Netgear WG111U User Manual download pdf (Page 77)

User’s Manual for the NETGEAR Super AG Wireless USB 2.0 Adapter WG111U

Wireless Networking Basics B-15

202-10065-01

Temporal Key Integrity Protocol (TKIP)

WPA uses TKIP to provide important data encryption enhancements including a per-packet key

mixing function, a message integrity check (MIC) named Michael, an extended initialization

vector (IV) with sequencing rules, and a re-keying mechanism. TKIP also provides for the

following:

• The verification of the security configuration after the encryption keys are determined.

• The synchronized changing of the unicast encryption key for each frame.

• The determination of a unique starting unicast encryption key for each preshared key

authentication.

Michael

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.

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Netgear WG111U User Manual Page 77