Which of the following represents the correct order of the WPA 4-Way Handshake steps?

• A. Proves knowledge of the PMK; Exchanges messages for generating PTK; Distributes an encrypted GTK to the client; Sets first initialization vector (IV).
• B. Distributes an encrypted GTK to the client; Proves knowledge of the PMK; Exchanges messages for generating PTK; Sets first initialization vector (IV).
• C. Exchanges messages for generating PTK; Proves knowledge of the PMK; Sets first initialization vector (IV); Distributes an encrypted GTK to the client.
• D. Sets first initialization vector (IV); Proves knowledge of the PMK; Exchanges messages for generating PTK; Distributes an encrypted GTK to the client.

Answer: (A)

The key idea here is how the WPA 4-Way Handshake establishes encryption keys in the correct order. The handshake starts by showing both sides know the PMK indirectly through deriving the PTK from the PMK and the nonces exchanged; this proves possession of the PMK without transmitting it. Once the PTK is derived and installed, the parties exchange additional messages to complete and confirm the PTK. Only after the PTK is in place is the GTK, used for multicast/broadcast traffic, distributed to the client and encrypted with that PTK. At this point the first initialization vector used for CCMP encryption is set, enabling secure data frames to follow. So the proper sequence is proving PMK knowledge, exchanging messages to generate and install the PTK, then distributing the GTK encrypted under the PTK and establishing the first IV.