350-401 Question 282
Single answerA network engineer is troubleshooting a WPA2-Enterprise wireless network where some clients are failing to authenticate. The engineer suspects an issue with the 4-way EAPOL handshake. Which part of the handshake is responsible for ensuring the client and the access point derive the same Pairwise Transient Key (PTK)?
- A
The access point sends the ANonce to the client.
- B
The client sends the SNonce and the MIC to the access point.
- C
The access point and the client exchange group keys (GTK).
- D
The client confirms the MIC back to the access point.
Show answer and explanation
Correct answer: B
Explanation
The 4-way EAPOL handshake ensures secure communication between a wireless client and an access point by deriving a Pairwise Transient Key (PTK) used for encryption. The PTK is derived during the second step of the handshake when the client sends its SNonce and the MIC to the access point. Both the access point and the client use the ANonce, SNonce, and other agreed-upon parameters to calculate the same PTK. This ensures secure encryption for the wireless session.
- A. Incorrect.
This step (access point sending the ANonce) provides the access point's random value, but it does not derive the Pairwise Transient Key (PTK). It is required for the PTK derivation in the next step.
- B. Correct.
This step involves the client calculating and sending the SNonce (its own random value) and the Message Integrity Code (MIC). Using the ANonce, SNonce, and other parameters, both the client and the access point derive the same PTK during this step.
- C. Incorrect.
The exchange of group keys (GTK) occurs later in the handshake and is unrelated to the derivation of the Pairwise Transient Key (PTK).
- D. Incorrect.
The client confirming the MIC back to the access point is the final step of the handshake, but it is only meant to confirm the integrity of the handshake and does not derive the PTK.