Enforcement and trust are opposite concepts in information security. This chapter reflects on the paradigm shift from traditional concepts of access control and policy enforcement toward to de-centralised methods for establishing trust between loosely connected entities. By delegating parts of enforcement tasks to trusted elements dispersed in a system, transitive trust relationships can be established. This is the most advanced evolvement of the organisational method of separation of duties within IT-security. The technological basis for trust in systems - Trusted Computing platforms - is described on conceptual levels allowing comparison with other top-level security concepts and mapping to application domains. Important applications in modern information systems and networks are e xhibited.