Protocol  . . . . . . . . . . . . . . . . . . . . . . 58

   Appendix B.  Significant Changes from RFC 3547 . . . . . . . . . . 59

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 60





















Weis, et al.            Expires January 13, 2011                [Page 3]

Internet-Draft                    GDOI                         July 2010


1.  Introduction

   Secure group and multicast applications require a method by which
   each group member shares common security policy and keying material.
   This document describes the Group Domain of Interpretation (GDOI),
   which is an ISAMKP [RFC2408] Domain of Interpretation (DOI), a group
   key management system.  The GDOI distributes security associations
   (SAs) for IPsec AH and ESP protocols and potentially other data
   security protocols used in group applications.  The GDOI uses the
   group key management model defined in [RFC4046], and described more
   generally by the The Multicast Group Security Architecture [RFC3740].

   In this group key management model, the GDOI protocol participants
   are a "group controller/key server" (GCKS) and a group member (GM).
   A group member contacts ("registers with") a GCKS to join the group.
   During the registration mutual authentication and authorization are
   achieved, after which the GCKS distributes current group policy and
   keying material to the group member over an authenticated and
   encrypted session.  The GCKS may also initiate contact ("rekeys")
   group members to provide updates to group policy.

   ISAKMP defines two "phases" of negotiation (p.16 of [RFC2408]).  A
   Phase 1 security association provides mutual authentication and
   authorization, and a security association that is used by the
   protocol participants to execute a phase 2 exchange.  This document
   incorporates (i.e., uses but does not re-define) the Phase 1 security
   association definition from the Internet DOI [RFC2407], [RFC2409].
   Phase 1 security association types other than ISAKMP are possible,
   and are noted in Appendix A.  Requirements of those phase 1 security
   associations are specified in Section 2.  The GDOI includes two new
   phase 2 ISAKMP exchanges (protocols), as well as necessary new
   payload definitions to the ISAKMP standard (p. 14 of [RFC2408]).
   These two new protocols are:

   1.  The GROUPKEY-PULL registration protocol exchange.  This exchange
       uses "pull" behavior since the member initiates the retrieval of
       these SAs from a GCKS.  It is protected by an ISAKMP phase 1
       protocol, as described above.  At the culmination of a GROUPKEY-
       PULL exchange, an authorized group member has received and
       installed a set of SAs that represent group policy, and it is
       ready to participate in secure group communications.

   2.  The GROUPKEY-PUSH rekey protocol exchange.  The rekey protocol is
       a datagram initiated ("pushed") by the GCKS, usually delivered to
       group members using a IP multicast address.  It is treated as a
       ISAKMP phase 2 protocol, where the "phase 1" cryptographic policy
       and keying material is included in the group policy distributed
       by the GCKS in the GROUPKEY-PULL exchange.  At the culmination of



Weis, et al.            Expires January 13, 2011                [Page 4]

Internet-Draft                    GDOI                         July 2010


       a GROUPKEY-PUSH exchange, all authorized group members have
       received and installed updates to group policy, and can continue
       to participate in secure group communications.  If a group
       management method is included in group policy (as described in
       Section 1.5.1), at the conclusion of the GROUPKEY-PUSH exchange
       some members of the group may have been de-authorized and no
       longer able to participate in the secure group communications.

      +--------------------------------------------------------------+
      |                                                              |
      |                    +--------------------+                    |
      |            +------>|     GDOI GCKS      |<------+            |
      |            |       +--------------------+       |            |
      |            |                 |                  |            |
      |       GROUPKEY-PULL          |             GROUPKEY-PULL     |
      |         PROTOCOL             |               PROTOCOL        |
      |            |                 |                  |            |
      |            v           GROUPKEY-PUSH            v            |
      |   +-----------------+     PROTOCOL     +-----------------+   |
      |   |                 |        |         |                 |   |
      |   |    GDOI GM(s)   |<-------+-------->|    GDOI GM(S)   |   |
      |   |                 |                  |                 |   |
      |   +-----------------+                  +-----------------+   |
      |            |                                    ^            |
      |            v                                    |            |
      |            +-Data Security Protocol (e.g., ESP)-+            |
      |                                                              |
      +--------------------------------------------------------------+

   Although the GROUPKEY-PUSH specified by this document can be used to
   refresh a Re-key SA, the most common use of GROUPKEY-PUSH is to
   establish a Data-security SA for a data security protocol.  In
   summary, GDOI is a group security association management protocol:
   All GDOI messages are used to create, maintain, or delete security
   associations for a group.  As described above, these security
   associations protect one or more key-encrypting keys, traffic-
   encrypting keys, or data shared by group members for multicast and
   groups security applications.

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].







Weis, et al.            Expires January 13, 2011                [Page 5]

Internet-Draft                    GDOI                         July 2010


1.2.  Terminology

   The following key terms are used throughout this document.

   Key Encrypting Key (KEK).  The symmetric cipher key used to protect
      the GROUPKEY-PUSH message.

   Logical Key Hierarchy (LKH).  A group management method defined in
      Section 5.4 of [RFC2627].

   Traffic Encryption Key (TEK).  The symmetric cipher key used to
      protect a data security protocol (e.g., IPsec ESP).

1.3.  GDOI Applications

   Secure multicast applications include video broadcast and multicast
   file transfer.  GDOI can also secure group applications that do not
   use multicast transport such as video-on-demand where the same
   encrypted content is delivered to each group member.

   A GDOI application may require Data-security SAs (such as IPsec ESP
   SAs), and/or a Rekey-SA (the SA used to protect GROUPKEY-PUSH
   messages).  For example, a secure multicast video broadcast may only
   need to distribute a single set of Data-Security SAs to protect the
   time-bounded broadcast.  In this case, no Rekey-SA may be necessary
   because the initial Data-security SAs will not be cryptographically
   overused, and there is no desire to de-authorize group members.

   In contrast, an always-on IP multicast application (e.g., stock-
   ticker delivery service) with many group members may require a policy
   of frequent change of Data-security SAs and regular de-authorization
   of group members.  In this case, the GCKS policy will regularly
   replace Data-security SAs with new SAs defining the same traffic
   selectors but new keying material.  This will result in a regularly-
   scheduled GROUPKEY-PUSH delivering the new SAs.  Additionally, the
   group membership on the GCKS may be frequently adjusted, which will
   result in GROUPKEY-PUSH exchange delivering a new Rekey SAs protected
   by a group management method.  Each GROUPKEY-PUSH may include Data-
   security SAs and/or a Rekey SA.  In all cases, the relevant policy is
   defined on the GCKS and relayed to group members.  Specific policy
   choices possible by the GCKS depends on each application and further
   discussion of policy is beyond the scope of this memo.

1.4.  Extending GDOI

   Not all secure multicast or multimedia applications can use IPsec ESP
   or AH.  Many Real Time Transport Protocol applications, for example,
   require security above the IP layer to preserve RTP header



Weis, et al.            Expires January 13, 2011                [Page 6]

Internet-Draft                    GDOI                         July 2010


   compression efficiencies and transport-independence [RFC3550].  A
   future RTP security protocol may benefit from using GDOI to establish
   group SAs.  Alternatively, GDOI can distribute message authentication
   code (MAC) policy and keys for legacy applications that have defined
   their own security associations [I-D.weis-gdoi-mac-tek].

   In order to add a new data security protocol, a new RFC MUST specify
   the data-security SA parameters conveyed by GDOI for that security
   protocol; these parameters are listed in Section 5.5.2 of this
   document.

   Data security protocol SAs MUST protect group traffic.  GDOI provides
   no restriction on whether that group traffic is transmitted as
   unicast or multicast packets.

1.5.  Forward and Backward Access Control

   Through GROUPKEY-PUSH, the GDOI supports group management methods
   such as LKH (section 5.4 of [RFC2627]) that have the property of
   denying access to a new group key by a member removed from the group
   (forward access control) and to an old group key by a member added to
   the group (backward access control).  An unrelated notion to PFS,
   "forward access control" and "backward access control" have been
   called "perfect forward security" and "perfect backward security" in
   the literature [RFC2627].

   Group management algorithms providing forward and backward access
   control other than LKH have been proposed in the literature,
   including OFT [OFT] and Subset Difference [NNL].  These algorithms
   could be used with GDOI, but are not specified as a part of this
   document.

1.5.1.  Forward Access Control Requirements

   When group membership is altered using a group management algorithm
   new Data-security SAs are usually also needed.  New SAs ensure that
   members who were denied access can no longer participate in the
   group.

   If forward access control is a desired property of the group, new
   Data-security SAs MUST NOT be included in a GROUPKEY-PUSH message
   which changes group membership.  This is required because the new
   Data-security SAs are not protected with the new KEK.  Instead, two
   sequential GROUPKEY-PUSH messages must be sent by the GCKS; the first
   changing the KEK, and the second (protected with the new KEK)
   distributing the new Data-security SAs.

   Note that in the above sequence, although the new KEK can effectively



Weis, et al.            Expires January 13, 2011                [Page 7]

Internet-Draft                    GDOI                         July 2010


   deny access to the group to some group members they will be able to
   view the new KEK policy.  If forward access control policy for the
   group includes keeping the KEK policy secret as well as the KEK
   itself secret, then two GROUPKEY-PUSH messages changing the KEK must
   occur before the new Data-security SAs are transmitted.

   If other methods of using LKH or other group management algorithms
   are added to GDOI, those methods MAY remove the above restrictions
   requiring multiple GROUPKEY-PUSH messages, providing those methods
   specify how forward access control policy is maintained within a
   single GROUPKEY-PUSH message.








































Weis, et al.            Expires January 13, 2011                [Page 8]

Internet-Draft                    GDOI                         July 2010


2.  GDOI Phase 1 protocol

   The GDOI GROUPKEY-PULL exchange is a "phase 2" protocol which MUST be
   protected by a "phase 1" protocol.  The "phase 1" protocol can be any
   protocol which provides for the following protections:

   o  Peer Authentication

   o  Confidentiality

   o  Message Integrity

   The following sections describe one such "phase 1" protocol.  Other
   protocols which may be potential "phase 1" protocols are described in
   Appendix A.  However, the use of the protocols listed there are not
   considered part of this document.

2.1.  ISAKMP Phase 1 protocol

   This document defines how the ISAKMP phase 1 exchanges as defined in
   [RFC2409] can be used a "phase 1" protocol for GDOI.  The following
   sections define characteristics of the ISAKMP phase 1 protocols that
   are unique for these exchanges when used for GDOI.

   Section 7.1 describes how the ISAKMP Phase 1 protocols meet the
   requirements of a GDOI "phase 1" protocol.

2.1.1.  DOI value

   The Phase 1 SA payload has a DOI value.  That value MUST be the GDOI
   DOI value as defined later in this document.

2.1.2.  UDP port

   IANA has assigned port 848 for the use of GDOI, which allows for an
   implementation to use separate ISAKMP implementations to service GDOI
   and IKEv1 [RFC2409].  A GCKS SHOULD listen on this port for GROUPKEY-
   PULL exchanges, and the GCKS MAY use this port to distribute
   GROUPKEY-PUSH messages.  An ISAKMP phase 1 exchange implementation
   supporting NAT Traversal [RFC3947] may move to port 4500 to process
   the GROUPKEY-PULL exchange.










Weis, et al.            Expires January 13, 2011                [Page 9]

Internet-Draft                    GDOI                         July 2010


3.  GROUPKEY-PULL Exchange

   The goal of the GROUPKEY-PULL exchange is to establish a Re-key
   and/or Data-security SAs at the member for a particular group.  A
   Phase 1 SA protects the GROUPKEY-PULL; there MAY be multiple
   GROUPKEY-PULL exchanges for a given Phase 1 SA.  The GROUPKEY-PULL
   exchange downloads the data security keys (TEKs) and/or group key
   encrypting key (KEK) or KEK array under the protection of the Phase 1
   SA.

3.1.  Authorization

   The Phase 1 identity SHOULD be used by a GCKS to authorize the Phase
   2 (GROUPKEY-PULL) request for a group key.  Similarly, a group member
   SHOULD ensure that the Phase 1 identity of the GCKS is an authorized
   GCKS.  When no authorization is performed, it is possible for a rogue
   GDOI participant to perpetrate a man-in-the-middle attack between a
   group member and a GCKS [MP04].

