Which of the following wireless security standards supported by Windows Vista provides the highest level of security?

WPA2 implements the full IEEE 802.11i standard and requires AES-CCMP (Counter Mode with CBC-MAC Protocol) as its mandatory encryption cipher. AES is a much stronger cipher than the RC4-based TKIP used by earlier WPA versions, and it eliminates the known cryptographic weaknesses found in WEP and original WPA. Windows Vista was the first mainstream Windows OS to natively support WPA2 in both Personal (PSK) and Enterprise (802.1X/EAP) modes.

WPA-PSK uses TKIP encryption with a pre-shared key, which is weaker than WPA2's mandatory AES-CCMP and is vulnerable to dictionary attacks when weak passphrases are used.

WPA-EAP uses 802.1X enterprise authentication but still relies on TKIP encryption like WPA-PSK, making its data encryption layer weaker than WPA2's AES-CCMP.

WEP uses the RC4 stream cipher with static keys and short initialization vectors, making it trivially crackable with freely available tools and offering the least security of all options listed.