Question: When reducing the effective key length of an Integrity Key (IK) in a telecom network, how should the remaining bits be handled to maintain security integrity?
Option 1: The least significant bits should be filled with random values to enhance entropy.
Option 2: The most significant bits should be set to zero, and the effective key information should be carried in the least significant bits.
Option 3: All bits should be rearranged in a specific pattern to maintain security without reducing the key's overall length.
Option 4: The remaining (least significant) bits shall be set to zero, with the most significant bits carrying the effective key information.
Explanation: This approach ensures that the essential (effective) part of the integrity key remains in the most significant bits, which typically hold more importance in cryptographic operations. Setting the remaining bits to zero prevents any potential information leakage or misuse of the reduced key length, maintaining the security integrity as specified for IK in telecom networks.