WDIFF

draft-ietf-eap-keying-10.txt --> draft-ietf-eap-keying-11.txt

EAP Working Group Bernard Aboba
INTERNET-DRAFT Dan Simon
Category: Standards Track Microsoft
<draft-ietf-eap-keying-10.txt>
<draft-ietf-eap-keying-11.txt> J. Arkko
5 March
3 April 2006 Ericsson
P. Eronen
Nokia
H. Levkowetz, Ed.
ipUnplugged

Extensible Authentication Protocol (EAP) Key Management Framework

By submitting this Internet-Draft, each author represents that any
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This Internet-Draft will expire on August 22, October 10, 2006.

Abstract

The Extensible Authentication Protocol (EAP), defined in [RFC3748],
enables extensible network access authentication. This document
provides a framework for the transport and usage of keying material
generated by EAP authentication algorithms, known as "methods". It
also specifies the EAP key hierarchy.

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Table of Contents

1. Introduction .......................................... 3
1.1 Requirements Language ........................... 3
1.2 Terminology ..................................... 3
1.3 Overview ........................................ 5
1.4 EAP Key Hierarchy ............................... 8
1.5 Security Goals .................................. 11
1.6 EAP Invariants .................................. 9 12
2. Lower Layer Operation ................................. 12 15
2.1 Overview ........................................ 12
2.2 Layering ........................................ 14
2.3 Transient Session Keys .......................... 16
2.4
2.2 Authenticator Architecture ...................... 19
2.5 Key Scope ....................................... 22 18
3. Key Management ........................................ 24 22
3.1 Secure Association Protocol ..................... 24 22
3.2 Key Scope ....................................... 25
3.3 Parent-Child Relationships ...................... 27
3.3 26
3.4 Local Key Lifetimes ............................. 27
3.4 26
3.5 Exported and Calculated Key Lifetimes ........... 28
3.5 27
3.6 Key Cache Synchronization ....................... 29
3.6 28
3.7 Key Strength .................................... 30
3.7 29
3.8 Key Wrap ........................................ 31 29
4. Handoff Vulnerabilities ............................... 31 30
4.1 Authorization ................................... 32 30
4.2 Correctness ..................................... 33 32
5. Security Considerations .............................. 36 34
5.1 Security Terminology ............................ 36
5.2 Threat Model .................................... 36
5.3 35
5.2 Authenticator Compromise ........................ 37
5.4 36
5.3 Spoofing ........................................ 38
5.5 36
5.4 Downgrade Attacks ............................... 39
5.6 37
5.5 Unauthorized Disclosure ......................... 39
5.7 38
5.6 Replay Protection ............................... 41
5.8 39
5.7 Key Freshness ................................... 42
5.9 40
5.8 Elevation of Privilege .......................... 43
5.10 41
5.9 Man-in-the-Middle Attacks ....................... 44
5.11 42
5.10 Denial of Service Attacks ....................... 44
5.12 42
5.11 Impersonation ................................... 45
5.13 43
5.12 Channel Binding ................................. 46 44
6. IANA Considerations ................................... 47 45
7. References ............................................ 47 45
7.1 Normative References ............................ 47 45
7.2 Informative References .......................... 47 46
Acknowledgments .............................................. 52 50
Author's Addresses ........................................... 53 50
Appendix A - Exported Parameters in Existing Methods ......... 54 52
Intellectual Property Statement .............................. 55 53
Disclaimer of Validity ....................................... 56 54
Copyright Statement .......................................... 56 54

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1. Introduction

The Extensible Authentication Protocol (EAP), defined in [RFC3748],
was designed to enable extensible authentication for network access
in situations in which the IP protocol is not available. Originally
developed for use with PPP [RFC1661], it has subsequently also been
applied to IEEE 802 wired networks [IEEE-802.1X]. [IEEE-802.1X], wireless networks
such as [IEEE-802.11i] and [IEEE-802.16e], and IKEv2 [RFC4306].

This document provides a framework for the transport and usage of
keying material generated by EAP authentication algorithms, known as
"methods". In EAP, keying material is generated by EAP methods.
Part of this keying material may be used by EAP methods themselves
and part of this material may be exported. The exported keying
material may be transported by AAA protocols or and used by Secure
Association Protocols in the generation or transport of session keys
which are used by lower layer ciphersuites. This document describes
each of these elements and provides a system-level security analysis.
It also specifies the EAP key hierarchy.

1.1. Requirements Language

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 BCP 14 [RFC2119].

1.2. Terminology

This document frequently uses the following terms:

AAA Authentication, Authorization and Accounting. AAA protocols with
EAP support include RADIUS [RFC3579] and Diameter [RFC4072]. In
this document, the terms "AAA server" and "backend authentication
server" are used interchangeably.

authenticator
The end of the link initiating EAP authentication. The term
Authenticator is used in [IEEE-802.1X], and authenticator has the
same meaning in this document.

peer The end of the link that responds to the authenticator. In
[IEEE-802.1X], this end is known as the Supplicant.

Supplicant
The end of the link that responds to the authenticator in
[IEEE-802.1X]. In this document, this end of the link is called
the peer.

backend authentication server
A backend authentication server is an entity that provides an
authentication service to an authenticator. When used, this server
typically executes EAP methods for the authenticator. This
terminology is also used in [IEEE-802.1X].

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EAP server

Channel Binding
The entity that terminates the communication within an EAP authentication method with the
peer. In the case where no backend authentication server is used,
the EAP of integrity-protected
channel properties such as endpoint identifiers which can be
compared to values communicated via out of band mechanisms (such as
via a AAA or lower layer protocol).

EAP server
The entity that terminates the EAP authentication method with the
peer. In the case where no backend authentication server is used,
the EAP server is part of the authenticator. In the case where the
authenticator operates in pass-through mode, the EAP server is
located on the backend authentication server.

security association
A set of policies and cryptographic state used to protect
information. Elements of a security association may include
cryptographic keys, negotiated ciphersuites and other parameters,
counters, sequence spaces, authorization attributes, etc.

Long Term Credential
EAP methods frequently make use of long term secrets in order to
enable authentication between the peer and server. In the case of
a method based on pre-shared key authentication, the long term
credential is the pre-shared key. In the case of a public-key
based method, the long term credential is the corresponding private
key.

Master Session Key (MSK)
Keying material that is derived between the EAP peer and server and
exported by the EAP method. The MSK is at least 64 octets in
length.

AAA-Key
The term AAA-Key is synonymous with MSK.

Extended Master Session Key (EMSK)
Additional keying material derived between the peer and server that
is exported by the EAP method. The EMSK is at least 64 octets in
length, and is never shared with a third party.

Initialization Vector (IV)
A quantity of at least 64 octets, suitable for use in an
initialization vector field, that is derived between the peer and
EAP server. Since the IV is a known value in methods such as EAP-
TLS [RFC2716], it cannot be used by itself for computation of any
quantity that needs to remain secret. As a result, its use has
been deprecated and EAP methods are not required to generate it.
However, when it is generated it MUST be unpredictable.

Pairwise Master Key (PMK)
Lower layers use the MSK in lower-layer dependent manner. For
instance, in [IEEE-802.11i] Octets 0-31 of the MSK are known as the

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Pairwise Master Key (PMK). In [IEEE-802.11i] the TKIP and AES CCMP
ciphersuites derive their Transient Session Keys (TSKs) solely from

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the PMK, whereas the WEP ciphersuite as noted in [RFC3580], derives
its TSKs from both halves of the MSK. In [802.16e], the MSK is
truncated to 40 20 octets for PMK and 20 octets for PMK2.

Transient EAP Keys (TEKs)
Session keys which are used to establish a protected channel
between the EAP peer and server during the EAP authentication
exchange. The TEKs are appropriate for use with the ciphersuite
negotiated between EAP peer and server for use in protecting the
EAP conversation. The TEKs are stored locally by the EAP method
and are not exported. Note that the ciphersuite used to set up the
protected channel between the EAP peer and server during EAP
authentication is unrelated to the ciphersuite used to subsequently
protect data sent between the EAP peer and authenticator.

Transient Session Keys (TSKs)
Session keys used to protect data exchanged after EAP
authentication has successfully completed, using the ciphersuite
negotiated between the EAP peer and authenticator.

AAA-Key
The term AAA-Key is synonymous with MSK.

1.3. Overview

EAP, defined in [RFC3748],

Where EAP key derivation is a two-party protocol spoken between supported, the conversation typically
takes place in three phases:

Phase 0: Discovery
Phase 1: Authentication
1a: EAP peer authentication
1b: AAA Key Transport (optional)
Phase 2: Secure Association Protocol
2a: Unicast Secure Association
2b: Multicast Secure Association (optional)

Of these phases, Phase 0, 1b and server. Within EAP, keying material Phase 2 are handled external to EAP.
Phases 0 and 2 are handled by the lower layer protocol and phase 1b
is generated typically handled by EAP
methods. Part of this keying material may be used by EAP methods
themselves and part of this material may be exported. In addition to
export of keying material, EAP methods may also export associated
parameters, and may import and export Channel Bindings from the lower
layer.

As illustrated in Figure 1, the EAP method key derivation has at the
root the long term credential utilized by the selected EAP method.
If authentication is based on a pre-shared key, the parties store AAA protocol.

In the
EAP method to be used discovery phase (phase 0), peers locate authenticators and the pre-shared key. The EAP server also
stores the peer's identity as well as other information associated
with it. This information
discover their capabilities. A peer may be used to determine whether locate an authenticator
providing access to
some service should be granted. The a particular network, or a peer stores information necessary
to choose which secret to use for may locate an
authenticator behind a bridge with which service.

If authentication is based on proof of possession of the private key
corresponding it desires to the public key contained within establish a certificate, the
parties store the EAP method to be used and the trust anchors used to
validate the certificates. The EAP server also stores the peer's
Secure Association. Discovery can occur manually or automatically,

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identity and the peer stores information necessary to choose which
certificate to use for which service.

Based

depending on the long term credential established between the peer and
the server, lower layer over which EAP methods derive two types of keys:

[1] Keys calculated locally by the runs.

Figure 1: Conversation Overview

The authentication phase (phase 1) may begin once the TEKs.
[2] Keying material exported by peer and
authenticator discover each other. This phase, if it occurs, always
includes EAP authentication (phase 1a). Where the chosen EAP method: MSK, EMSK, IV.

As noted method
supports key derivation, in [RFC3748] Section 7.10, phase 1a EAP methods generating keys are
required to calculate and export keying material is derived
on both the MSK peer and EMSK, the EAP server.

An additional step (phase 1b) is required in deployments which must be at
least 64 octets
include a backend authentication server, in length. EAP methods also may export order to transport keying
material from the IV;
however, backend authentication server to the use of authenticator.
In order to obey the IV principle of Mode Independence (see Section
1.6.1), where a backend server is deprecated. present, all keying material which
is required by the lower layer needs to be transported from the EAP methods also MAY export method-specific peer and
server
identifiers (peer-ID and server-ID), a method-specific EAP
conversation identifier known as the Method-ID, and to the lifetime of
the exported keys, known as the Key-Lifetime. EAP methods MAY also
support the import and export of Channel Bindings. New EAP method
specifications MUST define the Peer-ID, Server-ID and Method-ID. The
combination of the Peer-ID authenticator. Since existing TSK derivation and Server-ID uniquely specifies the
endpoints of
transport techniques depend solely on the EAP method exchange when they are provided.

Peer-ID

As described MSK, in [RFC3748] Section 7.3, existing
implementations, this is the identity provided only keying material replicated in the
EAP-Response/Identity, may be different from the peer identity
authenticated by the EAP method. Where the
AAA key transport phase 1b.

Successful completion of EAP method authenticates
the peer identity, that identity is exported authentication and key derivation by the method as the
Peer-ID. A suitable EAP a
peer name may not always be available.
Where an and EAP method server does not define a method-specific peer identity,
the Peer-ID is necessarily imply that the null string. The Peer-ID for existing EAP
methods peer is defined in Appendix A.

Server-ID

Where
committed to joining the network associated with an EAP method authenticates the server identity, that identity server.
Rather, this commitment is exported implied by the method as creation of a security
association between the Server-ID. A suitable EAP server
name may not always be available. Where an EAP method does not
define a method-specific peer identity, the Server-ID is and authenticator, as part of the null
string.
Secure Association Protocol (phase 2). The Server-ID for existing EAP methods is defined Secure Association
Protocol exchange (phase 2) occurs between the peer and authenticator
in
Appendix A. order to manage the creation and deletion of unicast (phase 2a)

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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---+
| | ^
| EAP Method | |
| | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ | |
| | | | | | |
| | EAP Method Key |<->| Long-Term | | |
| | Derivation | | Credential | | |
| | | | | | |
| | | +-+-+-+-+-+-+-+ | Local to |
| | | | EAP |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Method |
| | | | | |
| | | | | |
| | | | | |
| | | | | |
| | | | | |
| | +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+-+ | |
| | | TEK | |MSK, EMSK | |IV | | |
| | |Derivation | |Derivation | |Derivation | | |
| | | | | | |(Deprecated) | | |
| | +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+-+ | |
| | ^ | | | |
| | | | | | V
+-+-|-+-+-+-+-+-+-+-+-|-+-+-+-+-+-|-+-+-+-+-+-+-+-|-+-+-+-+ ---+
| | | | ^
| Peer-ID, | | | Exported |
| Server-ID, | Channel | MSK (64+B) | IV (64B) by |
| Method-ID, | Bindings | EMSK (64+B) | (Optional) EAP |
| Key-Lifetime | & Result | | Method |
V V V V V

Figure 1: EAP Method Parameter Import/Export

Method-ID

EAP method specifications deriving keys MUST specify a temporally
unique method identifier known as the Method-ID. The EAP Method-ID
uniquely identifies an EAP session of a given Type between an EAP
peer and server. The Method-ID is typically constructed from nonces
or counters used within the EAP method exchange. The Method-ID for
existing EAP methods is defined in Appendix A.

Session-ID

The Session-ID uniquely identifies an EAP session between an EAP peer
(as identified by the Peer-ID) and server (as identified by the
Server-ID). The EAP Session-ID consists of the concatenation of the

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Expanded EAP Type Code (including the Type, Vendor-ID and Vendor-Type
fields defined in [RFC3748] Section 5.7) and the Method-ID. The
inclusion of the Expanded Type Code in the EAP Session-Id ensures
that each EAP method has a distinct Session-ID space. Since an EAP
session is not bound to a particular authenticator or specific ports
on the peer and authenticator, the authenticator port or identity are
not included in the Session-Id.

Key-Lifetime

While EAP itself does not support key lifetime negotiation, it is
possible to specify methods that do. However, systems that rely on
such negotiation for exported keys would only function with these
methods. As a result, it is NOT RECOMMENDED to use this approach as
the sole way to determine key lifetimes.

Channel Bindings

Channel Bindings include lower layer parameters that are verified for
consistency between the EAP peer and server. In order to avoid
introducing media dependencies, EAP methods that transport Channel
Binding data MUST treat this data as opaque octets. Typically the
EAP method imports Channel Bindings from the lower layer on the peer,
and transmits them securely to the EAP server, which exports them to
the lower layer. However, transport may occur from EAP server to
peer, or may be bi-directional. On the side of the exchange (peer or
server) where Channel Bindings are verified, the lower layer passes
the result of the verification (TRUE or FALSE) up to the EAP method.

1.3.1. Key Naming

Each key created within the EAP key management framework has a name
(a unique identifier), as well as a scope (the parties to whom the
key is available). The scope of exported parameters is defined by
the EAP peer name (if securely exchanged within the method) and the
EAP server name (also only if securely exchanged). Where a peer or
server name is missing the null string is used.

MSK and EMSK Names
These parameters are exported by the EAP peer and EAP server, and
can be referred to using the EAP Session-ID and a binary or textual
indication of the parameter being referred to.

PMK Name
This document does not specify a naming scheme for the PMK. The
PMK is only identified by the key from which it is derived.

Note: IEEE 802.11i names the PMKID for the purposes of being able

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to refer to it in the Secure Association protocol; this naming is
based on a hash of the PMK itself as well as some other parameters
(see Section 8.5.1.2 [IEEE-802.11i]).

TEK Name
The TEKs may or may not be named. Their naming is specified in the
EAP method.

TSK Name
The TSKs are typically named. Their naming is specified in the
lower layer so that the correct set of transient session keys can
be identified for processing a given packet.

1.4. EAP Invariants

Certain basic characteristics, known as "EAP Invariants", hold true
for EAP implementations on all media:

Mode independence
Media independence
Method independence
Ciphersuite independence

1.4.1. Mode Independence

EAP is typically deployed in order to support extensible network
access authentication in situations where a peer desires network
access via one or more authenticators. Where authenticators are
deployed standalone, the EAP conversation occurs between the peer and
authenticator, and the authenticator must locally implement an EAP
method acceptable to the peer. However, one of the advantages of EAP
is that it enables deployment of new authentication methods without
requiring development of new code on the authenticator.

While the authenticator may implement some EAP methods locally and
use those methods to authenticate local users, it may at the same
time act as a pass-through for other users and methods, forwarding
EAP packets back and forth between the backend authentication server
and the peer. This is accomplished by encapsulating EAP packets
within the Authentication, Authorization and Accounting (AAA)
protocol, spoken between the authenticator and backend authentication
server. AAA protocols supporting EAP include RADIUS [RFC3579] and
Diameter [RFC4072].

It is a fundamental property of EAP that at the EAP method layer, the
conversation between the EAP peer and server is unaffected by whether
the EAP authenticator is operating in "pass-through" mode. EAP
methods operate identically in all aspects, including key derivation

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and parameter import/export, regardless of whether the authenticator
is operating as a pass-through or not.

The successful completion of an EAP method that supports key
derivation results in the export of keying material on the EAP peer
and server. Even though the EAP peer or server may import Channel-
Bindings that may include the identity of the EAP authenticator,
this information is treated as opaque octets. As a result, within
EAP the only relevant identities are the Peer-ID

and Server-ID.
Channel Bindings are only interpreted by the lower layer.

Within EAP, the primary function of the AAA protocol is to maintain
the principle of Mode Independence, so that as far as multicast (phase 2b) security associations between the EAP peer is
concerned, its conversation with the EAP authenticator, and all
consequences of that conversation, are identical, regardless of the
authenticator mode of operation.

1.4.2. Media Independence

One of
authenticator. The conversation between the goals of EAP parties is to allow shown in
Figure 1.

1.3.1. Examples

Existing EAP methods to function on any lower layer meeting the criteria outlined in [RFC3748], Section 3.1.
For example, as described layers implement phase 0, 2a and 2b in [RFC3748], EAP authentication can be run
over different
ways:

PPP [RFC1661], IEEE 802 wired networks [IEEE-802.1X], and IEEE
802.11 wireless LANs [IEEE-802.11i].

In order to maintain media independence, PPP, defined in [RFC1661] does not support discovery, nor does it is necessary
include a Secure Association Protocol.

PPPOE
PPPOE, defined in [RFC2516], includes support for a Discovery stage
(phase 0). In this step, the EAP peer sends a PPPoE Active
Discovery Initiation (PADI) packet to
avoid consideration of media-specific elements. For example, EAP
methods cannot be assumed to have knowledge of the lower layer over
which they are transported, and cannot be restricted to identifiers
associated broadcast address,
indicating the service it is requesting. The Access Concentrator
replies with a particular usage environment (e.g. MAC addresses).

