Question: During the GSM network operation phase, what is the primary purpose of the subscriber authentication key (Ki) stored on a personalized Subscriber Identity Module (SIM)?
Option 1: To encrypt voice and data transmissions between the User Equipment (UE) and the Base Transceiver Station (BTS)
Option 2: To authenticate the subscriber's identity to the GSM network, ensuring authorized access
Option 3: To generate cipher keys for secure communication between the SIM and the GSM network
Option 4: To control access to data stored on the SIM, restricting unauthorized functions
Explanation: The subscriber authentication key (Ki) is a crucial security attribute that plays a pivotal role in authenticating the subscriber's identity to the GSM network. This process ensures that only authorized users can access network services, thereby maintaining the security and integrity of the network. While Ki is indirectly related to encryption (via its use in generating cipher keys), its primary purpose as described in the context of GSM network operation is subscriber authentication.