Client adapter and method simplify security deployment in an EPN, including the shared services electrical power lines of a premises. With direct coupling, piggybacked adapter receives network signals and electrical from EPN-connected first adapter through a shared medium port. An authenticating adapter exchanges security management services and information with supplicant adapter. Two or more adapters may be piggybacked. Piggybacked adapters exchange security management service information without rogue intrusion. Exchanged information, stored, is later used to communicate securely. Defined adjacency (neighborhood) information can be exchanged, and a neighborhood established on an EPN, where one authorized neighbors securely communicate.