Note that media independence may be retained within EAP methods that
support Channel-Bindings or method-specific identification. An EAP
method need PPPOE Active Discovery Offer (PADO) packet
containing its name, the service name and an indication of the
services offered by the concentrator. The discovery phase is not be aware
secured. PPPOE, like PPP, does not include a Secure Association
Protocol.

IKEv2
IKEv2, defined in [RFC4306], handles the establishment of unicast
security associations (phase 2a), while the content establishment of an identifier in order to
use it. This enables an EAP method to use media-specific identifiers
multicast security associations (phase 2b) may be handled by a
group key management protocol such as MAC addresses without compromising media independence.
Channel-Bindings GDOI [RFC3547], GSAKMP
[GSAKMP], MIKEY [RFC3830], or GKDP [GKDP]. Several mechanisms have
been proposed for discovery of IPsec security gateways. [RFC2230]
discusses the use of KX Resource Records (RRs) for IPsec gateway
discovery; while KX RRs are treated as opaque octets supported by EAP methods, so that
handling them does many DNS server
implementations, they have not require media-specific knowledge.

1.4.3. Method Independence

By enabling pass-through, authenticators yet been widely deployed.
Alternatively, DNS SRV [RFC2782] can support any method
implemented on the peer be used for this purpose.
Where DNS is used for gateway location, DNS security mechanisms
such as DNSSEC ([RFC2535], [RFC2931]), TSIG [RFC2845], and server, not just locally implemented
methods. This allows Simple
Secure Dynamic Update [RFC3007] are available.

IEEE 802.11i
IEEE 802.11, defined in [IEEE-802.11], handles discovery via the authenticator to avoid implementing code
Beacon and Probe Request/Response mechanisms. IEEE 802.11 access
points periodically announce their Service Set Identifiers (SSIDs)
as well as capabilities using Beacon frames. Stations can query
for each EAP method required access points by peers. In fact, since sending a pass-through
authenticator is not required to implement any EAP methods at all, it
cannot be assumed Probe Request to support any EAP method-specific code. the broadcast
address. Neither Beacon nor Probe Request/Response frames are
secured. The 4-way handshake defined in [IEEE-802.11i] enables the
derivation of unicast (phase 2a) and multicast/broadcast (phase 2b)
secure associations. Since the group key exchange transports a

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As a result, as noted in [RFC3748], authenticators must by default

group key from the access point to the station, two 4-way
handshakes may be
capable required in order to support peer-to-peer
communications. A proof of supporting any EAP method. This the security of the IEEE 802.11i 4-way
handshake when used with EAP-TLS [RFC2716], is useful where there provided in [He].

IEEE 802.1X
IEEE 802.1X-2004, defined in [IEEE-802.1X] does not support
discovery (phase 0), nor does it provide for derivation of unicast
or multicast secure associations.

1.4. EAP Key Hierarchy

EAP, defined in [RFC3748], is
no single a two-party protocol spoken between the
EAP method that peer and server. Within EAP, keying material is both mandatory-to-implement generated by EAP
methods. Part of this keying material may be used by EAP methods
themselves and offers
acceptable security for part of this material may be exported. In addition to
export of keying material, EAP methods may also export associated
parameters, and may import and export Channel Bindings from the media lower
layer.

As illustrated in use. For example, Figure 2, the [RFC3748]
mandatory-to-implement EAP method (MD5-Challenge) does not provide
dictionary attack resistance, mutual authentication or key
derivation, derivation has at the
root the long term credential utilized by the selected EAP method.
If authentication is based on a pre-shared key, the parties store the
EAP method to be used and the pre-shared key. The EAP server also
stores the peer's identity as a result is not appropriate for well as other information associated
with it. This information may be used to determine whether access to
some service should be granted. The peer stores information necessary
to choose which secret to use in wireless
LAN for which service.

If authentication [RFC4017]. However, despite this it is possible
for based on proof of possession of the peer and authenticator private key
corresponding to interoperate as long as a suitable
EAP method is supported on the EAP server.

1.4.4. Ciphersuite Independence

Ciphersuite Independence is public key contained within a requirement for Media Independence.
Since lower layer ciphersuites vary between media, media independence
requires that certificate, the
parties store the EAP keying material needs method to be large enough (with
sufficient entropy) to handle any ciphersuite.

While EAP methods may negotiate used and the ciphersuite trust anchors used in protection of to
validate the certificates. The EAP conversation, server also stores the ciphersuite used for peer's
identity and the protection of peer stores information necessary to choose which
certificate to use for which service.

Based on the
data exchanged after EAP authentication has completed is negotiated long term credential established between the peer and authenticator within
the lower layer, outside server, EAP methods derive two types of
EAP.

For example, within PPP, keys:

[1] Keys calculated locally by the ciphersuite is negotiated within EAP method but not exported
by the
Encryption Control Protocol (ECP) defined in [RFC1968], after EAP
authentication is completed. Within [IEEE-802.11i], method, such as the AP
ciphersuites are advertised in TEKs.
[2] Keying material exported by the Beacon and Probe Responses prior
to EAP authentication, and method: MSK, EMSK, IV.

As noted in [RFC3748] Section 7.10, EAP methods generating keys are securely verified during a 4-way
handshake exchange.

Since the ciphersuites used
required to protect data depend on calculate and export the lower
layer, requiring MSK and EMSK, which must be at
least 64 octets in length. EAP methods have knowledge of lower layer
ciphersuites would compromise also may export the principle IV;
however, the use of Media Independence.
Since ciphersuite negotiation occurs in the lower layer, there IV is no
need for ciphersuite negotiation within EAP, and deprecated.

Aboba, et al. Standards Track [Page 8]

INTERNET-DRAFT EAP methods generate
keying material that is ciphersuite-independent.

Algorithms for deriving TSKs MUST NOT depend on the Key Management Framework 3 April 2006

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---+
| | ^
| EAP method,
although algorithms for TEK derivation MAY be specific to the Method | |
| | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ | |
| | | | | | |
| | EAP
method.

Advantages of ciphersuite-independence include:

Aboba, et al. Standards Track [Page 11]

Figure 2: EAP Key Management Framework 5 March 2006

Reduced update requirements
If Method Parameter Import/Export

EAP methods were to specify how to derive transient session keys
for each ciphersuite, they would need to be updated each time a new
ciphersuite is developed. In addition, backend authentication
servers might not be usable with all EAP-capable authenticators,
since the backend authentication server would also need to be
updated each time support for a new ciphersuite is added to the
authenticator.

Reduced EAP method complexity
Requiring each EAP method to include ciphersuite-specific code for
transient session key derivation would increase method complexity
and result in duplicated effort.

Simplified configuration
The ciphersuite is negotiated between the MAY export method-specific peer and authenticator
outside of EAP. Where the authenticator operates in "pass-through"
mode, the EAP server is not
identifiers (peer-ID and server-ID), a party to this negotiation, nor is it
involved in the data flow between the method-specific EAP peer
conversation identifier known as the Session-ID, and authenticator.
As a result, the EAP server may not have knowledge lifetime of
the
ciphersuites and negotiation policies implemented by exported keys, known as the Key-Lifetime. EAP methods MAY also
support the peer import and
authenticator, or be aware export of the ciphersuite negotiated between
them. For example, since ECP negotiation occurs after
authentication, when run over PPP, the Channel Bindings. New EAP peer method
specifications MUST define the Peer-ID, Server-ID and server may not
anticipate Method-ID. The
combination of the negotiated ciphersuite Peer-ID and therefore this
information cannot be provided to Server-ID uniquely specifies the EAP method.

2. Lower Layer Operation

2.1. Overview

Where EAP key derivation is supported,
endpoints of the conversation typically
takes place in three phases:

Phase 0: Discovery
Phase 1: Authentication
1a: EAP authentication
1b: AAA Key Transport (optional)
Phase 2: Secure Association Establishment
2a: Unicast Secure Association
2b: Multicast Secure Association (optional)

Of these phases, Phase 0, 1b and Phase 2 are handled external to EAP.
Phases 0 and 2 method exchange when they are handled by the lower layer protocol provided. The
Peer-ID, Server-ID, and phase 1b Method-ID for existing EAP methods is typically handled by a AAA protocol. In defined
in Appendix A.

Peer-ID

As described in [RFC3748] Section 7.3, the discovery phase
(phase 0), peers locate authenticators and discover their
capabilities. A peer identity provided in the
EAP-Response/Identity, may locate an authenticator providing access to
a particular network, or a be different from the peer may locate an authenticator behind a identity

Aboba, et al. Standards Track [Page 12] 9]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

bridge with which it desires to establish a Secure Association.
Discovery can occur manually or automatically, depending on the lower
layer over which EAP runs.

The authentication phase (phase 1) may begin once the peer and
authenticator discover each other. This phase, if it occurs, always
includes 3 April 2006

authenticated by the EAP authentication (phase 1a). method. Where the chosen EAP method
supports key derivation, in phase 1a EAP keying material is derived
on both authenticates
the peer and identity, that identity is exported by the method as the
Peer-ID. A suitable EAP server.

An additional step (phase 1b) is required in deployments which
include peer name may not always be available.
Where an EAP method does not define a backend authentication server, in order to transport keying
material from method-specific peer identity,
the backend authentication server to Peer-ID is the authenticator.
In order to obey null string.

Server-ID

Where the EAP method authenticates the principle of Mode Independence, where a backend server identity, that identity
is present, all keying material which is required exported by the lower
layer needs to be transported from method as the Server-ID. A suitable EAP server to the
authenticator. Since existing TSK derivation techniques depend
solely on
name may not always be available. Where an EAP method does not
define a method-specific peer identity, the MSK, in existing implementations, this Server-ID is the only
keying material replicated in null
string.

Method-ID

EAP method specifications deriving keys MUST specify a temporally
unique method identifier known as the AAA key transport phase 1b.

Successful completion of Method-ID. The EAP authentication and key derivation by Method-ID
uniquely identifies an EAP session of a
peer and given Type between an EAP server does not necessarily imply that the
peer and server. The Method-ID is
committed to joining typically constructed from nonces
or counters used within the network associated with EAP method exchange.

Session-ID

The Session-ID uniquely identifies an EAP server.
Rather, this commitment is implied by the creation of a security
association session between the an EAP peer
(as identified by the Peer-ID) and authenticator, as part of server (as identified by the
Secure Association Protocol (phase 2).
Server-ID). The Secure Association exchange (phase 2) occurs between EAP Session-ID consists of the peer and
authenticator in order to manage concatenation of the creation
Expanded EAP Type Code (including the Type, Vendor-ID and deletion of unicast
(phase 2a) Vendor-Type
fields defined in [RFC3748] Section 5.7) and multicast (phase 2b) security associations between the
peer and authenticator. Method-ID. The conversation between
inclusion of the parties is
shown Expanded Type Code in Figure 2.

Existing the EAP lower layers implement phase 0, 2a and 2b in different
ways:

PPP PPP, defined in [RFC1661] does not support discovery, nor does it
include Session-ID ensures
that each EAP method has a Secure Association Protocol.

PPPOE
PPPOE, defined in [RFC2516], includes support for distinct Session-ID space. Since an EAP
session is not bound to a Discovery stage
(phase 0). In this step, particular authenticator or specific ports
on the EAP peer sends a PPPoE Active
Discovery Initiation (PADI) packet to and authenticator, the broadcast address,
indicating authenticator port or identity are
not included in the service Session-ID.

Key-Lifetime

While EAP itself does not support key lifetime negotiation, it is requesting. The Access Concentrator
replies
possible to specify methods that do. However, systems that rely on
such negotiation for exported keys would only function with these
methods. As a PPPOE Active Discovery Offer (PADO) packet
containing its name, the service name and an indication of the
services offered by the concentrator. The discovery phase result, it is not
secured. PPPOE, like PPP, does not NOT RECOMMENDED to use this approach as
the sole way to determine key lifetimes.

Channel Bindings

Channel Bindings include a Secure Association lower layer parameters that are verified for
consistency between the EAP peer and server. In order to avoid
introducing media dependencies, EAP methods that transport Channel

Aboba, et al. Standards Track [Page 13] 10]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

Protocol.

IKEv2
IKEv2, defined in [RFC4306], handles

Binding data MUST treat this data as opaque octets. Typically the derivation of unicast
security associations (phase 2a), while
EAP method imports Channel Bindings from the derivation of multicast
security associations (phase 2b) is handled in a separate group key
management protocol, as described in [RFC4046]. Several mechanisms
have been proposed for discovery of IPsec security gateways.
[RFC2230] discusses lower layer on the use peer,
and transmits them securely to the EAP server, which exports them to
the lower layer or AAA layer. However, transport may occur from EAP
server to peer, or may be bi-directional. On the side of KX Resource Records (RRs) for IPsec
gateway discovery; while KX RRs the
exchange (peer or server) where Channel Bindings are supported by many DNS server
implementations, they have not yet been widely deployed.
Alternatively, DNS SRV [RFC2782] verified, the
lower layer or AAA layer passes the result of the verification (TRUE
or FALSE) up to the EAP method. While the verification can be used for this purpose.
Where DNS is used for gateway location, DNS security mechanisms
such as DNSSEC ([RFC2535], [RFC2931]), TSIG [RFC2845], and Simple
Secure Dynamic Update [RFC3007] are available.

IEEE 802.11i
IEEE 802.11, defined in [IEEE-802.11], handles discovery via done
either by the peer or the server, typically only the
Beacon and Probe Request/Response mechanisms. IEEE 802.11 access
points periodically announce server has the
knowledge to determine the correctness of the values, as opposed to
merely verifying their Service Set Identifiers (SSIDs) equality.

1.4.1. Key Naming

Each key created within the EAP key management framework has a name
(a unique identifier), as well as capabilities using Beacon frames. Stations can query
for access points by sending a Probe Request scope (the parties to whom the broadcast
address. Neither Beacon nor Probe Request/Response frames are
secured.
key is available). The 4-way handshake scope of exported parameters is defined in [IEEE-802.11i] enables by
the
derivation of unicast (phase 2a) EAP peer name (if securely exchanged within the method) and multicast/broadcast (phase 2b)
secure associations. Since the group key exchange transports
EAP server name (also only if securely exchanged). Where a
group key from peer or
server name is missing the access point to null string is used.

MSK and EMSK Names
These parameters are exported by the station, two 4-way
handshakes may EAP peer and EAP server, and
can be required in order referred to support peer-to-peer
communications.

IEEE 802.1X-2004
IEEE 802.1X-2004, defined in [IEEE-802.1X-2004] using the EAP Session-ID and a binary or textual
indication of the parameter being referred to.

PMK Name
This document does not support
discovery (phase 0), nor does it provide specify a naming scheme for derivation of unicast
or multicast secure associations.

2.2. Layering

As illustrated in Figure 3, on completion of EAP authentication, EAP
methods export the Master Session Key (MSK), Extended Master Session
Key (EMSK), Peer-ID, Server-ID, Session-ID and Key-Lifetime PMK. The
PMK is only identified by the key from which it is derived.

Note: IEEE 802.11i names the PMKID for the purposes of being able
to refer to it in the
EAP peer or authenticator layers. The Initialization Vector (IV) Secure Association protocol; this naming is
deprecated.
based on a hash of the PMK itself as well as some other parameters
(see Section 8.5.1.2 [IEEE-802.11i]).

TEK Name
The EAP peer and authenticator layers MUST NOT modify or cache keying
material TEKs may or parameters (including Channel Bindings) passing may not be named. Their naming is specified in either
direction between the
EAP method method.

TSK Name
The TSKs are typically named. Their naming is specified in the
lower layer and so that the EAP layer. correct set of transient session keys can
be identified for processing a given packet.

1.5. Security Goals

The goal of the EAP
layer also MUST NOT cache keying material or parameters (including
Channel Bindings) passed conversation is to it, whether by derive fresh session keys
between the EAP peer/authenticator peer and authenticator that are known only to those

Aboba, et al. Standards Track [Page 14] 11]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

layer, the lower layer or

Figure 2: Conversation Overview

Based on the Method-ID exported and authenticator to demonstrate
that they are authorized to perform their roles either by the each other
or by a trusted third party (the backend authentication server).

Completion of an EAP method, method exchange (Phase 1a) supporting key
derivation results in the derivation of EAP layer
forms keying material (MSK,
EMSK, TEKs) known only to the EAP Session-ID peer (identified by concatenating the EAP Expanded Type with Peer-ID)
and server (identified by the Method-ID. Together with Server-ID). Both the MSK, IV (deprecated), Peer-ID,
Server-ID, EAP peer and Key-Lifetime, the EAP layer passes
server know the Session-ID down exported keying material to the lower layer. The Method-ID be fresh. Key freshness
is exported by EAP methods rather
than discussed in Sections 3.4, 3.5 and 5.7.

Completion of the Session-ID so as to prevent AAA exchange (Phase 1b) results in the transport of
EAP methods keying material from writing into
each other's Session- ID space.

The EMSK MUST NOT be provided to an entity outside the EAP server or
peer, nor is it permitted (identified by the Server-ID)
to pass any quantity the EAP authenticator (identified by the NAS-Identifier) without
disclosure to an entity outside any other party. Both the EAP server or peer from which the EMSK could and EAP
authenticator know this keying material to be computed without
breaking some cryptographic assumption, such as inverting a one-way
function. As noted fresh. Disclosure
issues are discussed in [RFC3748] Section 7.10:

The EMSK is reserved for future use 5.6; security properties of AAA
protocols are discussed in Sections 5.2-5.8, and MUST remain on 5.11.

Completion of the Secure Association Protocol (Phase 2) results in
the derivation or transport of Transient Session Keys (TSKs) known
only to the EAP peer (identified by the Peer-ID) and EAP server where it is derived; it MUST NOT be
transported to, or shared with, additional parties, or used authenticator
(identified by the NAS-Identifier). Both the EAP peer and
authenticator know the TSKs to
derive any other keys. (This restriction will be relaxed in a
future document that specifies how fresh. Both the EMSK can be used.)

In order EAP peer and
authenticator demonstrate that they are authorized to preserve the perform their
roles. Authorization issues are discussed in Section 5.8 and 5.9;
security properties of keys derived within Secure Association Protocols are discussed in
Section 3.1.

1.6. EAP methods,
lower layers MUST NOT export keys passed down by Invariants

Certain basic characteristics, known as "EAP Invariants", hold true
for EAP methods. This
implies that implementations on all media:

Mode independence
Media independence
Method independence
Ciphersuite independence

1.6.1. Mode Independence

EAP keying material or parameters passed down is typically deployed to support extensible network access
authentication in situations where a lower
layer peer desires network access via
one or more authenticators. Where authenticators are for deployed
standalone, the exclusive use of that lower layer EAP conversation occurs between the peer and MUST NOT be
used within another lower layer. This prevents compromise
authenticator, and the authenticator must locally implement an EAP
method acceptable to the peer. However, when utilized in "pass-
through" mode, EAP enables deployment of one new authentication methods

Aboba, et al. Standards Track [Page 15] 12]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

lower layer from compromising other applications using EAP keying
parameters.

EAP keying material and parameters provided to a lower layer MUST NOT
be transported to another entity. For example, EAP keying material
and parameters passed down to the EAP peer lower layer MUST NOT leave
the peer; EAP keying material and parameters passed down or
transported to the EAP authenticator lower layer MUST NOT leave 3 April 2006

without requiring development of new code on the authenticator.

