WPA Protocol (Wi-Fi Protected Access) was accepted in 2002 to eliminate vulnerabilities of the WEP protocol. This protocol was accepted as a temporary solution because in that moment of time, the work on the new standard IEEE 802.11i (accepted in 2004) had already begun. WPA Protocol is a subset of 802.11i standard features, so implementation of 802.11i does not require any changes in technical devices. Changes are only necessary in software or firmware.
As WEP protocol does, WPA protocol uses also RC4 cipher, but involves new security mechanisms. Main parts of WPA protocol are: