Suppose that we are attempting to construct a hash function using an encryption algorithm. Specifically, consider using RSA with a known key. In this scheme, a message consisting of a sequence of blocks (i. e., X = [B1 B2]) is processed as follows: (1) Encrypt the first block B1 using RSA; (2) XOR the RSA-encrypted ciphertext with the second block B2; and (3) encrypt in RSA again. To formally write, the hash output is given by