6,743 research outputs found
Asynchronous Byzantine agreement protocols
AbstractA consensus protocol enables a system of n asynchronous processes, some of them faulty, to reach agreement. Both the processes and the message system are capable of cooperating to prevent the correct processes from reaching decision. A protocol is t-resilient if in the presence of up to t faulty processes it reaches agreement with probability 1. Byzantine processes are faulty processes that can deviate arbitrarily from the protocol; Fail-Stop processes can just stop participating in it. In a recent paper, t-resilient randomized consensus protocols were presented for t<n5. We improve this to t < n3, thus matching the known lower bound on the number of correct processes necessary for consensus. The protocol uses a general technique in which the behavior of the Byzantine processes is restricted by the use of a broadcast protocol that filters some of the messages. The apparent behavior of the Byzantine processes, filtered by the broadcast protocol, is similar to that of Fail-Stop processes. Plugging the broadcast protocol as a communicating primitive into an agreement protocol for Fail-Stop processes gives the result. This technique, of using broadcast protocols to reduce the power of the faulty processes and then using them as communication primitives in algorithms designed for weaker failure models, was used succesfully in other contexts
Dumbo-NG: Fast Asynchronous BFT Consensus with Throughput-Oblivious Latency
Despite recent progresses of practical asynchronous Byzantine fault tolerant
(BFT) consensus, the state-of-the-art designs still suffer from suboptimal
performance. Particularly, to obtain maximum throughput, most existing
protocols with guaranteed linear amortized communication complexity require
each participating node to broadcast a huge batch of transactions, which
dramatically sacrifices latency. Worse still, the f slowest nodes' broadcasts
might never be agreed to output and thus can be censored (where f is the number
of faults). Implementable mitigation to the threat either uses computationally
costly threshold encryption or incurs communication blow-up, thus causing
further efficiency issues.
We present Dumbo-NG, a novel asynchronous BFT consensus (atomic broadcast) to
solve the remaining practical issues. Its technical core is a non-trivial
direct reduction from asynchronous atomic broadcast to multi-valued validated
Byzantine agreement (MVBA) with quality property. Most interestingly, the new
protocol structure empowers completely concurrent execution of transaction
dissemination and asynchronous agreement. This brings about two benefits: (i)
the throughput-latency tension is resolved to approach peak throughput with
minimal increase in latency; (ii) the transactions broadcasted by any honest
node can be agreed to output, thus conquering the censorship threat with no
extra cost.
We implement Dumbo-NG and compare it to the state-of-the-art asynchronous BFT
with guaranteed censorship resilience including Dumbo (CCS'20) and
Speeding-Dumbo (NDSS'22). We also apply the techniques from Speeding-Dumbo to
DispersedLedger (NSDI'22) and obtain an improved variant of DispersedLedger
called sDumbo-DL for comprehensive comparison. Extensive experiments reveal:
Dumbo-NG realizes better peak throughput performance and its latency can almost
remain stable when throughput grows
- …