Question: In a GSM network, what is the significance of setting Byte 9 to '07' in the EFKc (GSM Ciphering key Kc) file during conformance testing for User Equipment (UE)?
Option 1: To indicate the UE's support for both ciphering and integrity protection.
Option 2: To signal the start of an authentication attempt to the network.
Option 3: To denote that no GSM Ciphering key Kc is available at the start of a test.
Option 4: To confirm successful decryption of previously transmitted data.
Explanation: Setting Byte 9 to '07' in the EFKc file specifically indicates to the testing environment that, initially, no valid GSM Ciphering key Kc is available on the User Equipment. This state reflects a pre-authentication scenario, allowing for the simulation of key generation and update processes following a successful authentication attempt, thus ensuring comprehensive conformance testing.