In one embodiment, the present invention includes a method for secure data exchange between an external network and an internal network (1 and 2) via a transaction interface (3), in which an external user can undertake predetermined data transactions within the internal network (2). An interface server (7) and interface memory (11) may be coupled between an external network and an internal network. The present invention discloses security techniquest that may be used, including encryption, request processing, and checking. In one embodiment, a first firewall is coupled between the external network and the interface server and a second firewall is coupled between the interface server and the internal network.