group cipher key (Tetra) (GCK)
Group Cipher Key (GCK) is an encryption key. Unlike the Derived Cipher Key(DCK), which is designed for encrypting individual conversations, the GCK key is used together with the Common Cipher Key( CCK) to encrypt group conversations.
The Group Cipher Key is used to encode the identity of the participants of a group and its participants on the air interface. All information - data and voice - on the traffic channel of Tetra's air interface is encrypted, as are theaddressing, signaling and data on the organization channel.