free c.
(* EKE - RSA

A -> B : A, { pkA }_kP
B -> A : { { K }_pkA }_ kP
A -> B : { Na }_K
B -> A : { Na, Nb }_K
A -> B : { Nb }_K

*)

(* Shared-key cryptography *)

fun encrypt/2.
reduc decrypt(encrypt(m,k),k) = m.
