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 ED.Transforming M with the two keys Pa and Sa succes- sively,in either order,yields the message M back. In order to design a workable public-key cryptosystem,we must figure out how to create a system in which we can reveal a transformation P()without thereby revealing how to compute the corresponding inverse transformation S40).This task appears formidable,but we shall see how to accomplish it.PKC是什么？