WDIFF

draft-ietf-msec-arch-00.txt --> draft-ietf-msec-arch-01.txt

Internet Engineering Task Force Thomas Hardjono (VeriSign)
INTERNET-DRAFT Brian Weis (Cisco)
draft-ietf-msec-arch-00.txt
draft-ietf-msec-arch-01.txt Expires November 2003
May 2003
November 2002

The Multicast Security (MSEC) Architecture

Status of this Memo

This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.

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."

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

Abstract

This document provides a foundation for the protocols developed by an overview and rationale of the Multicast Security (MSEC) group. multicast
security architecture used for large multicast groups. The document
begins by introducing a Multicast Security Reference Framework, and
proceeds to identify
functional areas which must the security services may be addressed as part of a secure
multicast solution.

Hardjono, Weis Expires May, November, 2003 1
MSEC Architecture October, 2002 May, 2003

Table of Contents

1. Introduction.......................................................2
1.1 Summary of Contents of Document.................................2 Document.................................3
1.2 Audience........................................................3
1.3 Related Documents...............................................3 Terminology.....................................................3
2. Architectural Design: The MSEC Multicast Security Reference Framework.................4 Framework...4
2.1 A The Reference Framework...........................................4 Framework.........................................4
2.2 Elements of the Reference Framework.............................5
2.2.1 Group Controller and Key Server.............................5 Server.............................6
2.2.2 Sender and Receiver.........................................6
2.2.3 Policy Server...............................................6 Server...............................................7
2.2.4 Centralized and Distributed Designs.........................7
3. Functional Areas...................................................7
3.1 Multicast Data..................................................7 Data..................................................8
3.2 Management of Keying Material...................................8
3.3 Multicast Security Policies.....................................8 Policies.....................................9
4. Group Security Associations (GSA).................................10
4.1 SAs and Multicast..............................................10
4.1
4.2 Structure of a GSA: Introduction...............................11
4.3 Structure of a GSA: Reasoning..................................11 Reasoning..................................12
4.4 Definition of GSA..............................................12
4.5 Typical Compositions of a GSA..................................14
5. Security Services.................................................14 Services.................................................15
5.2.1 Multicast Data Confidentiality.............................14 Confidentiality.............................15
5.2.2 Multicast Source Authentication and Data Integrity.........15
5.2.3. Integrity.........16
5.2.3 Multicast Group Authentication............................15 Authentication.............................16
5.2.4 Multicast Group Membership Management......................16 Management......................17
5.2.5 Multicast Key Management...................................16 Management...................................17
5.2.6 Multicast Policy Management................................17
6. MSEC Documents Roadmap............................................18
7. Conclusion........................................................19 Management................................18
8. Acknowledgments...................................................19 Security Considerations...........................................19
9. References........................................................19
9.1 Acknowledgments...................................................19
10. References.......................................................19
10.1 Normative References...........................................19
9.2 References..........................................19
10.2 Informative References.........................................20 References........................................19
Authors Addresses....................................................21 Addresses....................................................20

1. Introduction

Securing IP multicast communication is a complex task that involves
many aspects. Consequently, a secure IP multicast protocol suite must
have a number of functional areas that address different aspects of
the problem. solution. This document describes those functional areas, and
protocols which have been developed which fit into those component
areas.

1.1 Summary of Contents how
they are related.

This architecture is concerned with the securing of Document large multicast
groups. Whereas it can also be used for smaller groups, it is not
necessarily the most efficient means. For example, the Cliques

Hardjono, Weis Expires May, November, 2003 2
MSEC Architecture October, 2002 May, 2003

architecture [STW] is an efficient for small ad-hoc group
communication.

1.1 Summary of Contents of Document

This document provides an architectural overview of the work being
conducted in that outlines the MSEC Working Group.
security services required to secure large multicast groups. It
provides a Reference Framework for covering organizing the scope of various elements
within the problems in multicast
security, architecture, and explains the elements of the Reference
Framework.

The Reference Framework, in turn, provides Framework organizes the division elements of labor the architecture
along three Functional Areas pertaining to security. These cover the
treatment of data from a security perspective when it is to be sent
to a group, the management of keying material used to protect the
data
data, and the policies governing a group.

Another important item in this document is the definition and
explanation of Group Security Associations (GSA), which is the
multicast counterpart of the unicast Security Association (SA). The
GSA is specific to multicast security, and is the foundation of the
work on group key management.

1.2 Audience

This document is addressed to the technical community and community, implementers
of IP multicast security technology technology, and others interested in gaining
a general background understanding of multicast security. This
document assumes that the reader is familiar with the Internet
Protocol, the IPsec suite of protocols (e.g. IPsec, IKE, ISAKMP), IPsec [RFC2401], IKE
[RFC2409], ISAKMP [RFC2408]), related networking technology, and
general security terms and concepts.

1.3 Related Documents

Other documents provide detailed explanations of the Functional Areas
within the MSEC Reference Framework. These include the Terminology

The following set
of documents:

a. "Group Key Management Architecture" document [BCDL] -- a document
that provides the key management architecture for multicast
security, building on the terms are used throughout this document.

1-to-N

A group which has one sender and many receivers.

Group Security Association (GSA)
concept defined in the current document.

b. "Group Domain

A bundling of Interpretation" [BHHW] Security Associations (SAs) that together define
how a group communicates securely. The GSA may include an
registration protocol SA, a rekey protocol SA, and "GSAKMP Light" [HSC], one or more
data security protocol SAs.

M-to-N

A group which are two instances of protocols implementing the group key
management function.

c. "Multicast Encapsulating Security Payload" [BCCR], which provides
the definition for Multicast ESP, for data traffic.

d. "Multicast Source Authentication Transform Specification" [PCW],
which defines the use of has many senders and many receivers, where M and N
are not necessarily the TESLA algorithm for source
authentication in multicast. same value.

Hardjono, Weis Expires May, November, 2003 3
MSEC Architecture October, 2002 May, 2003

Security Association (SA)

A set of policy and cryptographic keys that provide security
services to network traffic that matches that policy.

2. Architectural Design: The MSEC Multicast Security Reference Framework

This section considers the complex problems issues of multicast security in
the context of a heuristic device, the Reference Framework diagram, shown in Figure 1.
The Reference Framework is used to classify functional areas,
functional elements, and interfaces.