While the authenticator may implement some EAP server, keying material requested by methods locally and passed down to
the AAA layer may be replicated
use those methods to the AAA layer on the
authenticator. On the authenticator, the AAA layer authenticate local users, it may provide the
replicated keying material to the lower layer over which at the same
time act as a pass-through for other users and methods, forwarding
EAP packets back and forth between the backend authentication conversation took place. This enables "mode
independence" to be maintained. However, server
and the EMSK MUST NOT be
transported peer. This is accomplished by the AAA layer.

As illustrated in Figure 4, a AAA client receiving transported encapsulating EAP
keying material and parameters passes them to packets
within the EAP authenticator Authentication, Authorization and EAP layers, which then provide them to Accounting (AAA)
protocol, spoken between the authenticator lower
layer using the same mechanisms that would be used if the and backend authentication
server. AAA protocols supporting EAP peer include RADIUS [RFC3579] and authenticator were conducting a stand-alone conversation. The
resulting key state in the lower layer
Diameter [RFC4072].

It is indistinguishable between
the standalone and pass-through cases, as required by the principle a fundamental property of mode independence.

2.3. Transient Session Keys

Where explicitly supported by EAP that at the lower EAP method layer, lower layers MAY cache the exported
conversation between the EAP keying material peer and parameters and/or TSKs. The
structure of this key cache server is defined unaffected by whether
the lower layer. So as to
enable interoperability, new lower layer specifications MUST
describe EAP key caching behavior. Unless explicitly specified by
the lower layer, the authenticator is operating in "pass-through" mode. EAP peer, server
methods operate identically in all aspects, including key derivation
and parameter import/export, regardless of whether the authenticator MUST assume
that peers and authenticators do not cache exported EAP keying
parameters
is operating as a pass-through or TSKs. Existing not.

The successful completion of an EAP lower layers and AAA layers handle method that supports key
derivation results in the caching export of EAP keying material and parameters on
the generation of transient
session keys in different ways:

IEEE 802.1X-2004
IEEE 802.1X-2004, defined in [IEEE-802.1X-2004] does not support
caching of EAP keying material peer and server. Even though the EAP peer or parameters. Once server may
import Channel-Bindings that may include the identity of the EAP
authentication completes, it
authenticator, this information is assumed that treated as opaque octets. As a
result, within EAP keying material the only relevant identities are the Peer-ID and parameters
Server-ID. Channel Bindings are discarded.

PPP PPP, defined in [RFC1661] does not support caching only interpreted by the lower layer.

Within EAP, the primary function of EAP keying
material or parameters. PPP ciphersuites derive their TSKs

Aboba, et al. Standards Track [Page 16]

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directly from the MSK, as described in [RFC2716]. This method AAA protocol is
NOT RECOMMENDED, since were PPP to support caching, this could
result in stale TSKs. As a result, once maintain
the PPP session principle of Mode Independence, so that as far as the EAP peer is
terminated,
concerned, its conversation with the EAP keying material authenticator, and parameters MUST be discarded.
Since caching all
consequences of that conversation, are identical, regardless of the
authenticator mode of operation.

1.6.2. Media Independence

One of the goals of EAP keying material is not permitted, within PPP
there is no way to handle TSK rekey without allow EAP re-authentication.
Perfect Forward Secrecy (PFS) is only possible within PPP if methods to function on any
lower layer meeting the
negotiated EAP method supports this.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| EAP method |
| |
| MSK, EMSK, Peer-ID, Channel |
| Server-ID, Method-ID Bindings |
| IV (deprecated), |
| Key-Lifetime |
| |
| V ^ ^ |
+-+-+-+-!-+-+-+-+-+-+-+-+-+-+-+-!-+-+-+-+-!-+-+
| ! ! ! |
| criteria outlined in [RFC3748], Section 3.1.
For example, as described in [RFC3748], EAP ! Peer or Authenticator ! ! |
| ! layer ! ! |
| ! ! ! |
+-+-+-+-!-+-+-+-+-+-+-+-+-+-+-+-!-+-+-+-+-!-+-+
| ! ! ! |
| authentication can be run
over PPP [RFC1661], IEEE 802 wired networks [IEEE-802.1X], and
wireless networks such as 802.11 [IEEE-802.11i] and 802.16
[IEEE-802.16e].

In order to maintain media independence, it is necessary for EAP ! layer ! ! |
| ! ! ! |
| ! Session-ID = ! ! |
| ! Expanded-Type || ! ! |
| ! Method-ID ! ! |
| ! ! ! |
+-+-+-+-!-+-+-+-+-+-+-+-+-+-+-+-!-+-+-+-+-!-+-+
| ! ! ! |
| Lower ! layer or AAA ! ! |
| ! ! ! |
| V V ^ |
| MSK, Peer-ID, Channel Result |
| Server-ID, Bindings |
| Session-ID, |
| Key-Lifetime, |
| IV (deprecated) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Flow to
avoid consideration of media-specific elements. For example, EAP parameters

Aboba, et al. Standards Track [Page 17]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

Peer Pass-through Authenticator Authentication
Server

+-+-+-+-+-+-+ +-+-+-+-+-+-+
| | | |
|EAP method | |EAP method |
| V | | V |
+-+-+-!-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-!-+-+-+
| ! | |EAP | EAP | | | ! |
| ! | |Peer | Auth.|
methods cannot be assumed to have knowledge of the lower layer over
which they are transported, and cannot be restricted to identifiers
associated with a particular usage environment (e.g. MAC addresses).

Aboba, et al. Standards Track [Page 13]

INTERNET-DRAFT EAP Auth. | | ! |
|EAP ! peer| | | +-----------+ | |EAP !Auth.|
| ! | | | ! | ! | | ! |
+-+-+-!-+-+-+ +-+-+-+-!-+-+-+-+-+-!-+-+-+-+ +-+-+-!-+-+-+
| ! | | ! | ! | | ! |
|EAP !layer| | Key Management Framework 3 April 2006

Note that media independence may be retained within EAP !layer| methods that
support Channel-Bindings or method-specific identification. An EAP !layer | |EAP !layer|
| ! | | ! | ! | | ! |
+-+-+-!-+-+-+ +-+-+-+-!-+-+-+-+-+-!-+-+-+-+ +-+-+-!-+-+-+
| V | | V | ! | | ! |
|Lower layer| | Lower layer| AAA ! /IP | | AAA ! /IP |
| | | | ! | | ! |
+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-!-+-+-+-+ +-+-+-!-+-+-+
! !
! !
+---------<-------+

Figure 4: Flow
method need not be aware of EAP Keying Material and Parameters

IKEv2
IKEv2, defined the content of an identifier in [RFC4306] only uses order to
use it. This enables an EAP method to use media-specific identifiers
such as MAC addresses without compromising media independence.
Channel-Bindings are treated as opaque octets by EAP methods, so that
handling them does not require media-specific knowledge.

1.6.3. Method Independence

By enabling pass-through, authenticators can support any method
implemented on the MSK for authentication
purposes peer and server, not key derivation. The EMSK, IV, Peer-ID, Server-ID
or Session-ID are not used. As a result, just locally implemented
methods. This allows the keying material
derived within IKEv2 authenticator to avoid implementing code
for each EAP method required by peers. In fact, since a pass-through
authenticator is independent of the not required to implement any EAP keying material and
rekey of IPsec SAs can methods at all, it
cannot be handled without requiring assumed to support any EAP re-
authentication. Since generation method-specific code.

As a result, as noted in [RFC3748], authenticators must by default be
capable of keying material supporting any EAP method. This is independent
of EAP, within IKEv2 it useful where there is possible to negotiate PFS, regardless of
the
no single EAP method that is used. IKEv2 both mandatory-to-implement and offers
acceptable security for the media in use. For example, the [RFC3748]
mandatory-to-implement EAP method (MD5-Challenge) does not cache EAP keying
material or parameters; once IKEv2 provide
dictionary attack resistance, mutual authentication completes it is
assumed that EAP keying material or key
derivation, and parameters are discarded. The
Session-Timeout attribute is therefore interpreted as a limit on
the VPN session time, rather than an indication of the MSK key
lifetime.

IEEE 802.11i
IEEE 802.11i enables caching of the MSK, but result is not the EMSK, IV,
Peer-ID, Server-ID, or Session-ID. More details about the
structure of the cache are available appropriate for use in [IEEE-802.11i]. In IEEE
802.11i, TSKs are derived from the MSK using wireless
LAN authentication [RFC4017]. However, despite this it is possible
for the 4-way handshake,
which includes peer and authenticator to interoperate as long as a nonce exchange. This guarantees TSK freshness

Aboba, et al. Standards Track [Page 18]

INTERNET-DRAFT suitable
EAP Key Management Framework 5 March 2006

even if the MSK method is reused. The 4-way handshake also enables TSK
rekey without supported on the EAP re-authentication. PFS server.

1.6.4. Ciphersuite Independence

Ciphersuite Independence is only possible within
IEEE 802.11i if the negotiated a requirement for Media Independence.
Since lower layer ciphersuites vary between media, media independence
requires that EAP method supports this.

IEEE 802.16e
IEEE 802.16e, defined keying material needs to be large enough (with
sufficient entropy) to handle any ciphersuite.

While EAP methods may negotiate the ciphersuite used in [IEEE-802.16e] supports caching protection of
the
MSK, but not EAP conversation, the EMSK, IV, Peer-ID, Server-ID or Session-ID. In
IEEE 802.16e, TSKs are generated by ciphersuite used for the authenticator without any
contribution by protection of the peer. The TSKs are encrypted, authenticated
data exchanged after EAP authentication has completed is negotiated
between the peer and integrity protected using authenticator within the MSK. As a result, TSK rekey lower layer, outside of
EAP.

For example, within PPP, the ciphersuite is
possible without negotiated within the
Encryption Control Protocol (ECP) defined in [RFC1968], after EAP re-authentication. PFS
authentication is not possible even
if completed. Within [IEEE-802.11i], the negotiated EAP method supports it.

AAA Existing implementations of RADIUS/EAP [RFC3579] or Diameter EAP
[RFC4072] do not support caching of EAP keying material or
parameters. In existing AAA client, proxy and server
implementations, exported EAP keying material (MSK, EMSK and IV) as
well as parameters and derived keys AP
ciphersuites are not cached and MUST be
presumed lost after advertised in the AAA exchange completes.

In order Beacon and Probe Responses prior
to avoid key reuse, the AAA layer MUST delete transported
keys once they EAP authentication, and are sent. The AAA layer MUST NOT retain keys that
it has previously sent. For example, securely verified during a AAA layer that has
transported the MSK MUST delete it, and keys MUST NOT be derived
from the MSK from that point forward.

2.4. Authenticator Architecture

This specification does not impose constraints on 4-way
handshake exchange.

Aboba, et al. Standards Track [Page 14]

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Since the architecture of ciphersuites used to protect data depend on the lower
layer, requiring EAP authenticator or peer. Any methods have knowledge of lower layer
ciphersuites would compromise the authenticator
architectures described principle of Media Independence.
Since ciphersuite negotiation occurs in [RFC4118] can be used. For example, it the lower layer, there is
possible no
need for multiple base stations lower layer ciphersuite negotiation within EAP, and a "controller" (e.g. WLAN
switch) EAP
methods generate keying material that is ciphersuite-independent.

In order to comprise allow a single ciphersuite to be usable within the EAP authenticator. In such keying
framework, a situation, specification MUST be provided describing how TSKs
suitable for use with the "base station identity" is irrelevant to ciphersuite are derived from exported EAP
keying parameters. To maintain Method Independence, algorithms for
deriving TSKs MUST NOT depend on the EAP method
conversation, except perhaps as an opaque blob to method, although algorithms
for TEK derivation MAY be used in Channel
Bindings. Many base stations can share specific to the same authenticator
identity. As a result, lower layers EAP method.

Advantages of ciphersuite-independence include:

Reduced update requirements
If EAP methods were to specify how to derive transient session keys
for each ciphersuite, they would need to identify EAP peers and
authenticators unambiguously, without incorporating implicit
assumptions about peer and authenticator architectures.

It should be understood that an EAP authenticator or peer:

[a] may contain one or more physical or logical ports;
[b] may advertise itself as one or more "virtual"
authenticators or peers;
[c] may utilize multiple CPUs;
[d] may updated each time a new
ciphersuite is developed. In addition, backend authentication
servers might not be usable with all EAP-capable authenticators,
since the backend authentication server would also need to be
updated each time support clustering services for load balancing or failover.

Aboba, et al. Standards Track [Page 19]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

Both a new ciphersuite is added to the
authenticator.

Reduced EAP method complexity
Requiring each EAP method to include ciphersuite-specific code for
transient session key derivation would increase method complexity
and result in duplicated effort.

Simplified configuration
The ciphersuite is negotiated between the peer and authenticator may have more than one physical
or logical port. A peer may simultaneously access
outside of EAP. Where the network via
multiple authenticators, or via multiple physical or logical ports on
a given authenticator. Similarly, an authenticator may offer network
access to multiple peers, each via a separate physical or logical
port. When a single physical authenticator advertises itself as
multiple "virtual authenticators", it operates in "pass-through"
mode, the EAP server is possible for not a single
physical port to belong party to multiple "virtual authenticators". The
situation this negotiation, nor is illustrated in Figure 5.

+-+-+-+-+
| EAP |
| Peer |
+-+-+-+-+
| | | Peer Ports
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
| | | | | | | | | Authenticator Ports
+-+-+-+-+ +-+-+-+-+ +-+-+-+-+
| | | | | |
| Auth. | | Auth. | | Auth. |
| | | | | |
+-+-+-+-+ +-+-+-+-+ +-+-+-+-+
\ | /
\ | /
\ | / it
involved in the data flow between the EAP over AAA \ | /
(optional) \ | /
\ | /
\ | /
\ | /
+-+-+-+-+
| peer and authenticator.
As a result, the EAP |
|Server |
+-+-+-+-+

Figure 5: Relationship server may not have knowledge of the
ciphersuites and negotiation policies implemented by the peer and
authenticator, or be aware of the ciphersuite negotiated between
them. For example, since ECP negotiation occurs after
authentication, when run over PPP, the EAP peer, authenticator peer and server may not
anticipate the negotiated ciphersuite and therefore this
information cannot be provided to the EAP method.

2. Lower Layer Operation

On completion of EAP authentication, keying material and material and
parameters exported by the EAP method are provided to the lower layer
and AAA layer (if present). These include the Master Session Key

Aboba, et al. Standards Track [Page 20] 15]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

2.4.1. Authenticator Identification

(MSK), Extended Master Session Key (EMSK), Peer-ID, Server-ID,
Session-ID and Key-Lifetime. The EAP method conversation Initialization Vector (IV) is between
deprecated.

In order to preserve the security of keys derived within EAP peer and server, as
identified by the Peer-ID and Server-ID. The authenticator identity,
if considered at all methods,
lower layers MUST NOT export keys passed down by the EAP method, is treated as an opaque blob methods. This
implies that EAP keying material or parameters passed down to a lower
layer are for the purposes exclusive use of Channel bindings. However, the Secure
Association Protocol conversation is between the peer and the
authenticator, that lower layer and therefore the authenticator MUST NOT be
used within another lower layer. This prevents compromise of one
lower layer from compromising other applications using EAP keying
parameters.

EAP keying material and peer identities
are relevant parameters provided to that exchange, a lower layer MUST NOT
be transported to another entity. For example, EAP keying material
and define parameters passed down to the scope of use of EAP peer lower layer MUST NOT leave
the peer; EAP keying material and parameters passed down or
transported to the lower layer.

Since an EAP authenticator may have multiple ports, lower layer MUST NOT leave the authenticator
identifiers used within
authenticator.

On the Secure Association Protocol exchange
SHOULD be distinct from any port identifier (e.g. MAC address).
Similarly, where a peer may have multiple ports, and sharing of EAP server, keying material requested by and parameters between peer ports of passed down to
the same link
type is allowed, AAA layer may be replicated to the peer identifier used within AAA layer on the Secure
Association Protocol exchange SHOULD also be distinct from any port
identifier.

Where
authenticator. On the peer and authenticator identify themselves within authenticator, the lower AAA layer using a port identifier such as a link provides the
replicated keying material to the lower layer address, this
creates a number of problems:

[1] It may not over which the EAP
authentication conversation took place. This enables "mode
independence" to be obvious maintained.

The EMSK MUST NOT be provided to an entity outside the EAP server or
peer, nor is it permitted to pass any quantity to an entity outside
the EAP server or peer from which authenticator ports are
associated with which authenticators.

[2] It may not the EMSK could be computed without
breaking some cryptographic assumption, such as inverting a one-way
function. The EMSK MUST NOT be obvious to transported by the authenticator which peer ports are
associated with which peers.

[3] It may not be obvious to AAA layer. As
noted in [RFC3748] Section 7.10:

The EMSK is reserved for future use and MUST remain on the EAP
peer which "virtual authenticator" and EAP server where it is communicating with.

[4] It may not derived; it MUST NOT be obvious
transported to, or shared with, additional parties, or used to
derive any other keys.

The EAP layer as well as the peer and authenticator which "virtual peer" it
is communicating with.

AAA protocols such as RADIUS [RFC3579] layers MUST NOT
modify or cache keying material or parameters (including Channel
Bindings) passing in either direction between the EAP method layer
and Diameter [RFC4072]
provide a mechanism for the identification of lower layer or AAA clients; since layer.

2.1. Transient Session Keys

Where explicitly supported by the lower layer, lower layers MAY cache
the exported EAP authenticator keying material and AAA client are always co-resident, parameters and/or TSKs. The
structure of this
mechanism key cache is applicable defined by the lower layer. So as to

Aboba, et al. Standards Track [Page 16]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

enable interoperability, new lower layer specifications MUST describe
EAP key caching behavior. Unless explicitly specified by the lower
layer, the identification of EAP
authenticators.

RADIUS [RFC2865] requires peer, server and authenticator MUST assume that an Access-Request packet contain one
or more of the NAS-Identifier, NAS-IP-Address peers
and NAS-IPv6-Address
attributes. Since a NAS may have more than one IP address, the
NAS-Identifier attribute is RECOMMENDED for the unambiguous
identification of the authenticators do not cache exported EAP authenticator.

Aboba, et al. Standards Track [Page 21]

INTERNET-DRAFT keying parameters or
TSKs. Existing EAP Key Management Framework 5 March 2006

From lower layers and AAA layers handle the point of view caching of the AAA server,
EAP keying material and
parameters are transported to the EAP authenticator identified by the NAS-Identifier attribute. Since an EAP authenticator MUST NOT
share generation of transient session keys in
different ways:

IEEE 802.1X-2004
IEEE 802.1X-2004, defined in [IEEE-802.1X] does not support caching
of EAP keying material or parameters with another party, if the parameters. Once EAP peer or AAA server detects use of authentication
completes, it is assumed that EAP keying material and parameters outside the scope
are discarded.

PPP PPP, defined by in [RFC1661] does not support caching of EAP keying
material or parameters. PPP ciphersuites derive their TSKs
directly from the NAS-Identifier, MSK, as described in [RFC2716]. This method is
NOT RECOMMENDED, since were PPP to support caching, this could
result in stale TSKs. As a result, once the PPP session is
terminated, EAP keying material and parameters MUST be considered compromised.

