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IEEE 802.11 Family

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  1. IEEE 802.11 Family Dr. Muid Mufti ID Technologies Islamabad

  2. 802.11 Variants • IEEE 802.11d • Additional regulatory domains • IEEE 802.11e • for improved quality of service • IEEE 802.11f • to regulate inter-access point hand offs • IEEE 802.11i • to improve WLAN security • IEEE 802.11n • Enhanced Speed and Robustness

  3. IEEE 802.11i Wireless Security

  4. Basic 802.11 Security • WEP • Wire Equivalent Privacy • Stream Cipher: RC4 • 40-bit key+24-bit Initialization Vector (IV)=64-bit RC4 key

  5. Basic 802.11 Vulnerabilities • No AP Authentication (i.e. two way auth.) • Key distribution problem • Shared key (i.e. key is the same for everyone) • No privilege and permission scheme can be defined • One can decrypt others information • The secret which is known by everyone is not secret! • Pair wise keys defined but rarely used

  6. WEP Weaknesses • Small IV space (IV Collision Problem) • Replay attacks once WEP key is revealed • Predictable IV due to poor implementation • CRC as integrity checking algorithm • RC4 vulnerability to known plain text attack • Static keys – in contrast to session / temporal keys

  7. 802.11i • Open Authentication • Pair wise keys • Session keys • 128 bit keys • Enhanced Encryption • TKIP • DES • CCMP – AES • IEEE 802.1X

  8. Four Way Authentication

  9. TKIP • Based on RC4 • 128-bit Key (per packet) • One key pair for each direction • Per packet key –temporal part • Per session key –Pair-wise Master Key (PMK) • Key encryption key • Pair-wise transient key (PTK) • MAC address of the station (TA) –i.e. unique for every client • 48-bit packet serial number

  10. TKIP

  11. CCMP • Counter Mode with Cipher Block Chaining Message Authentication Code Protocol • AES based

  12. Authentication 802.1X • Port-based network access control • Controlled port • Authorized • Unauthorized • Uncontrolled port

  13. EAP • Extensible Authentication Protocol (EAP) (RFC 2284) • EAP-MD5 • EAP-TLS (Certificates) • EAP-TTLS (Certificates and Passwords) • EAP-SIM • PEAP (Cisco) • LEAP (Cisco) • EAP over LAN (EAPOL)

  14. Authentication Authenticator Authentication Server Supplicant

  15. Wi-Fi Alliance • WPA • Wireless Protected Access • WPA-2

  16. IEEE 802.11e Qualitiy of Service

  17. 802.11e • EDCF - Enhanced DCF • HCF - Hybrid Coordination Function • QBSS • HC – Hybrid Controller • TC – Traffic Categories • TXOP – Transmission Opportunity • – granted by EDCF-TXOP or HC- poll TXOP • AIFS – Arbitration Interframe Space

  18. Arbitration IFS

  19. Traffic Categories

  20. IEEE 802.11n High Speed

  21. 802.11n • Expected to be finalized by Nov 2009 • High Data rates – 300 Mbps or above • Improved OFDM • Greater Stability • Shorter Cyclic Prefix • Block Ack • Frame Aggrgation

  22. MIMO Technology Multiple Antenna

  23. WiFi Alliance • Wi-Fi Alliance is certifying 802.11n products based on Draft 7 – Nov 2008