802.11 Wireless LAN Security

Wireless Security

Imagine extending a long Ethernet cable from your internal network outside your office and laying it on the ground in the parking lot. Anyone who wants to use your network can simply plug into that network cable. Connecting unsecured WLANs to your internal network has the potential to offer the same opportunity.

802.11-based devices communicate with one another using radio frequencies (RFs) as the carrier signal for data. The data is broadcast from the sender in the hopes that the receiver is within RF range. The drawback to this mechanism is that any other station within range of the RF also receives the data.

Without a security mechanism of some sort, any 802.11 station can process the data sent on a WLAN, as long as that receiver is in RF range. To provide a minimum level of security in a WLAN, you need two components:

• A means to decide who or what can use a WLAN— This requirement is satisfied by authentication mechanisms for LAN access control.

• A means to provide privacy for the wireless data— The requirement is satisfied by encryption algorithms.

As Figure 4-1 depicts, wireless security consists of both authentication and encryption. Neither mechanism alone is enough to secure a wireless network.


The 802.11 specification defines Open and Shared Key authentication and WEP to provide device authentication and data privacy, respectively. The Open and Shared Key algorithms both rely on WEP encryption and possession of the WEP keys for access control. Because of the importance of WEP in 802.11 security, the following section focuses on the basics of encryption and ciphers in general.