2.5. Key Scope

Where the discarded.
Since caching of EAP peer and authenticator cannot unambiguously identify
each other they may keying material is not be able permitted, within PPP
there is no way to determine the scope of transported handle TSK rekey without EAP keying material. This re-authentication.
Perfect Forward Secrecy (PFS) is particularly problematic only possible within PPP if the
negotiated EAP method supports this.

IKEv2
IKEv2, defined in [RFC4306] only uses the MSK for lower
layers where authentication
purposes and not key caching derivation. The EMSK, IV, Peer-ID, Server-ID
or Session-ID are not used. As a result, the keying material
derived within IKEv2 is supported.

For example, if the EAP peer cannot identify independent of the EAP authenticator,
it will keying material and
rekey of IPsec SAs can be unable to determine whether transported handled without requiring EAP re-
authentication. Since generation of keying material has been shared outside is independent
of its authorized scope, and
therefore needs to be considered compromised. There EAP, within IKEv2 it is also a
practical problem because the EAP peer will be unable possible to utilize negotiate PFS, regardless of
the EAP authenticator key method that is used. IKEv2 does not cache in an efficient way.

To avoid these problems, EAP keying
material or parameters; once IKEv2 authentication completes it is recomended
assumed that lower layers:

[1] Specify the lower layer parameters used to identify the
authenticator and peer;

[2] Communicate the lower layer identities between the peer and
authenticator within phase 0;

[3] Communicate the lower layer authenticator identity between the
authenticator EAP keying material and backend server within parameters are discarded. The
Session-Timeout attribute is therefore interpreted as a limit on
the NAS-Identifier
attribute;

[4] Include VPN session time, rather than an indication of the lower layer identities within channel bindings (if
supported) in phase 1a, ensuring that they are communicated between MSK key
lifetime.

IEEE 802.11i
IEEE 802.11i enables caching of the EAP peer and server;

[5] Securely verify MSK, but not the lower layer identities within phase 2a;

[6] Utilize EMSK, IV,
Peer-ID, Server-ID, or Session-ID. More details about the advertised lower layer identities to enable
structure of the peer
and authenticator to verify that keys cache are maintained within the
advertised scope;

Absent explicit specification within available in [IEEE-802.11i]. In IEEE
802.11i, TSKs are derived from the lower layer, after MSK using the
completion of phase 1b, EAP keying material and parameters are
bound to 4-way handshake,
which includes a nonce exchange. This guarantees TSK freshness
even if the MSK is reused. The 4-way handshake also enables TSK
rekey without EAP peer and authenticator, but are not bound to a
specific peer or authenticator port. re-authentication. PFS is only possible within

Aboba, et al. Standards Track [Page 22] 17]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

While

IEEE 802.11i if the negotiated EAP Keying Material passed down to method supports this.

IEEE 802.16e
IEEE 802.16e, defined in [IEEE-802.16e] supports caching of the lower layer is
MSK, but not
intrinsically bound to particular authenticator and peer ports,
Transient Session Keys MAY be bound to particular the EMSK, IV, Peer-ID, Server-ID or Session-ID. In
IEEE 802.16e, TSKs are generated by the authenticator and
peer ports without any
contribution by the Secure Association Protocol. However, a lower
layer MAY also permit peer. The TSKs to be used on multiple peer and/or
authenticator ports, providing that are encrypted, authenticated
and integrity protected using the MSK. As a result, TSK freshness rekey is guaranteed
(such
possible without EAP re-authentication. PFS is not possible even
if the negotiated EAP method supports it.

AAA Existing implementations of RADIUS/EAP [RFC3579] or Diameter EAP
[RFC4072] do not support caching of EAP keying material or
parameters. In existing AAA client, proxy and server
implementations, exported EAP keying material (MSK, EMSK and IV) as by keeping replay counter state within
well as parameters and derived keys are not cached and MUST be
presumed lost after the authenticator). AAA exchange completes.

In order to further limit the avoid key scope reuse, the following measures AAA layer MUST delete transported
keys once they are
suggested:

[a] sent. The lower AAA layer MAY specify additional restrictions on key usage,
such as limiting MUST NOT retain keys that
it has previously sent. For example, a AAA layer that has
transported the use of EAP keying material MSK MUST delete it, and parameters on
the EAP peer to keys MUST NOT be derived
from the port over which MSK from that point forward.

2.2. Authenticator Architecture

This specification does not impose constraints on the architecture of
the EAP conversation was
conducted.

[b] The backend authentication server and authenticator MAY implement
additional attributes in order to further restrict the scope or peer. Any of EAP
keying material. For example, in 802.11, the backend
authentication server may provide the authenticator with a list of
authorized Called or Calling-Station-Ids and/or SSIDs
architectures described in [RFC4118] can be used. For example, it is
possible for which multiple base stations and a "controller" (e.g. WLAN
switch) to comprise a single EAP
keying material is valid.

[c] Where the backend authentication server provides attributes
restricting authenticator. In such a situation,
the key scope, it "base station identity" is RECOMMENDED that restrictions be
securely communicated by the authenticator irrelevant to the peer. This can
be accomplished using the Secure Association Protocol, but also
can be accomplished via the EAP method or the lower layer.

2.5.1. Virtual Authenticators

When a single physical authenticator advertises itself
conversation, except perhaps as multiple
"virtual authenticators", an opaque blob to be used in Channel
Bindings. Many base stations can share the same authenticator
identity. As a result, lower layers need to identify EAP peers and
authenticators unambiguously, without incorporating implicit
assumptions about peer and authenticator may not architectures.

It should be
able to agree on the scope of the understood that an EAP keying material, creating a
security vulnerability. For example, the peer authenticator or peer:

[a] may assume that the
"virtual authenticators" are distinct and do not share a key cache,
whereas, depending on the architecture of the contain one or more physical authenticator,
a shared key cache may or logical ports;
[b] may not be implemented.

Where EAP keying material is shared between "virtual authenticators"
an attacker acting advertise itself as a peer could authenticate with the "Guest"
"virtual authenticator" and derive EAP keying material. If the
virtual one or more "virtual"
authenticators share a key cache, then the peer can or peers;
[c] may utilize
the EAP keying material derived multiple CPUs;
[d] may support clustering services for load balancing or failover.

Both the "Guest" network to obtain EAP peer and authenticator may have more than one physical
or logical port. A peer may simultaneously access to the "Corporate Intranet" virtual authenticator.

Several measures are recommended to address these issues: network via

Aboba, et al. Standards Track [Page 23] 18]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

[d] Authenticators are REQUIRED to cache associated authorizations
along with EAP keying material and parameters and to apply
authorizations consistently. This ensures that an attacker cannot
obtain elevated privileges even where the key cache is shared
between "virtual authenticators".

[e] It is RECOMMENDED that

multiple authenticators, or via multiple physical authenticators maintain separate
key caches for each "virtual authenticator".

[f] It is RECOMMENDED that or logical ports on
a given authenticator. Similarly, an authenticator may offer network
access to multiple peers, each "virtual authenticator" identify via a separate physical or logical
port. When a single physical authenticator advertises itself
distinctly to the backend authentication server, such as by
utilizing
multiple "virtual authenticators", it is possible for a distinct NAS-Identifier attribute. This enables the
backend authentication server single
physical port to utilize a separate credential belong to
authenticate each multiple "virtual authenticator".

3. Key Management

EAP as defined authenticators". The
situation is illustrated in [RFC3748] supports key derivation, but not key
management. While EAP methods may derive keying material, Figure 3.

+-+-+-+-+
| EAP does
not provide for the management of exported or derived keys. For
example, |
| Peer |
+-+-+-+-+
| | | Peer Ports
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
| | | | | | | | | Authenticator Ports
+-+-+-+-+ +-+-+-+-+ +-+-+-+-+
| | | | | |
| Auth. | | Auth. | | Auth. |
| | | | | |
+-+-+-+-+ +-+-+-+-+ +-+-+-+-+
\ | /
\ | /
\ | /
EAP does not support negotiation of the key lifetime of
exported or derived keys, nor does it support re-key. Although over AAA \ | /
(optional) \ | /
\ | /
\ | /
\ | /
+-+-+-+-+
| EAP
methods may support "fast reconnect" as defined in [RFC3748] Section
7.2.1, re-key of exported keys cannot occur without re-
authentication. In order to provide method independence, key
management of exported or derived keys SHOULD NOT be provided within |
|Server |
+-+-+-+-+

Figure 3: Relationship between EAP methods.

3.1. Secure Association Protocol

Since neither peer, authenticator and server

2.2.1. Authenticator Identification

The EAP nor method conversation is between the EAP methods provide key management support, it peer and server, as
identified by the Peer-ID and Server-ID. The authenticator identity,
if considered at all by the EAP method, is RECOMMENDED that key management facilities be provided within treated as an opaque blob
for the
Secure Association Protocol. This includes:

[a] Entity Naming. A basic feature purposes of a Channel bindings. However, the Secure

Aboba, et al. Standards Track [Page 19]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

Association Protocol conversation is between the explicit naming of the parties engaged in the exchange.
Without explicit identification, peer and the parties engaged in
authenticator, and therefore the
exchange authenticator and peer identities
are not identified relevant to that exchange, and define the scope of use of the EAP
keying
parameters negotiated during material passed down to the EAP exchange is undefined. As
shown in Figure 5, both lower layer.

Where the EAP peer and authenticator may have more
than one physical or virtual port, and as a result SHOULD cannot unambiguously identify
themselves in a manner that is independent of their attached ports.

[b] Mutual proof of possession
each other they may not be able to determine the scope of transported
EAP keying material. During This is particularly problematic for lower
layers where key caching is supported.

For example, if the
Secure Association Protocol EAP peer cannot identify the EAP authenticator,
it will be unable to determine whether transported EAP keying
material has been shared outside of its authorized scope, and
therefore needs to be considered compromised. There is also a
practical problem because the EAP peer and authenticator MUST
demonstrate possession of the keying material transported between will be unable to utilize the backend authentication server and
EAP authenticator (e.g. MSK), key cache in
order to demonstrate that an efficient way. Where the peer and
authenticator have been

Aboba, et al. Standards Track [Page 24]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

authorized. Since mutual proof of possession is not identify themselves within the same lower layer using a port
identifier such as
mutual authentication, a link layer address, this creates a number of
problems:

[1] It may not be obvious to the peer cannot verify which authenticator
assertions (including ports are
associated with which authenticators.

[2] It may not be obvious to the authenticator identity) as a result of
this exchange.

[c] Secure capabilities negotiation. In order which peer ports are
associated with which peers.

[3] It may not be obvious to protect against
spoofing during the discovery phase, ensure selection of peer which "virtual authenticator" it
is communicating with.

[4] It may not be obvious to the "best"
ciphersuite, and protect against forging of negotiated security
parameters, authenticator which "virtual peer" it
is communicating with.

Since an authenticator may have multiple ports, the authenticator
identifier used within the Secure Association Protocol MUST support secure
capabilities negotiation. This includes the secure negotiation of
usage modes, session parameters (such as security association
identifiers (SAIDs) and key lifetimes), ciphersuites exchange
SHOULD be distinct from any port identifier (e.g. MAC address).
Similarly, where a peer may have multiple ports, and required
filters, including confirmation sharing of security-relevant capabilities
discovered during phase 0. As part EAP
keying material and parameters between peer ports of secure capabilities
negotiation, the same link
type is allowed, the peer identifier used within the Secure
Association Protocol MUST support integrity exchange SHOULD also be distinct from any port
identifier.

AAA protocols such as RADIUS [RFC3579] and replay protection Diameter [RFC4072]
provide a mechanism for the identification of all messages.

[d] Key naming AAA clients; since
the EAP authenticator and selection. Where key caching AAA client are always co-resident, this
mechanism is supported, it may
be possible for applicable to the identification of EAP peer
authenticators.

RADIUS [RFC2865] requires that an Access-Request packet contain one

Aboba, et al. Standards Track [Page 20]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

or more of the NAS-Identifier, NAS-IP-Address and authenticator to share NAS-IPv6-Address
attributes. Since a NAS may have more than one key of a given type. As a result, IP address, the Secure Association
Protocol MUST explicitly name
NAS-Identifier attribute is RECOMMENDED for the keys used in unambiguous
identification of the proof EAP authenticator.

From the point of
possession exchange, so as to prevent confusion when more than one
set view of the AAA server, EAP keying material could potentially be used as and
parameters are transported to the basis for EAP authenticator identified by
the exchange. Use NAS-Identifier attribute. Since an EAP authenticator MUST NOT
share EAP keying material or parameters with another party, if the
EAP peer or AAA server detects use of EAP keying material and
parameters outside the key naming mechanism described in this
document is RECOMMENDED. scope defined by the NAS-Identifier, the
keying material MUST be considered compromised.

In order to support ensure that lower layer identifies are securely
verified by all parties, it is recommended that lower layers:

[a] Specify the lower layer parameters used to identify the correct processing of phase 2 security
associations,
authenticator and peer;

[b] Communicate the Secure Association (phase 2) protocol MUST
support lower layer identities between the naming of peer and
authenticator within phase 2 security associations 0;

[c] Communicate the lower layer authenticator identity between the
authenticator and associated
transient session keys, so that backend server within the correct set of transient
session keys can be identified for processing a given packet. The NAS-Identifier
attribute;

[d] Include the lower layer identities within channel bindings (if
supported) in phase 2 Secure Association Protocol also MUST support transient
session key activation and SHOULD support deletion, so 1a, ensuring that
establishment and re-establishment of transient session keys can be
synchronized they are communicated between
the parties. EAP peer and server;

[e] Generation of fresh transient session keys (TSKs). Where Securely verify the lower layer supports caching of exported EAP keying material, identities within phase 2a;

[f] Utilize the EAP
peer advertised lower layer may initiate a new session using keying material
that was derived in a previous session. Were identities to enable the TSKs peer
and authenticator to be
derived from verify that keys are maintained within the
advertised scope;

2.2.2. Virtual Authenticators

When a portion of single physical authenticator advertises itself as multiple
"virtual authenticators", the exported EAP keying material, this
would result in reuse of the session keys which could expose the
underlying ciphersuite peer and authenticator may not be
able to attack.

In lower layers where caching agree on the scope of the EAP keying material is supported, material, creating a
security vulnerability. For example, the Secure Association Protocol phase is REQUIRED, peer may assume that the
"virtual authenticators" are distinct and MUST support do not share a key cache,
whereas, depending on the derivation architecture of fresh unicast and multicast TSKs, even when the physical authenticator,
a shared key cache may or may not be implemented.

Where EAP keying material provided by the backend authentication server is shared between "virtual authenticators"
an attacker acting as a peer could authenticate with the "Guest"

Aboba, et al. Standards Track [Page 25] 21]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

not fresh. This is typically supported via

"virtual authenticator" and derive EAP keying material. If the exchange of nonces
or counters, which are
virtual authenticators share a key cache, then mixed with the exported peer can utilize
the EAP keying material
in order derived for the "Guest" network to generate fresh unicast (phase 2a) and possibly
multicast (phase 2b) session keys. By not using obtain
access to the "Corporate Intranet" virtual authenticator.

Several measures are recommended to address these issues:

[g] Authenticators are REQUIRED to cache associated authorizations
along with EAP keying material directly and parameters and to protect data, apply
authorizations consistently. This ensures that an attacker cannot
obtain elevated privileges even where the Secure Association Protocol
protects it against compromise.

[f] Key lifetime management. key cache is shared
between "virtual authenticators".

[h] It is RECOMMENDED that physical authenticators maintain separate
key caches for each "virtual authenticator".

[i] It is RECOMMENDED that each "virtual authenticator" identify itself
distinctly to the backend authentication server, such as by
utilizing a distinct NAS-Identifier attribute. This includes explicit enables the
backend authentication server to utilize a separate credential to
authenticate each "virtual authenticator".

3. Key Management

EAP as defined in [RFC3748] supports key derivation, but not key lifetime
negotiation or seamless re-key.
management. While EAP methods may derive keying material, EAP does
not support negotiation provide for the management of key lifetimes, nor exported or derived keys. Although
EAP methods may support "fast reconnect" as defined in [RFC3748]
Section 7.2.1, EAP does it not support re-key of exported keys without re-
authentication. As a result,
re-authentication. Existing EAP methods do not export the Secure Association Protocol may
handle re-key and determination of Key-
Lifetime parameter; in the interest of method independence, key lifetime. Where key
caching is supported, secure negotiation
management of exported or derived keys SHOULD NOT be provided within
EAP methods.

3.1. Secure Association Protocol

Since neither EAP nor EAP methods provide key lifetimes management support, it
is
RECOMMENDED. Lower layers RECOMMENDED that support re-key, but not key
caching, may not require key lifetime negotiation. To take an
example from IKE, management facilities be provided within the difference between IKEv1 and IKEv2
Secure Association Protocol. This includes:

[a] Entity Naming. A basic feature of a Secure Association Protocol is that
the explicit naming of the parties engaged in
IKEv1 SA lifetimes were negotiated. In IKEv2, each end the exchange.
Without explicit identification, the parties engaged in the
exchange are not identified and the scope of the SA EAP keying
parameters negotiated during the EAP exchange is
responsible for enforcing its own lifetime policy on undefined. As
shown in Figure 3, both the SA peer and re- authenticator may have more
than one physical or virtual port, and as a result SHOULD identify
themselves in a manner that is independent of their attached ports.

Aboba, et al. Standards Track [Page 22]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

[b] Mutual proof of possession of EAP keying material. During the SA when necessary.

[g] Key resynchronization. It is possible for
Secure Association Protocol the EAP peer or and authenticator to reboot or reclaim resources, clearing portions or
all MUST
demonstrate possession of the key cache. Therefore, key lifetime negotiation cannot
guarantee that keying material transported between
the key cache will remain synchronized, backend authentication server and authenticator (e.g. MSK), in
order to demonstrate that the peer
may and authenticator have been
authorized. Since mutual proof of possession is not be able to determine before attempting to use a key whether
it exists within the same as
mutual authentication, the peer cannot verify authenticator cache. It is therefore
RECOMMENDED for
assertions (including the Secure Association Protocol to provide authenticator identity) as a
mechanism for key state resynchronization. Since in this situation
one or more result of the parties initially do not possess a key with
which
this exchange.

[c] Secure capabilities negotiation. In order to protect against
spoofing during the resynchronization exchange, securing this
mechanism may be difficult.

[h] Key scope synchronization. Since discovery phase, ensure selection of the Discovery phase is handled
out-of-band, EAP does not provide a mechanism by which "best"
ciphersuite, and protect against forging of negotiated security
parameters, the peer can
determine Secure Association Protocol MUST support secure
capabilities negotiation. This includes the authenticator identity. secure negotiation of
usage modes, session parameters (such as security association
identifiers (SAIDs) and key lifetimes), ciphersuites and required
filters, including confirmation of security-relevant capabilities
discovered during phase 0. As a result, where part of secure capabilities
negotiation, the
authenticator has multiple ports Secure Association Protocol MUST support integrity
and replay protection of all messages.

[d] Key naming and selection. Where key caching is supported, the
EAP peer it may not
be able to determine the scope of validity of the
exported EAP keying material. Similarly, where possible for the EAP peer has
multiple ports, the and authenticator may not be able to determine
whether share more than
one key of a peer has authorization to use given type. As a particular key. To allow
key scope determination, result, the Secure Association
Protocol SHOULD
provide a mechanism by which MUST explicitly name the peer can determine keys used in the scope proof of
possession exchange, so as to prevent confusion when more than one
set of keying material could potentially be used as the basis for
the exchange. Use of the key cache on each authenticator, naming mechanism described in this
document is RECOMMENDED.

