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Versions: 00 01 02 03 04 05 06 07 RFC 4016

   PANA Working Group
   Internet Draft                                      M. Parthasarathy
   Category: Informational                               Tahoe Networks
   Document: draft-ietf-pana-threats-eval-04.txt               May 2003
   Expires: November 2003



              PANA Threat Analysis and Security Requirements



Status of this Memo

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

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 except that the right to
   produce derivative works is not granted.

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

   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at
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Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.


Abstract

   The PANA (Protocol for carrying authentication for Network Access)
   working group is developing methods for authenticating clients to the
   access network using IP based protocols. This document discusses the
   threats to such protocols. The security requirements arising out of
   these threats will be used as additional input to the PANA WG for
   designing the IP based network access authentication protocol.




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Table of Contents

   1.0 Introduction..................................................2
   2.0 Keywords......................................................2
   3.0 Terminology and Definitions...................................3
   4.0 Usage Scenarios...............................................4
   5.0 Trust Relationships...........................................4
   6.0 Threat Scenarios..............................................5
      6.1 PAA Discovery..............................................6
      6.2 Authentication.............................................7
      6.3 PaC leaving the network...................................10
      6.4 Service theft.............................................11
      6.5 PAA-EP communication......................................11
      6.6 Miscellaneous attacks.....................................12
   7.0 Summary of Requirements......................................13
   8.0 Security Considerations......................................14
   9.0 Normative References.........................................14
   10.0 Informative References......................................14
   11.0 Acknowledgments.............................................15
   12.0 Revision Log................................................15
   13.0 Author's Address............................................16
   14.0 Full Copyright Statement....................................16

1.0 Introduction

   The PANA (Protocol for carrying authentication for Network Access)
   working group is developing methods for authenticating clients to the
   access network using IP based protocols. This document discusses the
   threats to such IP based protocols.

   A client wishing to get access to the network must carry on multiple
   steps. First, it needs to discover the IP address of the PANA
   authentication agent (PAA) and then execute an authentication
   protocol to authenticate itself to the network. Once the client is
   authenticated, there might be other messages exchanged during the
   lifetime of the network access. This document discusses the threats
   in these steps without discussing any solutions. The requirements
   arising out of these threats will be used as input to the PANA
   working group.

2.0 Keywords

   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 [KEYWORDS].





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3.0 Terminology and Definitions

   Client Access Device

      A network element (e.g., notebook computer, PDA, etc.) that
      requires access to a provider's network.

   Network Access Server (NAS)

      Network device that provides access to the network.

   PANA Client (PaC)

      An entity in the edge subnet, who is wishing to obtain network
      access from a PANA authentication agent within a network. A PANA
      client is associated with a device and a set of credentials to
      prove its identity within the scope of PANA.

   PANA Authentication Agent (PAA)

      An entity whose responsibility is to authenticate the PANA client
      and grant network access service to the client's device.

   Authentication Server (AS)

      An entity that authenticates the PANA client. It may be co-located
      with PANA authentication agent or part of the back-end
      infrastructure.

   Device Identifier (DI)

      The identifier used by the network as a handle to control and
      police the network access of a client. Depending on the access
      technology, identifier might contain any of IP address, link-layer
      address, switch port number, etc. of a device. PANA authentication
      agent keeps a table for binding device identifiers to the PANA
      clients. At most one PANA client should be associated with a DI on
      a PANA authentication agent.

   Enforcement Point (EP)

      A node that is capable of filtering packets sent by the PANA
      client using the DI information authorized by PANA authentication
      agent.

   Compound methods





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      Authentication protocol where, sequence of methods are used one
      after an other or where methods are tunneled inside an another
      independently established tunnel between the client and server
      [TUN-EAP].

