Multi-hop Byzantine reliable broadcast with honest dealer made practical

We revisit Byzantine tolerant reliable broadcast with honest dealer algorithms in multi-hop networks. To tolerate Byzantine faulty nodes arbitrarily spread over the network, previous solutions require a factorial number of messages to be sent over the network if the messages are not authenticated (e.g., digital signatures are not available). We propose modifications that preserve the safety and liveness properties of the original unauthenticated protocols, while highly decreasing their observed message complexity when simulated on several classes of graph topologies, potentially opening to their employment

Une méthode efficace pour éviter la propagation des fake news

National audienceNous considérons un réseau utilisé pour propager des informations. Les sources d'informations fiables souhaitent que leurs messages parviennent à tous les récipiendaires sans altération. Cependant, des participants malveillants tentent de miner la crédibilité des sources en envoyant de faux messages qui semblent provenir des mêmes sources : des fake news. Les solutions existantes à ce problème difficile dans un contexte réparti sont basées sur la redondance des chemins d'information noeuds-disjoints, et nécessitent pour être mises en oeuvre un nombre factoriel (en la taille du réseau) de messages disséminés, et de calcul à chaque réception d'un message. Nous proposons des optimisations qui réduisent en pratique cette complexité, et nous montrons par des expérimentations sur différents types de réseaux que plusieurs ordres de grandeur peuvent être ainsi gagnés

Bloquer efficacement les "fake news" sans connaître leurs réseaux de propagation

National audienceNous considérons un réseau utilisé pour propager des informations. Ce réseau (modélisé à travers un graphe) n'est pas complet et certains nœuds doivent s'appuyer sur des intermédiaires pour communiquer. Cependant, la topologie du réseau est inconnue et un nombre limité de participants malveillants tentent de miner la crédibilité des sources d'information en envoyant de faux messages qui semblent provenir des mêmes sources : des "fake news". Les solutions existantes qui contrecarrent la diffusion de fake news dans ce scénario sont basées sur l'analyse des chemins parcourus par les informations dans le réseau, mais celles-ci peuvent disséminer un nombre factoriel de messages (en la taille du réseau) et nécessiter des calculs complexes aux nœuds pour vérifier l'authenticité de chaque information diffusée. Nous identifions des ensembles de conditions qui permettent une communication fiable entre les nœuds et de complexité optimale, en exploitant une reconstruction partielle de la topologie du réseau

Multi-hop Byzantine Reliable Broadcast with Honest Dealer Made Practical

We revisit Byzantine tolerant reliable broadcast with honest dealer algorithms in multi-hop networks. To tolerate Byzantine faulty nodes arbitrarily spread over the network, previous solutions require a factorial number of messages to be sent over the network if the messages are not authenticated (e.g. digital signatures are not available). We propose modifications that preserve the safety and liveness properties of the original unauthenticated protocols, while highly decreasing their observed message complexity when simulated on several classes of graph topologies, potentially opening to their employment

Boosting the Efficiency of Byzantine-tolerant Reliable Communication

Reliable communication is a fundamental primitive in distributed systems prone to Byzantine (i.e. arbitrary, and possibly malicious) failures to guarantee integrity, delivery and authorship of messages exchanged between processes. Its practical adoption strongly depends on the system assumptions. One of the most general (and hence versatile) such hypothesis assumes a set of processes interconnected through an unknown communication network of reliable and authenticated links, and an upper bound on the number of Byzantine faulty processes that may be present in the system, known to all participants. To this date, implementing a reliable communication service in such an environment may be expensive, both in terms of message complexity and computational complexity, unless the topology of the network is known. The target of this work is to combine the Byzantine fault-tolerant topol-ogy reconstruction with a reliable communication primitive, aiming to boost the efficiency of the reliable communication service component after an initial (expensive) phase where the topology is partially reconstructed. We characterize the sets of assumptions that make our objective achievable, and we propose a solution that, after an initialization phase, guarantees reliable communication with optimal message complexity and optimal delivery complexity

Multi-hop Byzantine Reliable Broadcast with Honest Dealer Made Practical

We revisit Byzantine tolerant reliable broadcast with honest dealer algorithms in multi-hop networks. To tolerate Byzantine faulty nodes arbitrarily spread over the network, previous solutions require a factorial number of messages to be sent over the network if the messages are not authenticated (e.g. digital signatures are not available). We propose modifications that preserve the safety and liveness properties of the original unauthenticated protocols, while highly decreasing their observed message complexity when simulated on several classes of graph topologies, potentially opening to their employment

Tractable reliable communication in compromised networks

Reliable communication is a fundamental primitive in distributed systems prone to Byzantine (i.e. arbitrary, and possibly malicious) failures to guarantee the integrity, delivery, and authorship of the messages exchanged between processes. Its practical adoption strongly depends on the system assumptions. Several solutions have been proposed so far in the literature implementing such a primitive, but some lack in scalability and/or demand topological network conditions computationally hard to be verified. This thesis aims to investigate and address some of the open problems and challenges implementing such a communication primitive. Specifically, we analyze how a reliable communication primitive can be implemented in 1) a static distributed system where a subset of processes is compromised, 2) a dynamic distributed system where part of the processes is Byzantine faulty, and 3) a static distributed system where every process can be compromised and recover. We define several more efficient protocols and we characterize alternative network conditions guaranteeing their correctness