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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

Wireless Technology and Security

April 9, 2003

Justin Mencl

CIS 492

overview
Overview
  • Current Wireless Technology
    • Infrared, Bluetooth, Wi-Fi
  • Security Issues
    • Concerns
    • Problem with WEP
  • Resources
slide3
IrDA
  • Infrared (IrDA)
    • Uses beams of light  line of sight communication
    • Data broadcast in straight line, 30° cone
    • User intervention required
bluetooth
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
bluetooth cont
Bluetooth (cont.)
  • Devices
    • Access Points
    • Keyboard/Mice
    • Car Stereos, Hands Free Kits
  • Advantages
    • Inexpensive – small radio module
    • Ease of use – automatic connection between device
wi fi
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)
wi fi flavors
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
wireless security
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
wi fi security concerns
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
wep algorithm
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

problems with wep
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
other problems
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
wep fixes
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!
is wep secure
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
resources
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