(3 pts) The CFB mode (cipher feedback mode) uses a block cipher as a stream cipher by XORing the plaintext with the keystream. Like other modes we have seen, there is an initial block (CO) that is generated at random by Alice and sent to Bob in the clear, Below is the equation describing the encryption algorithm. The inputs are the plaintext blocks P1, P2,... , CO is the initial block, and K is the key common to Alice and Bob. E is the block encryption function. The outputs are C1, C2,. S. Write equations far the decryption function, giving the plaintext blocks P1, P2,.. in terms of cO, CI