Dining Cryptographers with 0.924 Verifiable Collision Resolution

The dining cryptographers protocol implements a multiple access channel in which senders and recipients are anonymous. A problem is that a malicious participant can disrupt communication by deliberately creating collisions. We propose a computationally secure dining cryptographers protocol with collision resolution that achieves a maximum stable throughput of 0.924 messages per round and which allows to easily detect disruptors.Comment: 11 pages, 3 figure

Dining Cryptographers are Practical

The dining cryptographers protocol provides information-theoretically secure sender and recipient untraceability. However, the protocol is considered to be impractical because a malicious participant may disrupt the communication. We propose an implementation which provides information-theoretical security for senders and recipients, and in which a disruptor with limited computational capabilities can easily be detected.Comment: 12 page

Quantum Anonymous Transmissions

We consider the problem of hiding sender and receiver of classical and quantum bits (qubits), even if all physical transmissions can be monitored. We present a quantum protocol for sending and receiving classical bits anonymously, which is completely traceless: it successfully prevents later reconstruction of the sender. We show that this is not possible classically. It appears that entangled quantum states are uniquely suited for traceless anonymous transmissions. We then extend this protocol to send and receive qubits anonymously. In the process we introduce a new primitive called anonymous entanglement, which may be useful in other contexts as well.Comment: 18 pages, LaTeX. Substantially updated version. To appear at ASIACRYPT '0

Unconditional Sender and Recipient Untraceability in spite of Active Attacks

. A protocol is described which allows to send and receive messages anonymously using an arbitrary communication network, and it is proved to be unconditionally secure. This improves a result by DAVID CHAUM: The DC-net guarantees the same, but on the assumption of a reliable broadcast network. Since unconditionally secure Byzantine Agreement cannot be achieved, such a reliable broadcast network cannot be realized by algorithmic means. The solution proposed here, the DC + -net, uses the DC-net, but replaces the reliable broadcast network by a fail-stop one. By choosing the keys necessary for the DC-net dependently on the previously broadcast messages, the fail-stop broadcast can be achieved unconditionally secure and without increasing the complexity of the DC-net significantly, using an arbitrary communication network. Categories and Subject Descriptors: C.2.0 [Computer-Communication Networks]: General --- Security and protection, E.3 [Data Encryption], F.2.1 [Analysis of Algorithms..

Privacy in Mobile Agent Systems: Untraceability

Agent based Internet environments are an interesting alternative to existing approaches of building software systems. The enabling feature of agents is that they allow software development based on the abstraction (a "metaphor") of elements of the real world. In other words, they allow building software systems, which work as human societies, in which members share products and services, cooperate or compete with each other. Organisational, behavioural and functional models etc applied into the systems can be copied from the real world. The growing interest in agent technologies in the European Union was expressed through the foundation of the Coordination Action for Agent-Based Computing, funded under the European Commission's Sixth Framework Programme (FP6). The action, called AgentLink III is run by the Information Society Technologies (IST) programme. The long-term goal of AgentLink is to put Europe at the leading edge of international competitiveness in this increasingly important area. According to AgentLink "Roadmap for Agent Based Computing"; agent-based systems are perceived as "one of the most vibrant and important areas of research and development to have emerged in information technology in recent years, underpinning many aspects of broader information society technologies"; However, with the emergence of the new paradigm, came also new challenges. One of them is that agent environments, especially those which allow for mobility of agents, are much more difficult to protect from intruders than conventional systems. Agent environments still lack sufficient and effective solutions to assure their security. The problem which till now has not been addressed sufficiently in agent-based systems is privacy, and particularly the anonymity of agent users. Although anonymity was studied extensively for traditional message-based communication for which during the past twenty five years various techniques have been proposed, for agent systems this problem has never been directly addressed. The research presented in this report aimed at filling this gap. This report summarises results of studies aiming at the identification of threats to privacy in agent-based systems and the methods of their protection.JRC.G.6-Sensors, radar technologies and cybersecurit

A Survey on Routing in Anonymous Communication Protocols

The Internet has undergone dramatic changes in the past 15 years, and now forms a global communication platform that billions of users rely on for their daily activities. While this transformation has brought tremendous benefits to society, it has also created new threats to online privacy, ranging from profiling of users for monetizing personal information to nearly omnipotent governmental surveillance. As a result, public interest in systems for anonymous communication has drastically increased. Several such systems have been proposed in the literature, each of which offers anonymity guarantees in different scenarios and under different assumptions, reflecting the plurality of approaches for how messages can be anonymously routed to their destination. Understanding this space of competing approaches with their different guarantees and assumptions is vital for users to understand the consequences of different design options. In this work, we survey previous research on designing, developing, and deploying systems for anonymous communication. To this end, we provide a taxonomy for clustering all prevalently considered approaches (including Mixnets, DC-nets, onion routing, and DHT-based protocols) with respect to their unique routing characteristics, deployability, and performance. This, in particular, encompasses the topological structure of the underlying network; the routing information that has to be made available to the initiator of the conversation; the underlying communication model; and performance-related indicators such as latency and communication layer. Our taxonomy and comparative assessment provide important insights about the differences between the existing classes of anonymous communication protocols, and it also helps to clarify the relationship between the routing characteristics of these protocols, and their performance and scalability

A Taxonomy for and Analysis of Anonymous Communications Networks

Any entity operating in cyberspace is susceptible to debilitating attacks. With cyber attacks intended to gather intelligence and disrupt communications rapidly replacing the threat of conventional and nuclear attacks, a new age of warfare is at hand. In 2003, the United States acknowledged that the speed and anonymity of cyber attacks makes distinguishing among the actions of terrorists, criminals, and nation states difficult. Even President Obama’s Cybersecurity Chief-elect recognizes the challenge of increasingly sophisticated cyber attacks. Now through April 2009, the White House is reviewing federal cyber initiatives to protect US citizen privacy rights. Indeed, the rising quantity and ubiquity of new surveillance technologies in cyberspace enables instant, undetectable, and unsolicited information collection about entities. Hence, anonymity and privacy are becoming increasingly important issues. Anonymization enables entities to protect their data and systems from a diverse set of cyber attacks and preserves privacy. This research provides a systematic analysis of anonymity degradation, preservation and elimination in cyberspace to enhance the security of information assets. This includes discovery/obfuscation of identities and actions of/from potential adversaries. First, novel taxonomies are developed for classifying and comparing well-established anonymous networking protocols. These expand the classical definition of anonymity and capture the peer-to-peer and mobile ad hoc anonymous protocol family relationships. Second, a unique synthesis of state-of-the-art anonymity metrics is provided. This significantly aids an entity’s ability to reliably measure changing anonymity levels; thereby, increasing their ability to defend against cyber attacks. Finally, a novel epistemic-based mathematical model is created to characterize how an adversary reasons with knowledge to degrade anonymity. This offers multiple anonymity property representations and well-defined logical proofs to ensure the accuracy and correctness of current and future anonymous network protocol design

Unconditional Sender and Recipient Untraceability in spite of Active Attacks - Some Remarks

...................................................................................................1 2 Unconditional sender untraceability.............................................................2 2.1 Superposed sending ................................................................................2 2.2 Efficient and anonymity preserving multi-access protocols....................................5 2.3 Some remarks on sender untraceability schemes................................................8 3 Active attacks on untraceability ...................................................................9 3.1 Reliable broadcast................................................................................. 10 3.2 Fail-stop broadcast................................................................................ 11 3.2.1 Comparison of input characters ....................................................... 11 3.2.2 Message dependent key generation ...........................................