3.2.  Messages

   The GROUPKEY-PULL is a Phase 2 exchange.  Phase 1 computes SKEYID_a
   which is the "key" in the keyed hash used in the GROUPKEY-PULL HASH
   payloads.  When using the Phase 1 defined in this document, SKEYID_a
   is derived according to [RFC2409].  As with the IKEv1 HASH payload
   generation (Section 5.5 of [RFC2409], each GROUPKEY-PULL message
   hashes a uniquely defined set of values.  Nonces permute the HASH and
   provide some protection against replay attacks.  Replay protection is
   important to protect the GCKS from attacks that a key management
   server will attract.

   The GROUPKEY-PULL uses nonces to guarantee "liveness", or against
   replay of a recent GROUPKEY-PULL message.  The replay attack is only
   useful in the context of the current Phase 1.  If a GROUPKEY-PULL
   message is replayed based on a previous Phase 1, the HASH calculation
   will fail due to a wrong SKEYID_a.  The message will fail processing
   before the nonce is ever evaluated.  In order for either peer to get
   the benefit of the replay protection, it must postpone as much
   processing as possible until it receives the message in the protocol
   that proves the peer is live.  For example, the Responder MUST NOT
   adjust its internal state (e.g., keeping a record of the Initiator)
   until it receives a message with Nr included properly in the HASH
   payload.

   Nonces require an additional message in the protocol exchange to
   ensure that the GCKS does not add a group member until it proves
   liveliness.  The GROUPKEY-PULL member-initiator expects to find its
   nonce, Ni, in the HASH of a returned message.  And the GROUPKEY-PULL



Weis, et al.            Expires January 13, 2011               [Page 10]

Internet-Draft                    GDOI                         July 2010


   GCKS responder expects to see its nonce, Nr, in the HASH of a
   returned message before providing group-keying material as in the
   following exchange.


              Initiator (Member)                   Responder (GCKS)
              ------------------                   ----------------
              HDR*, HASH(1), Ni, ID     -->
                                        <--     HDR*, HASH(2), Nr, SA
              HDR*, HASH(3)             -->
                                        <--     HDR*, HASH(4), [SEQ,] KD

   Hashes are computed as follows:


        HASH(1) = prf(SKEYID_a, M-ID | Ni | ID)
        HASH(2) = prf(SKEYID_a, M-ID | Ni_b | Nr | SA)
        HASH(3) = prf(SKEYID_a, M-ID | Ni_b | Nr_b
        HASH(4) = prf(SKEYID_a, M-ID | Ni_b | Nr_b [ | SEQ | ] KD)

      * Protected by the Phase 1 SA, encryption occurs after HDR

   HDR is an ISAKMP header payload that uses the Phase 1 cookies and a
   message identifier (M-ID) as in IKEv1.  Note that nonces are included
   in the first two messages, with the GCKS returning only the SA policy
   payload before liveliness is proven.  The HASH payloads [RFC2409]
   prove that the peer has the Phase 1 secret (SKEYID_a) and the nonce
   for the exchange identified by message id, M-ID.  Once liveliness is
   established, the last message completes the real processing of
   downloading the KD payload.

   In addition to the Nonce and HASH payloads, the member-initiator
   identifies the group it wishes to join through the ISAKMP ID payload.
   The GCKS responder informs the member of the current value of the
   sequence number in the SEQ payload; the sequence number provides
   anti-replay state associated with a KEK.  The SEQ payload has no
   other use, and is omitted from the GROUPKEY_PULL exchange when a KEK
   attribute is not included in the SA payload.

   When a SEQ payload is included in the GROUPKEY-PULL exchange, it
   includes the most recently used sequence number for the group.  At
   the conclusion of a GROUPKEY-PULL exchange, the initiating group
   member MUST NOT accept any rekey message with both the KEK attribute
   SPI value and a sequence number less than or equal to the one
   received during the GROUPKEY-PULL.  When the first group member
   initiates a GROUPKEY-PULL exchange, the GCKS provides a Sequence
   Number of zero, since no GROUPKEY-PUSH messages have yet been sent.
   Note the sequence number increments only with GROUPKEY-PUSH messages.



Weis, et al.            Expires January 13, 2011               [Page 11]

Internet-Draft                    GDOI                         July 2010


   The GROUPKEY-PULL exchange distributes the current sequence number to
   the group member.

   The sequence number resets to a value of one with the usage of a new
   KEK attribute.  Thus the first packet sent for a given Rekey SA will
   have a Sequence Number of 1.  The sequence number increments with
   each successive rekey.

   The GCKS responder informs the member of the cryptographic policies
   of the group in the SA payload, which describes the DOI, KEK and/or
   TEK keying material, and authentication transforms.  The SPIs are
   also determined by the GCKS and downloaded in the SA payload chain
   (see Section 5.2).  The SA KEK attribute contains the ISAKMP cookie
   pair for the Re-key SA, which is not negotiated but downloaded.  The
   SA TEK attribute contains a SPI as defined in Section 5.5 of this
   document.  The second message downloads this SA payload.  If a Re-key
   SA is defined in the SA payload, then KD will contain the KEK; if one
   or more Data-security SAs are defined in the SA payload, KD will
   contain the TEKs.  This is useful if there is an initial set of TEKs
   for the particular group and can obviate the need for future TEK
   GROUPKEY-PUSH messages (described in section 4).

3.2.1.  ISAKMP Header Initialization

   Cookies are used in the ISAKMP header to identify a particular GDOI
   session.  The GDOI GROUPKEY-PULL exchange uses cookies according to
   ISAKMP [RFC2408].

   Next Payload identifies an ISAKMP or GDOI payload (see Section 5.0).

   Major Version is 1 and Minor Version is 0 according to ISAKMP
   (Section 3.1 of [RFC2408]).

   The Exchange Type has value 32 for the GDOI GROUPKEY-PULL exchange.

   Flags, Message ID, and Length are according to ISAKMP (Section 3.1 of
   [RFC2408]).

3.3.  Initiator Operations

   Before a group member (GDOI initiator) contacts the GCKS, it must
   determine the group identifier and acceptable Phase 1 policy via an
   out-of-band method.  Phase 1 is initiated using the GDOI DOI in the
   SA payload.  Once Phase 1 is complete, the initiator state machine
   moves to the GDOI protocol.

   To construct the first GDOI message the initiator chooses Ni and
   creates a nonce payload, builds an identity payload including the



Weis, et al.            Expires January 13, 2011               [Page 12]

Internet-Draft                    GDOI                         July 2010


   group identifier, and generates HASH(1).

   Upon receipt of the second GDOI message, the initiator validates
   HASH(2), extracts the nonce Nr, and interprets the SA payload.  The
   SA payload contains policy describing the security protocol and
   cryptographic protocols used by the group.  This policy describes the
   Re-key SA (if present), Data-security SAs, and other group policy.
   If the policy in the SA payload is acceptable to the initiator, it
   continues the protocol.

   The initiator constructs the third GDOI message by creating HASH(3).

   Upon receipt of the fourth GDOI message, the initiator validates
   HASH(4).

   If SEQ payload is present, the sequence number in the SEQ payload
   must be checked against any previously received sequence number for
   this group.  If it is less than the previously received number, it
   should be considered stale and ignored.  This could happen if two
   GROUPKEY-PULL messages happened in parallel, and the sequence number
   changed between the times the results of two GROUPKEY-PULL messages
   were returned from the GCKS.

   The initiator interprets the KD key packets, where each key packet
   includes the keying material for SAs distributed in the SA payload.
   Keying material is matched by comparing the SPIs in the key packets
   to SPIs previously sent in the SA payloads.  Once TEK keys and policy
   are matched, the initiator provides them to the data security
   subsystem, and it is ready to send or receive packets matching the
   TEK policy.  If this group has a KEK, the KEK policy and keys are
   marked as ready for use, and the initiator knows to expect the
   sequence number reset to 1 with the next Rekey SA, which will be
   encrypted with the new KEK attribute.  The initiator is now ready to
   receive GROUPKEY-PUSH messages.

   If the KD payload included an LKH array of keys, the initiator takes
   the last key in the array as the group KEK.  The array is then stored
   without further processing.

3.4.  Receiver Operations

   The GCKS (responder) passively listens for incoming requests from
   group members.  The Phase 1 authenticates the group member and sets
   up the secure session with them.

   Upon receipt of the first GDOI message the GCKS validates HASH(1),
   extracts the Ni and group identifier in the ID payload.  It verifies
   that its database contains the group information for the group



Weis, et al.            Expires January 13, 2011               [Page 13]

Internet-Draft                    GDOI                         July 2010


   identifier.

   The GCKS constructs the second GDOI message, including a nonce Nr,
   and the policy for the group in an SA payload, followed by SA GAP, SA
   KEK, and/or SA TEK payloads according to the GCKS policy.  (See
   Section 5.2.1 for details on how the GCKS chooses which payloads to
   send.)

   Upon receipt of the third GDOI message the GCKS validates HASH(3).

   The GCKS constructs the fourth GDOI message, including the SEQ
   payload (if the GCKS sends rekey messages), and the KD payload
   containing keys corresponding to policy previously sent in the SA TEK
   and SA KEK payloads.  If a group management algorithm is defined as
   part of group policy, the GCKS will first insert the group member
   into the group management structure (e.g., a leaf in the LKH tree),
   and then create an LKH array of keys and include it in the KD
   payload.  The first key in the array is associated with the group
   member leaf node, followed by each LKH node above it in the tree,
   culminating with the root node (which is also the KEK).































Weis, et al.            Expires January 13, 2011               [Page 14]

Internet-Draft                    GDOI                         July 2010


4.  GROUPKEY-PUSH Message

   GDOI sends control information securely using group communications.
   Typically this will be using IP multicast distribution of a GROUPKEY-
   PUSH message but it can also be "pushed" using unicast delivery if IP
   multicast is not possible.  The GROUPKEY-PUSH message replaces a Re-
   key SA KEK or KEK array, and/or creates a new Data-security SA.

              Member                               GCKS or Delegate
              ------                               ----------------
                              <---- HDR*, SEQ, [D,] SA, KD, SIG

      * Protected by the Re-key SA KEK; encryption occurs after HDR

   HDR is defined below.  The SEQ payload is defined in the Payloads
   section.  One or more D (Delete) payloads optionally specify the
   deletion of existing group policy.  The SA defines the policy (e.g.,
   protection suite) and attributes (e.g., SPI) for a replacement Re-key
   SA and/or Data-security SAs.  KD is the key download payload as
   described in the Payloads section.

   The SIG payload includes a signature of a hash of the entire
   GROUPKEY-PUSH message (excepting the SIG payload bytes) before it has
   been encrypted.  The HASH is taken over the string 'rekey', the
   GROUPKEY-PUSH HDR, followed by all payloads preceding the SIG
   payload.  The prefixed string ensures that the signature of the Rekey
   datagram cannot be used for any other purpose in the GDOI protocol.
   After the SIG payload is created using the signature of the above
   hash, with the receiver verifying the signature using a public key
   retrieved in policy received by a GROUPKEY-PULL exchange, or
   distributed in an earlier GROUPKEY-PUSH message.  The current KEK
   encryption key (previously distributed in a GROUPKEY-PULL exchange or
   GROUPKEY-PUSH message) encrypts all the payloads following the
   GROUPKEY-PUSH HDR.  Note: The rationale for this order of operations
   is given in Section 7.3.5.

   If the SA defines an LKH KEK array or single KEK, KD contains a KEK
   or KEK array for a new Re-key SA, which has a new cookie pair.  When
   the KD payload carries a new SA KEK attribute (section 5.3), a Re-key
   SA is replaced with a new SA having the same group identifier (ID
   specified in message 1 of section 3.2) and incrementing the same
   sequence counter, which is initialized in message 4 of section 3.2.
   Note the first packet for the given Rekey SA encrypted with the new
   KEK attribute will have a Sequence number of 1.  If the SA defines an
   SA TEK payload, this informs the member that a new Data-security SA
   has been created, with keying material carried in KD (Section 5.6).

   If the SA defines a large LKH KEK array (e.g., during group



Weis, et al.            Expires January 13, 2011               [Page 15]

Internet-Draft                    GDOI                         July 2010


   initialization and batched rekeying), parts of the array MAY be sent
   in different unique GROUPKEY-PUSH datagrams.  However, each of the
   GROUPKEY-PUSH datagrams MUST be a fully formed GROUPKEY-PUSH
   datagram.  This results in each datagram containing a sequence number
   and the policy in the SA payload, which corresponds to the KEK array
   portion sent in the KD payload.

