We now show how an attack with chosen ciphertext can be used to break an RSAencryption. $1.$ Show that the multiplicative property holds for RSA, i$.$e$.,$ show that the product of two ciphertexts is equal to the encryption of the product of the two respective plaintexts. $2027$ TheRSACryptosystem $2.$ This property can under certain circumstances lead to an attack. Assume that Bob first receives an encrypted message y$1$ from Alice which Oscar obtains by eavesdropping. At a later point in time, we assume that Oscar can send an inno cent looking ciphertext y$2$ to Bob, and that Oscar can obtain the decryption of y$2.$ In practice this could, for instance, happen if Oscar manages to hack into Bob$$s system such that he can get access to decrypted plaintext for a limited period of time.