Posted by arlene

In response to the vulnerability and criticism of WEP, the Wi-Fi Alliance created the Wi-Fi Protected Access (WPA) standard in 2003. WPA was designed to be an interim security solution until the completion of the IEEE 802.11i security standard, and its features are a blend of features originally developed for WEP and those being developed for 802.11i.

Like WEP, WPA uses RC4 encryption for its keys, but unlike WEP, WPA modifies the original key for greater security and supports an optional authentication server. WPA is the minimum recommended security standard for network hardware that supports it, such as 802.11g hardware that supports the full 802.11g standard, and most recent 802.11a hardware. Although some vendors of 802.11b hardware have provided upgrades to support WPA, most 802.11b hardware is not compatible with WPA security.

One of the main complaints about WEP, besides its limited-length keys, is the fact that the same key is used by both sides of the transmission, and the key does not change during a session. These factors make it easy to examine network traffic on a wireless network and eventually crack the encryption key.

WPA solves two problems associated with the earlier WEP security mechanisms. First, it usesencrypted techniques for authentication that should assist in preventing unauthorized clients from becoming part of the wireless network. Second, it uses a constantly changing key instead of the single shared key used for encryption by WEP. By changing in the encryption key at frequent intervals, WPA can be much more difficult to crack. The constant changing of encryption keys is known as the Temporal Key Integrity Protocol (TKIP). This key-changing method makes it very difficult for intruders to decipher keys used by your wireless network, especially when compared to the static keys known by both sides of the communications link used by the simple WEP standards.

WPA also includes an integrity check that is basically a check sum based on the network packet that can detect whether a packet is originating from a valid network user or an intruder who is attempting to crack the key used by your network. Thus, if an unauthorized user uses the standard techniques to attempt to determine a fixed key, you can detect these intrusion attempts and then deal with them.

Overcoming Potential Vulnerabilities in WPA

The version of WPA used in SOHO and small-business networks that lack an authentication server is known as WPA-Personal. The encryption key is known as a Pre-Shared Key (PSK); the PSK must be provided by a network client before it can log into a WPA-based wireless network. The original PSK is encrypted using the TKIP process, which changes the key repeatedly during a connection to help keep the connection secure. WPA-Personal is also known as WPA-PSK.

Although WPA is a stronger encryption standard than WEP, several potential weaknesses exist in the way users can configure WPA. These include

• Encryption keys that are too short—The longer the encryption key, the more secure the network is. Network experts recommend an encryption key of at least 20 characters. The Wireless Network Setup Wizard that Microsoft includes in Windows XP Service Pack 2 creates a 63-character WPA key.

• Plain-text encryption keys—A key such as The quick brown fox jumps over the iscertainly longer than the 20-character minimum recommended, but because it is comprised of recognizable words, it is relatively easy to crack. Instead, use mixed, random alphanumeric keys. For example, a key such as 2F1ACB67EF900 F77A would be much harder to crack because there are no recognizable words or alphanumeric patterns in it.

To see for yourself the threat that short, plain-text encryption keys pose to your WPA-based wireless network, you can download the WPA Cracker utility from tiny PEAP (www.tinypeap.com). The network packets WPA Cracker needs for analysis can be gathered with the Ethereal open-source network protocol analyzer available from www.ethereal.com. You should use WPA Cracker and similar tools to analyze your current WPA-based network configuration for vulnerabilities.

For larger, corporate networks, a more powerful version of WPA known as WPA-Enterprise can be used. WPA-Enterprise (also known as WPA-RADIUS) differs from WPA-Personal in these ways:

• A RADIUS or AAA server is used to authenticate individual users.
• Authentication uses the IEEE 802.1X standard developed in 2001.
• WPA supports the Extensible Authentication Protocol (EAP).

Regardless of the version of WPA you might select, your APs and network clients must be configured to use the same settings to make a connection possible, just as with the older WEP security standard.

Moving to WPA2 (IEEE 802.11 i)

Although WPA, particularly in its WPA-Enterprise version, is much more secure than WEP, it is not as secure as it could be. WPA was designed as an interim solution until the ratification of the IEEE 802.11i standard could take place. IEEE 802.11i was ratified in 2004, and the first products became available in the fall of 2004. IEEE 802.11i-compatible products are known as WPA2-compatible. WPA2 differs from WPA in the use of a stronger encryption algorithm. Although WEP and WPA used RC4 encryption, WPA2 uses the stronger AES encryption algorithm.

To upgrade existing WPA-compatible wireless network hardware to use WPA2/802.11i security, you might need to perform one or more of the following operations:

• Download and install updated client device drivers—Someclient adapters might not support WPA2 security because WPA2 security requires more intensive computation than WPA.

• Download and install updated router and AP firmware—Some wireless routes or APs might not support WPA2 security because WPA2 security requires more intensive computation than WPA.

Some vendors don’t explicitly state that their products support WPA2. Instead, they might list the security features the adapters support. cross-references security features to WPA/WPA2 security standards supported.

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