Question 28 - HPE6-A85 discussion

The part of WPA Key Hierarchy that is used to encrypt and/or decrypt data is Pairwise Temporal Key (PTK). PTK is a key that is derived from PMK Pairwise Master Key (PMK) is a key that is derived from PSK Pre-shared Key (PSK) is a key that is shared between two parties before communication begins , ANonce Authenticator Nonce (ANonce) is a random number generated by an authenticator (a device that controls access to network resources, such as an AP) , SNonce Supplicant Nonce (SNonce) is a random number generated by supplicant (a device that wants to access network resources, such as an STA) , AA Authenticator Address (AA) is MAC address of authenticator , SA Supplicant Address (SA) is MAC address of supplicant using Pseudo-Random Function (PRF). PTK consists of four subkeys:

KCK Key Confirmation Key (KCK) is used for message integrity check

KEK Key Encryption Key (KEK) is used for encryption key distribution

TK Temporal Key (TK) is used for data encryption

MIC Message Integrity Code (MIC) key

The subkey that is specifically used for data encryption is TK Temporal Key (TK). TK is also known as Pairwise Transient Key (PTK). TK changes periodically during communication based on time or number of packets transmitted.

The other options are not part of WPA Key Hierarchy because:

PMK: PMK is not part of WPA Key Hierarchy, but rather an input for deriving PTK.

KCK: KCK is part of WPA Key Hierarchy, but it is not used for data encryption, but rather for message integrity check.

Nonce: Nonce is not part of WPA Key Hierarchy, but rather an input for deriving PTK.