On the Privacy and Security of Internet Communications: an Attempt to Fix Some of the Current Conceptual and Practical Issues

Today’s technical and legal landscape present formidable challenges to privacy. The disclosure of private data has become commonplace due to carelessness, theft or legal actions. Increasing reliance on network services causes sensitive data to be cached, copied, and archived by third parties, often without users’ knowledge or control. Cloud computing and ubiquitous computing are becoming an integral part of everyday life. The social consequences of this development are profound, and the technological challenges posed by these paradigms are complex and interesting. While the lack of privacy has, in principle, always characterized Internet communications, never before Internet communication has revealed so much about the personal tastes of its users. This is because never before Internet has contained so much personal user data. This thesis is divided into four parts. The first part introduces different aspects of privacy that are dealt in this thesis, detailing the current privacy and anonymity landscape. The second part of this dissertation focuses on theoretical aspects, introducing new cryptographic algorithms and providing a formal analysis of their security. More specifically it presents the first anonymous identity-based encryption scheme based on the quadratic residuosity problem, which can be used as an anonymous encryption tool or as the fundamental block for a keyword searchable encryption scheme. This thesis also introduce the first sender and receiver public key deniable encryption scheme, which allows communicating parties to deny the existence of an encrypted message even in presence of an adversary who can coerce them into giving up their secret information. The third part of this thesis analyzes several network-related aspects of anonymity and privacy, and provides practical solutions. First it introduces a new pseudonymous authentication and authorization systems, which solves several problems related to digital certificates. Then it focuses on cloud storage presenting DenFS, the first shared deniable file system. Finally it illustrates an anonymous peer-to-peer file sharing system based on network coding, for which it provides efficient strategy for packet verification. The last part concludes this work and discusses some of the open problems. To my wife Miharu, for teaching me every day what is really important in life Every man should know that his conversations, his correspondence, and his personal life are private. (Lyndon B. Johnson)