Greetings. These are the proceedings of the 11th in our series of International Workshops on Security Protocols. Our theme this time was Where have all the Protocols gone? Once upon a time security protocols lived mainly in the network and transport layers. Now they increasingly hide in applications, or in specialised hardware. Does this trend lead to better security architectures, or is it an indication that we are addressing the wrong problems? The intention of the workshops is to provide a forum where incompletely workedoutideascanstimulatediscussion, openupnewlinesofinvestigation, and...

Here are the proceedings of the 12th International Workshop on Security P- tocols. We hope that you will enjoy them, and that they will cause you to think at least one heretical thought. Please write or e-mail and share it with us. Our theme this workshop was Authentic Privacy. Traditionally we have based authentication upon a rather strong notion of identity, and have then built other security services on top of authentication. Perhaps if we want a more nuanced notion of privacy, then we need to re-examine some of our assu- tions, particularly when attackers and defenders share the same...

This book constitutes the thoroughly refereed post-proceedings of the 15th International Workshop on Security Protocols, held in Brno, Czech Republic, in April 2007.The 15 revised full papers presented together with edited transcriptions of some of the discussions following the presentations have passed through multiple rounds of reviewing, revision, and selection. The topics addressed reflect the question "When is a Protocol Broken?" and how can it degrade gracefully in the face of partially broken assumptions, or how can it work under un(der)specified assumptions.