2.1 A The Reference Framework

Based

The reference framework is based on the three broad functional areas, a reference framework is
proposed areas
(Figure 1). The reference framework attempts to incorporate incorporates the main entities
and functions relating to multicast security, and
to depict depicts the inter-relations inter-
relations among them. At the same time, it It also
tries to express the complex expresses multicast security question from the
perspective of problem classification (i.e., the three functional
areas), from the
perspective of architectures (centralized and distributed), of
multicast group types (1-to-M or (1-to-N and M-to-N), and classes of protocols
(the exchanged messages). messages) needed to secure multicast packets.

The aim of the reference framework is to provide some general context
within which
around the functional areas can be identified and classified areas, and the relationships among between the
functional areas can be recognized. areas. Note that some issues span more than one so-called
functional area. In fact, the framework encourages the precise
identification and formulation of issues that involve more than one
functional area or those which are difficult to express in terms of a
single functional area. An example of such a case is the expression
of policies concerning group keys, which involves both the functional
areas of group key management and multicast policies.

When considering the reference framework (Figure 1) Figure 1, it is important to realize that the
singular "boxes" in the framework do not necessarily imply a
corresponding singular entity implementing a given function. Rather,
a box in the framework should be interpreted loosely as pertaining to
a given function related to a functional area. Whether that function
is in reality implemented as one or more physical entities is
dependent on the particular solution. As an example, the box labeled
"Key Server" must be interpreted in broad terms as referring to the
functions of key management.

Similarly, the Reference Framework acknowledges that some
implementations may in fact merge a number of the "boxes" into a
single physical entity. This could be true even across functional
areas. For example, an entity in a group could act as both a Group
Controller and a Sender to a group.

The reference framework can be viewed horizontally and vertically.
Horizontally, it displays both the entities and functions as singular
boxes, expressing each of the three broad functional areas.
Vertically, it expresses the basic architecture designs for

Hardjono, Weis Expires November, 2003 4
MSEC Architecture May, 2003

solutions, namely a centralized architecture and a distributed
architecture.

The protocols to be standardized are depicted in Figure 1 by the
arrows that connect the various boxes. See more details in Section 4,
below.

Hardjono, Weis Expires May, 2003 4
MSEC Architecture October, 2002

+-----------------------------------------------------------------+
| CENTRALIZED \ DISTRIBUTED |
| DESIGNS \ DESIGNS |
| FUNCTIONAL \ |
| AREAS \ |
| +------+ \ +------+ |
| Multicast |Policy|<-------\------------------------>|Policy| |
| Security |Server| \ |Server| |
| Policies +------+ \ +------+ |
| ^ \ ^ |
| | \ | |
| | \ | |
| v \ v |
| +------+ \ +------+ |
| Group |Group |<-------------- \---------------> |Group | |
| Key |Ctrl/ |<---------+ \ |Ctlr/ | |
| Management |Key | | \ |Key | |
| |Server| V \ |Server| |
| +------+ +--------+ \ +------+ |
| ^ | | \ ^ |
| | |Receiver| \ | |
| | | | | | |
| v +--------+ | | |
| +------+ ^ | V |
| | | | | +--------+ |
| Multicast |Sender|<---------+ |Sender|----------+ | | | |
| Data | |<--------------------- |---------------------- |-------->|Receiver| |
| Handling | | | | | |
| +------+ | +--------+ |
+-----------------------------------------------------------------+
Figure 1: MSEC Multicast Security Reference Framework

2.2 Elements of the Reference Framework

The Reference Framework diagram of Figure 1 contains boxes and
arrows. The boxes are the functional entities and the arrows are the
interfaces between them. Standard protocols are needed for the
interfaces, which support the multicast services between the
functional entities.

In some cases, a system implementing the multicast security
architecture may not need to implement protocols to account for every
interface. Rather, those interfaces may be satisfied through the use

Hardjono, Weis Expires November, 2003 5
MSEC Architecture May, 2003

of manual configuration, or even omitted if they are not necessary
for the application.

There are three sets of functional entities in both centralized and
distributed designs as discussed below.

2.2.1 Group Controller and Key Server

The Group Controller and Key Server (GCKS) represent both the entity
and functions relating to the issuance and management of
cryptographic keys used by a multicast group, which is subject to the
user-authentication and authorization checks conducted on the
candidate member of the multicast group.

Hardjono, Weis Expires May, 2003 5
MSEC Architecture October, 2002

In a distributed architecture the GCKS entity also interacts with
other GCKS entities to achieve scalability in the key management
related services. In such a case, each member of a multicast group
may interact with one or more GCKS entity (say, the "nearest" GCKS
entity, measured in terms of a well-defined and consistent metric).
Similarly, in a distributed architecture a GCKS entity may interact
with one or more Policy Servers, also arranged in a distributed
architecture.

We remark that the

The Key Server (KS) and the Group Controller (GC) have somewhat
different functionality and may in principle be regarded as separate
entities. Currently the framework regards the two entities as one
"box" in order to simplify the design, and in order not to mandate
standardization of the protocol between the KS and the GC. It is
stressed that the KS and GC need NOT not be co-located. Furthermore,
future designs may choose to standardize the protocol between the GC
and the KS, without altering other components.

2.2.2 Sender and Receiver

The Sender is an entity that sends data to the multicast group. In a
1-to-N multicast group only a single sender is allowed authorized to transmit
data to the group. In an M-to-N multicast group, many (or even all)
group members can are authorized to transmit data to the group.

Both Sender and Receiver must interact with the GCKS entity for the
purpose of key management. This includes user-authentication, user and/or device
authentication, user and/or device authorization, the obtaining of
keying material in accordance with some key management policies for
the group, obtaining new keys during key-updates, and obtaining other
messages relating to the management of keying material and security
parameters.

The influence of policies on both

Senders and Receivers is seen as
coming indirectly through may receive much of their policy from the GCKS entities, since the
entities. The event of joining a multicast group is typically coupled
with the Sender/Receiver obtaining keying material from a GCKS
entity. This does not preclude the direct interaction between the
Sender/Receiver and the Policy Server.

Hardjono, Weis Expires November, 2003 6
MSEC Architecture May, 2003

The reference framework displays two Receiver boxes corresponding to
the situation where both the Sender and Receiver employ the same GCKS
entity (centralized architecture) and where the Sender and Receiver
employ different GCKS entities (distributed architecture).

