| Exam 200-355 | Question id=2349 | Configuration of Client Connectivity |
When the pre-shared key authentication method is used for WPA or WPA2, for which two functions is the pre-shared key used?
| A. |
to act as the Group Transient Key during the bidirectional handshake | |
| B. |
to act as the Pairwise Master Key during the bidirectional handshake | |
| C. |
to derive the nonce at each side of the exchange | |
| D. |
to derive the Pairwise Transient Key |
Pre-shared key (PSK) is computed based on a shared secret (pass- phrase) which was previously shared between the two parties using some secure channel before it needs to be used. It is used to identify both peers to each other.
The strength of the PSK depends on the strength of the pass-phrase. The strength of the PSK is important, because WPA-Personal (and WPA2-Personal) use the PSK as the Pairwise Master Key (PMK). The PMK, when combined with two random numbers (nonces) and the MAC addresses of the access point and the client, produces a unique Pairwise Transient Key (PTK) that secures the unicast traffic between the access point and the client. A new PTK is produced each time a client connects to the access point.