WPA2: Second Generation WiFi Security

Wireless security at the basic level is traditionally implemented using WEP or

WPA. WEP as is common knowledge now, is very easy to crack and is not a

preferred mechanism for production-class wireless networks. WPA uses TKIP for

encryption and TKIP is not considered strong enough to be FIPS 140-2 compliant

and hence cannot be used readily by governmental deployments. While the second

generation WPA (known as WPA2 or 802.11i) is not designed to replace either WEP

or WPA, it is considered the strongest security mechanism thus far. This is

because besides TKIP, it can also use AES for encryption. AES encrypted data is

considered FIPS



140-2 compliant.

The 802.11i spec (WPA2)



The 802.11i specification for wireless LAN security was ratified by the IEEE

in June 2004 in a Standards Committee meeting at



Piscataway

,

NJ



. This specification



formally replaces WEP and other security features of the original IEEE 802.11

standard. It is also known as WPA2. Both WPA and WPA2 are secure methods of

communication using Wi-Fi. If you have equipment that supports only WPA, but not

WPA2, it's safe to continue using WPA. However, if you're buying new

equipment, you should buy products that support WPA2 with

Enterprise



mode. In March, Wi-Fi Alliance announced that the WPA2 security certification

program, the second generation of WPA, is now a mandatory feature for all new

Wi-Fi certified products.

New security features



Unlike older security standards, all of which define the physical layer

issues, WPA2 defines security mechanism that operates between the MAC (Media

Access Control) sub layer and the network layer. It has a better 128-bit

encryption with TKIP and AES.

TKIP:Unlike WEP, which uses a single key for

unicast data encryption and typically a separate key for multicast and broadcast

data encryption, WPA2 uses a set of four different keys for each client—AP

pair and a set of two different keys for multicast and broadcast traffic.

It derives TKIP using a four-way handshake process that is

the same as with WPA. This protocol is perfectly adequate to protect ordinary

Wi-Fi transmissions in a

SOHO

network.

AES: WPA2 equipment can also require AES (Advanced

Encryption Standards) for



encryption of data. AES was added to WPA to meet the needs of customers who

communicate with the



US



government and others which require this specific algorithm. This is the

feature that takes WPA2 a step further than WPA. The downside is that AES

support may require new hardware for many existing WLANs, as it needs a

dedicated chip to handle the encryption and decryption. But, the good news is

that AES meets FIPS (Federal Information Processing Standard) 140-2 requirement,

which is a government security criterion and provides stronger



encryption than WPA and TKIP.

Authentication process



Like WPA, WPA2 can be enabled in both



Enterprise



and Personal modes of



operation. For



Enterprise



mode, WPA2



requires authentication in two phases; the first is IEEE 802.1X authentication,

which is an open system authentication, and the second uses EAP (Extensible

Authentication Protocol). For home or small office networks, WPA2 Personal mode

supports the use of PSK (Pre-Shared Key). Based on the EAP or PSK authentication

process, WPA2 requires the determination of mutual PMK (Pairwise Master Key) for

key management. Personal mode requires only an access point and client device

while



Enterprise



mode typically requires RADIUS (Remote Authentication Dial-In User Service)

based authentication or other authentication server on the network.

Tip: If your WiFi usage

is in a

SOHO

network, PSK method of authentication may be adequate for your needs. It is

recommended that while using PSK authentication process mode, you should set a

password of at least 20 characters and make sure it doesn't



contain any names or dictionary words.

Robust Secure Network



Another element of WPA2 standard is RSN (Robust Secure Network). By default,

RSN uses AES and  CCMP (Countermode CBC MAC Protocol) and it is this, which

provides a stronger and scalable solution. CCMP uses Cipher Block Chaining

Message Authentication Code (CBC-MAC). This algorithm produces a Message

Integrity Code (MIC) that provides data origin authentication and data integrity

for wireless frame. Changing even one bit in a message produces a totally

different result. Messages are encrypted using a secret key (128 bits) and a 128

bit block of data. The end result is the encryption that is much harder to break

than even WPA.

Fast roaming



During a session, a series of messages are sent between wireless client and

wireless access point. While the wireless client roams between wireless access

points, there is a noticeable delay to perform authentication, which leads to

network interruptions and low connectivity. To minimize the delay of

authentication and reduce network interruptions, WPA2 equipment can optionally

support PMK caching and preauthentication for fast handoff. Therefore, access is

much faster when a wireless client roams back to the wireless access point to

which the client has already authenticated. This feature is helpful when there

are more than one access points in a network.

PMK caching



PMK caching is a feature through which a user can get re-authenticated quickly
to a wireless access point, authenticated to previously. It only needs to

perform the four-way handshake and determine new pairwise transient keys. In the

request frame, wireless client includes a PMK identifier that was determined

during the initial authentication and stored with both the wireless client and

wireless AP's PMK cache entries. These entries are stored for a finite amount

of time, which are then used for re-authentication process.

Preauthentication



Preauthentication is a process through which a wireless client has an option to
perform 802.1X authentication with another wireless AP in its range, while

itself already connected to its current AP. Through the existing wireless AP

connection, the wireless client sends a preauthentication request to another AP.

After that, PMK and its associated information is stored in PMK cache. Now, the

wireless client when connecting with the wireless AP to which it has already

preauthenticated, only needs to perform a four-way handshake.

In a nutshell



Despite the potential cost of implementing it, the new WPA2 is by far the

strongest security system for wireless networks. It's the most robust,

scalable and secure solution and will appeal particularly to enterprise users,

where key management and administration has been a major headache. WPA2 standard

has been specially designed to overcome the major security issues, which were

present in the older encryption standards. So WPA2 is the wireless security

standard that you can depend on.

Apurva Kothari, MD, Reckon Network