4.1.  Use of signature keys

   In order to avoid overusing its authentication signature key, the
   GCKS SHOULD NOT use the same key to sign the SIG payload in the
   GROUPKEY-PUSH message as was used for authentication in the GROUPKEY-
   PULL exchange.

4.2.  ISAKMP Header Initialization

   Unlike ISAKMP or IKEv1, the cookie pair is completely determined by
   the GCKS.  The cookie pair in the GDOI ISAKMP header identifies the
   Re- key SA to differentiate the secure groups managed by a GCKS.
   Thus, GDOI uses the cookie fields as an SPI.

   Next Payload identifies an ISAKMP or GDOI payload (see Section 5.0).

   Major Version is 1 and Minor Version is 0 according to ISAKMP
   (Section 3.1 of [RFC2408]).

   The Exchange Type has value 33 for the GDOI GROUPKEY-PUSH message.

   Flags MUST have the Encryption bit set according to [RFC2008, Section
   3.1].  All other bits MUST be set to zero.

   Message ID MUST be set to zero.

   Length is according to ISAKMP (Section 3.1 of [RFC2408]).

4.3.  Deletion of SAs

   There are times the GCKS may want to signal to receivers to delete
   SAs, for example at the end of a broadcast.  Deletion of keys may be
   accomplished by sending an ISAKMP Delete payload (Section 3.15 of
   [RFC2408]) as part of a GDOI GROUPKEY-PUSH message.

   One or more Delete payloads MAY be placed following the SEQ payload
   in a GROUPKEY-PUSH message.  If a GCKS has no further SAs to send to
   group members, the SA and KD payloads MUST be omitted from the
   message.

   The following fields of the Delete Payload are further defined as



Weis, et al.            Expires January 13, 2011               [Page 16]

Internet-Draft                    GDOI                         July 2010


   follows:

   o The Domain of Interpretation field contains the GDOI DOI.

   o The Protocol-Id field contains TEK protocol id values defined in
   Section 5.5 of this document.  To delete a KEK SA, the value of zero
   MUST be used as the protocol id.  Note that only one protocol id
   value can be defined in a Delete payload.  If a TEK SA and a KEK SA
   must be deleted, they must be sent in different Delete payloads.

   There may be circumstances where the GCKS may want to start over with
   a clean slate.  If the administrator is no longer confident in the
   integrity of the group, the GCKS can signal deletion of all policy of
   a particular TEK protocol by sending a TEK with a SPI value equal to
   zero in the delete payload.  For example, if the GCKS wishes to
   remove all the KEKs and all the TEKs in the group, the GCKS SHOULD
   send a delete payload with a spi of zero and a protocol_id of a TEK
   protocol_id value, followed by another delete payload with a spi of
   zero and protocol_id of zero, indicating that the KEK SA should be
   deleted.

4.4.  GCKS Operations

   GCKS or its delegate may initiate a Rekey message for one of several
   reasons, e.g., the group membership has changed or keys are due to
   expire.

   To begin the rekey datagram the GCKS builds an ISAKMP HDR with the
   correct cookie pair, and a SEQ payload that includes a sequence
   number which is one greater than the previous rekey datagram.  If the
   message is using the new KEK attribute for the first time, the SEQ is
   reset to 1 in this message.

   An SA payload is then added.  This is identical in structure and
   meaning to a SA payload sent in a GROUPKEY-PULL exchange.  If there
   are changes to the KEK (including due to group members being
   excluded, in the case of LKH), an SA_KEK attribute is added to the
   SA.  If there are one or more new TEKs then SA_TEK attributes are
   added to describe that policy.

   A KD payload is then added.  This is identical in structure and
   meaning to a KD payload sent in a GROUPKEY-PULL exchange.  If an
   SA_KEK attribute was included in the SA payload then corresponding
   KEK keys (or a KEK update array) is included.  A KEK update array is
   created by first determining which group members have been excluded,
   and then generating new keys as necessary and distribute LKH update
   arrays sufficient to provide the new KEK to remaining group members
   (see Section 5.4.1 of [RFC2627] for details).  TEK keys are also sent



Weis, et al.            Expires January 13, 2011               [Page 17]

Internet-Draft                    GDOI                         July 2010


   for each SA_TEK attribute included in the SA payload.

   In the penultimate step, the initiator hashes the string "rekey"
   followed by the key management message already formed.  The hash is
   signed, placed in a SIG payload and added to the datagram.

   Lastly, the payloads following the HDR are encrypted using the
   current KEK encryption key.  The datagram can now be sent.

4.5.  Group Member Operations

   A group member receiving the GROUPKEY-PUSH datagram matches the
   cookie pair in the ISAKMP HDR to an existing SA.  The message is
   decrypted, and the form of the datagram is validated.  This weeds out
   obvious ill-formed messages (which may be sent as part of a Denial of
   Service attack on the group).

   The sequence number in the SEQ payload is validated to ensure that it
   is greater than the previously received sequence number, and that it
   fits within a window of acceptable values.  The SIG payload is then
   validated.  If the signature fails, the message is discarded.

   The SA and KD payloads are processed which results in a new GDOI
   Rekey SA (if the SA payload included an SA_KEK attribute) and/or new
   IPsec SAs being added to the system.  If the KD payload includes an
   LKH update array, the group member compares the LKH ID in each key
   update packet to the LKH IDs that it holds.  If it finds a match, it
   decrypts the key using the key prior to it in the key array and
   stores the new key in the LKH key array that it holds.  The final
   decryption yields the new group KEK.





















Weis, et al.            Expires January 13, 2011               [Page 18]

Internet-Draft                    GDOI                         July 2010


5.  Payloads and Defined Values

   This document specifies use of several ISAKMP payloads, which are
   defined in accordance with RFC 2408.  The following payloads are
   extended or further specified.


                  Next Payload Type            Value
                  -----------------            -----
                  Security Association (SA)      1
                  Identification (ID)            5
                  Nonce (N)                     10

   Several payload formats specific to the group security exchanges are
   required.


                  Next Payload Type                Value
                  -----------------                -----
                  SA KEK Payload (SAK)              15
                  SA TEK Payload (SAT)              16
                  Key Download (KD)                 17
                  Sequence Number (SEQ)             18
                  SA Group Associated Policy (GAP) TBD-1

5.1.  Identification Payload

   The Identification Payload is defined in RFC 2408.  For the GDOI, it
   is used to identify a group identity that will later be associated
   with Security Associations for the group.  A group identity may map
   to a specific IP multicast group, or may specify a more general
   identifier, such as one that represents a set of related multicast
   streams.

   When used with the GDOI, the DOI Specific ID Data field MUST be set
   to 0.

   When used with the GDOI, the ID_KEY_ID ID Type MUST be supported by a
   conforming implementation, and MUST specify a four (4)-octet group
   identifier as its value.  Implementations MAY also support other ID
   Types.

5.2.  Security Association Payload

   The Security Association payload is defined in RFC 2408.  For the
   GDOI, it is used by the GCKS to assert security attributes for both
   Re-key and Data-security SAs.




Weis, et al.            Expires January 13, 2011               [Page 19]

Internet-Draft                    GDOI                         July 2010


        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        !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       !                              DOI                              !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !                           Situation                           !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ! SA Attribute Next Payload     !          RESERVED2            !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   The Security Association Payload fields are defined as follows:

   o Next Payload (1 octet) -- Identifies the next payload for the
   GROUPKEY-PULL or the GROUPKEY-PUSH message as defined above.  The
   next payload MUST NOT be a SAK Payload or SAT Payload type, but the
   next non-Security Association type payload.

   o RESERVED (1 octet) -- Must be zero.

   o Payload Length (2 octets) -- Is the octet length of the current
   payload including the generic header and all TEK and KEK payloads.

   o DOI (4 octets) -- Is the GDOI, which is value 2.

   o Situation (4 octets) -- Must be zero.

   o SA Attribute Next Payload (1 octet) -- Must be either a SAK Payload
   or a SAT Payload.  See section 5.2.1 for a description of which
   circumstances are required for each payload type to be present.

   o RESERVED (2 octets) -- Must be zero.

5.2.1.  Payloads following the SA payload

   Payloads that define specific security association attributes for the
   KEK and/or TEKs used by the group MUST follow the SA payload.  How
   many of each payload is dependent upon the group policy.  There may
   be zero or one SAK Payloads, zero or more GAP Payloads, and zero or
   more SAT Payloads, where either one SAK or SAT payload MUST be
   present.  When present, the order of the SA Attributes payloads must
   be: KEK, GAP, and TEKs.

   This latitude allows various group policies to be accommodated.  For
   example if the group policy does not require the use of a Re-key SA,
   the GCKS would not need to send an SA KEK attribute to the group
   member since all SA updates would be performed using the Registration



Weis, et al.            Expires January 13, 2011               [Page 20]

Internet-Draft                    GDOI                         July 2010


   SA.  Alternatively, group policy might use a Re-key SA but choose to
   download a KEK to the group member only as part of the Registration
   SA.  Therefore, the KEK policy (in the SA KEK attribute) would not be
   necessary as part of the Re-key SA message SA payload.

   Specifying multiple SATs allows multiple sessions to be part of the
   same group and multiple streams to be associated with a session
   (e.g., video, audio, and text) but each with individual security
   association policy.

   A GAP payload allows for the distribution of group-wise policy, such
   as instructions as to when to activate and de-activate SAs.

5.3.  SA KEK payload

   The SA KEK (SAK) payload contains security attributes for the KEK
   method for a group and parameters specific to the GROUPKEY-PULL
   operation.  The source and destination identities describe the
   identities used for the GROUPKEY-PULL datagram.


        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        !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !    Protocol   !  SRC ID Type  !         SRC ID Port           !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !SRC ID Data Len!          SRC Identification Data              ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ! DST ID Type   !         DST ID Port           !DST ID Data Len!
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !                    DST Identification Data                    ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !                                                               !
       ~                              SPI                              ~
       !                                                               !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !                           RESERVED2                           !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ~                        KEK Attributes                         ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   The SAK Payload fields are defined as follows:

   o Next Payload (1 octet) -- Identifies the next payload for the
   GROUPKEY-PULL or the GROUPKEY-PUSH message.  The only valid next
   payload types for this message are a GAP Payload, SAT Payload or zero



Weis, et al.            Expires January 13, 2011               [Page 21]

Internet-Draft                    GDOI                         July 2010


   to indicate that no SA Attribute payloads follow.

   o RESERVED (1 octet) -- Must be zero.

   o Payload Length (2 octets) -- Length of this payload, including the
   KEK attributes.

   o Protocol (1 octet) -- Value describing an IP protocol ID (e.g.,
   UDP/TCP) for the rekey datagram.

   o SRC ID Type (1 octet) -- Value describing the identity information
   found in the SRC Identification Data field.  Defined values are
   specified by the IPsec Identification Type section in the IANA
   isakmpd-registry [ISAKMP-REG].

   o SRC ID Port (2 octets) -- Value specifying a port associated with
   the source Id.  A value of zero means that the SRC ID Port field
   should be ignored.

   o SRC ID Data Len (1 octet) -- Value specifying the length of the SRC
   Identification Data field.

   o SRC Identification Data (variable length) -- Value, as indicated by
   the SRC ID Type.

   o DST ID Type (1 octet) -- Value describing the identity information
   found in the DST Identification Data field.  Defined values are
   specified by the IPsec Identification Type section in the IANA
   isakmpd-registry [ISAKMP-REG].

   o DST ID Prot (1 octet) -- Value describing an IP protocol ID (e.g.,
   UDP/TCP).

   o DST ID Port (2 octets) -- Value specifying a port associated with
   the source Id.

   o DST ID Data Len (1 octet) -- Value specifying the length of the DST
   Identification Data field.

   o DST Identification Data (variable length) -- Value, as indicated by
   the DST ID Type.

   o SPI (16 octets) -- Security Parameter Index for the KEK.  The SPI
   must be the ISAKMP Header cookie pair where the first 8 octets become
   the "Initiator Cookie" field of the GROUPKEY-PUSH message ISAKMP HDR,
   and the second 8 octets become the "Responder Cookie" in the same
   HDR.  As described above, these cookies are assigned by the GCKS.




