As more resources are added to computer networks, and as more vendors look to the World Wide Web as a viable marketplace, the importance of being able to restrict access and to insure some kind of acceptable behavior even in the presence of malicious intruders becomes paramount. People have looked to cryptography to help solve many of these problems. However, cryptography itself is only a tool....

Security protocols must be designed to ensure the integrity of electronic communications between participants. Although the design of secure communication protocols has improved over the years the tasks of building and validating these protocols remain inherently difficult. Security protocols may fail due to unintended use, malicious attacks, incorrect logic or incorrect transition from design ...

We investigate the security properties of isotropic channels, broadcast media in which a receiver cannot reliably determine whether a message originated from any particular sender and a sender cannot reliably direct a message away from any particular receiver. We show that perfect isotropism implies perfect (informationtheoretic) secrecy, and that asymptotically close to perfect secrecy can be ...

i Acknowledgements I would like to thank my supervisor, Professor Paulo Mateus, for his guidance, support and constant motivation throughout this year and especially on the final stage of this work. I would also like to thank Professor Luca Viganò for his support and for his talks here in Lisbon that provided the first interest for Security Protocol Model Checking and inspiration for this work....

State-of-the-art authenticated key exchange (AKE) protocols are proven secure in game-based security models. These models have considerably evolved in strength from the originalBellare-Rogaway model. However, so far only informal impossibility results, which suggestthat no protocol can be secure against stronger adversaries, have been sketched. At the sametime, there are many di...

The concept of a ceremony as an extension of network and security protocols was introduced by Ellison. There are no currently available methods or tools to check correctness of the properties in such ceremonies. The potential application for security ceremonies are vast and fill gaps left by strong assumptions in security protocols. Assumptions include the provision of cryptographic keys and co...

We live in time of computers and scientific and technological progress but this time is also marked with many attacks on big Internet companies. So with expand of Internet people start to protect information that they exchange through Internet. In the Internet world it is necessary for systems as Internet banking, Internet shopping or e-commerce to secure private information that are transferre...

We introduce χ-Spaces, a domain specific programming language tailored to the development of security protocols. χ-Spaces has a rigorous formal semantics which allows us to reason about the actual implementation of security protocols. In this manner we fill-in the gap between the formal specification of a protocol and its actual implementation.