Question 2. (30 points) Data owner Bob wants to store, at cloud service provider Alice, a file that contains a huge two-dimensional table (too large to fit in Bob's cell phone), whose entries Bob will access remotely one at a time from his cell phone. The table's entries contain items that are either confidential, or non-confidential: The latter are not encrypted, but the former are encrypted individually (because they are accessed one at a time, it is desirable to encrypt them separately from each other). Bob does the encryption of each item using a deterministic private-key scheme in which the plaintext space, ciphertext space, and key space are the set of all 128 bit strings; functions Enc and Dec require inputs of length exactly 128 bits, and produce outputs of same 128 bit length. Suppose every item to be individually encrypted is 160 bits long, and it is a requirement that the encrypted version stored in the table should be of exactly the same length as the plaintext (namely, 160 bits). It is acceptable if encryption (respectively, decryption) of a 160-bit item requires two uses of the 128-bit encryption function Enc (decryption Dec), as long as the encrypted version stored in the table is only 160 bits long (therefore padding a 160-bit item to make its length 256 bits and then encrypting each half separately is not acceptable, as it would result in using 256 bits of storage per item at the remote server). Give a solution to this problem, by describing in detail (i) how 160 bit item is encrypted (using Enc twice) before the resulting 160 ciphertext bits are stored in Alice's server (make sure you explain the exact nature of those 160 bits); and (ii) how the stored 160 bits of a confidential item are decrypted in Bob's cell phone after being retrieved from Alice's server (using Dec twice)