ed to exchange a shared secret. IEEE 802.11i and WPA2 The IEEE 802.1 11i standard defines security enhancements for 802.11 WLANs, providing stronger encryption, authentication and key management Chapter Eight strategies with the objective of creating a robust security network (RSN). The key features of the RSN are; A negotiation process that enables the appropriate confidentiality protocol for each traffic type to be selected during device association A key system that generates and manages two hierarchies of keys. Pairwise keys for unicast and group keys for multicast messages are established and authenticated through EAP handshakes during device association and authentication Two protocols to improve data confidentiality (TKIP and AES-CCMP). Key caching and pre-authentication are also included in 802.11i to reduce the time taken for roaming wireless stations to associate or re-associate with access points. WPA2 is the Wi-Fi Alliance's implementation of the final IEEE 802.11i standard and replaced WPA following the ratification of 802.11i in June 2004. WPA2 implements the advanced encryption standard (AES) encryption algorithm using counter mode with cipher block chaining message authentication code protocol (CCMP). TKIP and 802.11 authentication were included in the earlier release of WPA, and have been described above, while AES and CCMP are covered in the following sections. WPA and WPA2 both support Enterprise and Personal modes, and a comparison of the main elements is shown in Table 8-3. Table 8-3: WPA and WPA2 Compared Enterprise mode Personal mode Authentication: IEEE 802.1x/EAP Authentication: PSK Encryption: TKIP Encryption: TKIP Integrity: MIC Integrity: MIC Authentication: IEEE 802.1x/EAP Authentication: PSK Encryption: AES-counter mode Encryption: AES-counter mode Integrity: CBC-MAC (CCMP) Integrity: CBC-MAC (CCMP) Wireless LAN Security RSN Security Parameter Negotiation The negotiation of security parameters between RSN capable devices is enabled by including an RSN information element (IE) which i