Wi-Fi Protected Access (WPA and WPA2) is a class of systems to secure wireless networks.
WPA implements the majority of the IEEE 802.11i standard, WPA2 implements the full standard.

Personal WPA utilizes less scalable "pre-shared key" (PSK) mode,

where every allowed computer is given the same passphrase.

In PSK mode, security depends on the strength of the passphrase.

Data is encrypted using the RC4 stream cipher, with a 128-bit key and a 48-bit initialization vector (IV).

One major improvement in WPA over WEP is the Temporal Key Integrity Protocol (TKIP),

which dynamically changes keys as the system is used.

When combined with the much larger initialization vector, this defeats the well-known key recovery attacks on WEP.

 A more secure message authentication code, for improved payload integrity (usually known as a MAC,

 but here termed a MIC for "message integrity code")  is used in WPA,

 an algorithm named "Michael". The MIC used in WPA includes a frame counter,

 which prevents replay attacks being executed.

WPA2 implements the mandatory elements of 802.11i. In particular, in addition to TKIP and the Michael algorithm,

it introduces a new AES-based algorithm, CCMP, that is considered fully secure.