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Wireless Technology and Security. April 9, 2003. Justin Mencl CIS 492. Overview. Current Wireless Technology Infrared, Bluetooth, Wi-Fi Security Issues Concerns Problem with WEP Resources. IrDA. Infrared (IrDA) Uses beams of light  line of sight communication

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Wireless technology and security l.jpg

Wireless Technology and Security

April 9, 2003

Justin Mencl

CIS 492


Overview l.jpg
Overview

  • Current Wireless Technology

    • Infrared, Bluetooth, Wi-Fi

  • Security Issues

    • Concerns

    • Problem with WEP

  • Resources


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IrDA

  • Infrared (IrDA)

    • Uses beams of light  line of sight communication

    • Data broadcast in straight line, 30° cone

    • User intervention required


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Bluetooth

  • Short range wireless technology

  • Operates on unlicensed 2.4GHz radio frequency

    • Uses Frequency Hopping Spread Spectrum (FHSS)

  • Supported by more than 50 major companies

    • 3COM

    • Microsoft

    • Ericsson

    • Nokia


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Bluetooth (cont.)

  • Devices

    • Access Points

    • Keyboard/Mice

    • Car Stereos, Hands Free Kits

  • Advantages

    • Inexpensive – small radio module

    • Ease of use – automatic connection between device


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Wi-Fi

  • Most popular wireless LAN solution

  • Specified by IEEE 802.11

    • Includes 802.11a, 802.11b, 802.11g

  • Also uses radio frequencies – 2.4GHz and 5Ghz

    • Uses Direct Sequence Spread Spectrum (DSSS)


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Wi-Fi Flavors

  • IEEE 802.11b

    • Most popular flavor

    • Uses 2.4Ghz, 11 Mbps, Range of 1000 ft

  • IEEE 802.11a

    • Uses 5GHz frequency, 54 Mbps

    • Reduced range  More access points needed

  • IEEE 802.11g

    • Uses 2.4GHz – backward compatible with 802.11b

    • 54 Mbps


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Wireless Security

  • IrDA – minimal security concerns

  • Bluetooth

    • Uses stream cipher E0, more secure than Wi-Fi

    • Uses different keys for encryption and authentication

  • Wi-Fi

    • Uses stream cipher RC4(v, k)

    • Uses same keys for encryption and authentication


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Wi-Fi Security Concerns

  • Wired Equivalency Protocol (WEP)

    • Used to encrypt data

  • WEP implementation

    • Secret key to encrypt packets before sending

    • Integrity Check before receiving packets


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WEP Algorithm*

  • Sender and receiver share secret key k

  • Compute checksum c(M)

  • Pick Init Vector v, generate keystream RC4(v, k)

  • XOR <M, c(M) > and keystream  ciphertext

  • Transmit ciphertext

  • Use transmitted v and shared k to get keystream RC4(v, k)

  • XOR ciphertext with RC4(v, k) to get <M’, c’>

  • Check if c’=c(M’)

  • If so, accept M’ as message transmitted

* Taken from “Security Of The WEP Algorithm”, UC Berkeley



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Problems With WEP

  • Uses cipher stream – RC4(v, k)

  • Inherit security risk when using cipher streams:

    • You must NEVER encrypt two messages with same keystream

  • Keystream is RC4(v, k) which depends only on v, k

  • k is fixed shared secret that changes rarely, if ever

  • v is 24 bit value  only 2^24 values == 16 million

    • So after 16 million packets, you have to repeat a v value

  • Repeated v, same k  repeated keystream


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Other Problems…

  • Passive attacks to decrypt traffic based on statistical analysis.

  • Active attack to inject new traffic from unauthorized mobile stations, based on known plaintext.

  • Active attacks to decrypt traffic, based on tricking the access point.

  • Dictionary-building attack that, after analysis of about a day's worth of traffic, allows real-time automated decryption of all traffic


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WEP Fixes

  • Need both of the following:

    • Long Init Vector v that never repeats for the lifetime of the shared secret

    • Stong Message Authentication Code in replace of the CRC which depends on key k and Init Vector v

  • Again, BOTH need to be done!


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Is WEP Secure???

  • Don’t rely solely on WEP for security

  • KSU CNS does!!!

  • CIS Department does not

  • Wireless Best Practices

    • Treat wireless network as a public network

    • Put wireless network OUTSIDE your firewall

      • Use VPN, IPSec, ssh


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Resources

  • Wireless Technology

    • http://www.bluetooth.org

    • http://www.acsac.org/2002/case/wed-c-330-Innella.pdf

    • http://www.ieee802.org

  • Security of the WEP Algorithm, UC Berkeley

    • Nikita Borisov, Ian Goldberg, and David Wagner

    • http://www.isaac.cs.berkeley.edu/isaac/wep-faq.html

    • http://www.cypherpunks.ca/bh2001


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