Weis, et al.            Expires January 13, 2011               [Page 22]

Internet-Draft                    GDOI                         July 2010


   o RESERVED2 (4 octets) -- Must be zero.

   o KEK Attributes -- Contains KEK policy attributes associated with
   the group.  The following sections describe the possible attributes.
   Any or all attributes may be optional, depending on the group policy.

5.3.1.  KEK Attributes

   The following attributes may be present in a SAK Payload.  The
   attributes must follow the format defined in ISAKMP (Section 3.3 of
   [RFC2408]).  In the table, attributes that are defined as TV are
   marked as Basic (B); attributes that are defined as TLV are marked as
   Variable (V).


                ID Class                   Value    Type
                --------                   -----    ----
                RESERVED                     0
                KEK_MANAGEMENT_ALGORITHM     1        B
                KEK_ALGORITHM                2        B
                KEK_KEY_LENGTH               3        B
                KEK_KEY_LIFETIME             4        V
                SIG_HASH_ALGORITHM           5        B
                SIG_ALGORITHM                6        B
                SIG_KEY_LENGTH               7        B

   The KEK_MANAGEMENT_ALGORITHM attribute may only be included in a
   GROUPKEY-PULL message.

5.3.2.  KEK_MANAGEMENT_ALGORITHM

   The KEK_MANAGEMENT_ALGORITHM class specifies the group KEK management
   algorithm used to provide forward or backward access control (i.e.,
   used to exclude group members).  Defined values are specified in the
   following table.


                  KEK Management Type               Value
                  -------------------               -----
                  RESERVED                            0
                  LKH                                 1
                  RESERVED                           2-127
                  Private Use                       128-255








Weis, et al.            Expires January 13, 2011               [Page 23]

Internet-Draft                    GDOI                         July 2010


5.3.2.1.  LKH

   This type indicates the group management method described in Section
   5.4 of [RFC2627].

5.3.3.  KEK_ALGORITHM

   The KEK_ALGORITHM class specifies the encryption algorithm using with
   the KEK.  Defined values are specified in the following table.  An
   GDOI implementation MUST abort if it encounters and attribute or
   capability that it does not understand.


                   Algorithm Type  Value
                   --------------  -----
                   RESERVED           0
                   KEK_ALG_DES        1
                   KEK_ALG_3DES       2
                   KEK_ALG_AES        3
                   RESERVED         4-127
                   Private Use    128-255

   If a KEK_MANAGEMENT_ALGORITHM is defined which defines multiple keys
   (e.g., LKH), and if the management algorithm does not specify the
   algorithm for those keys, then the algorithm defined by the
   KEK_ALGORITHM attribute MUST be used for all keys which are included
   as part of the management.

5.3.3.1.  KEK_ALG_DES

   This type specifies DES using the Cipher Block Chaining (CBC) mode as
   described in [FIPS81].

5.3.3.2.  KEK_ALG_3DES

   This type specifies 3DES using three independent keys as described in
   "Keying Option 1" in [FIPS46-3].

5.3.3.3.  KEK_ALG_AES

   This type specifies AES as described in [FIPS197].  The mode of
   operation for AES is Cipher Block Chaining (CBC) as recommended in
   [SP.800-38A].

5.3.4.  KEK_KEY_LENGTH

   The KEK_KEY_LENGTH class specifies the KEK Algorithm key length (in
   bits).  The Group Controller/Key Server (GCKS) adds the KEK_KEY_LEN



Weis, et al.            Expires January 13, 2011               [Page 24]

Internet-Draft                    GDOI                         July 2010


   attribute to the SA payload when distributing KEK policy to group
   members.  The group member verifies whether or not it has the
   capability of using a cipher key of that size.  If the cipher
   definition includes a fixed key length (e.g., KEK_ALG_3DES), the
   group member can make its decision solely using KEK_ALGORITHM
   attribute and does not need the KEK_KEY_LEN attribute.  Sending the
   KEK_KEY_LEN attribute in the SA payload is OPTIONAL if the KEK cipher
   has a fixed key length.  Also, note that the KEK_KEY_LEN includes
   only the actual length of the cipher key (the IV length is not
   included in this attribute).

5.3.5.  KEK_KEY_LIFETIME

   The KEK_KEY_LIFETIME class specifies the maximum time for which the
   KEK is valid.  The GCKS may refresh the KEK at any time before the
   end of the valid period.  The value is a four (4) octet number
   defining a valid time period in seconds.

5.3.6.  SIG_HASH_ALGORITHM

   SIG_HASH_ALGORITHM specifies the SIG payload hash algorithm.  The
   following table defines the algorithms for SIG_HASH_ALGORITHM.


                   Algorithm Type  Value
                   --------------  -----
                   RESERVED           0
                   SIG_HASH_MD5       1
                   SIG_HASH_SHA1      2
                   SIG_HASH_SHA256   TBD-2
                   SIG_HASH_SHA384   TBD-3
                   SIG_HASH_SHA512   TBD-4
                   RESERVED         6-127
                   Private Use   128-255

   The SHA hash algorithms are defined in the Secure Hash
   Standard[FIPS.180-2.2002].

   If the SIG_ALGORITHM is SIG_ALG_ECDSA-256, SIG_ALG_ECDSA-384, or
   SIG_ALG_ECDSA-521 the hash algorithm is implicit in the definition,
   and SIG_HASH_ALGORITHM is not required to be present in a SAK
   Payload.

5.3.7.  SIG_ALGORITHM

   The SIG_ALGORITHM class specifies the SIG payload signature
   algorithm.  Defined values are specified in the following table.




Weis, et al.            Expires January 13, 2011               [Page 25]

Internet-Draft                    GDOI                         July 2010


                   Algorithm Type    Value
                   --------------    -----
                   RESERVED            0
                   SIG_ALG_RSA         1
                   SIG_ALG_DSS         2
                   SIG_ALG_ECDSS       3
                   SIG_ALG_RSA_PSS   TBD-6
                   SIG_ALG_ECDSA-256 TBD-7
                   SIG_ALG_ECDSA-384 TBD-8
                   SIG_ALG_ECDSA-521 TBD-9
                   RESERVED          8-127
                   Private Use     128-255

5.3.7.1.  SIG_ALG_RSA

   This algorithm specifies the RSA digital signature algorithm using
   the EMSA-PKCS1-v1_5 encoding method, as described in [RFC3447].

5.3.7.2.  SIG_ALG_DSS

   This algorithm specifies the DSS digital signature algorithm as
   described in Section 4 of [FIPS186-3].

5.3.7.3.  SIG_ALG_ECDSS

   This algorithm specifies the Elliptic Curve digital signature
   algorithm as described in Section 5 of [FIPS186-3].  This definition
   is deprecated in favor of the SIG_ALG_ECDSA family of algorithms.

5.3.7.4.  SIG_ALG_RSA_PSS

   This algorithm specifies the RSA digital signature algorithm using
   the EMSA-PSS encoding method, as described in [RFC3447].

5.3.7.5.  SIG_ALG_ECDSA-256

   This algorithm specifies the 256-bit Random ECP Group, as described
   in [RFC5903].  The format of the signature in the SIG payload MUST be
   as specified in [RFC4754].

5.3.7.6.  SIG_ALG_ECDSA-384

   This algorithm specifies the 384-bit Random ECP Group, as described
   in [RFC5903].  The format of the signature in the SIG payload MUST be
   as specified in [RFC4754].






Weis, et al.            Expires January 13, 2011               [Page 26]

Internet-Draft                    GDOI                         July 2010


5.3.7.7.  SIG_ALG_ECDSA-521

   This algorithm specifies the 521-bit Random ECP Group, as described
   in [RFC5903].  The format of the signature in the SIG payload MUST be
   as specified in [RFC4754].

5.3.8.  SIG_KEY_LENGTH

   The SIG_KEY_LENGTH class specifies the length of the SIG payload key
   in bits.

5.4.  Group Associated Policy

   RFC 3547 provides for the distribution of policy in the GROUPKEY-PULL
   exchange in an SA payload.  Policy can define GROUPKEY-PUSH policy
   (SA KEK) or traffic encryption policy (SA TEK) such as IPsec policy.
   There is a need to distribute group policy that fits into neither
   category.  Some of this policy is generic to the group, and some is
   sender-specific policy for a particular group member.

   GDOI distributes this associated group policy in a new payload called
   the SA Group Associated Policy (SA GAP).  The SA GAP payload follows
   any SA KEK payload, and is placed before any SA TEK payloads.  In the
   case that group policy does not include an SA KEK, the SA Attribute
   Next Payload field in the SA payload MAY indicate the SA GAP payload.

   The SA GAP payload is 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         !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !               Group Associated Policy Attributes              ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   The SA GAP payload fields are defined as follows:

   o  Next Payload (1 octet) -- Identifies the next payload present in
      the GROUPKEY-PULL or the GROUPKEY-PUSH message.  The only valid
      next payload type for this message is an SA TEK or zero to
      indicate there are no more security association attributes.

   o  RESERVED (1 octet) -- Must be zero.

   o  Payload Length (2 octets) -- Length of this payload, including the
      SA GAP header and Attributes.




Weis, et al.            Expires January 13, 2011               [Page 27]

Internet-Draft                    GDOI                         July 2010


   o  Group Associated Policy Attributes (variable) -- Contains
      attributes following the format defined in Section 3.3 of RFC
      2408.

   Several group associated policy attributes are defined in this memo.
   An GDOI implementation MUST abort if it encounters and attribute or
   capability that it does not understand.

5.4.1.  ACTIVATION_TIME_DELAY

   This attribute allows a GCKS to set the Activation Time Delay for SAs
   generated from TEKs.  The value is in seconds.  If a group member
   receives a TEK with an ATD value, but discovers that it has no
   current SAs matching the policy in the TEK, then it SHOULD create and
   install SAs from the TEK immediately.

5.4.2.  DEACTIVATION_TIME_DELAY

   This attribute allows a GCKS to set the Deactivation Time Delay for
   SAs generated from TEKs.  The value is in seconds.

5.4.3.  SENDER_ID

   Several new AES counter-based modes of operation have been specified
   for ESP [RFC3686],[RFC4106],[RFC4309],[RFC4543] and AH [RFC4543].
   These AES counter-based modes require that no two senders in the
   group ever send a packet with the same IV.  This requirement can be
   met using the method described in
   [I-D.ietf-msec-ipsec-group-counter-modes], which requires each sender
   to be allocated a unique Sender ID (SID).  The SENDER_ID attribute is
   used to distribute a SID to a group member during the GROUPKEY-PULL
   message.  Other algorithms with the same need may be defined in the
   future; the sender MUST use the IV construction method described
   above with those algorithms as well.

   The SENDER_ID attribute value contains the following fields.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !   SID Length  !                    SID Value                  ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   o  SID Length (1 octet) -- A natural number defining the number of
      bits to be used in the SID field of the counter mode transform
      nonce.





Weis, et al.            Expires January 13, 2011               [Page 28]

Internet-Draft                    GDOI                         July 2010


   o  SID Value (variable) -- The Sender ID value allocated to the group
      member.

5.4.3.1.  GCKS Semantics

   The GCKS maintains a SID counter (SIDC).  It is incremented each time
   a SENDER_ID attribute is distributed to a group member.  The first
   group member to register is given the SID of 1.

   Any group member registering will be given a new SID value, which
   allows group members to act as a group sender when an older SID value
   becomes unusable (as described in the next section).

   A GCKS MAY allocate multiple SID values in one SA GAP payload.
   Allocating several SID values at the same time to a group member
   expected to send at a high rate would obviate the need for the group
   member to re-register as frequently.

   If a GCKS allocates all SID values, it can no longer respond to GDOI
   registrations and must re-initialize the entire group.  This is done
   by issuing DELETE notifications for all ESP and AH SAs in a GDOI
   rekey message, resetting the SIDC to zero, and creating new ESP and
   AH SAs that match the group policy.  When group members re-register,
   the SIDs are allocated again beginning with the value 1 as described
   above.  Each re-registering group member will be given a new SID and
   the new group policy.

   The SENDER_ID attribute MUST NOT be sent as part of a GROUPKEY-PUSH
   message, because distributing the same sender-specific policy to more
   than one group member may reduce the security of the group.

