Fair exchange protocols with anonymity and non-repudiation for payments

I declare that this assignment is all my own work and that I have acknowledged all quotations from the published or unpublished works of other people. I declare that I have also read the statements on plagiarism in Section 1 of the Regulations Governing Examination and Assessment Offences and in accordance with it I submit this project report as my own work. Abstract Our daily routine requires the establishment and control of a number of electronic transactions. In addition, the average global internet usage as well as the web activity per person has increased throughout the last few years and business today is reliant on open networks and systems that are always connected to support constant communication. As a result, IT is a critical component for all organisations and there is, often, no fall-back position in case of a failure. Network protocols are required to facilitate economic transactions and to usually protect the participants mutually in this process. Often, in this context, they are required to provide fairness, anonymity and non-repudiation. This thesis aims to illustrate the evolution of these protocols and point out situations where some existing protocol schemes have mismanaged their expected services or tried to provide them in a weaker sense. Additionally, we review the proposed formal methods for protocol analysis in order to identify their results as well as their limitations. The main goals of this dissertation, however, are the optimisation of the Netbill protocol in order to make it more secure and fairer as well as suggestions for its adaptation in the modern social networking and payment infrastructure.