15 research outputs found
On Byzantine Broadcast in Loosely Connected Networks
We consider the problem of reliably broadcasting information in a multihop
asynchronous network that is subject to Byzantine failures. Most existing
approaches give conditions for perfect reliable broadcast (all correct nodes
deliver the authentic message and nothing else), but they require a highly
connected network. An approach giving only probabilistic guarantees (correct
nodes deliver the authentic message with high probability) was recently
proposed for loosely connected networks, such as grids and tori. Yet, the
proposed solution requires a specific initialization (that includes global
knowledge) of each node, which may be difficult or impossible to guarantee in
self-organizing networks - for instance, a wireless sensor network, especially
if they are prone to Byzantine failures. In this paper, we propose a new
protocol offering guarantees for loosely connected networks that does not
require such global knowledge dependent initialization. In more details, we
give a methodology to determine whether a set of nodes will always deliver the
authentic message, in any execution. Then, we give conditions for perfect
reliable broadcast in a torus network. Finally, we provide experimental
evaluation for our solution, and determine the number of randomly distributed
Byzantine failures than can be tolerated, for a given correct broadcast
probability.Comment: 1
Reliable Communication in a Dynamic Network in the Presence of Byzantine Faults
We consider the following problem: two nodes want to reliably communicate in
a dynamic multihop network where some nodes have been compromised, and may have
a totally arbitrary and unpredictable behavior. These nodes are called
Byzantine. We consider the two cases where cryptography is available and not
available. We prove the necessary and sufficient condition (that is, the
weakest possible condition) to ensure reliable communication in this context.
Our proof is constructive, as we provide Byzantine-resilient algorithms for
reliable communication that are optimal with respect to our impossibility
results. In a second part, we investigate the impact of our conditions in three
case studies: participants interacting in a conference, robots moving on a grid
and agents in the subway. Our simulations indicate a clear benefit of using our
algorithms for reliable communication in those contexts
Parameterizable Byzantine Broadcast in Loosely Connected Networks
We consider the problem of reliably broadcasting information in a multihop
asynchronous network, despite the presence of Byzantine failures: some nodes
are malicious and behave arbitrarly. We focus on non-cryptographic solutions.
Most existing approaches give conditions for perfect reliable broadcast (all
correct nodes deliver the good information), but require a highly connected
network. A probabilistic approach was recently proposed for loosely connected
networks: the Byzantine failures are randomly distributed, and the correct
nodes deliver the good information with high probability. A first solution
require the nodes to initially know their position on the network, which may be
difficult or impossible in self-organizing or dynamic networks. A second
solution relaxed this hypothesis but has much weaker Byzantine tolerance
guarantees. In this paper, we propose a parameterizable broadcast protocol that
does not require nodes to have any knowledge about the network. We give a
deterministic technique to compute a set of nodes that always deliver authentic
information, for a given set of Byzantine failures. Then, we use this technique
to experimentally evaluate our protocol, and show that it significantely
outperforms previous solutions with the same hypotheses. Important disclaimer:
these results have NOT yet been published in an international conference or
journal. This is just a technical report presenting intermediary and incomplete
results. A generalized version of these results may be under submission
Confinement de fautes Byzantines dans les réseaux multi-sauts asynchrones
International audienceOn considÚre le problÚme de la diffusion d'information dans un réseau multi-saut asynchrone, en présence de fautes Byzantines: certains noeuds du réseau peuvent adopter un comportement arbitraire. Les protocoles de diffusion existant reposent sur une forte connectivité du réseau. Dans cet article, nous proposons un protocole adapté aux réseaux faiblement connecté. Nous donnons une méthodologie pour construire un ensemble de noeuds fiable, et évaluons ses performances sur une topologie de grille, avec des fautes Byzantines aléatoirement distribuées
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
Self-Stabilizing Byzantine Resilient Topology Discovery and Message Delivery
Traditional Byzantine resilient algorithms use vertex disjoint paths to ensure message delivery in the presence of up to f Byzantine nodes. The question of how these paths are identified is related to the fundamental problem of topology discovery. Distributed algorithms for topology discovery cope with a never ending task, dealing with frequent changes in the network topology and unpredictable transient faults. Therefore, algorithms for topology discovery should be self-stabilizing to ensure convergence of the topology information following any such unpredictable sequence of events. We present the first such algorithm that can cope with Byzantine nodes. Starting in an arbitrary global state, and in the presence of f Byzantine nodes, each node is eventually aware of all the other non-Byzantine nodes and their connecting communication links. Using the topology information, nodes can, for example, route messages across the network and deliver messages from one end user to another. We present the first deterministic, cryptographic-assumptions-free, self-stabilizing, Byzantine-resilient algorithms for network topology discovery and end-to-end message delivery. We also consider the task of r-neighborhood discovery for the case in which and the degree of nodes are bounded by constants. The use of r-neighborhood discovery facilitates polynomial time, communication and space solutions for the above tasks. The obtained algorithms can be used to authenticate parties, in particular during the establishment of private secrets, thus forming public key schemes that are resistant to man-in-the-middle attacks of the compromised Byzantine nodes. A polynomial and efficient end-to-end algorithm that is based on the established private secrets can be employed in between periodical re-establishments of the secrets
Of Malicious Motes and Suspicious Sensors
How efficiently can a malicious device disrupt communication in a wireless network? Imagine a basic game involving two honest players, Alice and Bob, who want to exchange information, and an adversary, Collin, who can disrupt communication using a limited budget of B broadcasts. How long can Collin delay Alice and Bob from communicating? In fact, the trials and tribulations of Alice and Bob capture the fundamental difficulty shared by several n-player problems, including reliable broadcast, leader election, static k-selection, and t-resilient consensus. We provide round complexity lower boundsâand (nearly) tight upper boundsâfor each of those problems. These results imply bounds on adversarial efficiency, which we analyze in terms of jamming gain and disruption-free 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