4.0 Usage Scenarios

   PANA is intended to be used in an environment where there is no a
   priori trust relationship or security association between the PaC and
   other nodes like PAA and EP. In these environments, one may observe
   the following.

       o The link between PaC and PAA may be a shared medium
          (e.g., Ethernet) or may not be a shared medium (e.g., DSL
          network).

       o All the PaCs may be authenticated to the access network at
          layer 2 (e.g., 3GPP2 CDMA network) and share a security
          association with layer 2 authentication agent (e.g., 802.11
          [IEEE-802.11] Access point), but still do not trust each
          other.

   The scenarios mentioned above affect the threat model of PANA. This
   document discusses the various threats in the context of the above
   network access scenarios for a better understanding of the threats.
   In the following discussion, any reference to link that is not shared
   (or non-shared) is assumed to be physically secure. If such an
   assumption cannot be made about the link, then it becomes the same as
   the link that is being shared by more than one node.

5.0 Trust Relationships

   PANA authentication involves a client (PaC), PANA agent (PAA),
   Authentication server (AS) and an Enforcement point (EP).

   The entities that have a priori trust relationships before PANA
   begins are as follows.

     1) PAA and AS: PaC belonging to the same administrative domain as
        the AS, often needs to use resources provided by PAA that
        belongs to another administrative domain. PAA authenticates the
        PaC before providing local network access. The credentials
        provided by PaC for authentication may or may not be understood
        by PAA. If PAA does not understand the credentials, it needs to
        communicate with the AS in a different domain to verify the
        credentials. The threats in the communication path between PAA
        and AS are already covered in [RAD-EAP]. To counter these
        threats, the communication between PAA and AS are secured using
        a static or dynamic security association.


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     2) PAA and EP: PAA and EP belong to the same administrative domain.
        Hence, the network operator can setup a security association to
        protect the traffic exchanged between them. This document
        discusses the threats in this path.

     3) PaC and AS: PaC and AS belong to the same administrative domain
        and share a trust relationship. When PaC uses a different domain
        than its home for network access, it provides its credentials to
        the PAA in the visited network for authentication. The
        information provided by PaC traverses the PaC-PAA path and
        PAA-AS path. The threats in PAA-AS path are already discussed in
        [RAD-EAP]. This document discusses the threats in PaC-PAA path.

   It is possible that some of the entities like PAA, AS and EP are
   co-located. In those cases, it can be safely assumed that there are
   no significant external threats.

   The entities that do not have any trust relationship before PANA
   begins are as follows.

     1) PaC and PAA: PaC and PAA normally belong to two different
        administrative domains. They do not necessarily share a trust
        relationship initially. They establish a security association in
        the process of authentication. All messages exchanged between
        PaC and PAA are subject to various threats, which are discussed
        in this document.

     2) PaC and EP: EP belongs to the same administrative domain as PAA
        and hence PaC and EP do not necessarily share a trust
        relationship initially. When PaC is successfully authenticated,
        it may result in key establishment between PaC and PAA, which
        can be further used to secure the link between PaC and EP. For
        example, EAP keying framework [EAP-KEY], defines a three party
        EAP exchange where the clients derive the transient sessions
        keys to secure the link between the peer and NAS in their final
        step. Similarly, PANA will provide the ability to establish keys
        between PaC and EP that can be used to secure the link further.
        This is further discussed in section 6.4 below.

6.0 Threat Scenarios

   The PANA authentication client (PaC) needs to discover the PAA first.
   This involves either sending solicitations or waiting for
   advertisements. Once it has discovered the PAA, it will lead to
   authentication exchange with PAA. Once the access is granted, PaC
   will most likely exchange data with other nodes in the Internet. All
   of these are vulnerable to denial of service (DoS), man-in-the-middle
   (MITM) and service theft attacks.


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   The threats are grouped by the various stages the client goes through
   to gain access to the network. Section 6.1 discusses the threats
   related to PAA discovery. Section 6.2 discusses the threats related
   to authentication itself. Section 6.3 discusses the threats involved
   while leaving the network. Section 6.4 discusses service theft.
   Section 6.5 discusses the threats in PAA-EP path. Section 6.6
   discusses the miscellaneous threats.

