"In this project I will investigate four interrelated topics in cryptography from both a theoretical and practical perspective. Each topic is chosen such that it not only provides a testing ground for more general ideas, but it also is grounded in specific examples which can help guide the general principles. Each topic has the potential to make dramatic advances, both on the subject of cryptography itself and how it is used and deployed in the real world.We will be investigating application domains as diverse as cloud computing, electronic voting, protocols for trusted computing and privacy preserving methodologies. Each topic will be tackled however with common tools of provable security, and testing via implementation. In addition we aim to extend the tool box of techniques available to the cryptographer in terms of analysis and development methodologies, by being guided by the above application domains.This research will have a transformative affect on the subject of cryptography and how it is deployed in the real world. We aim to demonstrate that previous “blue-skies” research can have direct practical benefit in applications, by researching in a pipeline of theory-to-practice. In addition we aim to feed back the practical knowledge learned into new theoretical models which capture more realistically the scenarios faced in practice, thus making the pipeline two-way.Finally, the proposal builds on a wealth of knowledge and experience built up at Bristol over the last ten years in these explicit sub-areas. My group at Bristol is not only the best place to execute this ambitious programme of work, but, due to the unique combination of theoretical and practical perspectives we offer, possibly the only place capable of working on these interrelated fronts."