2.2.3 Policy Server

The Policy Server represents both the entity and functions used to
create and manage security policies specific to a multicast group.
The Policy Server interacts with the GCKS entity in order to install
and manage the security policies related to the membership of a given
multicast group and those related to keying material for a multicast
group.

Hardjono, Weis Expires May, 2003 6
MSEC Architecture October, 2002

The interactions between the Policy Server and other entities in the
reference framework is dependent to a large extent on the security
circumstances being addressed by a given policy.

2.2.4 Centralized and Distributed Designs

The need for solutions to be scalable to large groups across wide
geographic regions of the Internet requires the elements of the
framework to also function as a distributed system.

This implies that a GCKS entity must be able to interact securely
with other GCKS entities in a different location. These GCKS entities
will require a means of authenticating their peer GCKS entities, a
means of authorization (e.g., delegation certificates), and a means
of interacting securely to pass keys and policy.

Similarly, Policy Servers must interact with each other securely to
allow the communication and enforcement of policies across the
Internet.

3. Functional Areas

In order to begin to address the problems in securing IP multicast,
we identify three functional area emanating from the reference
framework.

The Reference Framework identifies three functional area areas. They are:

� Multicast data handling. This area covers problems concerning the security-related
treatments of multicast data by the sender and the receiver.
This functional area is further discussed in Section 3.1.

� Group Key Management. This area is concerned with the secure
distribution and refreshment of keying material. This functional
area is further discussed in Section 3.2.

� Multicast security policies. This area covers aspects of policy
in the context of multicast security, taking into consideration
the fact that policies may be expressed in different ways, that
they may exist at different levels in a given multicast security
architecture
architecture, and that they may be interpreted differently
according to the context in which they are specified and

Hardjono, Weis Expires November, 2003 7
MSEC Architecture May, 2003

implemented. This functional area is further discussed in
Section 3.3.

3.1 Multicast Data

In a secure multicast group, the data typically needs to be:

1. Encrypted using the group key, mainly for access control and
possibly also for confidentiality.

2. Authenticated, for verifying the source and integrity of the
data. Authentication takes two flavors:
2.1
a. Source authentication and data integrity. This
functionality guarantees that the data originate originated with the
claimed source and was not modified en route (either by a
group member or an external attacker).

Hardjono, Weis Expires May, 2003 7
MSEC Architecture October, 2002

2.2
b. Group authentication. This type of authentication only
guarantees that the data was generated (or last modified)
by some group member. It does not guarantee data integrity
unless all group members are trusted.

While multicast encryption and group authentication are fairly
standard and similar to encrypting and authenticating point-to-point
communication, source authentication for multicast is considerably
more involved. Consequently, off-the-shelf solutions (e.g., taken
from IPSec [RFC2406], TLS [RFC2246]) [RFC2406]) may be sufficient for
encryption. encryption and group
authentication. For source authentication, however, special-purpose
transformations are necessary. See [CP99] [CCPRRS] for further
elaboration on the concerns regarding the data transforms, on present solutions transforms.

Multicast data encrypted and/or authenticated by a sender should be
handled the same way by both centralized and remaining challenges. distributed receivers,
(as shown in Figure 1).

The "Multicast Encapsulating Security Payload" [BCCR] provides the
definition for Multicast ESP for data traffic. The "Multicast Source
Authentication Transform Specification" [PCW] defines the use of the
TESLA algorithm for source authentication in multicast.

3.2 Management of Keying Material

The term "keying material" refers to the cryptographic key keys belonging
to a group, the state associated with the keys keys, and the other
security parameters related to the keys. Hence, the management of
the cryptographic keys belonging to a group necessarily requires the
management of their associated state and parameters. A number of
solutions for specific problems issues must be addressed. These may include
the following:

� Methods for member identification and authentication.
� Methods to verify the membership to groups.

Hardjono, Weis Expires November, 2003 8
MSEC Architecture May, 2003

� Methods to establish a secure channel between a GCKS entity and
the member, for the purpose of delivery of shorter-term keying
material pertaining to a group.
� Methods to establish a long-term secure channel between one GCKS
entity and another, for the purpose of distributing shorter-term
keying material pertaining to a group.
� Methods to effect the changing of keys and keying material
� Methods to detect and signal failures and perceived compromises
to keys and keying material

The needs related to the management of keying material must be seen
in the context of the policies that prevail within the given
circumstance.

Core to the problem area of key management is Security Association (SA)
Management, which will be discussed further below.

A "Group Key Management Architecture" document [BCDL] further defines
the key management architecture for multicast security. It builds on
the Group Security Association (GSA) concept, and further defines the
roles of the Key Server and Group Controller.

"The Group Domain of Interpretation" [BHHW], "GSAKMP" [HSMC], and
"MIKEY" [ACLNM] are three instances of protocols implementing the
group key management function.

3.3 Multicast Security Policies

Multicast Security Policies must provide the rules for operation for
the other elements of the Reference Framework. While much of the
work for the Multicast Security Policy area is focused in the Policy
Controller, there Policies may
be distributed in an ad-hoc fashion in some instances. However,
better coordination and higher levels of assurance are potential areas achieved if a
Policy Controller distributes Security Policies policy to the group.

Multicast security policies must represent, or contain, more
information than a traditional peer-to-peer policy. In addition to
representing the security mechanisms for work the group communication, the
policy must also represent the rules for the governance of the secure
group. For example, policy would specify the authorization level
necessary in order for an entity to join a group. More advanced
operations would include the conditions when a group member must be
forcibly removed from the group, and what to do if the group members
need to resynchronize because of lost key management messages.

The application of policy at the Group Controller element and the
member (sender and receiver) elements. elements must be described. While there
is already a basis for security policy management in the IETF between the Policy Working Group and

Hardjono, Weis Expires May, 2003 8
MSEC Architecture October, 2002

the IP Security Policy Working Group, IETF,
multicast security policy management will extend extends the concepts developed
for unicast communication in the areas of:

� Policy creation,
� High-level policy translation, and
� Policy representation.

Hardjono, Weis Expires November, 2003 9
MSEC Architecture May, 2003

Examples of work in multicast security policies include the Dynamic
Cryptographic Context Management project [Din], Group Key Management
Protocol [Har1, Har2], and Antigone[McD].

