NETGEAR WG111U user manual Wireless Networking Basics

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

The primary information conveyed in the Beacon frames is the authentication method and the cipher suite. Possible authentication methods include 802.1X and Pre-shared key. Pre-shared key is an authentication method that uses a statically configured passphrase on both the stations and the access point. This removes the need for an authentication server, which in many home and small office environments will not be available nor desirable. Possible cipher suites include: WEP, TKIP, and AES (Advanced Encryption Standard). We’ll talk more TKIP and AES when addressing data privacy below.

•Authentication. EAP over 802.1X is used for authentication. Mutual authentication is gained by choosing an EAP type supporting this feature and is required by WPA. The 802.1X port access control prevents full access to the network until authentication completes. The 802.1X EAPOL-Key packets are used by WPA to distribute per-session keys to those stations successfully authenticated.

The supplicant in the station uses the authentication and cipher suite information contained in the information elements to decide which authentication method and cipher suite to use. For example, if the access point is using the Pre-shared key method then the supplicant need not authenticate using full-blown 802.1X. Rather, the supplicant must simply prove to the access point that it is in possession of the pre-shared key. If the supplicant detects that the service set does not contain a WPA information element then it knows it must use pre-WPA 802.1X authentication and key management in order to access the network.

•Key management. WPA features a robust key generation/management system that integrates the authentication and data privacy functions. Keys are generated after successful authentication and through a subsequent four-way handshake between the station and access point (AP).

•Data Privacy (Encryption). Temporal Key Integrity Protocol (TKIP) is used to wrap WEP in sophisticated cryptographic and security techniques to overcome most of its weaknesses.

•Data integrity. TKIP includes a message integrity code (MIC) at the end of each plain text message to ensure messages are not being spoofed.

Wireless Networking Basics B-11

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