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Wireless Network Security

Wireless Network Security. CSIS 5857: Encoding and Encryption. Wireless LAN Structure. Wireless LAN Terminology. Station : Device capable of IEEE 802.11 wireless connectivity (wireless laptop, etc.) Distribution System : Backbone system for long-distance communication (lines/satellite/etc.)

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Wireless Network Security

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  1. Wireless Network Security CSIS 5857: Encoding and Encryption

  2. Wireless LAN Structure

  3. Wireless LAN Terminology • Station: Device capable of IEEE 802.11 wireless connectivity (wireless laptop, etc.) • Distribution System: Backbone system for long-distance communication (lines/satellite/etc.) • Access point: Bridge between station and distribution system (or between stations in same BSS) • Basic Service Set (BSS): Set of stations in range of access point

  4. Wireless LAN Structure • Differences from LAN security: • Any transmission may be listened to by any device in range of access point  All transmissions must be secured • Other wireless devices in range of AP can attempt to connect to it  Any device wishing to communicate through access point must be authenticated

  5. 802.11i RSN Services • Access control: • Preventing access toaccess point until authentication • Authentication: • Mutual authentication between stations and access points, and key generation • Privacy: • Encrypting/hashing/etc. of messages to insure confidentiality/information integrity/etc.

  6. Authentication Server • Authentication server • Contacted by AP when station requests access • Uses authentication protocol to establish station identity

  7. IEEE 802.11i Operation Phases

  8. Discovery Phase • Station contacts AP • Challenge-response can be used to authenticate AP • Station passes security suite to AP (like SSL) • AP responds with chosen algorithms

  9. Authentication Phase • AP blocks communication with rest of network until authentication complete • AS performs all authentication functions • AP just passes data back and forth

  10. Authentication Phase • Station sends request to AP for connection to authentication server • Extensible authentication protocol (EAP) used for mutual authentication • AS generates keys for secure informationexchange

  11. Authentication Phase • Extensible Authentication Protocol: • Based on challenge-response • Station and AS share secret information (such as symmetric key) • AS sends challenge to station (via AP) • Station sends response • May repeat with multiple challenges (10 – 20) for added protection against replay attacks

  12. Key Management Phase • Possible methods: • Station and AP already share pre-shared key (PSK) previously installed on station • AS generates and sends master session key (MSK) to station as part of EAP challenge response • Used to generate pairwise master key

  13. Key Management Phase • HMAC-SHA1 used to generate Pairwise transient key from • Pairwise master key • MAC address of station and AP (prevents replay attacks) • PTK consists of • Key used for confirmation of other keys • Key used to encrypt other keys • Actual temporal key used to securely transmit data

  14. Key Management Phase • Handshake between station and AP used to establish and confirm keys used for secure transmission

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