Policy creation for secure multicast has several more dimensions than
the single administrator specified policy assumed in the existing
unicast policy frameworks. Secure multicast groups are usually large
and by their very nature extend over several administrative domains,
if not spanning a different domain for each user. There are several
methods that need to be explored for considered in the creation of a single,
coherent group security policy. They include a top-down specification
of the group policy from the group initiator and negotiation of the
policy between the group members (or prospective members).
Negotiation can be as simple as a strict intersection of the policies
of the members or extremely complicated using weighted voting
systems.

High-level policy

The translation of policy rules from one data model to another is
much more difficult in a multicast group environment, environment. This is
especially true when group membership spans multiple administrative
domains. When policies are Policies specified at a high level with a Policy Management tool, they
tool must then be translated into more precise rules that the available
security policy mechanisms can both understand and implement. When
dealing with multicast communication and its multiple participants,
it is essential that the individual translation performed for each
participant result in the use of a mechanism that is interoperable
with the results of all of the other translations. Typically, the
translation from high-level policy to
implementation mechanisms specific policy objects must
result in the same mechanism objects in order to achieve communication between
all of the group members. The requirement that policy translation
results in the same mechanism objects places constraints on the use and
representations in the high-level policies.

It is also important that policy negotiation and translation be
performed as an integral part of joining a group. Adding a member to
a group is meaningless if they will not be able to participate in the
group communications.

Multicast security policies must represent, or contain, more
information than a traditional peer-to-peer policy. In addition to
representing the security mechanisms for the group communication, the
policy must also represent the rules for the governance of the secure
group. Policy must be established for the basic group operations of
add and remove, as well as more advanced operations such as leave,
rejoin, or resynchronize.

Hardjono, Weis Expires May, 2003 9
MSEC Architecture October, 2002

4. Group Security Associations (GSA)

4.1 SAs and Multicast

It is clear that the The Security Association

A security associations (SA) for group key
management are more complex, or at least more numerous, than for
Internet key management [RFC2409]. The latter establishes a key
management SA to protect application SAs (where a minimum of two are
needed to key an Internet application process). However, group key
management requires at least three: There association is a registration SA
between the group member and the GCKS, a rekey SA between the GCKS
and all the group members, and an SA to protect application data from
sender-members to receiver-members. In fact, each sender to the
group may use a unique key for their data and use a separate SA:
there may be more SAs than there are group senders.

Group key management, therefore, uses commonly used term in cryptographic
systems [RFC2401, RFC2409]. It describes a different set of abstractions
than ISAKMP policy and IKE. Notwithstanding, the abstractions used in our
Group Key Management functional area may be built from the ISAKMP
abstractions. In our approach
cryptographic keys that provide security services for the Group network
traffic matching that policy. A Security Association (GSA)
includes the attributes of the Internet Security Architecture SA,
which is succinctly defined as usually
contains the encapsulation of keys and policies
[RFC2409] as follows. following attributes:

- An SA has selectors, such as source and destination transport addresses.
- An SA has properties, such as an security parameter index (SPI) or cookie
pair, and identities.

Hardjono, Weis Expires November, 2003 10
MSEC Architecture May, 2003

- An SA has cryptographic policy, such as the algorithms, modes, key
lifetimes, and key lengths used for authentication or
confidentiality.
- An SA has keys, such as authentication, encryption and signing keys.

As is discussed in the next section of this memo, a GSA contains the
SA attributes plus some additional ones. As shown in Figure 2 (a),
the GSA is

Group key management uses a superset different set of the SA.

� A GSA has group policy attributes, abstractions than point-
to-point key management systems, such as IKE [RFC2409].
Notwithstanding, the kind of signed
credential needed for group membership and whether the group abstractions used in the Group Key Management
functional area may be built from the point-to-point key management
abstractions.

4.2 Structure of a GSA: Introduction

Security associations (SAs) for group key management are more
complex, and are usually more numerous, than for point-to-point key
management algorithms. The latter establishes a key management SA to
protect application SAs (usually one or two, depending on the
protocol). However, group key management may require up to three or
more SAs. These SAs are described in later sections.

A GSA contains all of the SA attributes identified in the previous
section, as well some additional attributes pertaining to the group.
As shown in Figure 2, the GSA builds on the SA in two distinct ways.

� First, the GSA is a superset of an SA (Figure 2(a)).
� A GSA has group policy attributes, such as the kind of signed
credential needed for group membership, if group members will be
given new keys when a member is added (called "backward re-key" below)
below), or whether group members will be given new key when a
member is removed from the group ("forward re-key").
- A GSA has SAs also
includes an SA as attributes.

Hardjono, Weis Expires May, 2003 10
MSEC Architecture October, 2002 an attribute of itself.

� Second, the GSA is an aggregation of SAs (Figure 2(b)). A GSA is
comprised of multiple SAs, and these SAs may be used for several
independent purposes.

+------------------------------------------------------------+
| |
| +---------------+ +-------------------+ |
| | GSA | | GSA | |
| | | | +-----+ +-----+ | |
| | | | | SA1 | | SA2 | | |
| | +----+ | | +-----+ +-----+ | |
| | | SA | | | +-----+ | |
| | +----+ | | | SA3 | | |
| | | | +-----+ | |
| +---------------+ +-------------------+ |
| |
| (a) superset (b) aggregation |
| |
+------------------------------------------------------------+
Figure 2: Relationship of GSA to SA

4.1

Hardjono, Weis Expires November, 2003 11
MSEC Architecture May, 2003

4.3 Structure of a GSA: Reasoning

There are

Figure 3 shows three categories of SAs that can be aggregated into a GSA in Figure
2(b). We choose this structure to better realize a GSA in our key
management environment.
GSA. There is a need to maintain SAs between a Key Server and a group
member (either (both a sender, sender and a receiver or both) receiver) and among members. The Key Server is called the "GCKS," which is charged
with access control to the group keys, with policy distribution to
client members or prospective members, and with group key
dissemination to sender and receiver client members. This structure
is common in many group key management environments [HH, CP99,
RFC2627, BMS]. There are two SAs established between the GCKS and the
themselves. There are two SAs established between the GCKS and the
members, and there is an SA established among the sending and
receiving members as shown in Figure 3.