In order to support the correct processing of phase 2 security
associations, the Secure Association (phase 2) protocol MUST
support the naming of phase 2 security associations and by which associated
transient session keys, so that the authenticator correct set of transient
session keys can determine be identified for processing a given packet. The
phase 2 Secure Association Protocol also MUST support transient
session key activation and SHOULD support deletion, so that
establishment and re-establishment of transient session keys can be
synchronized between the scope parties.

[e] Generation of fresh transient session keys (TSKs). Where the key cache on lower
layer supports caching of exported EAP keying material, the EAP
peer lower layer may initiate a peer. This includes
negotiation new session using keying material
that was derived in a previous session. Were the TSKs to be
derived from a portion of the exported EAP keying material, this
would result in reuse of restrictions on key usage.

[i] Direct operation. Since the phase 2 Secure Association Protocol is
concerned with session keys which could expose the establishment of security associations between
underlying ciphersuite to attack.

Aboba, et al. Standards Track [Page 26] 23]

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the EAP peer and authenticator, including the derivation

In lower layers where caching of
transient session keys, only those parties have "a need to know" EAP keying material is supported,
the transient session keys. The Secure Association Protocol MUST
operate directly between the peer and authenticator, phase is REQUIRED, and MUST NOT
be passed-through to the backend authentication server, or include
additional parties.

[j] Bi-directional operation While some ciphersuites only require a
single set of transient session keys to protect traffic in both
directions, other ciphersuites require a unique set of transient
session keys in each direction. The phase 2 Secure Association
Protocol SHOULD provide for support
the derivation of fresh unicast and multicast
keys in each direction, so as not to require two separate phase 2
exchanges in order to create a bi-directional phase 2 security
association.

3.2. Parent-Child Relationships

When TSKs, even when the
keying material exported provided by EAP methods expires, all keying
material derived from the backend authentication server is
not fresh. This is typically supported via the exchange of nonces
or counters, which are then mixed with the exported keying material expires, including
in order to generate fresh unicast (phase 2a) and possibly
multicast (phase 2b) session keys. By not using EAP keying
material directly to protect data, the TSKs.

When an Secure Association Protocol
protects it against compromise.

[f] Key lifetime management. This includes explicit key lifetime
negotiation or seamless re-key. EAP does not support re-key
without re-authentication takes place, new keying material is
derived and exported by the existing EAP method, which eventually results in
replacement of calculated keys, including the TSKs. methods do not support
key lifetime negotiation. As a result, while the lifetime of calculated keys can be less than
or equal that Secure Association
Protocol may handle re-key and determination of the exported keys they are derived from, it cannot
be greater. key lifetime.
Where key caching is supported, secure negotiation of key lifetimes
is RECOMMENDED. Lower layers that support re-key, but not key
caching, may not require key lifetime negotiation. For example, when EAP re-authentication occurs, TSK a
difference between IKEv1 [RFC2409] and IKEv2 [RFC4306] is that in
IKEv1 SA lifetimes were negotiated; in IKEv2, each end of the SA is
responsible for enforcing its own lifetime policy on the SA and re-
key will also occur. However, this does not prohibit TSK re-key from
occurring prior
keying the SA when necessary.

[g] Key resynchronization. It is possible for the peer or
authenticator to expiration reboot or reclaim resources, clearing portions or
all of the key cache. Therefore, key lifetime of exported keys. For
example, TSK re-key negotiation cannot
guarantee that the key cache will remain synchronized, and the peer
may occur prior not be able to EAP re-authentication.

Failure determine before attempting to mutually prove possession of keying material during use a key whether
it exists within the authenticator cache. It is therefore
RECOMMENDED for the Secure Association Protocol exchange need to provide a
mechanism for key state resynchronization. Since in this situation
one or more of the parties initially do not possess a key with
which to protect the resynchronization exchange, securing this
mechanism may be grounds for deletion
of difficult.

[h] Key scope synchronization. To support key scope determination, the keying material by both parties; rate-limiting
Secure Association Protocol exchanges could be used to prevent SHOULD provide a brute force
attack.

3.3. Local Key Lifetimes

The Transient EAP Keys (TEKs) are session keys used to protect mechanism by which the
EAP conversation. The TEKs are internal to
peer can determine the EAP method scope of the key cache on each
authenticator, and are
not exported. TEKs are typically created during an EAP conversation,
used until by which the end authenticator can determine the
scope of the conversation and then discarded. However,
methods may re-key TEKs during a conversation.

When using TEKs within an EAP conversation or across conversations,

Aboba, et al. Standards Track [Page 27]

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it is necessary to ensure that replay protection and key separation
requirements are fulfilled. For instance, if cache on a replay counter is
used, TEK re-key MUST occur prior to wrapping of the counter.
Similarly, TSKs MUST remain cryptographically separate from TEKs
despite TEK re-keying or caching. peer. This prevents TEK compromise from
leading directly to compromise includes negotiation of
restrictions on key usage.

[i] Direct operation. Since the TSKs and vice versa.

EAP methods may cache local keying material which may persist for
multiple EAP conversations when fast reconnect phase 2 Secure Association Protocol is used [RFC 3748].
For example, EAP methods based on TLS (such as EAP-TLS [RFC2716])
derive and cache
concerned with the TLS Master Secret, typically for substantial
time periods. The lifetime establishment of other local keying material calculated
within security associations between
the EAP method is defined by peer and authenticator, including the method. Note that in
general, when using fast reconnect, there is no guarantee derivation of
transient session keys, only those parties have "a need to that know"
the
original long-term credentials are still in transient session keys. The Secure Association Protocol MUST

Aboba, et al. Standards Track [Page 24]

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operate directly between the possession of peer and authenticator, and MUST NOT
be passed-through to the
peer. For instance, backend authentication server, or include
additional parties.

[j] Bi-directional operation. While some ciphersuites only require a card hold holding the private key for EAP-TLS
may have been removed. EAP servers
single set of transient session keys to protect traffic in both
directions, other ciphersuites require a unique set of transient
session keys in each direction. The phase 2 Secure Association
Protocol SHOULD also verify that provide for the long-
term credentials are still valid, such derivation of unicast and multicast
keys in each direction, so as by checking that
certificate used not to require two separate phase 2
exchanges in order to create a bi-directional phase 2 security
association.

3.2. Key Scope

Absent explicit specification within the original authentication has not yet expired.

3.4. Exported lower layer, after the
completion of phase 1b, EAP keying material and Calculated Key Lifetimes

All parameters are bound
to the EAP methods generating keys peer and authenticator, but are required not bound to a specific
peer or authenticator port.

While EAP Keying Material passed down to the lower layer is not
intrinsically bound to generate the MSK particular authenticator and
EMSK, peer ports,
Transient Session Keys MAY be bound to particular authenticator and may optionally generate
peer ports by the IV. Secure Association Protocol. However, EAP, defined in
[RFC3748], does not support the negotiation of lifetimes for exported
keying material such a lower
layer MAY also permit TSKs to be used on multiple peer and/or
authenticator ports, providing that TSK freshness is guaranteed (such
as by keeping replay counter state within the authenticator).

In order to further limit the MSK, EMSK and IV.

Several mechanisms exist for managing key lifetimes: scope the following measures are
suggested:

[a] AAA attributes. AAA protocols The lower layer MAY specify additional restrictions on key usage,
such as RADIUS [RFC2865] and
Diameter [RFC4072] support the Session-Timeout attribute. The
Session-Timeout value represents limiting the maximum lifetime use of the
exported keys, EAP keying material and all keys calculated from it, parameters on
the
authenticator. Since existing backend authentication servers do
not cache keys exported by EAP methods, or keys calculated from
exported keys, the value of peer to the Session-Timeout attribute has no
bearing port over which on the key lifetime within the EAP conversation was
conducted.

[b] The backend authentication
server.

On server and authenticator MAY implement
additional attributes in order to further restrict the authenticator, where scope of EAP is used for authentication, the
Session-Timeout value represents the maximum session time prior to
re-authentication, as described
keying material. For example, in [RFC3580]. Where EAP is used
for pre-authentication, 802.11, the session may not start until some future
time, or backend
authentication server may never occur. Nevertheless, the Session-Timeout value
represents provide the time after authenticator with a list of
authorized Called or Calling-Station-Ids and/or SSIDs for which transported EAP
keying material,
and all keys calculated from it, will have expired on the
authenticator. If material is valid.

[c] Where the session subsequently starts, re- backend authentication will server provides attributes
restricting the key scope, it is RECOMMENDED that restrictions be initiated once
securely communicated by the Session-Time has expired. authenticator to the peer. This can
be accomplished using the Secure Association Protocol, but also
can be accomplished via the EAP method or the lower layer.

Aboba, et al. Standards Track [Page 28] 25]

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If the session never started, or started and ended, by default keys
transported

3.3. Parent-Child Relationships

When keying material exported by AAA and EAP methods expires, all keys calculated keying
material derived from them will be
expired by the authenticator prior to the future time indicated by
Session-Timeout.

Since exported keying material expires, including
the TSK lifetime TSKs.

When an EAP re-authentication takes place, new keying material is often determined by authenticator
resources, the backend authentication server has no insight into
the TSK derivation process,
derived and exported by the principle of ciphersuite
independence, it is not appropriate for the backend authentication
server to manage any aspect EAP method, which eventually results in
replacement of the TSK derivation process, calculated keys, including the TSK lifetime.

[b] Lower layer mechanisms. While AAA attributes TSKs.

As a result, while the lifetime of calculated keys can communicate be less than
or equal that of the
maximum exported keys they are derived from, it cannot
be greater. For example, when EAP re-authentication occurs, TSK re-
key lifetime, will also occur. However, this only serves does not prohibit TSK re-key from
occurring prior to synchronize expiration of the
key lifetime between the backend authentication server and of exported keys. For
example, TSK re-key may occur prior to EAP re-authentication.

Failure to mutually prove possession of keying material during the
authenticator. Lower layer mechanisms such as
Secure Association Protocol exchange need not be grounds for deletion
of the keying material by both parties; rate-limiting Secure
Association Protocol can then exchanges could be used to enable the lifetime of
exported and calculated prevent a brute force
attack.

3.4. Local Key Lifetimes

The Transient EAP Keys (TEKs) are session keys used to be negotiated between protect the peer
EAP conversation. The TEKs are internal to the EAP method and
authenticator.

Where TSKs are established as
not exported. TEKs are typically created during an EAP conversation,
used until the result end of the conversation and then discarded. However,
methods may re-key TEKs during a Secure Association
Protocol exchange, conversation.

When using TEKs within an EAP conversation or across conversations,
it is RECOMMENDED necessary to ensure that the Secure Association
Protocol include support for TSK resynchronization. Where the TSK
is taken from the MSK, there replay protection and key separation
requirements are fulfilled. For instance, if a replay counter is no need
used, TEK re-key MUST occur prior to manage wrapping of the TSK lifetime
as a counter.
Similarly, TSKs MUST remain cryptographically separate parameter, since from TEKs
despite TEK re-keying or caching. This prevents TEK compromise from
leading directly to compromise of the TSK lifetime TSKs and vice versa.

EAP methods may cache local keying material which may persist for
multiple EAP conversations when fast reconnect is used [RFC 3748].
For example, EAP methods based on TLS (such as EAP-TLS [RFC2716])
derive and MSK cache the TLS Master Secret, typically for substantial
time periods. The lifetime
are identical.

[c] System defaults. Where of other local keying material calculated
within the EAP method does not support the
negotiation of the exported key lifetime, and a key lifetime
negotiation mechanism is not provided defined by the lower lower, method. Note that in
general, when using fast reconnect, there may
be is no way for the peer guarantee to learn the exported key lifetime. In this
case it is RECOMMENDED that the peer assume a default value of the
exported key lifetime; 8 hours is recommended. Similarly,
original long-term credentials are still in the
lifetime possession of calculated keys can also be managed as the
peer. For instance, a system
parameter on card hold holding the authenticator.

[d] Method specific negotiation within EAP. While private key for EAP-TLS

Aboba, et al. Standards Track [Page 26]

INTERNET-DRAFT EAP itself does not
support lifetime negotiation, it would be possible to specify
methods that do. However, systems Key Management Framework 3 April 2006

may have been removed. EAP servers SHOULD also verify that rely on the long-
term credentials are still valid, such negotiation
for exported keys would only function with these methods. As a
result, it is NOT RECOMMENDED to use this approach as by checking that
certificate used in the sole way
to determine key lifetimes. original authentication has not yet expired.

3.5. Exported and Calculated Key cache synchronization

Issues arise when attempting Lifetimes

All EAP methods generating keys are required to synchronize generate the key cache on MSK and
EMSK, and may optionally generate the IV. However, EAP, defined in
[RFC3748], does not itself support the peer
and authenticator. Lifetime negotiation alone cannot guarantee key
cache synchronization.

Aboba, et al. Standards Track [Page 29]

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One problem is that the AAA protocol cannot guarantee synchronization of key lifetimes between for
exported keying material such as the peer MSK, EMSK and authenticator. Where IV.

Several mechanisms exist for managing key lifetimes:

[a] AAA attributes. AAA protocols such as RADIUS [RFC2865] and
Diameter [RFC4072] support the
Secure Association Protocol is not run immediately after EAP
authentication, Session-Timeout attribute. The
Session-Timeout value represents the maximum lifetime of the
exported keys, and all keys calculated key lifetimes will from it, on the
authenticator. Since existing backend authentication servers do
not be
known cache keys exported by EAP methods, or keys calculated from
exported keys, the peer during value of the hiatus. Where EAP pre-authentication
occurs, this can leave Session-Timeout attribute has no
bearing on the peer uncertain whether a subsequent
attempt to use key lifetime within the exported keys will prove successful.

However, even where backend authentication
server.

On the Secure Association Protocol is run
immediately after EAP, it authenticator, where EAP is still possible used for authentication, the authenticator to
reclaim resources if
Session-Timeout value represents the created key state is not immediately
utilized.

The lower layer may utilize Discovery mechanisms maximum session time prior to assist
re-authentication, as described in this.
For example, [RFC3580]. Where EAP is used
for pre-authentication, the authenticator manages session may not start until some future
time, or may never occur. Nevertheless, the key cache by deleting Session-Timeout value
represents the
oldest key first (LIFO), maximum time after which transported EAP keying
material, and all keys calculated from it, will have expired on the relative creation time of
authenticator. If the last key
to be deleted could session subsequently starts, re-
authentication will be advertised with initiated once the Discovery phase, enabling Session-Time has expired.
If the peer to determine whether a given key had been expired session never started, or started and ended, by default keys
transported by AAA and all keys calculated from them will be
expired by the authenticator key cache prematurely.

3.6. Key Strength

In order to guard against brute force attacks, EAP methods deriving
keys need prior to the future time indicated by
Session-Timeout. Note that in future additional attributes may be capable of generating keys with an appropriate
effective symmetric key strength. In order
specified to ensure that key
generation is not control the weakest link, it is RECOMMENDED that EAP
methods utilizing public key cryptography choose a public key that
has a cryptographic strength meeting lifetime of cached keys; these attributes
may modify the symmetric key strength
requirement.

As noted in [RFC3766] Section 5, this results meaning of the Session-Timeout attribute in specific
circumstances.

Since the following
required RSA or DH module TSK lifetime is often determined by authenticator
resources, the backend authentication server has no insight into
the TSK derivation process, and DSA subgroup size in bits, for a given
level by the principle of attack resistance in bits:

Attack Resistance RSA or DH Modulus DSA subgroup
(bits) size (bits) size (bits)
----------------- ----------------- ------------
70 947 128
80 1228 145
90 1553 153
100 1926 184
150 4575 279
200 8719 373
250 14596 475 ciphersuite
independence, it is not appropriate for the backend authentication
server to manage any aspect of the TSK derivation process,
including the TSK lifetime.

Aboba, et al. Standards Track [Page 30] 27]

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3.7. Key Wrap

As described in [RFC3579] Section 4.3, known problems exist in

[b] Lower layer mechanisms. While AAA attributes can communicate the
maximum exported key wrap specified in [RFC2548]. Where the same RADIUS shared secret
is used by a PAP authenticator and an EAP authenticator, there is a
vulnerability to known plaintext attack. Since RADIUS uses the
shared secret for multiple purposes, including per-packet
authentication, attribute hiding, considerable information is exposed
about the shared secret with each packet. This exposes the shared
secret to dictionary attacks. MD5 is used both to compute the RADIUS
Response Authenticator and the Message-Authenticator attribute, and
some concerns exist relating lifetime, this only serves to synchronize the security of this hash
[MD5Attack].

As discussed in [RFC3579] Section 4.3,
key lifetime between the security vulnerabilities
of RADIUS are extensive, backend authentication server and therefore development of an alternative
key wrap technique based on the RADIUS shared secret would not
substantially improve security. As a result, [RFC3759] Section 4.2
recommends running RADIUS over IPsec. The same approach is taken in
Diameter EAP [RFC4072], which defines cleartext key attributes, to be
protected by IPsec or TLS.

Where an untrusted AAA intermediary is present (such
authenticator. Lower layer mechanisms such as a RADIUS
proxy or a Diameter agent), and data object security is not used,
transported keying material may the Secure
Association Protocol can then be recovered by an attacker in
control of used to enable the untrusted intermediary. Possession of transported
keying material enables decryption of data traffic sent lifetime of
exported and calculated keys to be negotiated between the peer and a specific
authenticator. However, as long

Where TSKs are established as EAP keying
material or keys derived from the result of a Secure Association
Protocol exchange, it is only utilized by RECOMMENDED that the Secure Association
Protocol include support for TSK resynchronization. Where the TSK
is taken from the MSK, there is no need to manage the TSK lifetime
as a single
authenticator, compromise of separate parameter, since the transported keying material TSK lifetime and MSK lifetime
are identical.

[c] System defaults. Where the EAP method does not
enable an attacker to impersonate support the peer to another authenticator.
Vulnerability to an untrusted AAA intermediary can be mitigated by
implementation
negotiation of redirect functionality, as described in [RFC3588] the exported key lifetime, and [RFC4072].

4. Handoff Vulnerabilities

With EAP, a number of mechanisms are key lifetime
negotiation mechanism is not provided by the lower lower, there may
be utilized in order no way for the peer to reduce learn the latency of handoff between authenticators. One such mechanism is
EAP pre-authentication, in which EAP exported key lifetime. In this
case it is utilized to pre-establish EAP
keying material on an authenticator prior to arrival RECOMMENDED that the peer assume a default value of the peer.
Another such mechanism is
exported key caching, in which an EAP peer lifetime; 8 hours is recommended. Similarly, the
lifetime of calculated keys can re-
attach to an authenticator without having to re-authenticate using also be managed as a system
parameter on the authenticator.

[d] Method specific negotiation within EAP. Yet another mechanism is context transfer, While EAP itself does not
support lifetime negotiation, it would be possible to specify
methods that do. However, systems that rely on such as negotiation
for exported keys would only function with these methods. As a
result, it is defined
in [IEEE-802.11F] (now deprecated) and [CTP]. These mechanisms
introduce new security vulnerabilities, NOT RECOMMENDED to use this approach as discussed in the sections
that follow.