   Some of the threats discussed in the following sections may be
   specific to shared links. The threat may be absent on non-shared
   links. Hence, it is only required to prevent the threat on shared
   links. Instead of specifying a separate set of requirements for
   shared links and non-shared links, this document just specifies one
   set of requirements with the following wording: "PANA MUST be able to
   prevent threat X". This means that the PANA protocol should be
   capable of preventing threat X. The feature that prevents threat X
   may or may not be used depending on the deployment.

6.1 PAA Discovery

   PaC is in the process of discovering the PAA. The PAA is discovered
   by sending solicitations or receiving advertisements. Following are
   the possible threats.

   T6.1.1: A malicious node can pretend to be a PAA by sending a spoofed
   advertisement.

   In existing dial-up networks, the clients authenticate to the network
   but generally do not verify the authenticity of the messages coming
   from Network Access Server (NAS). This mostly works because the link
   between the device and the NAS is not shared with other nodes
   (assuming that nobody tampers with the physical link), and clients
   trust the NAS and the phone network to provide the service. Spoofing
   attacks are not present in this environment because the PaC may
   assume that the other end of the link is the PAA.

   In environments where the link is shared, this threat is present as
   any node can pretend to be a PAA. Even if the nodes are authenticated
   at layer 2, this threat is present. It is difficult to protect the
   discovery process, as there is no a priori trust relationship between
   PAA and PaC. It might be possible for the EP to filter out the
   packets coming from PaC that resembles PAA packets and hence this
   threat can be prevented in such environments.

   The advertisement may be used to include other information like
   supported authentication methods etc., besides the discovery of the
   PAA itself. This can lead to a bidding down attack, as a malicious
   node can send a spoofed advertisement with capabilities that indicate


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   less secure authentication methods than what the real PAA supports,
   thereby fooling the PaC into negotiating a less secure authentication
   method than what would otherwise be available. This is best avoided
   by limiting the amount of security-critical information sent during
   the PAA discovery process.

   Requirement 1

   PANA MUST not assume that the discovery process is protected. Since,
   it is difficult to protect the discovery process, the security-
   critical information exchanged during the discovery process SHOULD be
   limited.

6.2 Authentication

   This section discusses the threats specific to the authentication
   protocol. Section 6.2.1 discusses the possible threat associated with
   success/failure indications that are transmitted to PaC at the end of
   the authentication. Section 6.2.2 discusses the man-in-the-middle
   attack when compound methods are used. Section 6.2.3 discusses the
   replay attack and section 6.2.4 discusses about the device identifier
   attack.

6.2.1 Success or Failure Indications

   Some authentication protocols e.g., EAP, has a special message to
   indicate success or failure. An attacker can send false
   authentication success or failure message to the PaC. By sending
   false failure message, the attacker can prevent the client from
   accessing the network. By sending false success message, the attacker
   can prematurely end the authentication exchange effectively denying
   service for the PaC.

   If the link is not shared, then this threat is absent as ingress
   filtering can prevent the attacker from impersonating as the PAA.

   If the link is shared, it is easy to spoof these packets. If layer 2
   provides per-packet encryption with pair-wise keys, it might make it
   hard for the attacker to guess the success or failure packet that the
   client would accept. Even if the node is already authenticated at
   layer 2, it can still pretend to be a PAA and spoof the success or
   failure.

   This attack is possible if the success or failure indication is not
   protected using a security association between PaC and PAA. In order
   to avoid this attack, PaC and PAA should mutually authenticate each
   other. In the process of mutually authenticating each other, they
   should be able to establish keys to protect the success or failure
   indications. It may not be possible to protect the success or failure


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   indication always as the keys may not be established prior to
   transmitting the success or failure packet. If the client is re-
   authenticating to the network, it can use the previously established
   security association to protect the success or failure indications.
   Similarly, all PANA messages that are exchanged during the
   authentication prior to key establishment may not be protected.

