Second International Workshop on Formal Aspects in Security and Trust is an essential reference for both academic and professional researchers in the field of security and trust. Because of the complexity and scale of deployment of emerging ICT systems based on web service and grid computing concepts, we also need to develop new, scalable, and more flexible foundational models of pervasive security enforcement across organizational borders and in situations where there is high uncertainty about the identity and trustworthiness of the participating networked entites. On the other hand, the increasingly complex set of building activities sharing different resources but managed with different policies calls for new and business-enabling models of trust between members of virtual organizations and communities that span the boundaries of physical enterprises and loosely structured groups of individuals. The papers presented in this volume address the challenges posed by "ambient intelligence space" as a future paradigm and the need for a set of concepts, tools and methodologies to enable the user's trust and confidence in the underlying computing infrastructure. This state-of-the-art volume presents selected papers from the 2nd International Workshop on Formal Aspects in Security and Trust, held in conjuuctions with the 18th IFIP World Computer Congress, August 2004, in Toulouse, France. The collection will be important not only for computer security experts and researchers but also for teachers and adminstrators interested in security methodologies and research.