In a network user authentication system, a network user is identified for authentication purposes using the unique identifier for a dedicated physical communication line associated with the building in which the network user is located or a digital certificate which is associated with a secure component or communication line physically attached to a building. An authentication server initially verifies the identification of the dedicated communication line to be associated with a network service subscriber or issues a unique digital certificate to be associated with the dedicated communication line for authentication purposes. The digital certificate may be stored in a building gateway or in an edge site module which is connected to the secure components of a plurality of buildings and stores unique digital certificates for each building.