   Requirement 2

   PANA MUST be able to mutually authenticate PaC and PAA. PANA MUST be
   able to establish keys between PaC and PAA to protect the PANA
   messages.

6.2.2 MITM attack

   A malicious node can claim to be PAA to the real PaC and claim to be
   PaC to the real PAA. This is a man in the middle (MITM) attack where
   the PaC is fooled to think that it is communicating with real PAA and
   the real PAA is fooled to think that it is communicating with real
   PaC.

   If the link is not shared, this threat is absent as ingress filtering
   can prevent the attacker from acting as man in the middle.

   If the link is shared, this threat is present. Even if the layer 2
   provides per-packet protection, the attacker can act as man in the
   middle and launch this attack. An instance of MITM attack, when
   compound authentication methods are used is described in [TUN-EAP].
   In these attacks, the server first authenticates to the client. As
   the client has not proven its identity yet, the server acts as the
   man-in-the-middle, tunneling the identity of the legitimate client to
   gain access to the network. The attack is possible because there is
   no verification that the same entities participated among the
   compound methods. It is not possible to do such verification if
   compound methods are used without being able to create cryptographic
   binding among them. This implies that PANA will be vulnerable to such
   attacks if compound methods are used without being able to
   cryptographically bind them. Note that the attack does not exist if
   the keys derived during the tunnel establishment are not used for
   authenticating the client e.g., tunnel keys are used for just
   protecting the identity of the client.

   Requirement 3

   When compound authentication methods are used in PANA, the methods
   MUST be cryptographically bound.


6.2.3 Replay Attack


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   A malicious node can replay the messages that caused authentication
   failure or success at a later time to create false failures or
   success. The attacker can also potentially replay other messages of
   the PANA protocol to deny service to the PaC.

   If the link is not shared, this threat is absent as ingress filtering
   can prevent the attacker from impersonating as PAA and replay the
   packets.

   If the link is shared, this threat is present. If the packets are
   encrypted at layer 2 using pair-wise keys, it will make it hard for
   the attacker to learn the unencrypted (i.e., original) packet that
   needs to be replayed. Even if layer 2 provides replay protection, the
   attacker can still replay the PANA messages (layer 3) for denying
   service to the client.

   Requirement 4

   PANA MUST be able to protect itself against replay attacks.

6.2.4 Device Identifier Attack

   When the client is successfully authenticated, PAA sends access
   control information to EP for granting access to the network. The
   access control information typically contains the device identifier
   of the PaC, which is obtained from the IP headers and MAC headers of
   the packets exchanged during the authentication process. The attacker
   can gain unauthorized access into the network using the following
   steps.

     . An attacker pretends to be a PAA and sends advertisements. PaC
        gets fooled and starts exchanging packets with the attacker.
     . The attacker modifies the IP source address on the packet,
        adjusts the UDP/TCP checksum and forwards the packet to the real
        PAA. It does the same on return packets also.
     . When the real PaC is successfully authenticated, the attacker
        gains access to the network as the packets contained the IP
        address (and potentially the MAC address also) of the attacker.

   If the link is not shared, this threat is absent, as the attacker
   cannot impersonate as PAA and intercept the packets from PaC.

   If the link is shared, this threat is present. If the layer 2
   provides per-packet protection, it is not possible to change the MAC
   address and hence this threat may be absent in such cases if EP
   filters both on IP and MAC address.

   Requirement 5


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   PANA MUST be able to protect the device identifier against spoofing
   when it is exchanged between the PaC and PAA.


6.3 PaC leaving the network

   When the PaC leaves the network, it can inform the PAA before
   disconnecting from the network so that the resources used by PaC can
   be accounted properly. PAA may also choose to revoke the access any
   time if it deems necessary. Following are the possible threats.

