1. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 1 EAP Method Requirements for Emergency Services 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, 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 stuart@ok-brit.com 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.http:// ieee802.org/guides/bylaws/sb-bylaws.pdf stuart@ok-brit.compatcom@ieee.org Date: 2007-04-20 Authors:

2. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 2 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.

3. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 3 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

4. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 4 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

5. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 5 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

6. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 6 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

7. doc.: IEEE 802.11-07/0508r0 Submission May 2007 Matthew Gast, Trapeze NetworksSlide 7 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