The first category of SA (namely REG in Figure 3, for "registration
SA") is initiated by the member to pull GSA information from the
GCKS. This is how the member requests to join the secure group or has
its GSA keys re-initialized after being disconnected from the group
(e.g., when its host computer has been turned off during re-key
operations as described below). The GSA information pulled down from
the GCKS include the SA, keys and policy used to secure the data
transmission between sending and receiving members; this is DATA in
Figure 3, "for data security SA". Note that DATA is a category of
SA, and this implies that there may be multiple SAs established
between member senders and member receivers - at least as an option.
There may exist, for example, a single DATA SA in which all senders
share common keys and associated information. On the other hand,
there may be one or more DATA SAs that are unique to the particular
sender. A DATA SA may be reestablished or have its keys modified
through re-key operations, which occur over a REKEY SA (for "rekey
SA). Keys are pushed through a REKEY SA to support subscription
groups.

Hardjono, Weis Expires May, 2003 11
MSEC Architecture October, 2002

Thus, despite the fact that the data to be protected are multicast,
registration exchanges through a REG SA should be unicast or point-
to-point key determination exchanges. Some group key management
solutions rely solely point-to-point. Most others combine unicast
exchanges for initialization with multicast distribution for re-key.
In some cases, such as in a pure "pay-per-session" application, all
of the SA information needed for the session may be distributed at
the time of registration or selection of a session, i.e. over a REG
SA; re-key and re-initialization may not be necessary, so there is no
REKEY SA. For subscription groups where keying material is changed
as membership changes, a REKEY SA is needed to re-initialize a DATA
SA. members.

+------------------------------------------------------------+
| |
| +------------------+ |
| | GCKS | |
| | | |
| | REG REG | |
| | / REKEY \ | |
| +---/-----|----\---+ |
| / | \ |
| / | \ |
| / | \ |
| / | \ |
| / | \ |
| +-------------/------+ +----------/------+ | +------\-------------+ +------\----------+ |
| | REG | | | REG | |
| | REKEY-----+----REKEY | |
| | MEMBER SENDER | | MEMBER RECEIVER| RECEIVER | |
| | DATA----------DATA | |
| +--------------------+ +--------------------+ +-----------------+ +-----------------+ |
| |
| |
+------------------------------------------------------------+
Figure 3: GSA Structure and 3 categories of SAs

4.2

4.4 Definition of GSA

The GSA includes an aggregate of the three aforementioned categories of SAs. The
three categories of SAs correspond to the three kinds of
communications as seen from the point of view commonly required for group communications. The three
categories of the Receiver
(Member). SAs depicted in Figure 3 depicts this concept: are:

Hardjono, Weis Expires November, 2003 12
MSEC Architecture May, 2003

- Registration (REG) SA: SA (REG):
An SA is required for (bi-directional) unicast communications
between the GCKS and a group member (be it a Sender or Receiver).
This SA is established only between the GCKS and a Member. The
GCKS entity is charged with access control to the group keys,
with policy distribution to members (or prospective members), and
with group key dissemination to Sender and Receiver members. This
use of a (unicast) SA as a starting point for key management is

Hardjono, Weis Expires May, 2003 12
MSEC Architecture October, 2002
common in a number of group key management environments [HH,
CP99, [BHHW,
HSMC, CCPRRS, RFC2627, BMS, Bris99]. BMS,].

The Registration SA is initiated by the member to pull GSA
information from the GCKS. This is how the member requests to
join the secure group, or has its GSA keys re-initialized after
being disconnected from the group (e.g., when its host computer
has been turned off during re-key operations). The GSA
information pulled down from the GCKS is related to the other two
SAs defined as part of the GSA.

Note that this (unicast) SA is used to protect the other elements
of the GSA (such as the other following two categories of SAs),
either in a "push" or "pull" model. GSA. As such, this the Registration SA is crucial and is
inseparable from the other two SAs as in the definition of a GSA.

However, the requirement of a registration SA does not imply the
need of a registration protocol to create that Registration SA.
The registration SA could instead be setup through some manual
means, such as distributed on a smart card. Thus, what is
important is that a Registration SA exists, and is used to
protect the other SAs.

From the perspective of one given GCKS, there are as many unique
registration SAs as there are members (Senders and/or Receivers)
in the group. This may constitute a scalability concern for some
applications, so a
applications. A registration SA may be used established on-demand with
a short lifetime, whereas re-key and data security SAs are
established at least for the life of the sessions that they support.

- sessions that they
support.

Conversely the registration SA could be left in place for the
duration of the group lifetime, if scalability is not an issue.
Such a long term registration SA would be useful for re-
synchronization or deregistration purposes.

- Re-key SA (REKEY):
In some cases, a GCKS needs the ability to "push" new SAs as part
of the GSA. These new SAs must be sent to all group members. In
other cases, the GCKS needs the ability to quickly revoke access
to one or more group members. Both of these needs are satisfied
with the Re-key SA.

This Re-key (REKEY) SA:
An SA is required for the a unidirectional multicast transmission of key
management messages (unidirectional) from the GCKS to all group members. As such,
this SA is known by the GCKS and by all members of the group.

Hardjono, Weis Expires November, 2003 13
MSEC Architecture May, 2003

This SA is not negotiated, since all the group members must share
it. Thus, the GCKS must be the authentic source and act as the
sole point of contact for the group members to obtain this SA.

From

A rekey SA is not absolutely required to be part of a GSA. For
example, the perspective lifetime of each participant in some groups may be short enough such
that a group (GCKS and all
members), there rekey is at least one registration SA for not necessary. Conversely, the group.
Note that this allows policy for the possibility of the GCKS deploying
group could specify multiple re-key rekey SAs for of different types. For
example, if the GC and KS are separate entities, the GC may
deliver rekey messages that adjust the group key management purposes. membership, and the
KS may deliver rekey messages with new DATA SAs.

- Data Security (DATA) SA: SA (DATA):
The Data Security SA protects data between member senders and
member receivers.

One or more SAs are required for the multicast transmission of
data-messages (unidirectional) from the Sender to other group members. This SA is
known by the GCKS and by all members of the group.

Similarly, regardless

Regardless of the number of instances of this third category of
SA, this SA is not negotiated. Rather, all group members obtain
it from the GCKS. The GCKS itself does not use this category of
SA.

From the perspective of the Receivers, there is at least one data
security SA for the member sender (one or more) in the group.
This allows for If
the possibility of including group IDs (GID) in
transmission of has more than one data packets from security SA, the senders in data security
protocol must have a means of differentiating the group. SAs (e.g., with
a SPI).

