group transient key (802.11i) (GTK)
The Group Transient Key(GTK) is part of the key management ofWLANs according to 802.11i.
The GTK key is generated by the access point by combining the Group Master Key( GMK) with a random number function(PRF) and distributed to the WLAN stations with the Key Encryption Key( KEK) via a four-way handshake.
The GTK key is used for secure multicast and broadcast transmission. All WLAN stations connected to the same access point( AP) share this key. In addition, other multicast/broadcast keys are derived from the GTK key.