Dos and authentication in wireless public access networks
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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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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

Contents

  • Introduction

  • IEEE 802.11 and 802.1X

  • Proposed Access Control Architecture

  • Conclusions

DoS and Authentication in Wireless Public Access Networks


Introduction

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


Introduction1

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


Ieee 802 11 and 802 1x

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


Ieee 802 11 and 802 1x1

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


Ieee 802 11 and 802 1x2

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


Proposed access control system

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


Proposed access control system1

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


Proposed access control system2

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


Proposed access control system3

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


Proposed access control system4

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


Proposed access control system5

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


Conclusion

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


Dos and authentication in wireless public access networks

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DoS and Authentication in Wireless Public Access Networks


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