PKC是什么？ The public and secret keys for any participant are a"matched pair"in that they specify functions that are inverses of each other.That is, M SA(PA(M)), (31.35) M =Pa(SA(M)) (31.36) for any message M E D.Transforming M with the two keys Pa and S4 succes- sively,in either order,yields the message M back.PKC是什么？