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CSE 5/7349 – April 5 th 2006

CSE 5/7349 – April 5 th 2006. Wireless Networking. Compression. FEC. CRC. Modulation. Bits / Symbols / Baud. DSSS / FHSS. Wireless Security History. Cordless Phones Baby Monitors Networking. 802.11 Components. 802.11 modes. Infrastructure mode Ad-hoc mode (peer-to-peer).

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CSE 5/7349 – April 5 th 2006

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  1. CSE 5/7349 – April 5th 2006 Wireless Networking

  2. Compression

  3. FEC

  4. CRC

  5. Modulation

  6. Bits / Symbols / Baud

  7. DSSS / FHSS

  8. Wireless Security History • Cordless Phones • Baby Monitors • Networking

  9. 802.11 Components

  10. 802.11 modes • Infrastructure mode • Ad-hoc mode (peer-to-peer)

  11. Infrastructure mode Access Point Basic Service Set (BSS) – Single cell Station Extended Service Set (ESS) – Multiple cells

  12. Ad-hoc mode Independent Basic Service Set (IBSS)

  13. Open System Authentication

  14. MAC Address Locking

  15. Interception Range Station outside building perimeter. 100 metres Basic Service Set (BSS) – Single cell

  16. Interception

  17. Directional Antenna • Directional antenna provides focused reception. • D-I-Y plans available. • Aluminium cake tin. • 11 Mbps at 750 meters. • http://www.saunalahti.fi/~elepal/antennie.html

  18. 802.11b Security Services

  19. Wired Equivalence Privacy

  20. WEP – Sending

  21. Initialization Vector

  22. WEP – Receiving

  23. Shared Key Authentication • When station requests association with Access Point • AP sends random number to station • Station encrypts random number • Uses RC4, 40 bit shared secret key & 24 bit IV • Encrypted random number sent to AP • AP decrypts received message • Uses RC4, 40 bit shared secret key & 24 bit IV • AP compares decrypted random number to transmitted random number

  24. Security - Summary • Shared secret key required for: • Messages are encrypted. • Messages have checksum. • But SSID still broadcast in clear.

  25. Security Attacks

  26. 802.11 Insecurities

  27. IV Collision attack

  28. Limited WEP keys

  29. Brute Force Key Attack

  30. 128 bit WEP

  31. IV weakness

  32. Wepcrack

  33. Airsnort

  34. Safeguards

  35. Wireless as Untrusted LAN • Treat wireless as untrusted. • Similar to Internet. • Firewall between WLAN and Backbone. • Extra authentication required. • Intrusion Detection • WLAN / Backbone junction. • Vulnerability assessments

  36. Discover Unauthorised Use • Search for unauthorised access points or ad-hoc networks

  37. Location of AP

  38. IPSec VPN

  39. IEEE 802.11i

  40. 802.11i – Encryption Enhancements

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