Strengthening Simmons´ bound on impersonation

Simmons´ lower bound on impersonation P₁⩾2 ^-I(M;E) where M and E denote the message and the encoding rule, respectively, is strengthened by maximizing over the source statistics and by allowing dependence between the message and the encoding rule. The authors show that a refinement of their argument, which removes the assumption of independence between E and the source state S, leads to an even stronger bound