5.4.3.2.  Group Member Semantics

   The SENDER_ID attribute value distributed to the group member MUST be
   used by that group member as the Sender Identifier (SID) field
   portion of the IV.  The SID is used for all counter mode SAs
   distributed by the GCKS to be used for communications sent as a part
   of this group.

   When the Sender-Specific IV (SSIV) field for any IPsec SA is
   exhausted, the group member MUST no longer act as a sender using its
   active SID.  The group member SHOULD re-register, during which time
   the GCKS will issue a new SID to the group member.  The new SID
   replaces the existing SID used by this group member, and also resets
   the SSIV value to it's starting value.  A group member MAY re-
   register prior to the actual exhaustion of the SSIV field to avoid
   dropping data packets due to the exhaustion of available SSIV values
   combined with a particular SID value.



Weis, et al.            Expires January 13, 2011               [Page 29]

Internet-Draft                    GDOI                         July 2010


   A group member MUST NOT process SENDER_ID attribute present in a
   GROUPKEY-PUSH message.

5.5.  SA TEK Payload

   The SA TEK (SAT) payload contains security attributes for a single
   TEK associated with a group.


        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        !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ! Protocol-ID   !       TEK Protocol-Specific Payload           ~
       +-+-+-+-+-+-+-+-+                                               ~
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   The SAT Payload fields are defined as follows:

   o Next Payload (1 octet) -- Identifies the next payload for the
   GROUPKEY-PULL or the GROUPKEY-PUSH message.  The only valid next
   payload types for this message are another SAT Payload or zero to
   indicate there are no more security association attributes.

   o RESERVED (1 octet) -- Must be zero.

   o Payload Length (2 octets) -- Length of this payload, including the
   TEK Protocol-Specific Payload.

   o Protocol-ID (1 octet) -- Value specifying the Security Protocol.
   The following table defines values for the Security Protocol


             Protocol ID                       Value
             -----------                       -----
             RESERVED                            0
             GDOI_PROTO_IPSEC_ESP                1
             GDOI_PROTO_IPSEC_AH                TBD-5
             RESERVED                           3-127
             Private Use                      128-255

   o TEK Protocol-Specific Payload (variable) -- Payload which describes
   the attributes specific for the Protocol-ID.






Weis, et al.            Expires January 13, 2011               [Page 30]

Internet-Draft                    GDOI                         July 2010


5.5.1.  GDOI_PROTO_IPSEC_ESP/GDOI_PROTO_IPSEC_AH

   The TEK Protocol-Specific payload for ESP and AH is 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !    Protocol   !  SRC ID Type  !         SRC ID Port           !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !SRC ID Data Len!          SRC Identification Data              ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ! DST ID Type   !         DST ID Port           !DST ID Data Len!
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ! DST Identification Data                                       ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ! Transform ID  !                        SPI                    !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !      SPI      !       RFC 2407 SA Attributes                  ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   The SAT Payload fields are defined as follows:

   o Protocol (1 octet) -- Value describing an IP protocol ID (e.g.,
   UDP/TCP).  A value of zero means that the Protocol field should be
   ignored.

   o SRC ID Type (1 octet) -- Value describing the identity information
   found in the SRC Identification Data field.  Defined values are
   specified by the IPsec Identification Type section in the IANA
   isakmpd-registry [ISAKMP-REG].

   o SRC ID Port (2 octets) -- Value specifying a port associated with
   the source Id.  A value of zero means that the SRC ID Port field
   should be ignored.

   o SRC ID Data Len (1 octet) -- Value specifying the length of the SRC
   Identification Data field.

   o SRC Identification Data (variable length) -- Value, as indicated by
   the SRC ID Type.  Set to three bytes of zero for multiple-source
   multicast groups that use a common TEK for all senders.

   o DST ID Type (1 octet) -- Value describing the identity information
   found in the DST Identification Data field.  Defined values are
   specified by the IPsec Identification Type section in the IANA
   isakmpd-registry [ISAKMP-REG].




Weis, et al.            Expires January 13, 2011               [Page 31]

Internet-Draft                    GDOI                         July 2010


   o DST ID Prot (1 octet) -- Value describing an IP protocol ID (e.g.,
   UDP/TCP).  A value of zero means that the DST Id Prot field should be
   ignored.

   o DST ID Port (2 octets) -- Value specifying a port associated with
   the source Id.  A value of zero means that the DST ID Port field
   should be ignored.

   o DST ID Data Len (1 octet) -- Value specifying the length of the DST
   Identification Data field.

   o DST Identification Data (variable length) -- Value, as indicated by
   the DST ID Type.

   o Transform ID (1 octet) -- Value specifying which ESP or AH
   transform is to be used.  The list of valid values is defined in the
   IPsec ESP or IPsec AH Transform Identifiers section of the IANA
   isakmpd-registry [ISAKMP-REG].

   o SPI (4 octets) -- Security Parameter Index for ESP.

   o RFC 2407 Attributes -- ESP and AH Attributes from RFC 2407 Section 
   4.5.  The GDOI supports all IPsec DOI SA Attributes for
   GDOI_PROTO_IPSEC_ESP and GDOI_PROTO_IPSEC_AH excluding the Group
   Description (section 4.5 of [RFC2407], which MUST NOT be sent by a
   GDOI implementation and is ignored by a GDOI implementation if
   received.  The following attributes MUST be supported by an
   implementation supporting ESP and AH: SA Life Type, SA Life Duration,
   Encapsulation Mode.  An implementation supporting ESP must also
   support the Authentication Algorithm attribute if the ESP transform
   includes authentication/ The Authentication Algorithm attribute of
   the IPsec DOI is group authentication in GDOI.

5.5.1.1.  Harmonization with RFC 5374

   The Multicast Extensions to the Security Architecture for the
   Internet Protocol (RFC 5374) introduces new requirements for a group
   key management system distributing IPsec policy.  The following
   sections describe new GDOI requirements that result from harmonizing
   with that document.

5.5.1.1.1.  Group Security Policy Database Attributes

   RFC 5374 describes new attributes as part of the Group Security
   Policy Database (GSPD).  These attributes describe policy that a
   group key management system must convey to a group member in order to
   support those extensions.  The GDOI SA TEK payload distributes IPsec
   policy using IPsec security association attributes defined in



Weis, et al.            Expires January 13, 2011               [Page 32]

Internet-Draft                    GDOI                         July 2010


   [ISAKMP-REG].  This section defines how GDOI can convey the new
   attributes as IPsec Security Association Attributes.

5.5.1.1.2.  Address Preservation

   Applications use the extensions in RFC 5374 create encapsulate IPsec
   multicast packets that are IP multicast packets.  In order for the
   GDOI group member to appropriately setup the GSPD, the GCKS must
   provide that policy to the group member.

   Depending on group policy, several address preservation methods are
   possible: no address preservation ("None"), preservation of the
   original source address ("Source-Only"), preservation of the original
   destination address ("Destination-Only"), or both addresses ("Source-
   And-Destination").  This memo adds the "Address Preservation"
   security association attribute.  If this attribute is not included in
   a GDOI SA TEK payload provided by a GCKS, then Source-And-Destination
   address preservation has been defined for the SA TEK.

5.5.1.1.3.  SA Direction

   Depending on group policy, an IPsec SA created from an SA TEK payload
   may be required in one or both directions.  SA TEK policy used by
   multiple senders is required to be installed in both the sending and
   receiving direction ("Symmetric"), whereas SA TEK for a single sender
   should only be installed in the receiving direction by receivers
   ("Receiver-Only") and in the sending direction by the sender
   ("Sender-Only").  This memo adds the "SA Direction" security
   association attribute.  If the attribute is not included in a GDOI SA
   TEK payload, then the IPsec SA is treated as a Symmetric IPsec SA.

5.5.1.1.4.  Re-key rollover

   Section 4.2.1 of RFC 5374 specifies a key rollover method that
   requires two values be given it from the group key management
   protocol.  The Activation Time Delay (ATD) attribute allows the GCKS
   to specify how long after the start of a re-key event that a group
   member is to activate new TEKs.  The Deactivation Time Delay (DTD)
   attribute allows the GCKS to specify how long after the start of a
   re-key event that a group member is to deactivate existing TEKs.

   This memo adds new attributes by which a GCKS can relay these values
   to group members as part of the Group Associated Policy described in
   Section 5.







Weis, et al.            Expires January 13, 2011               [Page 33]

Internet-Draft                    GDOI                         July 2010


5.5.2.  Other Security Protocols

   Besides ESP and AH, GDOI should serve to establish SAs for secure
   groups needed by other Security Protocols that operate at the
   transport, application, and internetwork layers.  These other
   Security Protocols, however, are in the process of being developed or
   do not yet exist.

   The following information needs to be provided for a Security
   Protocol to the GDOI.

   o  The Protocol-ID for the particular Security Protocol

   o  The SPI Size

   o  The method of SPI generation

   o  The transforms, attributes and keys needed by the Security
      Protocol

   All Security Protocols must provide the information in the bulleted
   list above to guide the GDOI specification for that protocol.
   Definitions for the support of those Security Protocols in GDOI will
   be specified in separate documents.

   A Security Protocol MAY protect traffic at any level of the network
   stack.  However, in all cases applications of the Security Protocol
   MUST protect traffic which MAY be shared by more than two entities.

5.6.  Key Download Payload

   The Key Download Payload contains group keys for the group specified
   in the SA Payload.  These key download payloads can have several
   security attributes applied to them based upon the security policy of
   the group as defined by the associated SA Payload.
















Weis, et al.            Expires January 13, 2011               [Page 34]

Internet-Draft                    GDOI                         July 2010


        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 Key Packets         !            RESERVED2          !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ~                    Key Packets                                ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   The Key Download Payload fields are defined as follows:

   o 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 zero.

   o RESERVED (1 octet) -- Unused, set to zero.

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

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

   o Key Packets Several types of key packets are defined.  Each Key
   Packet has the following format.


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !   KD Type     !   RESERVED    !            KD Length          !
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       !    SPI Size   !                   SPI (variable)              ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!
       ~                    Key Packet Attributes                      ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-!

   o Key Download (KD) Type (1 octet) -- Identifier for the Key Data
   field of this Key Packet.











Weis, et al.            Expires January 13, 2011               [Page 35]

Internet-Draft                    GDOI                         July 2010


                          Key Download Type        Value
                          -----------------        -----
                          RESERVED                   0
                          TEK                        1
                          KEK                        2
                          LKH                        3
                          RESERVED                  4-127
                          Private Use             128-255

   "KEK" is a single key whereas LKH is an array of key-encrypting keys.

   o RESERVED (1 octet) -- Unused, set to zero.

   o Key Download Length (2 octets) -- Length in octets of the Key
   Packet data, including the Key Packet header.

   o SPI Size (1 octet) -- Value specifying the length in octets of the
   SPI as defined by the Protocol-Id.

   o SPI (variable length) -- Security Parameter Index which matches a
   SPI previously sent in an SAK or SAT Payload.

   o Key Packet Attributes (variable length) -- Contains Key
   information.  The format of this field is specific to the value of
   the KD Type field.  The following sections describe the format of
   each KD Type.

5.6.1.  TEK Download Type

   The following attributes may be present in a TEK Download Type.
   Exactly one attribute matching each type sent in the SAT payload MUST
   be present.  The attributes must follow the format defined in ISAKMP
   (Section 3.3 of [RFC2408]).  In the table, attributes defined as TV
   are marked as Basic (B); attributes defined as TLV are marked as
   Variable (V).


                TEK Class                 Value      Type
                ---------                 -----      ----
                RESERVED                     0
                TEK_ALGORITHM_KEY            1        V
                TEK_INTEGRITY_KEY            2        V
                TEK_SOURCE_AUTH_KEY          3        V

   If no TEK key packets are included in a Registration KD payload, the
   group member can expect to receive the TEK as part of a Re-key SA.
   At least one TEK must be included in each Re-key KD payload.
   Multiple TEKs may be included if multiple streams associated with the



Weis, et al.            Expires January 13, 2011               [Page 36]

Internet-Draft                    GDOI                         July 2010


   SA are to be rekeyed.

5.6.1.1.  TEK_ALGORITHM_KEY

   The TEK_ALGORITHM_KEY class declares that the encryption key for this
   SPI is contained as the Key Packet Attribute.  The encryption
   algorithm that will use this key was specified in the SAT payload.

