Recall that we use both a public key system and a hash function when computing digital signatures. Given M and S = [h(M)](Alice) (1) Precisely how is a digital signature computed and verified? (2) Suppose that the public key system used to compute and verify signatures is insecure, but the hash function is secure. Show that you can forge signatures. (3) Suppose that the hash function used to compute and verify signatures is insecure, but the public key system is secure. Show that you can forge signatures.