1. /25 In the one-time pad encryption scheme for messages of length l, it can some- times happen that the key is the all-zero string (i.e., the key is 0'). In this case, the encryption of a message m is given by m o' and therefore the ciphertext is identical to the message! (a) Do you think the one-time pad scheme should be modified so that the all-zero key is not used? Explain. (b) Explain how it is possible that the one-time pad is perfectly secure even though the above situation can occur with non-zero probability. One to three sentences should be enough to answer each of these ques- tions