Welcome once again to the proceedings of the International Security Protocols Workshop. The 15th workshop in our series took place in Brno, a beautiful city in the southeast of the Czech Republic famous also as setting for a blown espionage operation in “Tinker Tailor Soldier Spy.”

The theme of our deliberations this time was: “When is a Protocol Broken?”. We expect network protocols to degrade gracefully when their assumptions are broken, and even to recover from the error. Network protocol designers spend as much time thinking about recovery as about preventing failures in the first place, but we do not tend to think about recovering from a security protocol failure at all. Loss of confidentiality seems hard to reverse, but integrity and authentication are far more important security requirements in practice. How can (or should) we make security protocols more flexible at adapting to changed assumptions?

Our thanks are due to Vashek Matyas, Marek Kumpost and their colleagues from Masaryk University for the considerable work of organizing the event. Particular thanks once again to Lori Klimaszewska of the University of Cambridge Computing Service for transcribing the audio tapes, and to Vashek Matyas and Virgil Gligor for acting as members of the Programme Committee.