   In the case that the algorithm requires multiple keys (e.g., 3DES),
   all keys will be included in one attribute.

   DES keys will consist of 64 bits (the 56 key bits with parity bit).
   Triple DES keys will be specified as a single 192 bit attribute
   (including parity bits) in the order that the keys are to be used for
   encryption (e.g., DES_KEY1, DES_KEY2, DES_KEY3).

5.6.1.2.  TEK_INTEGRITY_KEY

   The TEK_INTEGRITY_KEY class declares that the integrity key for this
   SPI is contained as the Key Packet Attribute.  The integrity
   algorithm that will use this key was specified in the SAT payload.
   Thus, GDOI assumes that both the symmetric encryption and integrity
   keys are pushed to the member.  HMAC-SHA1 keys will consist of 160
   bits[RFC2404], HMAC-MD5 keys will consist of 128 bits[RFC2403].
   HMAC-SHA2 and AES-GMAC keys will have a key length equal to the
   output length of the hash functions [RFC4868][RFC4543].

5.6.1.3.  TEK_SOURCE_AUTH_KEY

   The TEK_SOURCE_AUTH_KEY class declares that the source authentication
   key for this SPI is contained in the Key Packet Attribute.  The
   source authentication algorithm that will use this key was specified
   in the SAT payload.

5.6.2.  KEK Download Type

   The following attributes may be present in a KEK Download Type.
   Exactly one attribute matching each type sent in the SAK payload MUST
   be present.  The attributes must follow the format defined in ISAKMP
   (Section 3.3 of [RFC2408]).  In the table, attributes defined as TV
   are marked as Basic (B); attributes defined as TLV are marked as
   Variable (V).









Weis, et al.            Expires January 13, 2011               [Page 37]

Internet-Draft                    GDOI                         July 2010


                KEK Class                 Value      Type
                ---------                 -----      ----
                RESERVED                     0
                KEK_ALGORITHM_KEY            1        V
                SIG_ALGORITHM_KEY            2        V

   If the KEK key packet is included, there MUST be only one present in
   the KD payload.

5.6.2.1.  KEK_ALGORITHM_KEY

   The KEK_ALGORITHM_KEY class declares the encryption key for this SPI
   is contained in the Key Packet Attribute.  The encryption algorithm
   that will use this key was specified in the SAK payload.

   If the mode of operation for the algorithm requires an Initialization
   Vector (IV), an explicit IV MUST be included in the KEK_ALGORITHM_KEY
   before the actual key.

5.6.2.2.  SIG_ALGORITHM_KEY

   The SIG_ALGORITHM_KEY class declares that the public key for this SPI
   is contained in the Key Packet Attribute, which may be useful when no
   public key infrastructure is available.  The signature algorithm that
   will use this key was specified in the SAK payload.

5.6.3.  LKH Download Type

   The LKH key packet is comprised of attributes representing different
   nodes in the LKH key tree.

   The following attributes are used to pass an LKH KEK array in the KD
   payload.  The attributes must follow the format defined in ISAKMP
   (Section 3.3 of [RFC2408]).  In the table, attributes defined as TV
   are marked as Basic (B); attributes defined as TLV are marked as
   Variable (V).















Weis, et al.            Expires January 13, 2011               [Page 38]

Internet-Draft                    GDOI                         July 2010


                KEK Class                 Value      Type
                ---------                 -----      ----
                RESERVED                     0
                LKH_DOWNLOAD_ARRAY           1        V
                LKH_UPDATE_ARRAY             2        V
                SIG_ALGORITHM_KEY            3        V
                RESERVED                    4-127
                Private Use               128-255

   If an LKH key packet is included in the KD payload, there must be
   only one present.

5.6.3.1.  LKH_DOWNLOAD_ARRAY

   This attribute is used to download a set of keys to a group member.
   It MUST NOT be included in a GROUPKEY-PUSH message KD payload if the
   GROUPKEY-PUSH is sent to more than the group member.  If an
   LKH_DOWNLOAD_ARRAY attribute is included in a KD payload, there must
   be only one present.

   This attribute consists of a header block, followed by one or more
   LKH keys.


       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !  LKH Version  !          # of LKH Keys        !  RESERVED     !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !                             LKH Keys                          !
      ~                                                               ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The KEK_LKH attribute fields are defined as follows:

   o LKH version (1 octet) -- Version of the LKH data format.  Must be
   one.

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

   o RESERVED (1 octet) -- Unused, set to zero.  Each LKH Key is defined
   as follows:








Weis, et al.            Expires January 13, 2011               [Page 39]

Internet-Draft                    GDOI                         July 2010


       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !             LKH ID            !    Key Type   !    RESERVED   !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        Key Creation Date                      !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                       Key expiration Date                     !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                           Key Handle                          !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !                                                               !
      ~                            Key Data                           ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o LKH ID (2 octets) -- Identity of the LKH node.  A GCKS is free to
   choose the ID in an implementation-specific manner (e.g., the
   position of this key in a binary tree structure used by LKH).

   o Key Type (1 octet) -- Encryption algorithm for which this key data
   is to be used.  This value is specified in Section 5.3.3.

   o RESERVED (1 octet) -- Unused, set to zero.

   o Key Creation Date (4 octets) -- Time value of when this key data
   was originally generated.  A time value of zero indicates that there
   is no time before which this key is not valid.

   o Key Expiration Date (4 octets) -- Time value of when this key is no
   longer valid for use.  A time value of zero indicates that this key
   does not have an expiration time.

   o Key Handle (4 octets) -- Value assigned by the GCKS to uniquely
   identify a key within an LKH ID.  Each new key distributed by the
   GCKS for this node will have a key handle identity distinct from
   previous or successive key handles specified for this node.

   o Key Data (variable length) -- Key data, which is dependent on the
   Key Type algorithm for its format.  If the mode of operation for the
   algorithm requires an Initialization Vector (IV), an explicit IV MUST
   be included in the Key Data field prepended to the actual key.

   The Key Creation Date and Key expiration Dates MAY be zero.  This is
   necessary in the case where time synchronization within the group is
   not possible.

   The first LKH Key structure in an LKH_DOWNLOAD_ARRAY attribute
   contains the Leaf identifier and key for the group member.  The rest



Weis, et al.            Expires January 13, 2011               [Page 40]

Internet-Draft                    GDOI                         July 2010


   of the LKH Key structures contain keys along the path of the key tree
   in order from the leaf, culminating in the group KEK.

5.6.3.2.  LKH_UPDATE_ARRAY

   This attribute is used to update the keys for a group.  It is most
   likely to be included in a GROUPKEY-PUSH message KD payload to rekey
   the entire group.  This attribute consists of a header block,
   followed by one or more LKH keys, as defined in the previous section.

   There may be any number of UPDATE_ARRAY attributes included in a KD
   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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !  LKH Version  !          # of LKH Keys        !  RESERVED     !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !            LKH ID             !           RESERVED2           !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !                           Key Handle                          !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !                            LKH Keys                           !
      ~                                                               ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o LKH version (1 octet) -- Version of the LKH data format.  Must be
   one.

   o Number of LKH Keys (2 octets) -- Number of distinct LKH keys in
   this sequence.

   o RESERVED (1 octet) -- Unused, set to zero.

   o LKH ID (2 octets) -- Node identifier associated with the key used
   to encrypt the first LKH Key.

   o RESERVED2 (2 octets) -- Unused, set to zero.

   o Key Handle (4 octets) -- Value assigned by the GCKS to uniquely
   identify the key within the LKH ID used to encrypt the first LKH Key.

   The LKH Keys are as defined in the previous section.  The LKH Key
   structures contain keys along the path of the key tree in order from
   the LKH ID found in the LKH_UPDATE_ARRAY header, culminating in the
   group KEK.  The Key Data field of each LKH Key is encrypted with the
   LKH key preceding it in the LKH_UPDATE_ARRAY attribute.  The first



Weis, et al.            Expires January 13, 2011               [Page 41]

Internet-Draft                    GDOI                         July 2010


   LKH Key is encrypted under the key defined by the LKH ID and Key
   Handle found in the LKH_UPDATE_ARRAY header.

5.6.3.3.  SIG_ALGORITHM_KEY

   The SIG_ALGORITHM_KEY class declares that the public key for this SPI
   is contained in the Key Packet Attribute, which may be useful when no
   public key infrastructure is available.  The signature algorithm that
   will use this key was specified in the SAK payload.

5.7.  Sequence Number Payload

   The Sequence Number Payload (SEQ) provides an anti-replay protection
   for GROUPKEY-PUSH messages.  Its use is similar to the Sequence
   Number field defined in the IPsec ESP protocol [RFC4303].


       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        !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      !                      Sequence Number                          !
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Sequence Number Payload fields are defined as follows:

   o 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 zero.

   o RESERVED (1 octet) -- Unused, set to zero.

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

   o Sequence Number (4 octets) -- This field contains a monotonically
   increasing counter value for the group.  It is initialized to zero by
   the GCKS, and incremented in each subsequently-transmitted message.
   Thus the first packet sent for a given Rekey SA will have a Sequence
   Number of 1.  The GDOI implementation keeps a sequence counter as an
   attribute for the Rekey SA and increments the counter upon receipt of
   a GROUPKEY-PUSH message.  The current value of the sequence number
   must be transmitted to group members as a part of the Registration SA
   payload.  A group member must keep a sliding receive window.  The
   window must be treated as in the ESP protocol [RFC4303] Section
   3.4.3.




Weis, et al.            Expires January 13, 2011               [Page 42]

Internet-Draft                    GDOI                         July 2010


5.8.  Nonce

   The data portion of the Nonce payload (i.e., Ni_b and Nr_b included
   in the HASHs) MUST be a value between 8 and 128 bytes.















































Weis, et al.            Expires January 13, 2011               [Page 43]

Internet-Draft                    GDOI                         July 2010


6.  Algorithm Selection

   For GDOI implementations to interoperate, they must support one or
   more security algorithms in common.  This section specifies the
   security algorithm implementation requirements for standards-
   conformant GDOI implementations.  In call cases the choices are
   intended to maintain at least 112 bits of security [SP.800-131].
   Algorithms not referenced in this section can also be used.

6.1.  KEK

   These tables list the algorithm selections for values related to the
   KEK.
                Requirement   KEK Management Algorithm
                -----------   ---------------------
                SHOULD        LKH

                Requirement   KEK Algorithm (notes)
                -----------   ---------------------
                MUST          KEK_ALG_AES with 128-bit keys
                SHOULD NOT    KEK_ALG_DES  (1)


                Requirement   KEK Signature Hash Algorithm (notes)
                -----------   ------------------------------------
                MUST          SIG_HASH_SHA256
                SHOULD        SIG_HASH_SHA1 (2)
                SHOULD NOT    SIG_HASH_MD5 (3)

                Requirement   KEK Signature Algorithm (notes)
                -----------   -------------------------------
                MUST          SIG_ALG_RSA with 2048-bit keys

   Notes:

   (1)  DES, with its small key size and corresponding security strength
        is of questionable security for general use

   (2)  The use of SIG_HASH_SHA1 as a signature hash algorithm used with
        GROUPKEY-PUSH messages remains safe at the time of this writing,
        and is a widely deployed signature hash algorithm.

   (3)  Although a real weakness with second preimage resistance with
        MD5 has not been found at the time of this writing, the security
        strength of MD5 has been shown to be rapidly declining over time
        and it's use should be understood and carefully weighed.





Weis, et al.            Expires January 13, 2011               [Page 44]

Internet-Draft                    GDOI                         July 2010


6.2.  TEK

   The following table lists the requirements for Security Protocol
   support for an implementation.

                Requirement   KEK Management Algorithm
                -----------   ---------------------
                MUST          GDOI_PROTO_IPSEC_ESP











































Weis, et al.            Expires January 13, 2011               [Page 45]

Internet-Draft                    GDOI                         July 2010


7.  Security Considerations

   GDOI is a security association (SA) management protocol for groups of
   senders and receivers.  Unlike a data security protocol, SA
   management includes a key establishment protocol to securely
   establish keys at communication endpoints.  This protocol performs
   entity authentication of the GDOI member or Group Controller/Key
   Server (GCKS), it provides confidentiality of key management
   messages, and it provides source authentication of those messages.
   This protocol also uses best-known practices for defense against man-
   in-middle, connection hijacking, replay, reflection, and denial-of-
   service (DOS) attacks on unsecured networks [STS], [RFC2522],
   [SKEME].  GDOI assumes the network is not secure and may be under the
   complete control of an attacker.

