Wireless Networks: Signaling and Security

William TuckerCEN 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 802.11 Standard

802.11a 802.11b 802.11g 802.11n

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 802.11 Standard

802.11a Fastest Maximum Speed (54 Mbps) Supports More Simultaneous Users Higher Cost Shorter Range

The 802.11 Standard

802.11b Slowest Maximum Speed (11 Mbps) Longer range (Less Obstruction) More Signal Noise (2.4 GHz)

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

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

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

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 802.11g at Close Range

Antennas

Responsible for converting electrical impulses into radio waves

Omni directional AntennasDirectional 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 802.11g

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?