Question: What happens to the SN Counter value when a new AS root key, KNG-RAN, is established in the associated 5G AS security context?
Option 1: The SN Counter value remains unchanged.
Option 2: The SN Counter value is incremented by 1.
Option 3: The SN Counter value is set to '0'.
Option 4: The SN Counter value is reset to a random number.
Explanation: According to the security architecture and procedures for 5G System, when a new AS root key, KNG-RAN, is established in the associated 5G AS security context, the Mobile Network (MN) shall set the SN Counter to '0'. This ensures that the Key Security Nonce (KSN) derivation starts with a fresh input.