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DoS and Authentication in Wireless Public Access Networks

DoS and Authentication in Wireless Public Access Networks. Daniel B. Faria, David R.Cheriton ACM WiSe’02 Youngjoo, Shin 2006.11.28. Contents. Introduction IEEE 802.11 and 802.1X Proposed Access Control Architecture Conclusions. Introduction. Context. 2000.

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DoS and Authentication in Wireless Public Access Networks

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  1. DoS and Authentication in Wireless Public Access Networks Daniel B. Faria, David R.Cheriton ACM WiSe’02 Youngjoo, Shin 2006.11.28

  2. Contents • Introduction • IEEE 802.11 and 802.1X • Proposed Access Control Architecture • Conclusions DoS and Authentication in Wireless Public Access Networks

  3. Introduction • Context 2000 Your 802.11 Wireless Network has No Clothes (Walker) 2001 Intercepting Mobile Communications : The Insecurity of 802.11 (Borisov et al.,) 2002 DoS and Authenticaion in Wireless Public Access Networks (Daniel B. Faria) 2004 IEEE 802.11i was ratified DoS and Authentication in Wireless Public Access Networks

  4. Introduction • Two objectives • Show that current 802.11/802.1X access control is vulnerable to DoS attacks due to the lack of essential security services and wrong assumptions about the environment • Propose an access control architecture that supports security and mobility • SIAP (Secure Internet Access Protocol) • SLAP (Secure Link Access Protocol) DoS and Authentication in Wireless Public Access Networks

  5. IEEE 802.11 and 802.1X • Wrong assumptions • IEEE 802.11 – “An access point is trusted” • IEEE 802.1X – “Secure association is provided” • Combining 802.11 and 802.1X AP AP is not authenticated 802.11 Association 802.1X Authentication Association is not secured Mobile Station IEEE 802.11/802.1X network DoS and Authentication in Wireless Public Access Networks

  6. IEEE 802.11 and 802.1X • Possible DoS attacks • Large number of associate requests attack • 802.1X authentication takes place after the association phase • An access point has to maintain state information after association and before 802.1X completes • Disassociation attack • Disassociation message contains no authentication element • Cause a supplicant (STA) to get logged off from an authenticated session DoS and Authentication in Wireless Public Access Networks

  7. IEEE 802.11 and 802.1X • Secure association must be provided • 802.11/802.1X • Associate-then-Authenticate order • We need to change the order to Authenticate-then-Associate order • Association message can be authenticated • New access control architecture is needed • To provide mutual authentication • To provide secure association • Without losing mobility DoS and Authentication in Wireless Public Access Networks

  8. Proposed Access Control System • A Two-protocol Architecture • SIAP (Secure Internet Access Protocol) • An authentication protocol running at the application layer • Mutually authenticate and generate fresh session keys • SLAP (Secure Link Access Protocol) • Lower-layer protocol • Receives the session keys from the authentication protocol • Provide confidentiality, integrity, and message authentication over packets SIAP SIAP UDP/TCP UDP/TCP Internet IP IP SLAP SLAP Link Layer Link Layer Station AP DoS and Authentication in Wireless Public Access Networks

  9. Proposed Access Control System • SIAP • Public key-based mutual authentication (1024-bit RSA keys) • Every client and AP has a public key signed by Certification Authority • SIAP handshake • Authenticate client and AP • Generate session key SIAP handshake DoS and Authentication in Wireless Public Access Networks

  10. Proposed Access Control System • SIAP handshake • SIAP_SERVER_ID_REQUEST • SIAP_SERVER_ID_RESPONSE • SIAP_NEW_HOST_REQUEST • SIAP_NEW_HOST_RESPONSE • SIAP_TICKET DoS and Authentication in Wireless Public Access Networks

  11. Proposed Access Control System • SLAP • After authentication, the generated session keys are passed from SIAP to SLAP • Encryption • AES-CTR mode (128 bits) • Counter = MAC address (48 bits) + Message Counter (64 bits) + Block Counter (16 bits) • Message authentication • HMAC-MD5 802.* SLAP IP Payload encryption Authentication (MAC) DoS and Authentication in Wireless Public Access Networks

  12. Proposed Access Control System • Illustration K K APa APb Authentication (T) Authentication (SIAP handshake) Secured Association Secured Association K, T DoS and Authentication in Wireless Public Access Networks

  13. Proposed Access Control System • Preliminary Results • Test bed • Client – 333 MHz Intel Pentium 2, 64 Mb RAM • AP – 900 MHz AMD Duron, 256 Mb RAM • SLAP overhead • Client : 50μs~330μs AP : 10μs~170μs • Total overhead : 460μs in one direction, RTT increases by 1ms • SIAP handshake overhead • Takes hundreds of milliseconds • Due to the private key operations DoS and Authentication in Wireless Public Access Networks

  14. Conclusion • Summary • Current 802.11/802.1X access control is vulnerable to DoS attacks due to the lack of essential security services and wrong assumptions about the environment • Propose a two layered access control architecture that supports security and mobility DoS and Authentication in Wireless Public Access Networks

  15. Question? DoS and Authentication in Wireless Public Access Networks

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