Wireless Networks: Signaling and Security William Tucker CEN 4516: Computer Networks FGCU: Fort Myers, FL: 09/05

Wireless Networks: Primer Networks are set up AD Hoc Or a Hardware/ Software Access Point is Used to Connect Devices

Wireless Networks: Primer Several Wireless Technologies  Bluetooth  IrDA  Standard a b g n

Wireless Networks: Primer Wireless Technologies (cont.)  PCS  WAP  WTLS  WML  Wi-Fi  HomeRF  Most of the above are not as popular

Bluetooth Low Cost Small Range (<10 M) Mediocre Speed (700 Kbps)

IrDA Used in Inventory Needs Clear LOS Needs short Distance Used Mostly in Desktop Cable Replacement

The Standard a  Fastest Maximum Speed (54 Mbps)  Supports More Simultaneous Users  Higher Cost  Shorter Range

The Standard b  Slowest Maximum Speed (11 Mbps)  Longer range (Less Obstruction)  More Signal Noise (2.4 GHz)

The Standard g  Fastest Maximum Speed (54 Mbps)  Longer range (Less Obstruction)  Backwards Compatible with b  Combines best of a and b

The Standard n  Utilizes Multiple Wireless Antennas  Coordinates Multiple Signals  Fastest Speeds ( Mbps)  No Word on Compatibility (Drafts)  Expected in 2006

Specifics Protocols operate on the physical layer MAC addressing is done at the Data Link layer Authentication is done by ‘handshake’ structure

Problem Definition: Wireless Networking:  Physical Limitations  Security Methods of Improvement  Signal Strengthening  Security Protocols

The Electromagnetic Spectrum Wireless Networks Operate at 2.4 GHz (2.4 x 10^6) Low Traffic and Standardized

Physical Propagation Radio Waves are sent via a transmitter and a receiver Data rate dependant on frequency Signal Strength is based on Power (Watts)

Signal Strength Signal power is amplitude of wave Attenuation occurs (Humidity) Amplifiers boost signal strength Weakening and Strengthening given in Decibels

Example of Signal Taken Using g at Close Range

Antennas Responsible for converting electrical impulses into radio waves Omni directional Antennas Directional Antennas

Physical Layer Security Has not been a major problem for wired networks Wireless is highly susceptible to physical sniffing No security by default

Wired Equivalent Privacy Uses encrypted keys Key Length (64, 128 bit) Initialization Vectors (24 bits)  16.7 Million Possibilities (Low)

Initialization Vectors No check for duplication Weakens the cryptographic system Weak Keys are used

Cracking WEP: How To Wireless Card capable of being ‘passive’ (sniffing) Packet/IV collection software Modified Brute Force WEP Cracking Software

Cracking WEP: Using Aircrack Aircrack includes Airodump Aircrack includes Aircrack Aircrack can be run on Windows! (using CygWin1.dll)

Aircrack Sniffing Example 15 min of collection on Medium Traffic 128 bit WEP g

Aircrack Cracking Example 500k IV’s found from packets

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!

Questions?