The increasing relevance of security to real-life applications, such as electronic commerce and Internet banking, is attested by the fast-growing number of - search groups, events, conferences, and summer schools that address the study of foundations for the analysis and the design of security aspects. The “Int- national School on Foundations of Security Analysis and Design” (FOSAD, see http://www.sti.uniurb.it/events/fosad/)has been one of the foremost events - tablished with the goal of disseminating knowledge in this critical area, especially for young researchers approaching the field and graduate students coming from less-favoured and non-leading countries. The FOSAD school is held annually at the Residential Centre of Bertinoro (http://www.ceub.it/), in the fascinating setting of a former convent and ep- copal fortress that has been transformed into a modern conference facility with computing services and Internet access. Since the first school, in 2000, FOSAD has attracted more than 250 participants and 50 lecturers from allover the world. A collection of tutorial lectures from FOSAD 2000 was published in Springer’s LNCS volume 2171. Some of the tutorials given at the two successive schools (FOSAD 2001 and 2002) are gathered in a second volume, LNCS 2946. To c- tinue this tradition, the present volume collects a set of tutorials fromthe fourth FOSAD, held in 2004, and from FOSAD 2005.