The Cambridge International Workshop on Security Protocols has now run for eight years. Each year we set a theme, focusing upon a speci?c aspect of security protocols, and invite position papers. Anybody is welcome to send us a position paper (yes, you are invited) and we don't insist they relate to the current theme in an obvious way. In our experience, the emergence of the theme as a unifying threadtakesplaceduringthediscussionsattheworkshopitself.Theonlyground rule is that position papers should formulate an approach to some unresolved issues, rather than being a description of a ?nished piece of work. Whentheparticipantsmeet,wetrytofocusthediscussionsupontheconc- tual issues which emerge. Security protocols link naturally to many other areas of Computer Science, and deep water can be reached very quickly. Afterwards, we invite participants to re-draft their position papers in a way which exposes the emergent issues but leaves open the way to their further development. We also prepare written transcripts of the recorded discussions. These are edited (in some cases very heavily) to illustrate the way in which the di?erent arguments and perspectives have interacted. We publish these proceedings as an invitation to the research community. Although many interesting results ?rst see the light of day in a volume of our proceedings, laying claim to these is not our primary purpose of publication. Rather, we bring our discussions and insights to a wider audience in order to suggest new lines of investigation which the community may fruitfully pursue.