基于故障分类优化拜占庭容错服务

本文在Byzantine fault tolerant状态机复制容错系统研究基础上,将主复件故障划分为Muteness故障和Non-Muteness故障,对主复件进行Muteness故障检测。当系统中主复件故障只是Muteness故障时,Muteness故障检测结果可以缩短view change时间,优化系统性能,提高了系统可用性。     

P2P存储系统拜占庭容错机制研究*

综述了近年来P2P存储系统拜占庭错误冗余相关技术的研究成果;概述了P2P存储系统容错的要求与技术,对现有拜占庭错误冗余技术进行了总结;详细分析对比了目前各种典型拜占庭容错系统的容错方式,探讨了P2P存储系统中拜占庭容错技术需要改进的关键问题,并对未来的研究方向进行了讨论;最后,给出了一个实际环境下的解决方案框架。     

拜占庭系统技术研究综述

随着分布式系统规模的增大,设计复杂度也不断提升,系统可靠性所面临的问题也越来越严峻。由于拜占庭协议能够容忍包括人为失误、软件bug和安全漏洞等各种形式的错误,其系统技术和实现方法越来越受到研究者们的重视。介绍和总结了目前拜占庭系统技术的研究成果,分析了目前拜占庭系统的研究现状,并探讨了拜占庭系统的发展趋势。通过分析得出：1)拜占庭系统性能上仍然与已经实用的非拜占庭系统相距较大,占用资源数量仍然较多,需要进一步研究其性能和资源优化技术;2)通过检测错误或者定期修复来降低系统中的错误,是延长系统可持续运行时间的方法,需要研究新的、高效的全面检测拜占庭服务器、合理定期修复等保障系统可持续运行的方法;3)实际应用背景和需求及其特定错误类型的处理方法对拜占庭协议和功能等提出了不一样的要求,需要研究拜占庭系统在实际中的应用和可用性。     

基于Quorum系统容错技术综述

Quorum系统是一种新型冗余拓扑的集合系统。在“冗余”设计的基础上,quorum通过交叉的结点把有效数据复制到其他quorum的结点中,增加了Quorum系统数据冗余性。当某些结点发生故障或者错误时,通过选举协议,从含有故障结点quorum的有效结点中选举出有效数据;或者采用互斥协议,从不含故障或者错误结点的有效quorum的结点中获得有效数据,系统仍能可靠运行。分析了各种Quorum肌系统的容错方式、性能比较,探讨了Quorum系统发展中需要改进的关键问题,并展望了未来的研究方向。     

WMN中拜占庭容错网络结构及算法

为提高无线Mesh网络(WMN)的可靠性,以可信计算领域中的拜占庭容错原理为基础,引入拜占庭单元概念,构建一个WMN拜占庭容错网络结构,并提出一种拜占庭算法,用以改进现有WMN路由协议.仿真结果表明,改进的路由协议能对异常节点信息进行容错处理,获得正确的节点信息,增强网络的容错能力,达到提升WMN可靠性的目的.     

分布式WSN系统中的拜占庭故障算法研究

在分布式WSN系统中,簇内有相当多的无线传感器节点,这些节点可能会部署在各种环境中,采用从单个传感器上所获取信息可靠性不高。为了提高系统的可靠性,需要对多个传感器节点采集数据进行综合,这样就可以有效地提高所获得数据的精度和可信度。研究了在系统节点发生拜占庭故障的情况下,利用现有WSN的数据融合方法以及安全系统中的拜占庭将军问题,提出了一种新的基于OM算法与贝叶斯检测算法的容错检测算法,合理而有效的进行数据融合,减小拜占庭故障对系统的影响,从而使所有节点做出一致决定。通过仿真得出该算法可以保证节点决策具有较高一致性的情况下仍有较高的故障节点减少率。     

具有监督机制的高效拜占庭容错算法

共识机制作为区块链技术的核心内容,在不同应用领域各有差异.针对联盟链应用场景,应用广泛的实用拜占庭容错(PBFT)算法仍然存在效率及安全性问题,因此从网络模型、共识本质及安全攻击等角度对PBFT算法进行研究,提出了一种高效监督拜占庭容错算法(Efficient Supervised Byzantine Fault To...     

基于投票机制的拜占庭容错共识算法

针对现有的区块链中实用拜占庭容错（PBFT）共识算法、基于动态授权的拜占庭容错（DDBFT）共识算法、联盟拜占庭容错（CBFT）共识算法普遍存在能耗高、效率低、扩展性差等问题，通过引入投票机制，提出了基于投票机制的拜占庭容错（VPBFT）共识算法。首先，以PBFT算法为基础，将网络中的节点划分为四类具有不同职责的节点。其次，算法中的投票节点具有投票和评分权，监督生产节点诚实可靠地生产数据块；生产有效的数据块的生产节点优先进入下一轮，候选节点能够被选为生产节点，而普通节点则能够成为投票节点或候选节点。最后，不同类型的节点之间具有一定的数量关系，能够在不同类型节点的数目或网络中的节点总数发生变化时动态调整参数，从而使得算法适应动态网络。通过性能仿真分析可知，VPBFT算法相较于PBFT、DDBFT、CBFT等共识算法，具有低能耗、低时延、高容错性和高动态性。     

