Answer:
a ciphertext-only attack
Step-by-step explanation:
Based on the scenario being described within the question it can be said that the type of attack being performed is known as a ciphertext-only attack . This is an attack model in which the attacker in which the attacker gains access to one set of ciphertexts with the main goal of forcing the server to renegotiate the encryption being used down to a weaker cipher and hopefully deducing the plaintexts or even the key.