   T6.3.1: A malicious node can pretend to be a PAA and revoke the
   access to PaC.

   T6.3.2: A malicious node can pretend to be a real PaC and transmit a
   disconnect message.

   T6.3.3: PaC can leave the network without notifying the PAA or EP
   e.g., the Ethernet cable is unplugged, system crash. An attacker can
   pretend to be the PaC and start using the network.

   If the link is not shared, threats T6.3.1 and T6.3.2 are absent.
   Threat T6.3.3 may still be present. If there is no layer 2 indication
   or the layer 2 indication cannot be relied up on, then the threat
   T6.3.3 is still present on non-shared links.

   If the link is shared, all of the above threats are present as any
   node on the link can spoof the disconnect message. Even if the layer
   2 has per-packet authentication, the attacker can pretend to be a PaC
   e.g. by spoofing the IP address, and disconnect from the network.
   Similarly, any node can pretend to be a PAA and revoke the access to
   the PaC. Hence, T6.3.1 and T6.3.2 are possible even on links where
   layer 2 is secured. Threat T6.3.3 can be prevented if layer 2
   provides per-packet authentication. The attacker cannot subsume the
   PaC that left the network without knowing the keys that protect the
   packet at layer 2.

   In some link layers, e.g., 802.11 [IEEE-802.11], disassociate and
   de-authenticate messages are not protected (even with [IEEE-
   802.11i]). In such link layers, protecting PANA messages may not be
   very useful as the attacker can attack using the link layer
   mechanisms rather than PANA.

   Requirement 6

   PANA MUST be able to protect disconnect and revocation messages. PANA
   MUST NOT depend on PaC sending a disconnect message.



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6.4 Service theft

   An attacker can gain unauthorized access into the network by stealing
   the service from another client. Once the PaC is successfully
   authenticated, EP will have filters in place to prevent unauthorized
   access into the network. The filters will be based on something that
   will be carried on every packet. For example, the filter could be
   based on IP and MAC address where the packets will be dropped unless
   the packets coming with certain IP address match the MAC address
   also. Following are the possible threats.

   T6.4.1: Attacker can spoof both the IP and MAC address of an
   authorized client to gain unauthorized access. Attacker can launch
   this attack easily by just sniffing the wire for IP and MAC address.
   This lets the attacker use the network without any authorization,
   getting a free service.

   If the link is not shared, this threat is absent as ingress filtering
   can prevent one node from impersonating as another node.

   If the link is shared, this threat is present. If layer 2 provides
   per-packet protection using pair-wise keys, it can prevent the
   attacker from gaining unauthorized access.

   PANA MUST be able to prevent service theft. In some cases e.g. non-
   shared links, it is sufficient to provide access control information
   like IP address, MAC address, etc., to EP, which in turn can prevent
   unauthorized users from gaining access to the network by policing the
   packets for matching addresses. In the case of shared links, this
   information is not sufficient to prevent service theft. PANA MUST be
   able to bootstrap a shared secret between the PaC and PAA which can
   be further used to setup a security association (e.g., IPsec) between
   PaC and EP to prevent service theft on shared links.

   Requirement 7

   PANA MUST securely bind the authenticated session to the device
   identifier of the client, to prevent service theft. PANA MUST be able
   to bootstrap a shared secret between the PaC and PAA which can be
   further used to setup a security association between PaC and EP to
   provide cryptographic protection against service theft on shared
   links.

6.5 PAA-EP communication

   After a successful authentication, PAA needs to communicate the
   access control information of the PaC to EP so that PaC will be
   allowed to access the network. The information communicated would


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   contain at least the device identifier of the PaC. If strong security
   is needed, PAA will communicate a shared secret known only to PaC and
   PAA, for setting up a security association between PaC and EP.
   Following are the possible threats.

