6.Block cipher is more complicated to implement than stream cipher and thus achieves a higher level of security, i.e., harder to break. (True/False)

7.The ciphertext-only attack is the easiest to defend against as the attacker knows the least information comparing with other types of attack on encrypted messages. (True/False)

8.An intelligent search approach involves trying every possible key until an intelligible translation of the ciphertext into plaintext is obtained. (True/False)

9.The Feistel structure is a particular example of the more general structure used by all symmetric block ciphers. (True/False)

10.When designing a biometric authentication-based system, achieving low levels of false match rate and false non-match rate simultaneously is difficult, as these two goals contradict with each other. (True/False)