There are a number of possibilities with respect to the number of
data security SAs and the use of Group IDs (GIDs):

(i) SAs:

1. Each sender in the group could be assigned a unique dta data
security SA, thereby resulting in each receiver having to

Hardjono, Weis Expires May, 2003 13
MSEC Architecture October, 2002
maintain as many data security SAs as there are senders in the
group.

(ii) In this case, each sender may be verified using source
origin authentication techniques.

2. The entire group deploys a single data security SA for all
senders, together with all
senders. Receivers would then be able to maintain only one data
security SA.

3. A combination of 1. and 2.

4.5 Typical Compositions of a GSA

Depending on the multicast group policy, many compositions of a GSA
are possible. For illustrative purposes, this section describes a few
possible compositions.

Hardjono, Weis Expires November, 2003 14
MSEC Architecture May, 2003

� A group of memory-constrained members may require only a REG SA,
and a single DATA SA.
� A "pay-per-session" application, where all of the SA information
needed for the use session may be distributed over a REG SA. Re-key
and re-initialization of GIDs. Receivers would
then DATA SAs may not be able to filter based on the GIDs, whilst maintaining
only one data security necessary, so there
is no REKEY SA.

(iii)
� A combination of (i) and (ii) above. subscription group, where keying material is changed as
membership changes. A REG SA is needed to distribute other SAs; a
REKEY SA is needed to re-initialize a DATA SA at the time
membership changes.

5. Security Services

Referring to our the Reference Diagram, this section identifies security
services for designated interfaces of Figure 1. In this section,
distinct security services are assigned to specific interfaces. For
example, multicast source authentication, data authentication, and
confidentiality occur on the multicast data interface between Senders
and Receivers in Figure 1. Authentication and confidentiality
services may also be needed between the Key Server and key clients
(i.e., the Senders and Receivers of Figure 1), but the services that
are needed for multicast key management may be unicast as well as
multicast. A security service for multicast security, therefore,
identifies a specific function along one or more Figure 1 interfaces.

This paper does not attempt to analyze the trust relationships,
detailed functional requirements, performance requirements, suitable
algorithms, and protocol specifications for IP multicast and
application-layer multicast security. Instead, we propose these
tasks as future work that work will occur
as the functional building
blocks security services are further defined and realized in
algorithms and protocols.

We identify a set of security services in the following sections.
This preliminary list of services is intended to serve as a basis for
discussion in the MSEC working group.

5.2.1 Multicast Data Confidentiality

This security service handles the encryption of multicast data at the
Sender's end and the decryption at the Receiver's end. This security
service may also apply the keying material that is provided by
Multicast Key Management in accordance with Multicast Policy
Management, but it is independent of both.

An important part of the future work on the Multicast Data Confidentiality building block security
service is in the identification of and motivation for specific
ciphers that should be used for multicast data. Obviously, not all
ciphers will be suitable for IP multicast and application-layer
multicast traffic. Since this traffic will usually be connectionless
UDP flows, stream ciphers may be unsuitable unsuitable, though hybrid
stream/block ciphers may have advantages over some block ciphers. Those working on this security service will need to
evaluate the real-time and other requirements of multicast senders
and receivers, and recommend a small set of promising ciphers and

Hardjono, Weis Expires May, 2003 14
MSEC Architecture October, 2002

data protocols for IP multicast and application-layer multicast data
confidentiality.

Regarding application-layer multicast, some consideration is needed
to consider the effects of sending encrypted data in a multicast
environment lacking admission-control, where practically any
application program can join a multicast event independently of its
participation in a multicast security protocol. Thus, this security

Hardjono, Weis Expires November, 2003 15
MSEC Architecture May, 2003

service is also concerned with the effects of multicast
confidentiality services, intended services (intended and otherwise, otherwise) on application
programs in all
programs. Effects to both senders and receivers. receivers is considered.

In Figure 1, the Multicast Data Confidentiality security service is
placed in Multicast Data Handling Area along the interface between
Senders and Receivers. The algorithms and protocols that are
realized from work on this security service may be applied to other
interfaces and areas of Figure 1 when multicast data confidentiality
is needed.

5.2.2 Multicast Source Authentication and Data Integrity

This security service handles source authentication and integrity
verification of multicast data. It includes the transforms to be made
both at the Sender's end and at the Receiver's end. It assumes that
the appropriate signature and verification keys are provided via
Multicast Key Management in accordance with Multicast Policy
Management as described below. Work done by MSEC Working Group
members suggests that this This is one of the harder areas of
multicast
security. This is security due to the connectionless and real-time
requirements of many IP multicast applications. There are classes of
application-layer multicast security, however, where offline source
and data authentication will suffice. As discussed previously, not
all multicast applications require real-time authentication and data-
packet integrity. A robust solution to multicast source and data
authentication, however, is necessary for a Whole Protocol complete solution to
multicast security.

In Figure 1, the Multicast Source and Data Authentication security
service is placed in Multicast Data Handling Area along the interface
between Senders and Receivers. The algorithms and protocols that are
produced for this functional area may have applicability to building
blocks security
services in other functional area that use multicast services such as
Group Key Management.

5.2.3.

5.2.3 Multicast Group Authentication

This security service provides a limited amount of authenticity of
the transmitted data: It only guarantees that the data originated
with (or was last modified by) one of the group members. It does not
guarantee authenticity of the data in case that other group members
are not trusted.

Hardjono, Weis Expires May, 2003 15
MSEC Architecture October, 2002

The advantage of group authentication is that it is guaranteed via
relatively simple and efficient cryptographic transforms. Therefore,
when source authentication is not paramount paramount, group authentication
becomes useful. In addition, performing group authentication is
useful even when source authentication is later performed: it
provides a simple-to-verify weak integrity check that is useful as a
measure against denial-of -service denial-of-service attacks.

Hardjono, Weis Expires November, 2003 16
MSEC Architecture May, 2003

The Multicast Group Authentication security service is placed in the
Multicast Data Handling Area along the interface between Senders and
Receivers.

5.2.4 Multicast Group Membership Management

This security service describes the functionality of registration of
members with the Group Controller, and de-registration of members. members
from the Group Controller. These are security functions, which are
independent from IP multicast group "join" and "leave" operations
that the member may need to perform (i.e., IGMP [RFC3376], MLD
[RFC3019]).