   T6.5.1: Attacker can eavesdrop to learn the information communicated
   between PAA and EP. The attacker can further use this information to
   spoof the real PaC and also setup an security association for gaining
   access to the network. This threat is absent, if the attacker cannot
   eavesdrop the link e.g., PAA and EP are communicating on a separate
   link from that of visiting PaCs.

   T6.5.2: Attacker can pretend to be PAA and send false information to
   EP for gaining access to the network. The attacker has to send its
   own device identifier and also a shared secret in the case of
   stronger security so that EP will let the attacker access the
   network.

   If the communication between PAA and EP is protected, these threats
   are absent.

   Requirement 8

   The communication between PAA and EP MUST be protected against
   eavesdropping and spoofing attacks.

6.6 Miscellaneous attacks

   T6.5.1: There are various forms of DoS attacks that can be launched
   on the PAA or AS. A few are mentioned below. As it is hard to defend
   against some of the DoS attacks, the protocol should be designed
   carefully to mitigate or prevent such attacks.

     . Attacker can bombard the PAA with lots of authentication
        requests. If PAA and AS are not collocated, PAA may have to
        allocate resources to store some state about PaC locally before
        it receives the response from the backend AS. This can deplete
        memory resources on PAA.
     . The attacker can force the PAA or AS to make computationally
        intensive operations with minimal effort, that can deplete the
        CPU resources of the PAA or AS.

   T6.5.2: PaC acquires IP address before PANA authentication begins
   using methods like e.g., DHCP in IPv4 and auto-configuration in IPv6
   [PANAREQ]. If IP addresses are assigned before authentication, it
   opens up the possibility of DoS attack where malicious nodes can
   deplete the IP addresses by assigning multiple IP addresses. If
   stateless auto-configuration [ADDRCONF] is used, the attacker can
   respond to duplicate address detection probes sent by any node on the


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   network effectively not allowing the node to configure a link local
   address. If stateful mechanism is used in IPv6 e.g., DHCPv6, then
   this attack is still possible. Address depletion attack is not
   specific to PANA, but a known attack in DHCP [DHCP-AUTH]. If PANA
   assumes that the client has an IP address already, it opens up the
   network to the DoS attack.

   Requirement 9

   PANA SHOULD not assume that the PaC has acquired an IP address before
   PANA begins.


7.0 Summary of Requirements

        1. PANA MUST not assume that the discovery process is protected.
          Since, it is difficult to protect the discovery process, the
          security-critical information exchanged during the discovery
          process SHOULD be limited.

        2. PANA MUST be able to mutually authenticate PaC and PAA. PANA
          MUST be able to establish keys between PaC and PAA to protect
          the PANA messages.

        3. When compound authentication methods are used in PANA, the
          methods MUST be cryptographically bound.

        4. PANA MUST be able to protect itself against replay attacks.

        5. PANA MUST be able to protect the device identifier against
          spoofing when it is exchanged between the PaC and PAA.

        6. PANA MUST be able to protect disconnect and revocation
          messages. PANA MUST NOT depend on PaC sending a disconnect
          message.

        7. PANA MUST securely bind the authenticated session to the
          device identifier of the client, to prevent service theft.
          PANA MUST be able to bootstrap a shared secret between the
          PaC and PAA which can be further used to setup a security
          association between PaC and EP to provide cryptographic
          protection against service theft on shared links.

        8. The communication between PAA and EP MUST be protected
          against eavesdropping and spoofing attacks.

        9. PANA SHOULD not assume that the PaC has acquired an IP
          address before PANA begins.



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8.0 Security Considerations

   This document discusses various threats with IP based network access
   protocol.

9.0 Normative References

   [PANAUS] Y. Ohba et. al, "Problem Space and Usage Scenarios for
   PANA", draft-ietf-pana-usage-scenarios-03.txt

   [KEYWORDS] S. Bradner, "Key words for use in RFCS to indicate
   requirement levels", RFC 2119, March 1997.