   GDOI assumes that the host computer is secure even though the network
   is insecure.  GDOI ultimately establishes keys among members of a
   group, which MUST be trusted to use those keys in an authorized
   manner according to group policy.  The security of GDOI, therefore,
   is as good as the degree to which group members can be trusted to
   protect authenticators, encryption keys, decryption keys, and message
   authentication keys.

   There are three phases of GDOI as described in this document: an
   ISAKMP Phase 1 protocol, a new exchange called GROUPKEY-PULL which is
   protected by the ISAKMP Phase 1 protocol, and a new message called
   GROUPKEY-PUSH.  Each phase is considered separately below.

7.1.  ISAKMP Phase 1

   As described in this document, GDOI uses the Phase 1 exchanges
   defined in [RFC2409] to protect the GROUPKEY-PULL exchange.
   Therefore all security properties and considerations of those
   exchanges (as noted in [RFC2409]) are relevant for GDOI.

   GDOI may inherit the problems of its ancestor protocols [FS00], such
   as identity exposure, absence of unidirectional authentication, or
   stateful cookies [PK01].  GDOI could benefit, however, from
   improvements to its ancestor protocols just as it benefits from years
   of experience and work embodied in those protocols.  To reap the
   benefits of future IKE improvements, however, GDOI would need to be
   revised in a future standards-track RFC, which is beyond the scope of
   this specification.

7.1.1.  Authentication

   Authentication is provided via the mechanisms defined in [RFC2409],
   namely Pre-Shared Keys or Public Key encryption.



Weis, et al.            Expires January 13, 2011               [Page 46]

Internet-Draft                    GDOI                         July 2010


7.1.2.  Confidentiality

   Confidentiality is achieved in Phase 1 through a Diffie-Hellman
   exchange that provides keying material, and through negotiation of
   encryption transforms.

   The Phase 1 protocol will be protecting encryption and integrity keys
   sent in the GROUPKEY-PULL protocol.  The strength of the encryption
   used for Phase 1 SHOULD exceed that of the keys send in the GROUPKEY-
   PULL protocol.

7.1.3.  Man-in-the-Middle Attack Protection

   A successful man-in-the-middle or connection-hijacking attack foils
   entity authentication of one or more of the communicating entities
   during key establishment.  GDOI relies on Phase 1 authentication to
   defeat man-in-the-middle attacks.

7.1.4.  Replay/Reflection Attack Protection

   In a replay/reflection attack, an attacker captures messages between
   GDOI entities and subsequently forwards them to a GDOI entity.
   Replay and reflection attacks seek to gain information from a
   subsequent GDOI message response or seek to disrupt the operation of
   a GDOI member or GCKS entity.  GDOI relies on the Phase 1 nonce
   mechanism in combination with a hash-based message authentication
   code to protect against the replay or reflection of previous key
   management messages.

7.1.5.  Denial of Service Protection

   A denial of service attacker sends messages to a GDOI entity to cause
   that entity to perform unneeded message authentication operations.
   GDOI uses the Phase 1 cookie mechanism to identify spurious messages
   prior to cryptographic hash processing.  This is a "weak" form of
   denial of service protection in that the GDOI entity must check for
   good cookies, which can be successfully imitated by a sophisticated
   attacker.  The Phase 1 cookie mechanism is stateful, and commits
   memory resources for cookies, but stateless cookies are a better
   defense against denial of service attacks.

7.2.  GROUPKEY-PULL Exchange

   The GROUPKEY-PULL exchange allows a group member to request SAs and
   keys from a GCKS.  It runs as a "phase 2" protocol under protection
   of the Phase 1 security association.





Weis, et al.            Expires January 13, 2011               [Page 47]

Internet-Draft                    GDOI                         July 2010


7.2.1.  Authentication

   Peer authentication is not required in the GROUPKEY-PULL protocol.
   It is running in the context of the Phase 1 protocol, which has
   previously authenticated the identity of the peer.

   Message authentication is provided by HASH payloads in each message,
   where the HASH is defined to be over SKEYID_a (derived in the Phase 1
   exchange), the ISAKMP Message-ID, and all payloads in the message.
   Because only the two endpoints of the exchange know the SKEYID_a
   value, this provides confidence that the peer sent the message.

7.2.2.  Confidentiality

   Confidentiality is provided by the Phase 1 security association,
   after the manner described in [RFC2409].

7.2.3.  Man-in-the-Middle Attack Protection

   Message authentication (described above) includes a secret known only
   to the group member and GCKS when constructing a HASH payload.  This
   prevents man-in-the-middle and connection-hijacking attacks because
   an attacker would not be able to change the message undetected.

7.2.4.  Replay/Reflection Attack Protection

   Nonces provide freshness of the GROUPKEY-PULL exchange.  The group
   member and GCKS exchange nonce values first two messages.  These
   nonces are included in subsequent HASH payload calculations.  The
   Group member and GCKS MUST NOT perform any computationally expensive
   tasks before receiving a HASH with its own nonce included.  The GCKS
   MUST NOT update the group management state (e.g., LKH key tree) until
   it receives the third message in the exchange with a valid HASH
   payload including its own nonce.

   Implementations SHOULD keep a record of recently received GROUPKEY-
   PULL messages and reject messages that have already been processed.
   This enables an early discard of the replayed messages.

7.2.5.  Denial of Service Protection

   A GROUPKEY-PULL message identifies its messages using a cookie pair
   from the Phase 1 exchange that precedes it.  The cookies provide a
   weak form of denial of service protection as described above, in the
   sense that a GROUPKEY-PULL message with invalid cookies will be
   discarded.

   The replay protection mechanisms described above provide the basis



Weis, et al.            Expires January 13, 2011               [Page 48]

Internet-Draft                    GDOI                         July 2010


   for denial of service protection.

7.2.6.  Authorization

   A GCKS implementation should maintain an authorization list of
   authorized group members.  Group members will specifically list each
   authorized GCKS in its Group Peer Authorization Database (GPAD)
   [RFC5374].

7.3.  GROUPKEY-PUSH Exchange

   The GROUPKEY-PUSH exchange is a single message that allows a GCKS to
   send SAs and keys to group members.  This is likely to be sent to all
   members using an IP multicast group.  This provides an efficient
   rekey and group membership adjustment capability.

7.3.1.  Authentication

   The GROUPKEY-PULL exchange identifies a public key that is used for
   message authentication.  The GROUPKEY-PUSH message is digitally
   signed using the corresponding private key held by the GCKS or its
   delegate.  This digital signature provides source authentication for
   the message.  Thus, GDOI protects the GCKS from impersonation in
   group environments.

7.3.2.  Confidentiality

   The GCKS encrypts the GROUPKEY-PUSH message with an encryption key
   that was established by the GROUPKEY-PULL exchange.

7.3.3.  Man-in-the-Middle Attack Protection

   This combination of confidentiality and message authentication
   services protects the GROUPKEY-PUSH message from man-in-middle and
   connection-hijacking attacks.

7.3.4.  Replay/Reflection Attack Protection

   The GROUPKEY-PUSH message includes a monotonically increasing
   sequence number to protect against replay and reflection attacks.  A
   group member will recognize a replayed message by comparing the
   sequence number to a sliding window, in the same manner as the ESP
   protocol uses sequence numbers.

   Implementations SHOULD keep a record of recently received GROUPKEY-
   PUSH messages and reject duplicate messages.  This enables an early
   discard of the replayed messages.




Weis, et al.            Expires January 13, 2011               [Page 49]

Internet-Draft                    GDOI                         July 2010


7.3.5.  Denial of Service Protection

   A cookie pair identifies the security association for the GROUPKEY-
   PUSH message.  The cookies thus serve as a weak form of denial-of-
   service protection for the GROUPKEY-PUSH message.

   The digital signature used for message authentication has a much
   greater computational cost than a message authentication code and
   could amplify the effects of a denial of service attack on GDOI
   members who process GROUPKEY-PUSH messages.  The added cost of
   digital signatures is justified by the need to prevent GCKS
   impersonation: If a shared symmetric key were used for GROUPKEY-PUSH
   message authentication, then GCKS source authentication would be
   impossible and any member would be capable of GCKS impersonation.

   The potential of the digital signature amplifying a denial of service
   attack is mitigated by the order of operations a group member takes,
   where the least expensive cryptographic operation is performed first.
   The group member first decrypts the message using a symmetric cipher.
   If it is a validly formed message then the sequence number is checked
   against the replay window.  Only if the sequence number is valid is
   the digital signature verified.  Thus in order for a denial of
   service attack to be mounted, an attacker would need to know both the
   symmetric encryption key used for confidentiality, and a valid
   sequence number.  Generally speaking this means only current group
   members can effectively deploy a denial of service attack.

7.3.6.  Forward Access Control

   If a group management algorithm (such as LKH) is used, forward access
   control may not be ensured in some cases.  This can happen if some
   group members are denied access to the group in the same GROUPKEY-
   PUSH message as new policy and TEKs are delivered to the group.  As
   discussed in Section 1.5.1, forward access control can be maintained
   by sending multiple GROUPKEY-PUSH messages, where the group
   membership changes are sent from the GCKS separate from the new
   policy and TEKs.














Weis, et al.            Expires January 13, 2011               [Page 50]

Internet-Draft                    GDOI                         July 2010


8.  IANA Considerations

   This memo requests IANA to make several additions to existing
   registries, and to add sever new GDOI registries.  When the new
   registries are added, the following terms are to be applied as
   described in the Guidelines for Writing an IANA Considerations
   Section in RFCs [RFC5226]: Standards Action, and Private Use.

8.1.  Additions to current registries

   The GDOI KEK Attribute named SIG_HASH_ALGORITHM [GDOI-REG] should be
   assigned several new Algorithm Type values from the RESERVED space to
   represent the SHA-256, SHA-384, and SHA-512 hash algorithms as
   defined in [FIPS.180-2.2002].  The new algorithm names should be
   SIG_HASH_SHA256, SIG_HASH_SHA384, and SIG_HASH_SHA512 respectively
   and have the values of TBD-2, TBD-3, and TBD-4 respectively.

   The GDOI KEK Attributed named SIG_ALGORITHM [GDOI-REG] should be
   assigned a new Algorithm Type value from the RESERVED space to
   represent the RSA PSS encoding type.  The new algorithm name should
   be SIG_ALG_RSA_PSS, and has the value of TBD-6.

   A new GDOI SA TEK type Protocol-ID type [GDOI-REG] should be assigned
   from the RESERVED space.  The new algorithm id should be called
   GDOI_PROTO_IPSEC_AH, refers to the IPsec AH encapsulation, and has a
   value of TBD-5.

   A new Next Payload Type [ISAKMP-REG] should be assigned.  The new
   type is called "SA Group Associated Policy (GAP)", and has a value of
   TBD-1.

8.2.  New registries

   A new namespace should be created in the GDOI Payloads registry
   [GDOI-REG] to describe SA GAP Payload Values.  The following rules
   apply to define the attributes in SA SSA Payload Values:

              Attribute Type         Value       Type
              ----                   -----       ----
              RESERVED                 0
              ACTIVATION_TIME_DELAY    1          B
              DEACTIVATION_TIME_DELAY  2          B
              SENDER_ID                3          V
              Standards Action        4-127
              Private Use           128-255

   A new IPsec Security Association Attribute [ISAKMP-REG] defining the
   preservation of IP addresses is needed.  The attribute class is



Weis, et al.            Expires January 13, 2011               [Page 51]

Internet-Draft                    GDOI                         July 2010


   called "Address Preservation", and it is a Basic type.  The following
   rules apply to define the values of the attribute:

              Name                      Value
              ----                      -----
              Reserved                  0
              None                      1
              Source-Only               2
              Destination-Only          3
              Source-And-Destination    4
              Standards Action         5-61439
              Private Use          61440-65535

   A new IPsec Security Association Attribute [ISAKMP-REG] defining the
   SA direction is needed.  The attribute class is called "SA
   Direction", and it is a Basic type.  The following rules apply to
   define the values of the attribute:

              Name                      Value
              ----                      -----
              Reserved                  0
              Sender-Only               1
              Receiver-Only             2
              Symmetric                 3
              Standards Action         4-61439
              Private Use          61440-65535

























Weis, et al.            Expires January 13, 2011               [Page 52]

Internet-Draft                    GDOI                         July 2010


9.  Acknowledgements

   This text updates RFC 3547, and the authors with to thank Mark
   Baugher and Hugh Harney for their extensive contributions.

