Which component of WPA uses a rekeying mechanism to provide fresh encryption and integrity keys?

• A. WEP
• B. TKIP
• C. AES-CCMP
• D. PSK

Answer: (B)

The mechanism that provides fresh encryption and integrity keys in WPA is TKIP. TKIP was designed to fix the flaws of WEP by introducing per-packet keying and a rekeying process. It generates a new per-frame key for encryption by mixing a Temporal Key with the IV and the devices’ addresses, and the four-way handshake refreshes the keying material (the Pairwise Transient Key) used to derive these per-packet keys. This means the actual encryption and integrity keys change frequently, so even if one key were compromised, past frames remain protected. WEP uses a static key with no rekeying, PSK is just an authentication key, and AES-CCMP, while also using refreshed keys via the handshake, is a different, stronger encryption method; the rekeying mechanism described in WPA’s context is most directly associated with TKIP.