wireless networks: signaling and security william tucker cen 4516: computer networks fgcu: fort...
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Wireless Networks: Signaling and Security
William TuckerCEN 4516: Computer Networks
FGCU: Fort Myers, FL: 09/05
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Wireless Networks: Primer
Networks are set up AD Hoc
Or a Hardware/ Software Access Point is Used to Connect Devices
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Wireless Networks: Primer
Several Wireless Technologies Bluetooth IrDA 802.11 Standard
802.11a 802.11b 802.11g 802.11n
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Wireless Networks: Primer
Wireless Technologies (cont.) PCS WAP WTLS WML Wi-Fi HomeRF Most of the above are not as popular
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Bluetooth
Low Cost
Small Range (<10 M)
Mediocre Speed (700 Kbps)
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IrDA
Used in Inventory
Needs Clear LOS
Needs short Distance
Used Mostly in Desktop Cable Replacement
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The 802.11 Standard
802.11a Fastest Maximum Speed (54 Mbps) Supports More Simultaneous Users Higher Cost Shorter Range
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The 802.11 Standard
802.11b Slowest Maximum Speed (11 Mbps) Longer range (Less Obstruction) More Signal Noise (2.4 GHz)
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The 802.11 Standard
802.11g Fastest Maximum Speed (54 Mbps) Longer range (Less Obstruction) Backwards Compatible with 802.11b Combines best of 802.11a and b
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The 802.11 Standard
802.11n Utilizes Multiple Wireless Antennas Coordinates Multiple Signals Fastest Speeds (100-200+ Mbps) No Word on Compatibility (Drafts) Expected in 2006
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802.11 Specifics
Protocols operate on the physical layer
802.11 MAC addressing is done at the Data Link layer
Authentication is done by ‘handshake’ structure
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Problem Definition:
Wireless Networking: Physical Limitations Security
Methods of Improvement Signal Strengthening Security Protocols
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The Electromagnetic Spectrum
Wireless Networks Operate at 2.4 GHz
(2.4 x 10^6)
Low Traffic and Standardized
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Physical Propagation
Radio Waves are sent via a transmitter and a receiver
Data rate dependant on frequency
Signal Strength is based on Power (Watts)
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Signal Strength
Signal power is amplitude of wave
Attenuation occurs (Humidity)Amplifiers boost signal strength
Weakening and Strengthening given in Decibels
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Example of Signal
Taken Using 802.11g at Close Range
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Antennas
Responsible for converting electrical impulses into radio waves
Omni directional AntennasDirectional Antennas
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Physical Layer Security
Has not been a major problem for wired networks
Wireless is highly susceptible to physical sniffing
No security by default
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Wired Equivalent Privacy
Uses encrypted keys
Key Length (64, 128 bit)
Initialization Vectors (24 bits) 16.7 Million Possibilities (Low)
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Initialization Vectors
No check for duplication
Weakens the cryptographic system
Weak Keys are used
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Cracking WEP: How To
Wireless Card capable of being ‘passive’ (sniffing)
Packet/IV collection software
Modified Brute Force WEP Cracking Software
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Cracking WEP: Using Aircrack
Aircrack includes Airodump
Aircrack includes Aircrack
Aircrack can be run on Windows!(using CygWin1.dll)
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Aircrack Sniffing Example
15 min of collection on Medium Traffic 128 bit WEP 802.11g
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Aircrack Cracking Example
500k IV’s found from packets
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Conclusion
If using WEP, use 128 bit keys Use MAC Address Filtering Don’t Broadcast Your SSID Download Useful Programs
and Most of all…
Enable Some Security!
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Questions?