The secure trust relationship between communicating programs is established at any policy defined level down to individual program instances. Policy enforcement modules installed on host computer systems support qualified encrypted communications channels between discretely selected program instances. Program instances are qualified to establish communication channels, each defined by a unique session encryption key, based on an evaluation of security data including the individual process execution contexts, user authorizations, and access attributes of the program instances. A security appliance server performs the policy-based qualification based on a mutually interdependent evaluation of the security data for both the communications channel source and target program instances.