TLS $(2)(5-5-5$ points$)$: Consider the following attacks to internet security and describe how

each is countered by a particular feature of TLS$.$ Assume the size of the secret key used by

TLS is $128$ bits.

$($a$)$ Brute$-$Force Cryptanalytic Attack: An exhaustive search of the key space for a conventional

encryption algorithm.

$($b$)$ Known$-$Plaintext Dictionary Attack: Many messages contain predictable plaintext, such as

the $\text{'}$HTTP GET' command. An attacker constructs a dictionary containing every possi$-$

ble encryption of the known$-$plaintext message. The attacker can look up the ciphertext

in the dictionary to determine the secret key.

$($c$)$ Replay Attack: Earlier SSL messages are replayed.