Wi-Fi Protected Access

Wi-Fi Protected Access (WPA), Wi-Fi Protected Access 2 (WPA2), and Wi-Fi Protected Access 3 (WPA3) are the three security certification programs developed after 2000 by the Wi-Fi Alliance to secure wireless computer networks. The Alliance defined these in response to serious weaknesses researchers had found in the previous system, Wired Equivalent Privacy (WEP).

WPA (sometimes referred to as the TKIP standard) became available in 2003. The Wi-Fi Alliance intended it as an intermediate measure in anticipation of the availability of the more secure and complex WPA2, which became available in 2004 and is a common shorthand for the full IEEE 802.11i (or IEEE 802.11i-2004) standard.

In January 2018, the Wi-Fi Alliance announced the release of WPA3, which has several security improvements over WPA2.

As of 2023, most computers that connect to a wireless network have support for using WPA, WPA2, or WPA3. All versions thereof, at least as implemented through May, 2021, are vulnerable to compromise.

WEP (Wired Equivalent Privacy) is an early encryption protocol for wireless networks, designed to secure WLAN connections. It supports 64-bit and 128-bit keys, combining user-configurable and factory-set bits. WEP uses the RC4 algorithm for encrypting data, creating a unique key for each packet by combining a new Initialization Vector (IV) with a shared key (it has 40 bits of vectored key and 24 bits of random numbers). Decryption involves reversing this process, using the IV and the shared key to generate a key stream and decrypt the payload. Despite its initial use, WEP's significant vulnerabilities led to the adoption of more secure protocols.

The Wi-Fi Alliance intended WPA as an intermediate measure to take the place of WEP pending the availability of the full IEEE 802.11 standard. WPA could be implemented through firmware upgrades on wireless network interface cards designed for WEP that began shipping as far back as 1999. However, since the changes required in the wireless access points (APs) were more extensive than those needed on the network cards, most pre-2003 APs were not upgradable by vendor-provided methods to support WPA.

The WPA protocol implements the Temporal Key Integrity Protocol (TKIP). WEP uses a 64-bit or 128-bit encryption key that must be manually entered on wireless access points and devices and does not change. TKIP employs a per-packet key, meaning that it dynamically generates a new 128-bit key for each packet and thus prevents the types of attacks that compromise WEP.

WPA also includes a Message Integrity Check, which is designed to prevent an attacker from altering and resending data packets. This replaces the cyclic redundancy check (CRC) that was used by the WEP standard. CRC's main flaw is that it does not provide a sufficiently strong data integrity guarantee for the packets it handles. Well-tested message authentication codes existed to solve these problems, but they require too much computation to be used on old network cards. Researchers have since discovered a flaw in WPA that relied on older weaknesses in WEP and the limitations of the message integrity code hash function, named Michael, to retrieve the key-stream from short packets to use for re-injection and spoofing.