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Wireless Networks - Energy, Security

Wireless Networks - Energy, Security. Christine E. Price, Krishna M. Sivalingam, Prathima Agarwal and Jyh-Cheng Chen, "A Survey of Energy Efficient Network Protocols for Wireless and Mobile Networks", Accepted for ACM/Baltzer Journal on Wireless Networks, Jan 2001

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Wireless Networks - Energy, Security

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  1. Wireless Networks - Energy, Security • Christine E. Price, Krishna M. Sivalingam, Prathima Agarwal and Jyh-Cheng Chen, "A Survey of Energy Efficient Network Protocols for Wireless and Mobile Networks", Accepted for ACM/Baltzer Journal on Wireless Networks, Jan 2001 • Nikita Borisov (University of California, Berkeley, USA); Ian Goldberg (Zero Knowledge Systems, Canada); and David Wagner (University of California, Berkeley, USA). "Intercepting Mobile Communications: The Insecurity of 802.11", Mobicom 2001 4/598N: Computer Networks

  2. Note: Overall energy consumed depends on the components, peripherals and their energy states iPAQ battery capacity – 2*950mAh (2*2850mWh @ 3V) Motivation: Energy consumption for iPAQ Source: Compaq researchers, Sukjae Cho, Paul Havinga, Mark Stemm 4/598N: Computer Networks

  3. Energy conservation techniques • Physical layer • Avoid collisions (wasted energy) • Packet delivery at well defined intervals • How do new nodes join? What about throughput? • Reduce switching between transmit and receiving • MAC layer • IEEE 802.11 - scheduled rendezvous mechanism 4/598N: Computer Networks

  4. IEEE 802.11b power saving mode (PSM) • Scheduled rendezvous mechanism using beacons • Access point (AP) informs client of pending packets at predefined intervals (beacon interval) • Clients transition to lower energy consuming states between scheduled beacons beacon 1 2 2 1 2 1 Access point beacon with data Beacon Interval Wait Interval PS poll 1 1 Client 1 sleep PS data 2 2 Client 2 sleep 4/598N: Computer Networks

  5. Energy conservation • Network layer • Balance topology maintenance with energy overhead • Broadcast/unicast differences • Analysis of ad-hoc routing protocols from an energy perspective • TCP • TCP probing - not all packet loss is congestion related 4/598N: Computer Networks

  6. Security • 802.11 networks utilize Wireless Equivalent Privacy protocol (WEP) • Confidentiality: Prevent casual eavesdropping • Access control: Protect access to wireless infrastructure • Data integrity: Prevent unauthorized tampering • WEP utilizes a shared secret (WEP key, array of 4 shared keys) • Checksumming P = M,c(M) • Encryption C=PRC4(v,k) • Transmission v,C 4/598N: Computer Networks

  7. Risks • Keystream reuse: If you know the keystream v, and information about the plain text message, then you can get the cipher text • Certain IP packets are predictable • Proactively create packets by sending known strings, say via SPAM • Buggy implementation - broadcasting encrypted and unencrypted • Build a dictionary of known keystream values • By IEEE standard, v is only 24 bits wide • Dictionary valid irrespective of the encryption key width • Keystream can be reused many times • Some cards always start with 0 • Shared keys are usually same for all clients 4/598N: Computer Networks

  8. Message authentication failure • WEP checksum is a linear function • Crypto experts would never use such a scheme • Protocol was developed like a network protocol - liberal • Use client association packets • IP redirection to have access point do the work for us • Use TCP client check summing mechanism • End-to-end mechanisms such as VPN/IPSEC helps • Treat wireless LANs as untrusted 4/598N: Computer Networks

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