Question: What is the primary purpose of deriving SRTP-MK, SRTP-MS, and SRTP-MKI from keys like GMK, PCK, and SPK in Mission Critical Push To Talk (MCPTT) media plane control?
Option 1: To authenticate user equipment (UE) for voice call setup in LMR systems.
Option 2: To encrypt media or floor control messages in SRTP for secure communication.
Option 3: To manage Quality of Service (QoS) parameters for prioritized traffic.
Option 4: To facilitate interworking between different Land Mobile Radio (LMR) systems.
Explanation: The derivation of SRTP-MK, SRTP-MS, and SRTP-MKI from keys such as GMK, PCK, and SPK is primarily for securing the communication in MCPTT. Specifically, these derived keys are used for the encryption of media or floor control messages transmitted via Secure Real-time Transport Protocol (SRTP), ensuring confidentiality and integrity of the mission-critical communications.