New outer bounds for wiretap channel with action-dependent states

The action-dependent states (ADSs) in wiretap channel is revisited. The transmitter aims to convey a confidential message to the receiver and protect it from the wiretapper as possible as he can. Actions are taken by the transmitter to influence the channel state information. For such a channel, Dai et al. first got an outer bound on the capacity-equivocation region which contains all the achievable transmission rates. We find a new outer bound and prove it is better than Dai´s in terms of approximating the maximum rate at which the confidential message can be transmitted in perfect secrecy. Furthermore, the new outer bound provides the engineer with a more precise target to achieve higher transmission rates in the capacity-equivocation region.