19 research outputs found
Good-case Early-Stopping Latency of Synchronous Byzantine Reliable Broadcast: The Deterministic Case (Extended Version)
This paper considers the good-case latency of Byzantine Reliable Broadcast
(BRB), i.e., the time taken by correct processes to deliver a message when the
initial sender is correct. This time plays a crucial role in the performance of
practical distributed systems. Although significant strides have been made in
recent years on this question, progress has mainly focused on either
asynchronous or randomized algorithms. By contrast, the good-case latency of
deterministic synchronous BRB under a majority of Byzantine faults has been
little studied. In particular, it was not known whether a goodcase latency
below the worst-case bound of t + 1 rounds could be obtained. This work answers
this open question positively and proposes a deterministic synchronous
Byzantine reliable broadcast that achieves a good-case latency of max(2, t + 3
-- c) rounds, where t is the upper bound on the number of Byzantine processes
and c the number of effectively correct processes
Context Adaptive Cooperation
Reliable broadcast and consensus are the two pillars that support a lot of
non-trivial fault-tolerant distributed middleware and fault-tolerant
distributed systems. While they have close definitions, they strongly differ in
the underlying assumptions needed to implement each of them. Reliable broadcast
can be implemented in asynchronous systems in the presence of crash or
Byzantine failures while Consensus cannot. This key difference stems from the
fact that consensus involves synchronization between multiple processes that
concurrently propose values, while reliable broadcast simply involves
delivering a message from a predefined sender. This paper strikes a balance
between these two agreement abstractions in the presence of Byzantine failures.
It proposes CAC, a novel agreement abstraction that enables multiple processes
to broadcast messages simultaneously, while guaranteeing that (despite
potential conflicts, asynchrony, and Byzantine behaviors) the non-faulty
processes will agree on messages deliveries. We show that this novel
abstraction can enable more efficient algorithms for a variety of applications
(such as money transfer where several people can share a same account). This is
obtained by focusing the need for synchronization only on the processes that
actually need to synchronize
A Modular Approach to Construct Signature-Free BRB Algorithms under a Message Adversary
International audienceThis paper explores how reliable broadcast can be implemented without signatures when facing a dual adversary that can both corrupt processes and remove messages. More precisely, we consider an asynchronous n-process message-passing system in which up to t processes are Byzantine and where, at the network level, for each message broadcast by a correct process, an adversary can prevent up to d processes from receiving it (the integer d defines the power of the message adversary). So, unlike previous works, this work considers that not only can computing entities be faulty (Byzantine processes), but, in addition, that the network can also lose messages. To this end, the paper adopts a modular strategy and first introduces a new basic communication abstraction denoted k2-cast, which simplifies quorum engineering, and studies its properties in this new adversarial context. Then, the paper deconstructs existing signature-free Byzantine-tolerant asynchronous broadcast algorithms and, with the help of the k2-cast communication abstraction, reconstructs versions of them that tolerate both Byzantine processes and message adversaries. Interestingly, these reconstructed algorithms are also more efficient than the Byzantine-tolerant-only algorithms from which they originate
Asynchronous Byzantine Reliable Broadcast With a Message Adversary
This paper considers the problem of reliable broadcast in asynchronous authenticated systems, in which n processes communicate using signed messages and up to t processes may behave arbitrarily (Byzantine processes). In addition, for each message m broadcast by a correct (i.e., non-Byzantine) process, a message adversary may prevent up to d correct processes from receiving m. (This message adversary captures network failures such as transient disconnections, silent churn, or message losses.) Considering such a "double" adversarial context and assuming n > 3t + 2d, a reliable broadcast algorithm is presented. Interestingly, when there is no message adversary (i.e., d = 0), the algorithm terminates in two communication steps (so, in this case, this algorithm is optimal in terms of both Byzantine tolerance and time efficiency). It is then shown that the condition n > 3t + 2d is necessary for implementing reliable broadcast in the presence of both Byzantine processes and a message adversary (whether the underlying system is enriched with signatures or not)
A Modular Approach to Construct Signature-Free BRB Algorithms under a Message Adversary
This paper explores how reliable broadcast can be implemented without signatures when facing a dual adversary that can both corrupt processes and remove messages.More precisely, we consider an asynchronous -process message-passing systems in which up to processes are Byzantine and where, at the network level, for each message broadcast by a correct process, an adversary can prevent up to processes from receiving it (the integer defines the power of the message adversary).So, unlike previous works, this work considers that not only can computing entities be faulty (Byzantine processes), but, in addition, that the network can also lose messages.To this end, the paper adopts a modular strategy and first introduces a new basic communication abstraction denoted -cast, which simplifies quorum engineering, and studies its properties in this new adversarial context.Then, the paper deconstructs existing signature-free Byzantine-tolerant asynchronous broadcast algorithms and, with the help of the -cast communication abstraction, reconstructs versions of them that tolerate both Byzantine processes and message adversaries.Interestingly, these reconstructed algorithms are also more efficient than the Byzantine-tolerant-only algorithms from which they originate
Asynchronous Byzantine Reliable Broadcast With a Message Adversary
This paper considers the problem of reliable broadcast in asynchronous authenticated systems, in which n processes communicate using signed messages and up to t processes may behave arbitrarily (Byzantine processes). In addition, for each message m broadcast by a correct (i.e., non-Byzantine) process, a message adversary may prevent up to d correct processes from receiving m. (This message adversary captures network failures such as transient disconnections, silent churn, or message losses.) Considering such a "double" adversarial context and assuming n > 3t + 2d, a reliable broadcast algorithm is presented. Interestingly, when there is no message adversary (i.e., d = 0), the algorithm terminates in two communication steps (so, in this case, this algorithm is optimal in terms of both Byzantine tolerance and time efficiency). It is then shown that the condition n > 3t + 2d is necessary for implementing reliable broadcast in the presence of both Byzantine processes and a message adversary (whether the underlying system is enriched with signatures or not)
A Modular Approach to Construct Signature-Free BRB Algorithms under a Message Adversary
International audienceThis paper explores how reliable broadcast can be implemented without signatures when facing a dual adversary that can both corrupt processes and remove messages. More precisely, we consider an asynchronous n-process message-passing system in which up to t processes are Byzantine and where, at the network level, for each message broadcast by a correct process, an adversary can prevent up to d processes from receiving it (the integer d defines the power of the message adversary). So, unlike previous works, this work considers that not only can computing entities be faulty (Byzantine processes), but, in addition, that the network can also lose messages. To this end, the paper adopts a modular strategy and first introduces a new basic communication abstraction denoted k2-cast, which simplifies quorum engineering, and studies its properties in this new adversarial context. Then, the paper deconstructs existing signature-free Byzantine-tolerant asynchronous broadcast algorithms and, with the help of the k2-cast communication abstraction, reconstructs versions of them that tolerate both Byzantine processes and message adversaries. Interestingly, these reconstructed algorithms are also more efficient than the Byzantine-tolerant-only algorithms from which they originate