Aboba, et al. Standards Track [Page 31]

INTERNET-DRAFT EAP sole way
to determine key lifetimes.

3.6. Key Management Framework 5 March 2006

4.1. Authorization

In a typical network access scenario (dial-in, wireless LAN, etc.)
access control mechanisms are typically applied. These mechanisms
include user authentication as well as authorization for the offered
service.

As a part of cache synchronization

Issues arise when attempting to synchronize the authentication process, key cache on the backend authentication
server determines peer
and authenticator.

While the user's authorization profile. The user
authorizations are transmitted by AAA protocol can enable the backend authentication server
to provide guidance on the EAP authenticator (also known as the Network Access Server or
authenticator) and with the lifetime of transported EAP keying material, in Phase
1b of
material to the EAP conversation. Typically, authenticator, this does not address the profile is determined
based on problem of
key lifetime synchronization between the user identity, but a certificate presented by peer and authenticator.
Where the user
may also provide authorization information.

The backend authentication server is responsible for making a user
authorization decision, answering EAP method does not export the following questions:

[a] Is this a legitimate user for this particular network?

[b] Is this user allowed Key-Lifetime parameter, the type
lifetime of access he or she is requesting?

[c] Are there any specific parameters (mandatory tunneling, bandwidth,
filters, and so on) that the access network should EAP keying material may not be aware defined until
completion of for
this user?

[d] Is this user within the subscription rules regarding time of day?

[e] Is this user Secure Association Protocol, if ever. This can
leave the peer uncertain how long the authenticator will maintain EAP
keying material within his limits for concurrent sessions?

[f] Are there any fraud, credit limit, or other concerns that indicate
that access should be denied?

While the authorization decision key cache.

However, key lifetime negotiation alone cannot guarantee key cache
synchronization. Even where the Secure Association Protocol is in principle simple, run

Aboba, et al. Standards Track [Page 28]

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immediately after EAP and determines the process lifetime of EAP keying
material, it is complicated still possible for the authenticator to reclaim
resources.

The lower layer may utilize the Discovery phase 0 to improve key
cache synchronization. For example, if the authenticator manages the
key cache by deleting the distributed nature of oldest key first (LIFO), the decision making.
Where brokering entities or proxies are involved, all relative
creation time of the AAA
entities in last key to be deleted could be advertised
within the chain Discovery phase, enabling the peer to determine whether
keying material had been prematurely expired from the authenticator
key cache.

3.7. Key Strength

In order to guard against brute force attacks, EAP methods deriving
keys need to be capable of generating keys with an appropriate
effective symmetric key strength. In order to ensure that key
generation is not the weakest link, it is RECOMMENDED that EAP
methods utilizing public key cryptography choose a public key that
has a cryptographic strength meeting the home backend
authentication server are involved symmetric key strength
requirement.

As noted in [RFC3766] Section 5, this results in the decision. For instance, a
broker can disallow access even if the home backend authentication
server would allow it, following
required RSA or a proxy can add authorizations (e.g.,
bandwidth limits).

Decisions can be based on static policy definitions DH module and profiles as
well as dynamic state (e.g. time of day or limits on the number DSA subgroup size in bits, for a given
level of
concurrent sessions). In addition to the Accept/Reject decision made
by the AAA chain, parameters attack resistance in bits:

Attack Resistance RSA or constraints can be communicated to
the authenticator.

Aboba, et al. Standards Track [Page 32]

INTERNET-DRAFT EAP DH Modulus DSA subgroup
(bits) size (bits) size (bits)
----------------- ----------------- ------------
70 947 128
80 1228 145
90 1553 153
100 1926 184
150 4575 279
200 8719 373
250 14596 475

3.8. Key Management Framework 5 March 2006 Wrap

The criteria for Accept/Reject decisions or key wrap specified in [RFC2548], which is based on an MD5-based
stream cipher, has known problems, as described in [RFC3579] Section
4.3. RADIUS uses the reasons shared secret for choosing
particular authorizations are typically not communicated to the
authenticator, only multiple purposes, including
per-packet authentication and attribute hiding, considerable
information is exposed about the final result. As a result, shared secret with each packet.
This exposes the authenticator
has no way shared secret to know what the decision was based on. Was a set of
authorization parameters sent because this service dictionary attacks. MD5 is always provided used
both to compute the user, or was the decision based on the time/day RADIUS Response Authenticator and the
capabilities of the requesting authenticator device?

4.2. Correctness

When Message-
Authenticator attribute, and concerns exist relating to the AAA exchange is bypassed via use security
of techniques such as key
caching, this creates challenges hash [MD5Collision].

Aboba, et al. Standards Track [Page 29]

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As discussed in ensuring that authorization is
properly handled. These include:

[a] Consistent application of session time limits. Bypassing AAA
should not automatically increase the available session time,
allowing a user to endlessly extend their network access by
changing [RFC3579] Section 4.3, the point security vulnerabilities
of attachment.

[b] Avoidance RADIUS are extensive, and therefore development of privilege elevation. Bypassing AAA should an alternative
key wrap technique based on the RADIUS shared secret would not result
in
substantially improve security. As a user being granted access to services which they are not
entitled to.

[c] Consideration of dynamic state. In situations in which dynamic
state result, [RFC3759] Section 4.2
recommends running RADIUS over IPsec. The same approach is involved taken in the access decision (day/time, simultaneous
session limit) it should be possible
Diameter EAP [RFC4072], which defines cleartext key attributes, to take this state into
account either before be
protected by IPsec or after access TLS.

Where an untrusted AAA intermediary is granted. Note that
consideration present (such as a RADIUS
proxy or a Diameter agent), and data object security is not used,
transported keying material may be recovered by an attacker in
control of network-wide state such the untrusted intermediary. Possession of transported
keying material enables decryption of data traffic sent between the
peer and a specific authenticator. However, as simultaneous session
limits can typically long as EAP keying
material or keys derived from it are only be taken into account utilized by the backend
authentication server.

[d] Encoding of restrictions. Since a authenticator may not be aware single
authenticator, compromise of the criteria considered transported keying material does not
enable an attacker to impersonate the peer to another authenticator.
Vulnerability to an untrusted AAA intermediary can be mitigated by a backend authentication server when
allowing access,
implementation of redirect functionality, as described in order [RFC3588]
and [RFC4072].

4. Handoff Vulnerabilities

With EAP, several mechanisms are available to ensure consistent authorization during
a fast reduce the latency in
handoff it may be necessary between authenticators:

[1] EAP pre-authentication. This utilizes EAP to explicitly encode the
restrictions within the authorizations provided by the backend
authentication server.

[e] State validity. The introduction pre-establish EAP
keying material on an authenticator prior to arrival of fast handoff should not render the authentication server incapable of keeping track of network-
wide state.

A handoff mechanism capable peer.
Use of addressing these concerns pre-authentication within IEEE 802.11 is said described in
[8021XHandoff] and [IEEE-802.11i].

[2] Key caching. This mechanism enables an EAP peer to
be "correct". One condition re-attach to an
authenticator without requiring EAP re-authentication.

[3] Context transfer, such as is defined in [IEEE-802.11F] (now
deprecated) and [RFC4067]. Use of context transfer for correctness handoff
latency improvement is described in [IEEE-02-758].

[4] Proactive key distribution, such as follows: For a
handoff to be "correct" it MUST establish on the new device is described in [IEEE-02-758]
and [I-D.irtf-aaaarch-handoff].

The sections that follow discuss the same
context as would have been created had security vulnerabilities
introduced by the new device completed above mechanisms.

4.1. Authorization

In a AAA
conversation with the backend authentication server. typical network access scenario (dial-in, wireless LAN, etc.)
access control mechanisms are typically applied. These mechanisms

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A properly designed handoff scheme will only succeed if it is
"correct"

include user authentication as well as authorization for the offered
service.

As a part of the authentication process, the backend authentication
server determines the user's authorization profile. The user
authorizations are transmitted by the backend authentication server
to the EAP authenticator (also known as the Network Access Server or
authenticator) along with the transported EAP keying material, in
Phase 1b of the EAP conversation. Typically, the profile is
determined based on the user identity, but a certificate presented by
the user may also provide authorization information.

The backend authentication server is responsible for making a user
authorization decision, which requires answering the following
questions:

[a] Is this way. If a successful handoff would establish
"incorrect" state, it legitimate user for this particular network?

[b] Is the user allowed the type of access he or she is preferable requesting?

[c] Are there any specific parameters (mandatory tunneling, bandwidth,
filters, and so on) that the access network should be aware of for it to fail,
this user?

[d] Is the user operating within the time of day subscription rules?

[e] Is the user within his limits for concurrent sessions?

[f] Are there any fraud, credit limit, or other concerns that indicate
that access should be denied?

While the authorization decision is in order to avoid
creation principle simple, the process
is complicated by the distributed nature of incorrect context.

Some backend authentication server and authenticator configurations the decision making.
Where brokering entities or proxies are incapable of meeting this definition involved, all of "correctness". For
example, if the old and new device differ AAA
entities in their capabilities, it
may be difficult the chain from the authenticator to meet this definition of correctness in a handoff
mechanism that bypasses AAA. Backend the home backend
authentication servers often
perform conditional evaluation, server are involved in which the authorizations returned
in an Access-Accept message are contingent on decision. For instance, a
broker can disallow access even if the authenticator home backend authentication
server would allow it, or a proxy can add authorizations (e.g.,
bandwidth limits).

Decisions can be based on static policy definitions and profiles as
well as dynamic state such as the (e.g. time of day or limits on the number of simultaneous
sessions. For example, in a heterogeneous deployment, the backend
authentication server might return different authorizations depending
on
concurrent sessions). In addition to the authenticator making Accept/Reject decision made
by the request, in order AAA chain, parameters or constraints can be communicated to make sure that
the requested service is consistent with authenticator.

The criteria for Accept/Reject decisions or the authenticator
capabilities.

If differences between reasons for choosing
particular authorizations are typically not communicated to the new and old device would result in

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authenticator, only the
backend authentication server sending final result. As a different set of messages result, the authenticator
has no way to know what the new device than were decision was based on. Was a set of
authorization parameters sent because this service is always provided
to the old device, then if user, or was the handoff
mechanism bypasses AAA, then decision based on the handoff cannot be carried out
correctly.

For example, if some time/day and the
capabilities of the requesting authenticator devices within a deployment
support dynamic VLANs while others do not, then attributes present in device?

4.2. Correctness

When the Access-Request (such AAA exchange is bypassed via use of techniques such as the authenticator-IP-Address,
authenticator-Identifier, Vendor-Identifier, etc.) could key
caching, it can be examined challenging to determine when VLAN attributes will be returned, as described in
[RFC3580]. VLAN support ensure that authorization is defined in [IEEE-802.1Q]. If a handoff
bypassing
properly handled. Challenges include:

[a] Consistent application of session time limits. Bypassing AAA
should not automatically increase the backend authentication server were to occur between a
authenticator supporting dynamic VLANs and another authenticator
which does not, then available session time,
allowing a guest user with access restricted to a guest
VLAN could be given unrestricted endlessly extend their network access to by
changing the network.

Similarly, point of attachment.

[b] Avoidance of privilege elevation. Bypassing AAA should not result
in a network where user being granted access is restricted based on the day
and time, Service Set Identifier (SSID), Calling-Station-Id or other
factors, unless the restrictions to services which they are encoded within the
authorizations, or a partial AAA conversation not
entitled to.

[c] Consideration of dynamic state. In situations in which dynamic
state is included, then a
handoff could result involved in the user bypassing access decision (day/time, simultaneous
session limit) it should be possible to take this state into
account either before or after access is granted. Note that
consideration of network-wide state such as simultaneous session
limits can typically only be taken into account by the backend
authentication server.

[d] Encoding of restrictions.

In practice, these considerations limit Since a authenticator may not be aware
of the situations criteria considered by a backend authentication server when
allowing access, in which order to ensure consistent authorization during
a fast handoff mechanisms bypassing AAA can be expected to be successful.
Where the deployed devices implement the same set of services, it may be possible necessary to do successful handoffs explicitly encode the
restrictions within such mechanisms.
However, where the supported services differ between devices, authorizations provided by the backend
authentication server.

[e] State validity. The introduction of fast handoff may not succeed. For example, [RFC2865] section 1.1 states:

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"A authenticator that does should not implement a given service MUST NOT
implement the RADIUS attributes for that service. For example, a
authenticator that is unable to offer ARAP service MUST NOT
implement render
the RADIUS attributes for ARAP. A authenticator MUST
treat a RADIUS access-accept authorizing an unavailable service as
an access-reject instead."

Note that this behavior only applies to attributes that are known,
but not implemented. For attributes that are unknown, [RFC2865]
Section 5 states:

"A RADIUS authentication server MAY ignore Attributes with an unknown Type. incapable of keeping track of network-
wide state.

A
RADIUS client MAY ignore Attributes with an unknown Type."

In order to perform a correct handoff, if a new device is provided
with RADIUS context handoff mechanism capable of addressing these concerns is said to
be "correct". One condition for correctness is as follows:

For a known but unavailable service, then handoff to be "correct" it MUST
process this context establish on the new device
the same way it context as would handle a RADIUS Access-
Accept requesting an unavailable service. This MUST cause have been created had the
handoff to fail. However, if a new device is provided
completed a AAA conversation with RADIUS
context that indicates an unknown attribute, then this attribute MAY
be ignored.

Although the backend authentication
server.

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A properly designed handoff scheme will only succeed if it may seem somewhat counter-intuitive, failure is indeed
the
"correct" result where in this way. If a known but unsupported service successful handoff would establish
"incorrect" state, it is
requested. Presumably a correctly configured preferable for it to fail, in order to avoid
creation of incorrect context.

Some authenticator and backend authentication server would not request that a configurations
are incapable of meeting this definition of "correctness". For
example, if the old and new device carry out differ in their capabilities, a service
handoff mechanism that bypasses AAA may find it
does not implement. This implies difficult to meet
this definition of correctness. Backend authentication servers often
perform conditional evaluation, in which the authorizations returned
in an Access-Accept message are contingent on the authenticator or on
dynamic state such as the time of day or number of simultaneous
sessions. For example, in a heterogeneous deployment, the backend
authentication server might return different authorizations depending
on the authenticator making the request, in order to make sure that if
the requested service is consistent with the authenticator
capabilities.

If differences between the new and old device were to
complete a AAA conversation that it would be likely to receive
different service instructions. In such result in the
backend authentication server sending a case, failure different set of the
handoff is the desired result. This will cause messages to
the new device to go
back than were sent to the AAA server in order to receive old device, then if the appropriate service
definition.

In practice, this implies that handoff mechanisms which bypass AAA
are most likely to
mechanism bypasses AAA, the handoff cannot be successful within a homogeneous device
deployment within a single administrative domain. carried out correctly.

For example, it
would not if some authenticators support dynamic VLANs while
others do not, then attributes present in the Access-Request (such as
the NAS-IP-Address, NAS-IPv6-Address, NAS-Identifier, etc.) could be advisable
examined to carry out determine when VLAN attributes will be returned, as
described in [RFC3580]. VLAN support is defined in [IEEE-802.1Q].
If a fast handoff bypassing AAA the backend authentication server were to
occur between a authenticator providing confidentiality supporting dynamic VLANs and another
authenticator that which does not support this service. The correct result
of such not, then a handoff would guest user with access
restricted to a guest VLAN could be given unrestricted access to the
network.

Similarly, in a failure, since if network where access is restricted based on the handoff were
blindly carried out, day
and time, Service Set Identifier (SSID), Calling-Station-Id or other
factors, unless the restrictions are encoded within the
authorizations, or a partial AAA conversation is included, then a
handoff could result in the user bypassing the restrictions.

In practice, these considerations limit the user would situations in which fast
handoff mechanisms bypassing AAA can be moved from a secure expected to an
insecure channel without permission from be successful.
Where the backend authentication
server. Thus deployed devices implement the definition same set of a "known but unsupported service"
MUST encompass requests for unavailable security services. This
includes vendor-specific attributes related services, it may
be possible to security, do successful handoffs within such as
those described in [RFC2548]. mechanisms.
However, where the supported services differ between devices, the
handoff may not succeed. For example, [RFC2865] section 1.1 states:

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5. Security Considerations

"A authenticator that does not implement a given service MUST NOT
implement the RADIUS attributes for that service. For example, a
authenticator that is unable to offer ARAP service MUST NOT
implement the RADIUS attributes for ARAP. A authenticator MUST
treat a RADIUS access-accept authorizing an unavailable service as
an access-reject instead."

Note that this behavior only applies to attributes that are known,
but not implemented. For attributes that are unknown, [RFC2865]
Section 5 states:

"A RADIUS server MAY ignore Attributes with an unknown Type. A
RADIUS client MAY ignore Attributes with an unknown Type."

In order to analyze whether perform a correct handoff, if a new device is provided
with RADIUS context for a known but unavailable service, then it MUST
process this context the EAP conversation achieves its
security goals, same way it would handle a RADIUS Access-
Accept requesting an unavailable service. This MUST cause the
handoff to fail. However, if a new device is provided with RADIUS
context that indicates an unknown attribute, then this attribute MAY
be ignored.

Although it may seem somewhat counter-intuitive, failure is first necessary to state those goals as well as
the underlying security assumptions.

The overall goal of indeed
the EAP conversation "correct" result where a known but unsupported service is to derive fresh session
keys between the EAP peer and authenticator
requested. Presumably a correctly configured backend authentication
server would not request that are known only to
those parties, and for both a device carry out a service that it
does not implement. This implies that if the EAP peer and authenticator new device were to
demonstrate
complete a AAA conversation that they are authorized it would be likely to perform their roles either by
each other or by receive
different service instructions. In such a trusted third party (the backend authentication
server).

The principals case, failure of the authentication phase are
handoff is the EAP peer and
server. Completion of an EAP method exchange supporting key
derivation results in desired result. This will cause the derivation of EAP keying material (MSK,
EMSK, TEKs) known only new device to go
back to the EAP peer (identified by the Peer-ID)
and server (identified by the Server-ID). Both the EAP peer and EAP backend server know the exported keying material in order to be fresh.

The principals of receive the appropriate
service definition.

In practice, this implies that handoff mechanisms which bypass AAA Key transport exchange
are the EAP
authenticator and the EAP server. Completion of the AAA exchange
results in the transport of EAP keying material from the EAP server
(identified by the Server-ID) most likely to be successful within a homogeneous device
deployment within a single administrative domain. For example, it
would not be advisable to the EAP carry out a fast handoff bypassing AAA
between a authenticator (identified by
the NAS-Identifier) without disclosure to any other party. Both the
EAP server providing confidentiality and EAP another
authenticator know that does not support this keying material to be
fresh. service. The principals correct result
of such a handoff would be a failure, since if the Secure Association Protocol are the EAP peer
(identified by the Peer-ID) and authenticator (identified by handoff were
blindly carried out, then the NAS-
Identifier). Completion of user would be moved from a secure to an
insecure channel without permission from the Secure Association Protocol results
in backend authentication
server. Thus the derivation definition of TSKs known only a "known but unsupported service"
MUST encompass requests for unavailable security services. This
includes vendor-specific attributes related to the security, such as
those described in [RFC2548].

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authenticator. Both Key Management Framework 3 April 2006

5. Security Considerations

In order to analyze whether the EAP peer and authenticator know the TSKs conversation achieves its
security goals, it is first necessary to
be fresh.

