question: What is the main difference between key-based security and keyless security in information-theoretic secrecy? option 1: Keyless security guarantees perfect secrecy, while key-based security guarantees strong secrecy. option 2: Keyless security uses secret keys to ensure confidentiality, while key-based security does not use secret keys. option 3: Key-based security guarantees perfect secrecy, while keyless security guarantees strong secrecy. option 4: Key-based security uses secret keys to ensure confidentiality, while keyless security does not use secret keys. option 5: Key-based security guarantees secure communication under any state that may occur, while keyless security guarantees secure communication by hiding the secure message across different fading states. 