Which
of the following keys is derived from a preshared key and Extensible Authentication Protocol (EAP)?
A.
Pairwise Transient Key
B.
Group Temporal Key
C.
Private Key
D.
Pairwise Master Key
Explanation:
Pairwise Master Key (PMK) is the highest order key used within the 802.11i
amendment. It is derived directly from a preshared key and can
also be derived from the Extensible Authentication Protocol (EAP). It is a cryptography key that is
used to derive lower level keys.
Answer option B is incorrect. Group Temporal Key (GTK) is a random value that is assigned by the
broadcast/multicast source. It is used to
protect broadcast/multicast medium access control (MAC) protocol data units. It is derived from a
group master key (GMK).
Answer option A is incorrect. Pairwise Transient Key (PTK) is a 64-byte key that comprises the
following:
16 bytes of EAPOL-Key Confirmation Key (KCK): This key is used to compute MIC on WPA EAPOL Key
message.
16 bytes of EAPOL-Key Encryption Key (KEK): AP uses this key to encrypt additional data sent (in the
‘Key Data’ field) to the client.
16 bytes of Temporal Key (TK): This key is used to encrypt/decrypt unicast data packets.
8 bytes of Michael MIC Authenticator Tx Key: This key is used to compute MIC on unicast data
packets transmitted by the AP.8 bytes of Michael MIC Authenticator Rx Key: This key is used to compute MIC on unicast data
packets transmitted by the station.
Pairwise Transient Key is derived from the pairwise master key (PMK), Authenticator address (AA),
Supplicant address (SPA), Authenticator
nonce (A Nonce), and Supplicant nonce (S Nonce) using pseudo-random function (PRF).
Answer option C is incorrect. Private Key is not derived from a preshared key and Extensible
Authentication Protocol (EAP). This key is used in
cryptography techniques.