5.1. Terminology describe the threat model.
The terms "Cryptographic binding", "Cryptographic separation", "Key
strength" and "Mutual authentication" are defined in [RFC3748] and
are used with the same meaning here.

5.2.

5.1. Threat Model

The EAP threat model is described in [RFC3748] Section 7.1. The
security properties of EAP methods (known as "security claims",
described in [RFC3784] Section 7.2.1), address these threats. EAP
method requirements for applications such as Wireless LAN
authentication are described in [RFC4017]. The RADIUS threat model

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is described in [RFC3579] Section 4.1, and responses to these threats
are described in [RFC3579] Sections 4.2 and 4.3.

However, in addition to threats against EAP and AAA, there are other
system-level threats worth discussing. These include:

[1] An attacker may compromise or steal an EAP authenticator, in an
attempt to gain access to other EAP authenticators or obtain long-
term secrets.

[2] An attacker may compromise an EAP authenticator in an effort to
commit fraud. For example, a compromised authenticator may provide
incorrect information to the EAP peer and/or server via out-of-band
mechanisms (such as via a AAA or lower layer protocol). This
includes impersonating another authenticator, or providing
inconsistent information to the peer and EAP server.

[3] An attacker may try to modify or spoof packets, including Discovery
or Secure Association Protocol frames, EAP or AAA packets.

[4] An attacker may attempt a downgrade attack in order to exploit
known weaknesses in an authentication method or cryptographic
transform.

[5] An attacker may attempt to induce an EAP peer, authenticator or
server to disclose keying material to an unauthorized party, or
utilize keying material outside the context that it was intended
for.

[6] An attacker may replay packets.

[7] An attacker may cause an EAP peer, authenticator or server to reuse
an stale key. Use of stale keys may also occur unintentionally.

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For example, a poorly implemented backend authentication server may
provide stale keying material to an authenticator, or a poorly
implemented authenticator may reuse nonces.

[8] An authenticated attacker may attempt to obtain elevated privilege
in order to access information that it does not have rights to.

In order to address these threats, [Housley] provides a description
of mandatory system security properties. Issues relating system
security requirements are discussed in the sections that follow.

5.3.

5.2. Authenticator Compromise

In the event that an authenticator is compromised or stolen, an
attacker may gain access to the network via that authenticator, or

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may obtain the credentials required for that authenticator/AAA client
to communicate with one or more backend authentication servers.
However, this should not allow the attacker to compromise other
authenticators or the backend authentication server, or obtain long-
term user credentials.

The implications of this requirement are many, but some of the more
important are as follows:

No Key Sharing
An EAP authenticator MUST NOT share any keying material with
another EAP authenticator, since if one EAP authenticator were
compromised, this would enable the compromise of keying material on
another authenticator. In order to be able to determine whether
keying material has been shared, it is necessary for the identity
of the EAP authenticator to be defined and understood by all
parties that communicate with it.

No AAA Credential Sharing
AAA credentials (such as RADIUS shared secrets, IPsec pre-shared
keys or certificates) MUST NOT be shared between AAA clients, since
if one AAA client were compromised, this would enable an attacker
to impersonate other AAA clients to the backend authentication
server, or even to impersonate a backend authentication server to
other AAA clients.

No Compromise of Long-Term Credentials
An attacker obtaining TSKs, TEKs or EAP keying material such as the
MSK MUST NOT be able to obtain long-term user credentials such as
pre-shared keys, passwords or private-keys without breaking a
fundamental cryptographic assumption.

5.4.

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5.3. Spoofing

The use of per-packet authentication and integrity protection
provides protection against spoofing attacks. Diameter [RFC3588]
provides support for per-packet authentication and integrity
protection via use of IPsec or TLS. RADIUS/EAP [RFC3579] provides
for per-packet authentication and integrity protection via use of the
Message-Authenticator attribute.

[RFC3748] Section 7.2.1 describes the "integrity protection" security
claim and [RFC4017] requires use of EAP methods supporting this
claim.

In order to prevent forgery of Secure Association Protocol frames,
per-frame authentication and integrity protection is RECOMMENDED on
all messages. [IEEE-802.11i] supports per-frame integrity protection

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and authentication on all messages within the 4-way handshake except
the first message. An attack leveraging this ommission is described
in [Analysis].

5.5.

5.4. Downgrade Attacks

The ability to negotiate the use of a particular cryptographic
algorithm provides resilience against compromise of a particular
cryptographic algorithm. This is usually accomplished by including
an algorithm identifier in the protocol, and by specifying the
algorithm requirements in the protocol specification. In order to
prevent downgrade attacks, secure confirmation of the "best"
ciphersuite is required.

[RFC3748] Section 7.2.1 describes the "protected ciphersuite
negotiation" security claim that refers to the ability of an EAP
method to negotiate the ciphersuite used to protect the EAP
conversation, as well as to integrity protect the negotiation.
[RFC4017] requires EAP methods satisfying this security claim.

Diameter [RFC3588] provides support for cryptographic algorithm
negotiation via use of IPsec or TLS. RADIUS [RFC3579] does not
support the negotiation of cryptographic algorithms, and relies on
MD5 for integrity protection, authentication and confidentiality,
despite known weaknesses in the algorithm [MD5Attack]. [MD5Collision]. This issue
can be addressed via use of RADIUS over IPsec, as described in
[RFC3579] Section 4.2.

As a result, EAP methods and AAA protocols are capable of addressing
downgrade attacks. To ensure against downgrade attacks within lower
layer protocols, algorithm independence is REQUIRED with lower layers
using EAP for key derivation. For interoperability, at least one

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suite of mandatory-to-implement algorithm MUST be selected. Lower
layer protocols supporting EAP for key derivation SHOULD also support
secure ciphersuite negotiation. As described in [RFC1968], PPP ECP
does not provide support for secure ciphersuite negotiation.
However, [IEEE-802.11i] does support secure ciphersuite negotiation.

5.6.

5.5. Unauthorized Disclosure

While preserving algorithm independence, confidentiality of all
keying material MUST be maintained. To prevent unauthorized disclose
of keys, each party in the EAP conversation MUST be authenticated to
the other parties with whom it communicates. Keying material MUST be
bound to the appropriate context.

[RFC3748] Section 7.2.1 describes the "mutual authentication" and
"dictionary attack resistance" claims, and [RFC4017] requires EAP

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methods satisfying these claims. EAP methods complying with
[RFC4017] therefore provide for mutual authentication between the EAP
peer and server. Binding of EAP keying material (MSK, EMSK) to the
appropriate context is provided by the Peer-ID and Server-ID which
are exported along with the keying material.

Diameter [RFC3588] provides for per-packet authentication and
integrity protection via IPsec or TLS, and RADIUS/EAP [RFC3579] also
provides for per-packet authentication and integrity protection.
Where the NAS/authenticator and backend authentication server
communicate directly and credible keywrap is used (see Section 3.7), 3.8),
this ensures that the AAA Key Transport phase achieves its security
objectives: mutually authenticating the AAA client/authenticator and
backend authentication server and providing EAP keying material to
the EAP authenticator and to no other party. [RFC2607] Section 7
describes the security issues ocurring when the authenticator and
backend authentication server do not communicate directly.

As noted in Section 3.1, the Secure Association Protocol does not by
itself provide for mutual authentication between the EAP peer and
authenticator, even if mutual possession of EAP keying material is
proven. However, where Where the NAS/authenticator and backend authentication
server communicate directly, the backend authentication server can
verify the correspondence between NAS identification attributes, the
source address of packets sent by the NAS, and the AAA credentials.
As long as the NAS has not shared its AAA credentials with another
NAS, this allows the backend authentication server to authenticate
the NAS. Using Channel Bindings, the EAP peer can then determine
whether the NAS/authenticator has provided the same identifying
information to the EAP peer and backend authentication server.

Peer and authenticator authorization MUST be performed.

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Authorization is REQUIRED whenever a peer associates with a new
authenticator. Authorization checking prevents an elevation of
privilege attack, and ensures that an unauthorized authenticator is
detected. Authorizations SHOULD be synchronized between the EAP
peer, server, authenticator. Once the EAP conversation exchanges are
complete, all of these parties should hold the same view of the
authorizations associated the other parties. If peer authorization
is restricted, then the peer SHOULD be made aware of the restriction.

The AAA exchange provides the EAP authenticator with authorizations
relating to the EAP peer. However, neither the EAP nor AAA exchanges
provides authorizations to the EAP peer. In order to ensure that all
parties hold the same view of the authorizations it is RECOMMENDED
that the Secure Association Protocol enable communication of
authorizations between the EAP authenticator and peer.

In order to enable key binding and authorization of all parties, it

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is RECOMMENDED that the parties use a set of identities that are
consistent between the conversation phases. RADIUS [RFC2865] and
Diameter NASREQ [RFC4005] require that the NAS/EAP authenticator
identify itself by including one or more identification attributes
within an Access-Request packet (NAS-Identifier, NAS-IP-Address, NAS-
IPv6-Address).

Since the backend authentication server provides EAP keying material
for use by the EAP authenticator as identified by these attributes,
where an EAP authenticator may have multiple ports, it is RECOMMENDED
for the EAP authenticator to identify itself using NAS identification
attributes during the Secure Association Protocol exchange with the
EAP peer. This enables the EAP peer to determine whether EAP keying
material has been shared between EAP authenticators as well as to
confirm with the backend authentication server that an EAP
authenticator proving possession of EAP keying material during the
Secure Association Protocol was authorized to obtain it. Typically,
the NAS-Identifier attribute is most convenient for this purpose,
since a NAS/authenticator may have multiple IP addresses.

Similarly, the backend authentication server authorizes the EAP
authenticator to provide access to Consistently identifying
the EAP peer identified by the
Peer-ID, securely verified during authenticator enables the EAP authentication exchange.
In order peer to determine whether EAP
keying material has been shared between EAP peers, where authenticators as well as
to confirm with the backend authentication server that an EAP peer has multiple ports it is
RECOMMENDED for the
authenticator proving possession of EAP peer to identify itself using the Peer-ID keying material during the
Secure Association Protocol exchange with the EAP
authenticator.

5.7. was authorized to obtain it.
Identification issues are discussed in Section 2.2 and key scope
issues are discussed in Section 3.2.

5.6. Replay Protection

Replay protection allows a protocol message recipient to discard any
message that was recorded during a previous legitimate dialogue and
presented as though it belonged to the current dialogue.

[RFC3748] Section 7.2.1 describes the "replay protection" security
claim and [RFC4017] requires use of EAP methods supporting this
claim.

Diameter [RFC3588] provides support for replay protection via use of
IPsec or TLS. RADIUS/EAP [RFC3579] protects against replay of keying
material via the Request Authenticator. However, some RADIUS packets
are not replay protected. In Accounting, Disconnect and CoA-Request
packets the Request Authenticator contains a keyed MAC rather than a
Nonce. The Response Authenticator in Accounting, Disconnect and CoA
Response packets also contains a keyed MAC whose calculation does not
depend on a Nonce in either the Request or Response packets.
Therefore unless an Event-Timestamp attribute is included or IPsec is

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used, the recipient may not be able to determine whether these
packets have been replayed.

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In order to prevent replay of Secure Association Protocol frames,
replay protection is REQUIRED on all messages. [IEEE-802.11i]
supports replay protection on all messages within the 4-way
handshake.

5.8.

5.7. Key Freshness

A session key should be considered compromised if it remains in use
too long. As noted in [Housley], session keys MUST be strong and
fresh, while preserving algorithm independence. A fresh
cryptographic key is one that is generated specifically for the
intended use. Each session deserves an independent session key;
disclosure of one session key MUST NOT aid the attacker in
discovering any other session keys.

Fresh keys are required even when a long replay counter (that is, one
that "will never wrap") is used to ensure that loss of state does not
cause the same counter value to be used more than once with the same
session key.

EAP, AAA and the lower layer each bear responsibility for ensuring
the use of fresh, strong session keys:

EAP EAP methods need to ensure the freshness and strength of EAP keying
material provided as an input to session key derivation. [RFC3748]
Section 7.10 states that "EAP methods SHOULD ensure the freshness
of the MSK and EMSK, even in cases where one party may not have a
high quality random number generator. A RECOMMENDED method is for
each party to provide a nonce of at least 128 bits, used in the
derivation of the MSK and EMSK." The contribution of nonces
enables the EAP peer and server to ensure that exported EAP keying
material is fresh.

[RFC3748] Section 7.2.1 describes the "key strength" and "session
independence" security claims, and and [RFC4017] requires use of
EAP methods supporting these claims as well as being capable of
providing an equivalent key strength of 128 bits or greater.

AAA The AAA protocol needs to ensure that transported keying material
is fresh and is not utilized outside its recommended lifetime.
Replay protection is necessary for key freshness, but an attacker
can deliver a stale (and therefore potentially compromised) key in
a replay-protected message, so replay protection is not sufficient.

The EAP Session-ID, derived from the EAP Type and Method-ID (based

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on the nonces contributed by the peer and server) enables the EAP
peer, authenticator and server to distinguish EAP conversations.
However, unless the authenticator keeps track of EAP Session-IDs,

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the authenticator cannot use the Session-ID to guarantee the
freshness of EAP keying material.

As described in [RFC3580] Section 3.17, When sent in an Access-
Accept along with a Termination-Action value of RADIUS-Request, the
Session-Timeout attribute specifies the maximum number of seconds
of service provided prior to re-authentication. [IEEE-802.11i]
also utilizes the Session-Timeout attribute to limit the maximum
time that EAP keying material may be cache. cached. Therefore the use of
the Session-Timeout attribute enables the backend authentication
server to limit the exposure of EAP keying material.

Lower Layer
The
As described in Section 3.1, the lower layer Secure Association
Protocol MUST generate a fresh session key for each session, even
if the keying material and parameters provided by EAP methods are
cached, or either the peer or authenticator lack a high entropy
random number generator. A RECOMMENDED method is for the peer and
authenticator to each provide a nonce or counter used in session
key derivation. If a nonce is used, it is RECOMMENDED that it be
at least 128 bits.

5.9.

5.8. Elevation of Privilege

Parties MUST NOT have access to keying material that is not needed to
perform their own role. A party has access to a particular key if it
has access to all of the secret information needed to derive it. If
a post-EAP handshake Secure Association Protocol is used to establish session keys, the post-EAP
handshake it
MUST specify the scope for session keys.

Transported EAP keying material is permitted to be accessed by the
EAP peer, authenticator and server. The EAP peer and server derive
the transported keying material during the process of mutually
authenticating each other using the selected EAP method. During the
Secure Association Protocol, the EAP peer utilizes the transported
EAP keying material to demonstrate to the authenticator that it is
the same party that authenticated to the EAP server and was
authorized by it. The EAP authenticator utilizes the transported EAP
keying material to prove to the peer not only that the EAP
conversation was transported through it (this could be demonstrated
by a man-in-the-middle), but that it was uniquely authorized by the
EAP server to provide the peer with access to the network. Unique
authorization can only be demonstrated if the EAP authenticator does
not share the transported keying material with a party other than the
EAP peer and server.

TSKs are permitted to be accessed only by the EAP peer and
authenticator (see Section 1.5). As discussed in Section 2.1, PPP

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INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

TSKs are permitted to be accessed only by the EAP peer

and
authenticator. Since 802.11i derive the TSKs can be determined from the transported EAP keying material;
802.16e utilizes transported EAP keying material and for TSK keywrap;
IKEv2 utilizes transported EAP keying material only to authenticate
the cleartext derivation of the Secure Association
Protocol exchange, TSKs.

Where demonstration of authorization depends entirely on possession
of transported EAP keying material (such as in PPP, 802.11i and
802.16e), this enables the backend authentication server will have access to masquerade as the
authenticator, and possibly to obtain the TSKs unless it the backend
server deletes the transported EAP keying material after sending it.

5.10.

5.9. Man-in-the-middle Attacks

As described in [I-D.puthenkulam-eap-binding], EAP method sequences
and compound authentication mechanisms may be subject to man-in-the-
middle attacks. When such attacks are successfully carried out, the
attacker acts as an intermediary between a victim and a legitimate
authenticator. This allows the attacker to authenticate successfully
to the authenticator, as well as to obtain access to the network.

In order to prevent these attacks, [I-D.puthenkulam-eap-binding]
recommends derivation of a compound key by which the EAP peer and
server can prove that they have participated in the entire EAP
exchange. Since the compound key must not be known to an attacker
posing as an authenticator, and yet must be derived from quantities
that are exported by EAP methods, it may be desirable to derive the
compound key from a portion of the EMSK. In order to provide proper
key hygiene, it is recommended that the compound key used for man-in-
the-middle protection be cryptographically separate from other keys
derived from the EMSK.

5.11.

5.10. Denial of Service Attacks

Key caching may result in vulnerability to denial of service attacks.
For example, EAP methods that create persistent state may be
vulnerable to denial of service attacks on the EAP server by a rogue
EAP peer.

To address this vulnerability, EAP methods creating persistent state
may wish to limit the persistent state created by an EAP peer. For
example, for each peer an EAP server may choose to limit persistent
state to a few EAP conversations, distinguished by the EAP Session-
ID. This prevents a rogue peer from denying access to other peers.

Similarly, to conserve resources an authenticator may choose to limit
the persistent state corresponding to each peer. This can be
accomplished by limiting each peer to persistent sttate state corresponding
to a few EAP converations, conversations, distinguished by the EAP Session-ID.

Aboba, et al. Standards Track [Page 42]

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Depending on the media, creation of new TSKs may or may not imply
deletion of previously derived TSKs. Where there is no implied
deletion, the authenticator may choose to limit the number of TSKs

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INTERNET-DRAFT EAP Key Management Framework 5 March 2006
and associated state that can be stored for each peer.

5.12.

5.11. Impersonation

Both the RADIUS [RFC2865] and Diameter [RFC3588] protocols are
potentially vulnerable to impersonation by a rogue authenticator.
While AAA both protocols such as RADIUS [RFC2865] or Diameter [RFC3588] support mutual authentication between the
authenticator (known as the AAA client) and the backend
authentication server (known as the backend authentication server),
the security mechanisms vary
according to the AAA protocol. vary.

In RADIUS, the shared secret used for authentication is determined by
the source address of the RADIUS packet. As noted in [RFC3579]
Section 4.3.7, it is highly desirable that the source address be
checked against one or more NAS identification attributes so as to
detect and prevent impersonation attacks.

When RADIUS requests Access-Requests are forwarded by a proxy, the NAS-IP-Address NAS-IP-
Address or NAS-IPv6-Address attributes may not correspond to the
source address. Since the NAS-Identifier attribute need not contain
an FQDN, it also may not correspond to the source address, even
indirectly. [RFC2865] Section 3 states:

A RADIUS server MUST use the source IP address of the RADIUS
UDP packet to decide which shared secret to use, so that
RADIUS requests can be proxied.

This implies that it is possible for a rogue authenticator to forge
NAS-IP-Address, NAS-IPv6-Address or NAS-Identifier attributes within
a RADIUS Access-Request in order to impersonate another
authenticator. Among other things, this can result in messages (and
transorted
transported keying material) being sent to the wrong authenticator.
Since the rogue authenticator is authenticated by the RADIUS proxy or
server purely based on the source address, other mechanisms are
required to detect the forgery. In addition, it is possible for
attributes such as the Called-Station-Id and Calling-Station-Id to be
forged as well.

