Transcript May 2007 doc.: IEEE 802.11-07/0508r0 EAP Method Requirements for Emergency Services Date: 2007-04-20 Authors: Name Matthew Gast Company Address Phone Trapeze Networks 5753 W.

May 2007
doc.: IEEE 802.11-07/0508r0
EAP Method Requirements for Emergency
Services
Date: 2007-04-20
Authors:
Name
Matthew Gast
Company
Address
Phone
Trapeze
Networks
5753 W. Las Positas +1 925 474
Blvd, Pleasanton,
2273
CA 94588 USA
email
[email protected]
m
Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in
this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE
Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit
others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11.
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement
"IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents
essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is
essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair
[email protected] as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being
developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <[email protected]>.
Submission
Slide 1
Matthew Gast, Trapeze Networks
May 2007
doc.: IEEE 802.11-07/0508r0
Abstract
This presentation discusses requirements for the EAP
method for use with emergency calls over 802.11
networks, and is intended to serve as a basis for asking
the IETF to recommend an EAP method for such a
deployment scenario.
Submission
Slide 2
Matthew Gast, Trapeze Networks
May 2007
doc.: IEEE 802.11-07/0508r0
Types of Emergency Calls in 802.11u
• Unencrypted calls on networks using the Emergency Services Only
(ESO) bit for signaling
– APs advertising the ESO bit will accept any non-AP STA without L2
security
– Network responsible for enforcing access control to only VoIP services
with VLANs, ACLs, etc.
• Encrypted calls using public credentials
– Network is shared with other uses
– Default Emergency Services NAI gives non-AP STAs a user name to send
in 802.1X/EAPOL to get access to emergency services
– Key exchange for L2 data security requires a PMK, which must be
exchanged by either PSK or EAP method
• Regulatory requirements may require use of link encryption,
which forces use of the public credential case
Submission
Slide 3
Matthew Gast, Trapeze Networks
May 2007
doc.: IEEE 802.11-07/0508r0
Why not just use a PSK?
• The PSK must be widely known
– It should be the same for every network in the world, so that a
phone can be used in any network for emergency services
– The only practical way to get this to happen is to put the PSK into
the standard, where everybody can read it
• 802.11 PSKs can have poor DoS resistance
Submission
Slide 4
Matthew Gast, Trapeze Networks
May 2007
doc.: IEEE 802.11-07/0508r0
EAP Issues with Emergency Calls
• Negotiating compatible method may take time
– This is a problem for TGu to solve
• Existing EAP methods were designed for closed
networks
– OK to have pre-configured trust relationships, and important to get
cryptography right
• May depend on reachability of AS
– Should be an optional implementation choice for AP vendor to do
something simple
Submission
Slide 5
Matthew Gast, Trapeze Networks
May 2007
doc.: IEEE 802.11-07/0508r0
Requirement #1: No Pre-configured Trust
Relationship
• Every 802.11 network that uses public credentials for
emergency services needs to identify itself
– Credentials (PSK or certificate) should not be published
– PSK has scaling problems and potential security issues
– Implementations should not require multiple certificate chains to
validate trust because many devices will have small storage (e.g.
phones); single certificate may be challenging
• Anonymous cryptography is acceptable, since the
network will need to manage access rights as part of
allowing session establishment
Submission
Slide 6
Matthew Gast, Trapeze Networks
May 2007
doc.: IEEE 802.11-07/0508r0
Requirement #2: “Small” Number of
Messages
• Emergency calls are a lower security bar
– Users are anonymous at L2 in this scenario – user accounts not
required
– Acceptable to eliminate some crypto features (e.g. perfect forward
secrecy) to reduce message count and handshake time
– Implementation of L2 security within AP should be possible; some
networks may look up access rights via AS
• Each round-trip message adds latency
– Wireless latency is small, AP-to-AS latency can be larger
depending on deployment
Submission
Slide 7
Matthew Gast, Trapeze Networks