   The authors are grateful to Catherine Meadows for her careful review
   and suggestions for mitigating the man-in-the-middle attack she had
   previously identified.  Yoav Nir provided many useful technical and
   editorial comments and suggestions for improvement.










































Weis, et al.            Expires January 13, 2011               [Page 53]

Internet-Draft                    GDOI                         July 2010


10.  References

10.1.  Normative References

   [I-D.ietf-msec-ipsec-group-counter-modes]
              McGrew, D. and B. Weis, "Using Counter Modes with
              Encapsulating Security Payload (ESP) and Authentication
              Header (AH) to Protect Group Traffic",
              draft-ietf-msec-ipsec-group-counter-modes-05 (work in
              progress), March 2010.

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

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.

   [RFC5374]  Weis, B., Gross, G., and D. Ignjatic, "Multicast
              Extensions to the Security Architecture for the Internet
              Protocol", RFC 5374, November 2008.

10.2.  Informative References

   [FIPS.180-2.2002]
              National Institute of Standards and Technology, "Secure
              Hash Standard", FIPS PUB 180-2, August 2002, <http://
              csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf>.

   [FIPS186-3]
              "Digital Signature Standard (DSS)", United States of
              America, National Institute of Science and
              Technology Federal Information Processing Standard (FIPS)
              186-2, June 2009.

   [FIPS197]  "Advanced Encryption Standard (AES)", United States of
              America, National Institute of Science and
              Technology Federal Information Processing Standard (FIPS)
              197, November 2001.

   [FIPS46-3]
              "Data Encryption Standard (DES)", United States of
              America, National Institute of Science and
              Technology Federal Information Processing Standard (FIPS)
              46-3, October 1999.




Weis, et al.            Expires January 13, 2011               [Page 54]

Internet-Draft                    GDOI                         July 2010


   [FIPS81]   "DES Modes of Operation", United States of America,
              National Institute of Science and Technology Federal
              Information Processing Standard (FIPS) 81, December 1980.

   [FS00]     Ferguson, N. and B. Schneier, Counterpane, "A
              Cryptographic Evaluation of IPsec",
              <http://www.counterpane.com/ipsec.html>.

   [GDOI-REG]
              Internet Assigned Numbers Authority, "Group Domain of
              Interpretation (GDOI) Payload Type Values", IANA Registry,
              December 2004,
              <http://www.iana.org/assignments/gdoi-payloads>.

   [I-D.weis-gdoi-mac-tek]
              Weis, B. and S. Rowles, "GDOI Generic Message
              Authentication Code Policy", draft-weis-gdoi-mac-tek-01
              (work in progress), June 2010.

   [ISAKMP-REG]
              "'Magic Numbers' for ISAKMP Protocol",
              <http://www.iana.org/assignments/isakmp-registry>.

   [MP04]     Meadows, C. and D. Pavlovic, "Deriving, Attacking, and
              Defending the GDOI Protocol", ESORICS 2004 pp. 53-72,
              September 2004.

   [NNL]      Naor, D., Noal, M., and J. Lotspiech, "Revocation and
              Tracing Schemes for Stateless Receivers", Advances in
              Cryptology, Crypto '01,  Springer-Verlag LNCS 2139, 2001,
              pp. 41-62, 2001,
              <http://www.wisdom.weizmann.ac.il/~naor/>.

   [OFT]      McGrew, D. and A. Sherman, "Key Establishment in Large
              Dynamic Groups Using One-Way Function Trees", Manuscript,
               submitted to IEEE Transactions on Software Engineering,
              1998, <http://download.nai.com/products/media/nai/misc/
              oft052098.ps>.

   [PK01]     Perlman, R. and C. Kaufman, "Analysis of the IPsec Key
              Exchange Standard", WET-ICE conference , 2001,
              <http://sec.femto.org/wetice-2001/papers/radia-paper.pdf>.

   [RFC2403]  Madson, C. and R. Glenn, "The Use of HMAC-MD5-96 within
              ESP and AH", RFC 2403, November 1998.

   [RFC2404]  Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
              ESP and AH", RFC 2404, November 1998.



Weis, et al.            Expires January 13, 2011               [Page 55]

Internet-Draft                    GDOI                         July 2010


   [RFC2407]  Piper, D., "The Internet IP Security Domain of
              Interpretation for ISAKMP", RFC 2407, November 1998.

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

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

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

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

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

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

   [RFC3686]  Housley, R., "Using Advanced Encryption Standard (AES)
              Counter Mode With IPsec Encapsulating Security Payload
              (ESP)", RFC 3686, January 2004.

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

   [RFC3947]  Kivinen, T., Swander, B., Huttunen, A., and V. Volpe,
              "Negotiation of NAT-Traversal in the IKE", RFC 3947,
              January 2005.

   [RFC4046]  Baugher, M., Canetti, R., Dondeti, L., and F. Lindholm,
              "Multicast Security (MSEC) Group Key Management
              Architecture", RFC 4046, April 2005.

   [RFC4106]  Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
              (GCM) in IPsec Encapsulating Security Payload (ESP)",
              RFC 4106, June 2005.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4309]  Housley, R., "Using Advanced Encryption Standard (AES) CCM
              Mode with IPsec Encapsulating Security Payload (ESP)",



Weis, et al.            Expires January 13, 2011               [Page 56]

Internet-Draft                    GDOI                         July 2010


              RFC 4309, December 2005.

   [RFC4430]  Sakane, S., Kamada, K., Thomas, M., and J. Vilhuber,
              "Kerberized Internet Negotiation of Keys (KINK)",
              RFC 4430, March 2006.

   [RFC4543]  McGrew, D. and J. Viega, "The Use of Galois Message
              Authentication Code (GMAC) in IPsec ESP and AH", RFC 4543,
              May 2006.

   [RFC4754]  Fu, D. and J. Solinas, "IKE and IKEv2 Authentication Using
              the Elliptic Curve Digital Signature Algorithm (ECDSA)",
              RFC 4754, January 2007.

   [RFC4868]  Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
              384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5903]  Fu, D. and J. Solinas, "Elliptic Curve Groups modulo a
              Prime (ECP Groups) for IKE and IKEv2", RFC 5903,
              June 2010.

   [SKEME]    Krawczyk, H., "SKEME: A Versatile Secure Key Exchange
              Mechanism for Internet", ISOC Secure Networks and
              Distributed Systems Symposium San Diego, 1996.

   [SP.800-131]
              Barker, E. and A. Roginsky, "Recommendation for the
              Transitioning of Cryptographic Algorithms and Key
              Lengths", United States of America, National Institute of
              Science and Technology DRAFT NIST Special Publication 800-
              131, June 2010.

   [SP.800-38A]
              Dworkin, M., "Recommendation for Block Cipher Modes of
              Operation", United States of America, National Institute
              of Science and Technology NIST Special Publication 800-38A
              2001 Edition, December 2001.

   [STS]      Diffie, W., Van Oorschot, P., and M. Wiener,
              "Authentication and Authenticated Key Exchanges", Designs,
              Codes and Cryptography, 2, 107-125 (1992), Kluwer Academic
              Publishers, 1992.





Weis, et al.            Expires January 13, 2011               [Page 57]

Internet-Draft                    GDOI                         July 2010


Appendix A.  Alternate GDOI Phase 1 protocols

   This section describes a manner in which other protocols could be
   used as GDOI Phase 1 protocols in place of the ISAKMP Phase 1
   protocol.  However, they are not specified as a part of this
   document.  A separate document MUST be written in order for another
   protocol to be used as a GDOI Phase 1 protocol.

   Other possible phase 1 protocols are also described in [RFC4046].

   Any GDOI phase 1 protocol MUST satisfy the requirements specified in
   Section 2 of this document.

A.1.  IKEv2 Exchange

   Version 2 of the IKE protocol (IKEv2) [RFC4306] has been
   published.That protocol simplifies IKE processing, and combines the
   two phases of IKE.  An IKEv2 Phase 1 negotiates an IPsec SA during
   phase 1, which was not possible in IKE.  However, IKEv2 also defines
   a phase 2 protocol.  The phase 2 protocol is protected by the Phase
   1, similar in concept to how IKE Quick Mode is protected by the IKE
   Phase 1 protocols in [RFC2409].

   It would be possible to define GDOI as a phase 2 protocol protected
   by an IKEv2 initial exchange.  Alternatively, it would be possible to
   define a new protocol re-using some of the IKEv2 initial exchange
   (e.g., IKE_SA_INIT).

A.2.  KINK Protocol

   The Kerberized Internet Negotiation of Keys (KINK) [RFC4430] has
   defined a method of encapsulating an IKEv1 Quick Mode [RFC2409]
   encapsulated in Kerberos KRB_AP_REQ and KRB_AP_REP payloads.  KINK
   provides a low-latency, computationally inexpensive, easily managed,
   and cryptographically sound method of setting up IPsec security
   associations.

   The KINK message format includes a GDOI field in the KINK header.
   The [RFC4430] document defines the DOI for the IPsec DOI.

   A new DOI for KINK could be defined which would encapsulate a
   GROUPKEY-PULL exchange in the Kerberos KRB_AP_REQ and KRB_AP_REP
   payloads.  As such, GDOI would benefit from the computational
   efficiencies of KINK.







Weis, et al.            Expires January 13, 2011               [Page 58]

Internet-Draft                    GDOI                         July 2010


Appendix B.  Significant Changes from RFC 3547

   The following significant changes have been made from RFC 3547.

   o  The Proof of Possession (POP) payload was removed from the
      GROUPKEY-PULL exchange.  It provided an alternate form of
      authorization, but its use was underspecified.  Furthermore,
      Meadows and Pavlovic [MP04] discussed a man-in-the-middle attack
      on the POP authorization method, which would require changes to
      its semantics.  No known implementation of RFC 3547 supported the
      POP payload, so it was removed.  Removal of the POP payload
      obviated the need for the CERT payload in that exchange and it was
      removed as well.

   o  The Key Exchange Payloads (KE_I, KE_R) payloads were removed from
      the GROUPKEY-PULL exchange.  However, the specification for
      computing keying material for the additional encryption function
      in RFC 3547 is faulty.  Furthermore, it has been observed that
      because the GDOI registration message uses strong ciphers and
      provides authenticated encryption, additional encryption of the
      keying material in a GDOI registration message provides negligible
      value.  Therefore, the use of KE payloads is deprecated in this
      memo.

   o  The Certificate Payload (CERT) was removed from the GROUPKEY-PUSH
      exchange.  The use of this payload was underspecified.  In all
      known use cases, the public key of used to verify the GROUPKEY-
      PUSH payload is distributed directly from the key server as part
      of the GROUPKEY-PULL exchange.

   o  Supported cryptographic algorithms were changed to meet current
      guidance.  Implementations are required to support AES with 128-
      bit keys to encrypt the rekey message, and SHA-256 for
      cryptographic signatures.  The use of DES is deprecated.

   o  New protocol support for AH.

   o  New protocol definitions were added to conform to the most recent
      Security Architecture for the Internet Protocol [RFC4301] and the
      Multicast Extensions to the Security Architecture for the Internet
      Protocol[RFC5374].

   o  New protocol definitions were added to support Using Counter Modes
      with ESP and AH to Protect Group
      Traffic[I-D.ietf-msec-ipsec-group-counter-modes].






Weis, et al.            Expires January 13, 2011               [Page 59]

Internet-Draft                    GDOI                         July 2010


Authors' Addresses

   Brian Weis
   Cisco Systems
   170 W. Tasman Drive
   San Jose, California  95134-1706
   USA

   Phone: +1-408-526-4796
   Email: bew@cisco.com


   Sheela Rowles
   Cisco Systems
   170 W. Tasman Drive
   San Jose, California  95134-1706
   USA

   Phone: +1-408-527-7677
   Email: sheela@cisco.com


   Thomas Hardjono
   MIT
   77 Massachusetts Ave.
   Cambridge, Massachusets  02139
   USA

   Phone: +1-781-729-9559
   Email: hardjono@mit.edu





















Weis, et al.            Expires January 13, 2011               [Page 60]

Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/