Secure Authentication System for Public WLAN Roaming Ana Sanz Merino Yasuhiko Matsunaga Manish Shah Takashi Suzuki Randy Katz

2 Agenda 1. Challenges and our Solution 2. Testbed Description 3. Performance Measurement

3 Loose Trust Relationship in Current Public Wireless LAN Roaming User WLAN Service Provider ID Provider (ISPs, Card Companies) WLAN Service Provider Strong Trust No Trust Weak Trust Each WLAN system is isolated, deploys different authentication schemes

4 Challenges and Our Solutions Confederate service providers under different trust levels and with different authentication schemes to offer wider coverage Inter-system handover with minimal user intervention SSO Roaming with Authentication Adaptation Select proper authentication method and protect privacy of user information per WLAN provider Policy Engine Client Avoid theft of wireless service without assuming pre- shared secret between user and network L2/Web Compound Authentication

5 Authentication Adaptation Flow Authentication Negotiation Protocol  XML-based User Terminal (3)Select authentication method according to user’s preferences WLAN Service Provider (2) Authentication Capabilities Statement: - provider id - authentication methods - charging options - required user information (4) Authentication Query: - selected authn. method - selected charging option - user information (5) Authenticate the user (6) Authentication Statement (1) Authentication Capabilities Query

6 Authentication Capabilities Statement Example vancouver.cs.berkeley.edu_SP …... ID Provider C Prepaid basic A Radius Liberty Radius

7 Authentication Capabilities Statement Example Liberty Prepaid basic A Constant private_contents private_contents Access to private contents through the provider’s web portal

8 Auth Adaptation User Interface

9 Policy Engine Control automatic submission of user authentication information according to communication context Authentication/Authorization flow adaptation WLAN Service ProviderUser Terminal Network Access Client Web Browser Policy Check EAP/ 802.1X Policy Repository Context End User Auth Info. Repository Network Access Server Capability Policy Engine

10 Policy Rule Example … ID Provider C Prepaid basic A… Prepaid basic B… Prepaid premium A… Radius… Liberty… ID Provider B Prepaid basic A… Radius… vancouver.cs.berkeley.edu_SP <provisional_action name=”user_acknowledgement”/> ID Provider C Prepaid basic A Radius TRUE T00:00:00Z

11 Radius Prepaid basic A my_user my_password my_contract_number Authentication Query Example

12 L2/Web Compound Authentication Access Point Client RADIUS/Web Server (1) 802.1x TLS guest authentication External Network (2) Establish L2 Session Key (3) Web Auth (with L2 session key digest) (4)Firewall Control Prevent theft of service, eavesdropping, message alteration Don’t work for L2 DoS attack – out of scope

13 WLAN Secure Roaming Testbed Liberty id provider WinXP Client Identity Provider #2 Radius HTTPS Service Provider #1 RADIUS Web Portal Radius 802.1x RADIUS Service Provider #2 SOAP HTTPS Liberty id provider Identity Provider #1 Liberty Service provider ANP Server Firewall Radius Linux Client ANP Client Policy Engine Roaming Client Radius 802.1x Web Portal Liberty Service provider ANP Server ANP Fire wall Xsuppli cant

14 Layer 2 Roaming User Interface

15 Delay Profile Evaluation (Units: sec) Proxy-based (RADIUS) Redirect-based (Liberty) LocalRoamingLocalRoaming Web Authentication Policy Engine Authn. Capabilities Announcement Link Layer (802.1x) Authentication Total

16 Conclusions 1. Secure public WLAN roaming made possible by accommodating multiple authentication scheme and ID providers with an adaptation framework 2. Policy Engine reflects user authentication scheme preference and protects privacy of user information 3. Compound L2/Web authentication ensures cryptographically-protected access 4. Confirmed with prototype, measured performance shows reasonable delay for practical use 5. Exploits industry-standard authentication architectures: Radius, Liberty alliance