Registration includes member authentication, notification and
negotiation of security parameters, and logging of information
according to the policies of the group controller and the would-be
member. (Typically, an out-of-band advertisement of group information
would occur before the registration takes place. The registration
process will typically be invoked by the would-be member.)

De-registration may occur either at the initiative of the member or
at the initiative of the group controller. It would result in logging
of the de-registration event by the group controller and an
invocation of the appropriate mechanism for terminating the
membership of the de-registering member (see Section 5.2.5).

This security service also describes the functionality of the
communication related to group membership among different GC+KS GCKS
servers in a distributed group design.

In Figure 1, the Multicast Group Membership security service is
placed in the Group Key Management Area and has interfaces to Senders
and Receivers.

5.2.5 Multicast Key Management

This security service describes the functionality of distributing and
updating the cryptographic keying material throughout the life of the
group. Components of this building security service may include:

- GC+KS GCKS to Client (Sender or Receiver) notification regarding
current keying material (e.g. group encryption and
authentication keys, auxiliary keys used for group management,
keys for source authentication, etc).
- Updating of current keying material, depending on circumstances
and policies.

Hardjono, Weis Expires May, 2003 16
MSEC Architecture October, 2002 policies.
- Termination of groups in a secure manner, including the
multicast group itself and the associated keying material.

Among the problems to be solved by responsibilities of this security service is the secure
management of keys between Key Servers and Clients, the addressing
issues for the multicast distribution of keying material, and the

Hardjono, Weis Expires November, 2003 17
MSEC Architecture May, 2003

scalability or other performance requirements for multicast key
management [RFC2627, BMS].

To allow for an interoperable and secure IP multicast security
protocol, this security service may need to specify host abstractions
such as a group security association database (GSAD) and a group
security policy database (GSPD) for IP multicast security. The
degree of overlap between IP multicast and application-layer
multicast key management needs to be considered. Thus, work on this security
service must take takes into account the key management requirements for IP
multicast, the key management requirements for application-layer
multicast, and to what degree specific realizations of a Multicast
Key Management security service can satisfy both. ISAKMP, moreover,
has been designed to be extensible to multicast key management for
both IP multicast and application-layer multicast security [RFC2408].
Thus, multicast key management protocols may use the existing ISAKMP
standard's Phase 1 and Phase 2 protocols, possibly with needed
extensions (such as an ISAKMP Domain of
Interpretation for IP multicast GDOI [BHHW] or application-layer multicast
security).

This security service also describes the functionality of the
communication related to key management among different GC+KS GCKS servers
in a distributed group design.

Multicast Key Management appears in both the centralized and
distributed designs as shown in Figure 1 and is placed in the Group
Key Management Area.

5.2.6 Multicast Policy Management

This security service handles all matters related to multicast group
policy including membership policy and multicast key management
policy. Indeed, one of the first tasks in further defining this
security service is identifying the different areas of multicast
policy. Multicast Policy Management includes the design of the policy
server for multicast security, the particular policy definitions that
will be used for IP multicast and application-layer multicast
security, and the communication protocols between the Policy Server
and the Key Server. This security service may be realized using a
standard policy infrastructure such as a Policy Decision Point (PDP)
and Policy Enforcement Point (PEP) architecture. architecture [RFC2748]. Thus, it
may not be necessary to re-invent a separate architecture for
multicast security policy; we expect that this work will evaluate use of the products of IETF efforts in the areas of network and
security policy. At minimum, however, this security service will be

Hardjono, Weis Expires May, 2003 17
MSEC Architecture October, 2002

realized in a set of policy definitions, such as multicast security
conditions and actions.

The Multicast Policy Management security service describes the
functionality of the communication between an instance of a GC+KS to
an instance the Policy Server. The information transmitted may
include policies concerning groups, memberships, keying material
definition and their permissible uses, and other information. This
security service also describes communication between and among
Policy Servers. Thus, the Multicast Policy Management security
service is placed in Problem Area 3, along the interface between Key
Servers and Policy Servers. Group members are not expected to
directly participate in this security service. However, this option
is not ruled out.

6. MSEC Documents Roadmap

The roadmap of MSEC WG documents is shown the in the following.

+--------------+
| MSEC |
| Requirements |
+--------------+
:
:
+--------------+
| MSEC |
| Architecture |
+--------------+
:
.....................:.......................
: : :
+--------------+ +--------------+ +--------------+
| Policy | | GKM | | Data Security|
| Architecture | | Architecture | | Architecture |
+--------------+ +--------------+ +--------------+
: : :
: : :
. +------------+ : +------------+ :
. | GDOI | : |TESLA/MESP | :
| Resolution |-: | |-:
| | : | | :
+------------+ : +------------+ :
: :
: :
+------------+ : +------------+ :
| GSAKMP- | : | | :
| Resolution |-: | TBD |-:
| | : | | :
+------------+ : +------------+ :
: :

Hardjono, Weis Expires May, 2003 18
MSEC Architecture October, 2002

: :
+------------+ : +------------+ :
| | : | | :
| RE-KEY |-: | TBD |-:
| | : | | :
+------------+ : +------------+ :
: :
. .
. .

Figure 4: MSEC Document Roadmap

7. Conclusion

This document has provided an architectural overview of the work
being conducted in the MSEC Working Group and introduced several
important aspects
products of the standardization IETF efforts in the MSEC WG.

A Reference Framework for covering the scope areas of the problems network and security policy.
At minimum, however, this security service will be realized in a set
of policy definitions, such as multicast security was introduced, conditions and a division of labor along
three Functional Areas pertaining to
actions.

The Multicast Policy Management security was discussed. These
cover service describes the treatment
functionality of the communication between an instance of data from a security perspective when it is to
be sent GCKS to a group,
an instance the management of Policy Server. The information transmitted may
include policies concerning groups, memberships, keying material used to protect
the data
definition and the policies governing a group. their permissible uses, and other information. This document

Hardjono, Weis Expires November, 2003 18
MSEC Architecture May, 2003

security service also defined the notion of describes communication between and among
Policy Servers. Group Security Associations
(GSA), which members are not expected to directly
participate in this security service. However, this option is the foundation not
ruled out.

8. Security Considerations

This document describes methods and guidelines for protecting
multicast and group traffic with cryptographic protocols.

9. Acknowledgments

Much of the work on group key management text in
the MSEC Working Group.