As recommended in

[RFC3579] Section 4.3.7, this vulnerability 4.3.7 describes how an EAP pass-through
authenticator acting as a AAA client can be detected if it attempts
to impersonate another authenticator (such by sending incorrect
Called-Station-ID [RFC2865], NAS-Identifier [RFC2865], NAS-IP-Address
[RFC2865] or NAS-IPv6-Address [RFC3162] attributes via the AAA
protocol). This vulnerabilityh can be mitigated by having RADIUS
proxies check NAS identification attributes against the source

Aboba, et al. Standards Track [Page 43]

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address.

While [RFC3588] requires use of the Route-Record AVP, this utilizes
FQDNs, so that impersonation detection requires DNS A/AAAA A, AAAA and PTR
RRs
Resource Records (RRs) to be properly configured. As a result, it appears that
Diameter is as vulnerable to this attack as RADIUS, if not more so.
To

Aboba, et al. Standards Track [Page 45]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006 address this vulnerability, it is necessary to allow the backend
authentication server to communicate with the authenticator directly,
such as via the redirect functionality supported in [RFC3588].

5.13.

5.12. Channel Binding

It is possible for a compromised or poorly implemented EAP
authenticator to communicate incorrect information to the EAP peer
and/or server. This may enable an authenticator to impersonate
another authenticator or communicate incorrect information via out-
of-band mechanisms (such as via AAA or the lower layer).

Where EAP is used in pass-through mode, the EAP peer does not verify
the identity of the pass-through authenticator. Within the Secure
Association Protocol, the EAP peer and authenticator only demonstrate
mutual possession of the transported EAP keying material. This
creates a potential security vulnerability, described in [RFC3748]
Section 7.15.

[RFC3579] Section 4.3.7 describes how an EAP pass-through
authenticator acting as

As described in the previous section, it is possible for a proxy to
detect a AAA client can be detected if it attempts attempting to impersonate another authenticator
(such by sending incorrect Called-Station-ID [RFC2865], NAS-Identifier NAS-
Identifier [RFC2865], NAS-IP-Address [RFC2865] or NAS-IPv6-Address
[RFC3162] attributes via the AAA protocol). However, it is possible
for a pass-through authenticator acting as a AAA client to provide
correct information to the backend authentication server while
communicating misleading information to the EAP peer via the lower
layer.

For example, a compromised authenticator can utilize another
authenticator's Called-Station-Id or NAS-Identifier in communicating
with the EAP peer via the lower layer, or for layer. Also, a pass-through
authenticator acting as a AAA client to can provide an incorrect peer
Calling-Station-Id [RFC2865][RFC3580] to the AAA server via the AAA
protocol.

As noted in [RFC3748] Section 7.15, this vulnerability can be
addressed by EAP methods that support a protected exchange of channel
properties such as endpoint identifiers, including (but not limited
to): Called-Station-Id [RFC2865][RFC3580], Calling-Station-Id
[RFC2865][RFC3580], NAS-Identifier [RFC2865], NAS-IP-Address
[RFC2865], and NAS-IPv6-Address [RFC3162].

Aboba, et al. Standards Track [Page 44]

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Using such a protected exchange, it is possible to match the channel
properties provided by the authenticator via out-of-band mechanisms
against those exchanged within the EAP method. For example, see [I-
D.arkko-eap-service-identity-auth].

Aboba, et al. Standards Track [Page 46]

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It is also possible to achieve Channel Bindings without transporting
data over EAP. For example, see [draft-ohba-eap-aaakey-binding]. [I-D.draft-ohba-eap-aaakey-binding].
In this approach the authenticator informs the backend server about
the Channel Binding parameters using AAA, and the backend server
calculates transported keying material based on this parameter set,
making it impossible for the peer and authenticator to complete the
Secure Association Protocol if there was a mismatch in the
parameters.

The main difference between these approaches is that Channel Binding
support within an EAP method may require upgrading or changing the
EAP method, impacting both the peer and the server. Where Channel
Bindings are implemented in AAA, the peer, authenticator and the
backend server need to be upgraded, but the EAP method need not be
modified.

6. IANA Considerations

This document specification does not create request the creation of any new name spaces parameter
registries, nor does it
allocate require any protocol parameters. other IANA assignments.

7. References

7.1. Normative References

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

[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October
1998.

[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J. and H.
Lefkowetz, "Extensible Authentication Protocol (EAP)", RFC
3748, June 2004.

7.2. Informative References

[Analysis] He, C. and J. Mitchell, "Analysis of the 802.11i 4-Way
Handshake", Proceedings of the 2004 ACM Workshop on
Wireless Security, pp. 43-50, ISBN: 1-58113-925-X.

[CTP] Loughney, J., Nakhjiri, M., Perkins, C.

[GKDP] Dondeti, L., Xiang, J. and R. Koodli,
"Context Transfer S. Rowles, "GKDP: Group Key
Distribution Protocol", draft-ietf-seamoby-ctp-11.txt, Internet draft (work in progress), August 2004.
draft-ietf-msec-gkdp-01, March 2006.

Aboba, et al. Standards Track [Page 47] 45]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

[DESMODES]
National Institute of Standards

[GSAKMP] Harney, H., Meth, U., Colegrove, A., and Technology, "DES Modes of
Operation", FIPS PUB 81, December 1980, <http://
www.itl.nist.gov/fipspubs/fip81.htm>.

[FIPSDES] National Institute G. Gross, "GSAKMP:
Group Secure Association Group Management Protocol",
Internet draft (work in progress), draft-ietf-msec-gsakmp-
sec-10, May 2005.

[He] He, C., Sundararajan, M., Datta, A. Derek, A. and J. C.
Mitchell, "A Modular Correctness Proof of Standards TLS and Technology, "Data
Encryption Standard", FIPS PUB 46, January 1977. IEEE
802.11i", ACM Conference on Computer and Communications
Security (CCS '05), November, 2005.

[Housley] Housley, R. and B. Aboba, "AAA Key Management", draft-housley-
aaa-key-mgmt-01.txt, draft-
housley-aaa-key-mgmt-01.txt, Internet draft (work in
progress), November 2005.

[IEEE-802]
Institute of Electrical and Electronics Engineers, "IEEE
Standards for Local and Metropolitan Area Networks: Overview
and Architecture", ANSI/IEEE Standard 802, 1990.

[IEEE-802.11]
Institute of Electrical and Electronics Engineers,
"Information technology - Telecommunications and
information exchange between systems - Local and
metropolitan area networks - Specific Requirements Part 11:
Wireless LAN Medium Access Control (MAC) and Physical Layer
(PHY) Specifications", IEEE IEEE Standard 802.11-2003,
2003.

[IEEE-802.1X]
Institute of Electrical and Electronics Engineers, "Local
and Metropolitan Area Networks: Port-Based Network Access
Control", IEEE Standard 802.1X-2004, December 2004.

[IEEE-802.1Q]
Institute of Electrical and Electronics Engineers, "IEEE
Standards for Local and Metropolitan Area Networks: Draft
Standard for Virtual Bridged Local Area Networks", IEEE
Standard 802.1Q/D8, January 1998.

[IEEE-802.11i] [IEEE802.11i] Institute
of Electrical and Electronics Engineers, "Supplement to STANDARD FOR
Standard for Telecommunications and Information Exchange
between
Between Systems - LAN/MAN Specific Requirements - Part 11:
Wireless LAN Medium Access Control (MAC) and physical layer Physical Layer
(PHY)
specifications: Specifications: Specification for Enhanced Security",
IEEE 802.11i, December July 2004.

[IEEE-802.11F]
Institute of Electrical and Electronics Engineers,
"Recommended Practice for Multi-Vendor Access Point
Interoperability via an Inter-Access Point Protocol Across

Aboba, et al. Standards Track [Page 48]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006
Distribution Systems Supporting IEEE 802.11 Operation",
IEEE 802.11F, July 2003 (now deprecated).

Aboba, et al. Standards Track [Page 46]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

[IEEE-802.16e]
Institute of Electrical and Electronics Engineers, "IEEE
Standard for Local and Metropolitan Area Networks: Part 16:
Air Interface for Fixed and Mobile Broadband Wireless
Access Systems: Amendment for Physical and Medium Access
Control Layers for Combined Fixed and Mobile Operations in
Licensed Bands" IEEE 802.16e, August 2005.

[IEEE-02-758]
Mishra, A., Shin, M., Arbaugh, W., Lee, I. and K. Jang,
"Proactive Caching Strategies for IAPP Latency Improvement
during 802.11 Handoff", IEEE 802.11 Working Group,
IEEE-02-758r1-F Draft 802.11I/D5.0, November 2002.

[IEEE-03-084]
Mishra, A., Shin, M., Arbaugh, W., Lee, I. and K. Jang,
"Proactive Key Distribution to support fast and secure
roaming", IEEE 802.11 Working Group, IEEE-03-084r1-I,
http://www.ieee802.org/11/Documents/DocumentHolder/
3-084.zip, January 2003.

[IEEE-03-155]
Aboba, B., "Fast Handoff Issues", IEEE 802.11 Working Group,
IEEE-03-155r0-I, http://www.ieee802.org/11/
Documents/DocumentHolder/3-155.zip, March 2003.

[I-D.ietf-roamops-cert]
Aboba, B., "Certificate-Based Roaming", draft-ietf-roamops-
cert-02 (work in progress), April 1999.

[I-D.puthenkulam-eap-binding]
Puthenkulam, J., "The Compound Authentication Binding
Problem", draft-puthenkulam-eap-binding-04 (work in
progress), October 2003.

[I-D.arkko-pppext-eap-aka]
Arkko, J. and H. Haverinen, "EAP AKA Authentication", draft-
arkko-pppext-eap-aka-15.txt (work in progress), December 2004.

[I-D.arkko-eap-service-identity-auth]
Arkko, J. and P. Eronen, "Authenticated Service Information
for the Extensible Authentication Protocol (EAP)", draft-
arkko-eap-service-identity-auth-02.txt (work in progress),
May 2005.

Aboba, et al. Standards Track [Page 49]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

[I-D.ohba-eap-aaakey-binding]
Ohba, Y., "AAA-Key Derivation with Channel Binding", draft-
ohba-eap-aaakey-binding-00.txt (work in progress), May
2005.

[MD5Attack]
Dobbertin, H., "The Status of

[I-D.irtf-aaaarch-handoff]
Arbaugh, W. and B. Aboba, "Handoff Extension to RADIUS",
draft-irtf-aaaarch-handoff-04.txt (work in progress),
October 2003.

[MD5Collision]
Klima, V., "Tunnels in Hash Functions: MD5 After Collisions
Within a Recent Attack",
CryptoBytes, Vol.2 No.2, 1996.

[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981. Minute", Cryptology ePrint Archive, March 2006,
http://eprint.iacr.org/2006/105.pdf

Aboba, et al. Standards Track [Page 47]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

[RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
RFC 1661, July 1994.

[RFC1968] Meyer, G. and K. Fox, "The PPP Encryption Control Protocol
(ECP)", RFC 1968, June 1996.

[RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997.

[RFC2246] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A.
and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246,
January 1999.

[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.

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

[RFC2419] Sklower, K. and G. Meyer, "The PPP DES Encryption Protocol,
Version 2 (DESE-bis)", RFC 2419, September 1998.

[RFC2420] Kummert, H., and D. Carrel, "The PPP Triple-DES Encryption Protocol (3DESE)", Internet Key Exchange
(IKE)", RFC 2420, September 2409, November 1998.

[RFC2516] Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.
and R. Wheeler, "A Method for Transmitting PPP Over
Ethernet (PPPoE)", RFC 2516, February 1999.

[RFC2535] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.

[RFC2548] Zorn, G., "Microsoft Vendor-specific RADIUS Attributes",
RFC 2548, March 1999.

[RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
Implementation in Roaming", RFC 2607, June 1999.

Aboba, et al. Standards Track [Page 50]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

[RFC2716] Aboba, B. and D. Simon, "PPP EAP TLS Authentication
Protocol", RFC 2716, October 1999.

[RFC2782] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.

[RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D. and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, May 2000.

[RFC2865] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865,
June 2000.

[RFC2931] Eastlake, D., "DNS Request and Transaction Signatures
(SIG(0)s )", RFC 2931, September 2000.

[RFC3007] Wellington, B., "Simple Secure Domain Name System (DNS)
Dynamic Update", RFC 3007, November 2000.

[RFC3078] Pall, G.

[RFC3547] Baugher, M., Weis, B., Hardjono, T. and G. Zorn, "Microsoft Point-To-Point Encryption
(MPPE) Protocol", RFC 3078, March 2001.

[RFC3079] Zorn, G., "Deriving Keys for use with Microsoft Point-to-Point
Encryption (MPPE)", H. Harney, "The
Group Domain of Interpretation", RFC 3079, March 2001. 3547, July 2003.

[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible Authentication

Aboba, et al. Standards Track [Page 48]

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Protocol (EAP)", RFC 3579, September 2003.

[RFC3580] Congdon, P., Aboba, B., Smith, A., Zorn, G. and J. Roese,
"IEEE 802.1X Remote Authentication Dial In User Service
(RADIUS) Usage Guidelines", RFC 3580, September 2003.

[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For Public
Keys Used For Exchanging Symmetric Keys", RFC 3766, April
2004.

[RFC4005] Calhoun, P., Zorn, G., Spence, D.

[RFC3830] Arkko, J., Carrara, E., Lindholm, F., Naslund, M. and D. Mitton, "Diameter
Network Access Server Application", K.
Norrman, "MIKEY: Multimedia Internet KEYing", RFC 4005, 3830,
August 2005. 2004.

[RFC4017] Stanley, D., Walker, J. and B. Aboba, "EAP Method
Requirements for Wireless LANs", RFC 4017, March 2005.

Aboba, et al. Standards Track [Page 51]

INTERNET-DRAFT EAP Key Management Framework 5 March 2006

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

[RFC4067] Loughney, J., Nakhjiri, M., Perkins, C. and R. Koodli,
"Context Transfer Protocol (CXTP)", RFC 4067, July 2005.

[RFC4072] Eronen, P., Hiller, T. and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.

[RFC4118] Yang, L., Zerfos, P. and E. Sadot, "Architecture Taxonomy
for Control and Provisioning of Wireless Access Points
(CAPWAP)", RFC 4118, June 2005.

[RFC4186] Haverinen, H. and J. Salowey, "Extensible Authentication
Protocol Method for Global System for Mobile Communications
(GSM) Subscriber Identity Modules (EAP-SIM)", RFC 4186,
January 2006.

[RFC4187] Arkko, J. and H. Haverinen, "Extensible Authentication
Protocol Method for 3rd Generation Authentication and Key
Agreement (EAP-AKA)", RFC 4187, January 2006.

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

Aboba, et al. Standards Track [Page 49]

INTERNET-DRAFT EAP Key Management Framework 3 April 2006

[8021XHandoff]
Pack, S. and Y. Choi, "Pre-Authenticated Fast Handoff in a
Public Wireless LAN Based on IEEE 802.1X Model", School of
Computer Science and Engineering, Seoul National
University, Seoul, Korea, 2002.

Acknowledgments

Thanks to Arun Ayyagari, Ashwin Palekar, and Tim Moore of Microsoft,
Dorothy Stanley of Agere, Bob Moskowitz of TruSecure, Jesse Walker of
Intel, Joe Salowey of Cisco and Russ Housley of Vigil Security for
useful feedback.

Aboba, et al. Standards Track [Page 52]

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Author

Authors' Addresses

Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

EMail: bernarda@microsoft.com
Phone: +1 425 706 6605
Fax: +1 425 936 7329

Dan Simon
Microsoft Research
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

EMail: dansimon@microsoft.com
Phone: +1 425 706 6711
Fax: +1 425 936 7329

Jari Arkko
Ericsson
Jorvas 02420
Finland

Phone:
EMail: jari.arkko@ericsson.com

Pasi Eronen
Nokia Research Center
P.O. Box 407
FIN-00045 Nokia Group
Finland

Aboba, et al. Standards Track [Page 50]

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EMail: pasi.eronen@nokia.com

Henrik Levkowetz (editor)
ipUnplugged AB
Arenavagen 27
Stockholm S-121 28
SWEDEN

Phone: +46 708 32 16 08
EMail: henrik@levkowetz.com

Aboba, et al. Standards Track [Page 53] 51]

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Appendix A - Exported Parameters in Existing Methods

This Appendix specifies Method-ID, Peer-ID, Server-ID and Key-
Lifetime for EAP methods that have been published prior to this
specification. Future EAP method specifications MUST include a
definition of the Method-ID, Peer-ID, and Server-ID (could be the
empty string) and MAY also define the Key-Lifetime (assumed to be
indeterminate if not described).

EAP-Identity

The EAP-Identity method is defined in [RC3748]. It does not
derive keys, and therefore does not define the Key-Lifetime or
Method-ID. The Peer-ID exported by the Identity method is
determined by the octets included within the EAP-
Response/Identity. The Server-ID is the empty string (zero
length).

EAP-Notification

The EAP-Notification method is defined in [RFC3748]. It does not
derive keys and therefore does not define the Key-Lifetime and
Method-ID. The Peer-ID and Server-ID are the empty string (zero
length).

EAP-GTC

The EAP-GTC method is defined in [RFC3748]. It does not derive
keys and therefore does not define the Key-Lifetime and Method-ID.
The Peer-ID and Server-ID are the empty string.

EAP-OTP

The EAP-OTP method is defined in [RFC3748]. It does not derive
keys and therefore does not define the Key-Lifetime and Method-ID.
The Peer-ID and Server-ID are the empty string.

EAP-TLS

EAP-TLS is defined in [RFC2716]. The EAP-TLS Method-Id is the
concatenation of the peer and server nonces. The Peer-ID and
Server-ID are the contents of the altSubjectName in the peer and
server certificates. EAP-TLS does not negotiate a Key-Lifetime.

EAP-AKA

EAP-AKA is defined in [RFC4187]. The EAP-AKA Method-Id is the
contents of the RAND field from the AT_RAND attribute, followed by

Aboba, et al. Standards Track [Page 54] 52]

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AT_RAND attribute, followed by

the contents of the AUTN field in the AT_AUTN attribute.

The Peer-ID is the contents of the Identity field from the
AT_IDENTITY attribute, using only the Actual Identity Length
octets from the beginning, however. Note that the contents are
used as they are transmitted, regardless of whether the
transmitted identity was a permanent, pseudonym, or fast re-
authentication identity. The Server-ID is an empty string. EAP-
AKA does not negotiate a key lifetime.

EAP-SIM

EAP-SIM is defined in [RFC4186]. The EAP-SIM Method-Id is the
contents of the RAND field from the AT_RAND attribute, followed by
the contents of the NONCE_MT field in the AT_NONCE_MT attribute.

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on the procedures with respect to rights in RFC documents can be
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Copies of IPR disclosures made to the IETF Secretariat and any
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The IETF invites any interested party to bring to its attention any
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this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.

Aboba, et al. Standards Track [Page 55] 53]

INTERNET-DRAFT EAP Key Management Framework 5 March 3 April 2006

Disclaimer of Validity

This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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Copyright (C) The Internet Society (2006). This document is subject
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Acknowledgment

Funding for the RFC Editor function is currently provided by the
Internet Society.

Open Issues

Open issues relating to this specification are tracked on the
following web site:

http://www.drizzle.com/~aboba/EAP/eapissues.html

Aboba, et al. Standards Track [Page 56] 54]

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