Netgear Double 108 Mbps Wireless PC Card WG511U User Manual download pdf (Page 72)

User’s Manual for the NETGEAR Double 108 Mbps Wireless PC Card 32-bit CardBus WG511U

B-20 Wireless Networking Basics

August 2004

With 802.11 and WEP, data integrity is provided by a 32-bit integrity check value (ICV) that is

appended to the 802.11 payload and encrypted with WEP. Although the ICV is encrypted, you can

use cryptanalysis to change bits in the encrypted payload and update the encrypted ICV without

being detected by the receiver.

With WPA, a method known as Michael specifies a new algorithm that calculates an 8-byte

message integrity code (MIC) using the calculation facilities available on existing wireless

devices. The MIC is placed between the data portion of the IEEE 802.11 frame and the 4-byte ICV.

The MIC field is encrypted together with the frame data and the ICV. Michael also provides replay

protection. A new frame counter in the IEEE 802.11 frame is used to prevent replay attacks.

• AES Support

One of the encryption methods supported by WPA beside TKIP is the advanced encryption

standard (AES), although AES support will not be required initially for Wi-Fi certification. This is

viewed as the optimal choice for security conscience organizations, but the problem with AES is

that it requires a fundamental redesign of the NIC’s hardware in both the station and the access

point. TKIP was a pragmatic compromise that allows organizations to deploy better security while

AES capable equipment is being designed, manufactured, and incrementally deployed.

Is WPA Perfect?

WPA is not without its vulnerabilities. Specifically, it is susceptible to denial of service (DoS)

attacks. If the access point receives two data packets that fail the Message Integrity Code (MIC)

check within 60 seconds of each other then the network is under an active attack, and as a result,

the access point employs counter measures, which includes disassociating each station using the

access point. This prevents an attacker from gleaning information about the encryption key and

alerts administrators, but it also causes users to lose network connectivity for 60 seconds. More

than anything else, this may just prove that no single security tactic is completely invulnerable.

WPA is a definite step forward in WLAN security over WEP and has to be thought of as a single

part of an end-to-end network security strategy.

Product Support for WPA

Starting in August, 2003, new NETGEAR, Inc. Wi-Fi certified products will support the WPA

standard. Existing NETGEAR, Inc. wireless products that had their Wi-Fi certification approved

before August, 2003 will have one year to add WPA so as to maintain their Wi-Fi certification.

WPA requires software changes to the following:

• Wireless access points

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Netgear Double 108 Mbps Wireless PC Card WG511U User Manual Page 72