Byzantine agreement means achieving reliable broadcast on a point-to-point network of n processors, of which up to t may be maliciously faulty. A well-known result by Pease, Shostak, and Lamport says that perfect Byzantine agreement is only possible if t < n/3. In contrast, so-called authenticated protocols achieve Byzantine agreement for any t based on computational assumptions, typically the ...

This work addresses Byzantine vector consensus (BVC), wherein the input at each process is a d-dimensional vector of reals, and each process is expected to decide on a decision vector that is in the convex hull of the input vectors at the fault-free processes [3, 8]. The input vector at each process may also be viewed as a point in the d-dimensional Euclidean space R, where d > 0 is a finite in...

This thesis describes a Byzantine Fault Tolerant Coordination framework for Web Service Atomic Transaction (WS-AT). In the framework, all core services, including transaction activation, registration, and completion & distributed commit, are replicated and protected by Byzantine fault tolerance mechanisms. The traditional Two-Phase Commit (2PC) protocol is extended by a Byzantine fault tolerant...

Information-theoretic private information retrieval (PIR) protocols, such as those described by Chor et al. [5], provide a mechanism by which users can retrieve information from a database distributed across multiple servers in such a way that neither the servers nor an outside observer can determine the contents of the data being retrieved. More recent PIR protocols also provide protection aga...

This paper explores the problem of reaching approximate consensus in synchronous point-to-point networks, where each directed link of the underlying communication graph represents a communication channel between a pair of nodes. We adopt the transient Byzantine link failure model [15, 16], where an omniscient adversary controls a subset of the directed communication links, but the nodes are ass...

Byzantine-fault-tolerant service protocols like Q/U and FaB Paxos that optimistically order requests can provide increased efficiency and fault scalability. However, these protocols require n ≥ 5b + 1 servers (where b is the maximum number of faults tolerated), owing to their use of opaque Byzantine quorum systems; this is 2b more servers than required by some non-optimistic protocols. In this ...

After the Practical Byzantine Fault Tolerance work [2], the distributed systems literature has improved quality and performance of *BFT systems. Through this definition we address all the solutions, deriving from [2], for State Machine Replication (SMR) that are based on node active replication (usally 3f+1 replicas for f faults), and where servers are always synchronized on the set of operatio...

Distributed systems are everywhere. As everyday lives become more and more dependent on distributed systems, they are expected to withstand different kinds of failures. Different models of failures exist which aim at modeling network errors, hardware failures, soft errors, etc. This thesis concentrates on dealing with a combination of two different kinds of fault tolerance. The Byzantine failur...

Reliability and security of broadcasting is critical in Wireless Sensor Networks (WSNs). Since reliability and security compete for the same resources, we are interested in jointly solving for error control coding (to achieve reliability) and integrity for a broadcast scenario. We assume Byzantine attacks in which the adversary can compromise nodes and then drop (or modify) the legitimate packe...