10.0 Informative References

   [PANAREQ] A. Yegin et al., "Protocol for Carrying Authentication for
   Network Access (PANA) Requirements and Terminology", draft-ietf-pana-
   requirements-04.txt

   [RADIUS] C. Rigney et. al, "Remote Authentication Dial In User
   Service", RFC2865, June 2000.

   [EAP-KEY] B. Aboba et. al, "EAP keying framework", draft- aboba-
   pppext-key-problem-06.txt

   [ADDRCONF] S. Thomson et. al, "IPv6 Stateless Address
   Autoconfiguration", RFC2462, December 1998.

   [DHCP-AUTH] R. Droms, et. al "Authentication for DHCP messages",
   RFC3118, June 2001.

   [RAD-EAP] B. Aboba, et. al, "Radius support for Extensible
   authentication protocol", draft-aboba-radius-rfc2869bis-21.txt

   [TUN-EAP] J. Puthenkulam et. al, "The compound authentication
   binding problem", draft-puthenkulam-eap-binding-02.txt

   [IPSEC] S. Kent et. al, "Security architecture for the Internet
   Protocol", RFC 2401, November 1998.

   [IEEE-802.11i] Institute of Electrical and Electronics Engineers
   "Unapproved Draft Supplement to Standard for Telecommunications and
   Information Exchange Between systems - LAN/MAN Specific Requirements
   - Part 11: Wireless LAN Medium Access Control (MAC) and Physical
   Layer (PHY) Specifications: Specification for Enhanced Security",
   IEEE Draft 802.11i (work in progress), 2003.




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   [IEEE-802.11] Institute of Electrical and Electronics Engineers,
   "Information Technology - Telecommunications and Information Exchange
   between Systems - Local and Metropolitan Area Network - Specific
   Requirements - Part 11: Wireless LAN Medium Access  Control (MAC) and
   Physical Layer (PHY) Specifications", IEEE Standard 802.11, 1999.

11.0 Acknowledgments

   The author would like to thank the following people (in no specific
   order) for providing valuable comments: Alper Yegin, Basavaraj Patil,
   Pekka Nikander, Bernard Aboba, Francis Dupont, Michael Thomas,
   Yoshihiro Ohba, Gabriel Montenegro, Tschofenig Hannes, Bill
   Sommerfeld, N. Asokan, Pete McCan and Derek Atkins.

12.0 Revision Log

   Changes between 03 and 04

   -Added a new requirement for the disconnect notification.
   -Trust relationship section was rewritten.
   -Device identifier attack requirements was rewritten.
   -Service theft requirement was rewritten.
   -Added a new section for PAA-EP threats.

   Changes between revision 02 and 03

  -Changed Requirement 1 to include text about weak authentication
  suites.
  -Rearranged the order of definitions in terminology section.
  -Removed some confusing text with respect to IPsec from the Service
  theft section.

   Changes between revision 01 and 02

  -Renamed the section "Assumptions" to "Trust relationships" and added
  more text to clarify the relationship between PaC and EP.
  -Added more text for threats in PAA – AS path.
  -Merged the "Type of Attacks" section into "Threat Scenarios"
  -Removed the requirement on DoS attack.
  -Reworded most of the requirements.

  Changes between revision 00 and 01

  -Removed unused terms from section 3.0.
  -Removed identity protection as a threat after feedback from Atlanta
  IETF55 meeting.
  -Renamed the section "Attacks on Normal Data communication" to
  "Service theft". Removed confidentiality as a requirement from that
  section.


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  -Added a new threat "Device Identifier attack".

13.0 Author's Address

   Mohan Parthasarathy
   Tahoe Networks
   3052 Orchard Drive
   San Jose, CA 95134

   Phone: 408-944-8220
   Email: mohanp@tahoenetworks.com

14.0 Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
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   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
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   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.


   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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   Acknowledgement

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






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