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IEEE 802.11i

The IEEE 802.11i standard for WLAN security, adopted in 2004, replaces the WEP protocol and eliminates its weak points. 802.11i prescribes the Advanced Encryption Standard( AES) with Counter Mode with CBC- MAC Protocol( CCMP) as the encryption method; Wireless Robust Authentication Protocol( WRAP) can also be used as an option. The CCMP protocol describes how the AES algorithm is applied to WLAN data packets and is used for authentication.

802.11i uses the Extensible Authentication Protocol( EAP), whose messages are encapsulated, as the transport protocol for the authentication methods between the WLAN devices and the access points, and RADIUS as the authentication infrastructure. The integrity of the plaintext headers is ensured with the Message Integrity Check( MIC).

Authentication procedure in 802.11i

Authentication procedure in 802.11i

The Advanced Encryption Standard (AES) works with a 128-bitkey and a 48-bit initialization vector( IV) that changes constantly and is discarded if repeated. Since older WLANs still work with the Temporal Key Integrity Protocol( TKIP) and Wired Equivalent Privacy (WEP), these are optionally permitted in addition to the WRAP protocol.

Authentication in 802.11i is based on a sophisticated key hierarchy with multiple hierarchy levels. There are only two types of keys: the pairwise keys for unicast transmissions and the group keys for multicasting. As far as the hierarchy levels are concerned, a pairwise master key( PMK) is derived from a pairwise key( MK), and from this in turn a pairwise transient key( PTK). The keys for the distribution of the cipher keys and the encryption of the data are obtained from the latter: The Key Confirmation Key( KCK), the Key Encryption Key( KEK), from which in turn the Group Transient Key( GTK) is derived, and the Temporal Key( TK).

Informations:
Englisch: IEEE 802.11i
Updated at: 12.05.2014
#Words: 275
Links: IEEE 802, standard (STD), security, protocol, audio engineering society (AES)
Translations: DE
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