Question: What is the primary security requirement for the network authentication function f1, specifically for the input parameters (K; SQN, RAND, AMF) to produce MAC-A (or XMAC-A)?
Option 1: Ensuring K can be easily derived from RAND and SQN for efficient authentication.
Option 2: Guaranteeing a fixed output (MAC-A or XMAC-A) regardless of variations in SQN and RAND.
Option 3: Allowing AMF to independently authenticate without relying on K.
Option 4: Making it computationally infeasible to derive K from knowledge of RAND, SQN, AMF, and MAC-A (or XMAC-A).
Explanation: This option aligns with the fundamental principle of cryptographic security for authentication functions, ensuring that even with full knowledge of the non-secret inputs (RAND, SQN, AMF) and the output (MAC-A or XMAC-A), an attacker cannot feasibly compute the secret key (K). This prevents unauthorized access and maintains the integrity of the network authentication process.