(a) A signature ?(m) = (?1, ?2) in the DSA is not allowed to have ?2 = 0. Show that if a message were signed with a signature in which ?2 = 0, then it would be easy for an adversary to compute the secret key x. (b) A signature in the DSA is not allowed to have ?1 = 0. Show that if a signature in which ?1 = 0 is known, then the value of y used in that signature can be determined. Given that value of y, show that it is now possible to forge a signature (with ?1 = 0) for any desired message (i.e., a selective forgery can be carried out).