8. Acknowledgments

This this document was derived from an IRTF SMuG Working Group draft that
was originally two research
papers. The framework for this document came from a paper co-authored
by Thomas Hardjono, Ran Canetti, Mark Baugher, and Pete Dinsmore.

9.
Description of the GSA came from a document co-authored by Hugh
Harney, Mark Baugher, and Thomas Hardjono.

10. References

9.1

10.1 Normative References

[RFC2401] S. Kent, R. Atkinson, Security Architecture for the
Internet Protocol, November 1998.

[RFC2408] D. Maughan, M. Shertler, M. Schneider, J. Turner, Internet
Security Association and Key Management Protocol, November 1998.

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

10.2 Informative References

[ACLNM] J. Arkko, et. al., MIKEY: Multimedia Internet KEYing, draft-
ietf-msec-mikey-06.txt, February, 2003. Work in Progress.

[BCCR] M. Baugher, R. Canetti, P. Cheng, P. Rohatgi, MESP: A
Multicast Framework for the Ipsec ESP, draft-ietf-msec-mesp-01.txt.
IETF, October 2002. Work in Progress.

[BCDL] M. Baugher, R. Canetti, L. Dondeti, F. Lindholm, Group Key
Management Architecture, draft-ietf-msec-gkmarch-03.txt. IETF,
October 2002. Work in Progress.

[HSC] H. Harney, A. Schuett, A. Colegrove, GSAKMP Light. draft-ietf-
msec-gsakmp-light-sec-01.txt. draft-ietf-msec-gkmarch-04.txt. IETF, July 2002. March
2003. Work in Progress.

[BHHW] M. Baugher, T. Hardjono, H. Harney, B. Weis, The Group Domain
of Interpretation, draft-ietf-msec-gdoi-06.txt. IETF, February 2002.
Work in Progress.

Hardjono, Weis Expires May, 2003 19
MSEC Architecture October, 2002

[BCCR] M. Baugher, R. Canetti, P. Cheng, P. Rohatgi, MESP: Multicast
Encapsulating Security Payload, draft-ietf-msec-mesp-00.txt. IETF,
October 2002. Work in Progress.

[PCW] A. Perrig, R. Canetti, B. Whillock, TESLA: Multicast Source
Authentication Transform Specification. draft-ietf-msec-tesla-spec-
00.txt. draft-ietf-msec-gdoi-07.txt. IETF, October December 2002.
Work in Progress.

9.2 Informative References

[BMS] D. Balenson, D. McGrew, A. Sherman, Key Management for Large
Dynamic Groups: One-Way Function Trees and Amortized Initialization,
http://www.ietf.org/internet-drafts/draft-balenson-groupkeymgmt-oft-
http://www.securemulticast.org/draft-balenson-groupkeymgmt-oft-
00.txt, February 1999, Work in Progress.

[CP99] R. Canetti and B. Pinkas, A taxonomy of multicast security
issues, http://search.ietf.org/internet-drafts/draft-irtf-smug-
taxonomy-01.txt, April 1999, Work in Progress.

Hardjono, Weis Expires November, 2003 19
MSEC Architecture May, 2003

[CCPRRS] Canetti, R., Cheng P. C., Pendarakis D., Rao, J., Rohatgi
P., Saha D., "An architecture for secure IP multicast", NDSS 2000.

[Din] Dinsmore, P., Balenson, D., Heyman, M., Kruus, P., Scace, C.,
and Sherman, A., "Policy-Based Security Management for Large Dynamic
Groups: An Oerview Overview of the DCCM Project," DARPA Information
Survivability Conference and Exposition, To Be Published.
http://download.nai.com/products/media/nai/doc/discex-110199.doc.

[Har1] Harney, H., and Muckenhirn, C., "Group Key Management
Protocol (GKMP) Specification," RFC 2093, July 1997.

[Har2] Harney, H., and Muckenhirn, C., "Group Key Management
Protocol (GKMP) Architecture," RFC 2094, July 1997.

[HH]

[HSMC] H. Harney, E. Harder, Group Secure Association Key Management
Protocol, http://search.ietf.org/internet-drafts/draft-harney-
sparta-gsakmp-sec-00.txt, April 1999, A. Schuett, U. Meth, A. Colegrove, GSAKMP. draft-
ietf-msec-gsakmp- sec-01.txt. IETF, February 2003. Work in Progress.

[McD] McDaniel, P., Honeyman, P., and Prakash, A., "Antigone:
A Flexible Framework for Secure Group Communication," Proceedings of
the Eight USENIX Security Symposium, pp 99-113, August, 1999.

[RFC2246] Dierks, T. and C. Allen, The TLS Protocol Version 1.0,
RFC 2246, January 1999.

[PCW] A. Perrig, R. Canetti, B. Whillock, TESLA: Multicast Source
Authentication Transform Specification. draft-ietf-msec-tesla-spec-
00.txt. IETF, October 2002. Work in Progress.

[RFC2406] S. Kent, R. Atkinson, IP Encapsulating Security Payload
(ESP),November 1998.

[RFC2408] D. Maughan, M. Shertler, M. Schneider, J. Turner, Internet
Security Association and Key Management Protocol, November 1998.

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

Hardjono, Weis Expires May, 2003 20
MSEC Architecture October, 2002

[RFC2627] D. M. Wallner, E. Harder, R. C. Agee, Key Management for
Multicast: Issues and Architectures, September 1998.

[RFC2748] D. Durham, et. al., The COPS (Common Open Policy Service)
Protocol, January, 2000.

[RFC3019] B. Haberman, Worzella, R., IP Version 6 Management
Information Base for The Multicast Listener Discovery Protocol,
January, 2001.

[RFC3376] B. Cain, et. al., Internet Group Management Protocol,
Version 3, October, 2002.

[STW] M. Steiner, Tsudik, G., Waidner, M., CLIQUES: A New Approach to
Group key Agreement, IEEE ICDCS'98 , May 1998.

Authors Addresses

Hardjono, Weis Expires November, 2003 20
MSEC Architecture May, 2003

Thomas Hardjono
VeriSign
401 Edgewater Place, Suite 280
Wakefield, MA 01880
(781) 245-6996
thardjono@verisign.com

Brian Weis
Cisco Systems
170 W. Tasman Drive,
San Jose, CA 95134-1706, USA
(408) 526-4796
bew@cisco.com

Hardjono, Weis Expires May, November, 2003 21
----