网络异常情况下的拜占庭容错算法研究

随着电子商务网站等分布式应用的高速发展,系统的可用性已经受到了越来越多的重视。关键的服务不仅需要能够容忍良性错误,还需要能够容忍拜占庭错误。针对当前大部分的拜占庭容错算法主要针对算法正常执行的问题,提出了考虑出错情况下的拜占庭容错算法。该算法主要考虑实际过程中服务请求端和服务提供端的主复制品可能发生错误而没有响应,或者因网络拥塞而使响应没有及时送达等网络异常的情况。该算法解决了其他拜占庭容错算法在网络发生异常的情况下不能正常工作的问题,具有更强的适应性。     

一种可应用于联盟链的拜占庭容错共识算法

针对联盟链应用场景,分析了目前应用最广泛的PBFT（practical Byzantine fault tolerance,实用拜占庭容错）算法中的高通信成本和主节点选取的问题,提出了OBFT（optimistic Byzantine fault tolerance,乐观同步拜占庭容错）算法。首先,针对高通信成本问题,OBFT算法通过动态超时时间实现了乐观同步拜占庭容错,并且结合了PBFT算法中的检查点协议,当触发超时时,说明此时节点处于异步状态,为了实现拜占庭容错,算法切换回部分同步拜占庭容错,即执行PBFT算法的commit阶段,并且以stable checkpoint为新一轮乐观拜占庭容错的起点。其次利用积分制优化了主节点选取过程,保证可供选择的主节点符合区块链最长链原则。最后通过本地多节点仿真实验表明,OBFT算法提升了数据吞吐量和可拓展性,并且有效地降低了交易延迟。     

基于门限签名方案的BQS系统的服务器协议

利用冗余复制技术,BQS(Byzantine quorum system)系统在异步信道上提供了能容忍f台服务器拜占庭失效的存储服务.COCA系统和CODEX系统设计了一种结合门限签名方案和BQS系统的服务器协议,完成了TSS-BQS(threshold signature schemes-BQS)系统.与普通BQS系统相比,具有更易于支持Proactive Recovery,简化客户端密钥管理和客户端通信的优点.基于相同的系统模型和信道假设,提出了一种新的服务器协议,满足TSS-BQS系统的安全要求;而且与已有协议相比,该协议只需更少的通信轮数,在读/写并发情况下执行效果 更优.     

Byzantine quorum systems

Summary. Quorum systems are well-known tools for ensuring the consistency and availability of replicated data despite the benign failure of data repositories. In this paper we consider the arbitrary (Byzantine) failure of data repositories and present the first study of quorum system requirements and constructions that ensure data availability and consistency despite these failures. We also consider the load associated with our quorum systems, i.e., the minimal access probability of the busiest server. For services subject to arbitrary failures, we demonstrate quorum systems over servers with a load of , thus meeting the lower bound on load for benignly fault-tolerant quorum systems. We explore several variations of our quorum systems and extend our constructions to cope with arbitrary client failures. Received: October 1996 / Accepted June 1998     

Using Byzantine Fault-Tolerance to Improve Dependability in Federated Cloud Computing

Computing Clouds are typically characterized as large scale systems that exhibit dynamic behavior due to variance in workload. However, how exactly these characteristics affect the dependability of Cloud systems remains unclear. Furthermore provisioning reliable service within a Cloud federation, which involves the orchestration of multiple Clouds to provision service, remains an unsolved problem. This is especially true when considering the threat of Byzantine faults. Recently, the feasibility of Byzantine Fault-Tolerance within a single Cloud and federated Cloud environments has been debated. This paper investigates Cloud reliability and the applicability of Byzantine Fault-Tolerance in Cloud computing and introduces a Byzantine fault-tolerance framework that enables the deployment of applications across multiple Cloud administrations. An implementation of this framework has facilitated in-depth experiments producing results comparing the reliability of Cloud applications hosted in a federated Cloud to that of a single Cloud.     

A new solution for the Byzantine agreement problem

Reliability is an important research topic in distributed computing systems consisting of a large number of processors. To achieve reliability, the fault-tolerance scheme of the distributed computing system must be revised. This kind of problem is known as a Byzantine agreement (BA) problem. It requires all fault-free processors to agree on a common value, even if some components are corrupt. Consequently, there have been significant studies of this agreement problem in distributed systems. However, the traditional BA protocols focus on running ⌊(n−1)/3⌋+1 rounds of message exchange continuously to make each fault-free processor reach an agreement. In other words, since having a large number of messages results in a large protocol overhead, those protocols are inefficient and unreasonable, especially for some network environments which have large number of processors. In this study, we propose a novel and efficient protocol to reduce the number of messages. Our protocol can collect, compare and replace the received values to find the reliable processors and replace the values sent by the unreliable processors. Subsequently, each processor can agree on a common value through three rounds of message exchange. Furthermore, the proposed protocol can use the minimum number of messages to tolerate the maximum number of faulty components in a distributed system.     

On Byzantine generals with alternative plans

This paper proposes a variation of the Byzantine generals problem (or Byzantine consensus). Each general has a set of good plans and a set of bad plans. The problem is to make all loyal generals agree on a good plan proposed by a loyal general, and never on a bad plan.