基于节点可信度的改进PBFT算法

本文主要是对区块链的核心技术—共识算法进行深入了解,在联盟链中难以避免会有恶意节点的存在,在节点达成共识的过程中,恶意节点将会散布不实信息,影响数据的一致性。本文对区块链防作弊技术进行研究,提出了一种基于节点可信度的NRPBFT(node-reliability-based PBFT consensus algorithm)共识算法,利用节点的可信度将所有的节点分成普通节点和共识节点,提高了共识的效率,降低了主节点作恶的可能性。     

一种高效的联盟链网络构建设计

区块链已经成为了下一代最有前途的技术之一,以联盟链为主的区块链项目正不断应用落地.不同于比特币、以太坊等公链设施,联盟链多用于建立商业组织之间的信任.在联盟链网络中,所有节点必须经过授权才能加入网络,因此,其网络性能很大程度上依赖于网络的规模和消息传播机制.为了提高联盟链网络性能,文中提出了一种高效的联盟链网络构建设计...     

基于区块链高速共识方法的物联网源端数据存储技术研究

针对物联网源端数据在传输过程中易被篡改、可信度低等痛点，结合区块链技术分布式存储、数据可溯源、不可篡改等特性，在传统的物联网数据传输方式的基础上，研究了基于区块链高速共识方法的物联网源端数据存储方式。将区块链共识节点部署在采集侧的区块链物联网关，并使用区块链对采集传感器设备进行身份认证，保证数据只能由经过区块链认证的设备上链，确保数据从源头可信。同时将区块链共识节点部署于服务器机房和物联网采集侧，保证了当采集侧区块链共识节点由于故障断开连接时，区块链网络仍能稳定运行。同时，研究并优化了区块链主节点选举方法和共识方法，以达到提高联盟链稳定性和数据传输安全性的目的，实现物联网采集数据从源头到存储全程可信、可控、可溯源。     

网络共识区块链模型构建与实现

针对B/S架构以服务器作为中心存在安全隐患的问题,提出一种真实网络环境下共识区块链方案。方案基于网络中存在的多个节点,利用区块链去中心化机制存储交易数据,利用共识机制完成记账权校验。为了保护交易数据的隐私,方案对交易数据进行了哈希加密运算,同时,为了解决网络中不同节点数据同步的问题,根据最长区块链来更新网络中的节点。为了验证模型,使用Python语言编写仿真程序,通过flask框架搭建3个节点的Web框架。实验表明,提出方案能实现交易数据上链及多个节点数据同步,并实现网络中任何节点发送并存储数据,能有效对交易数据进行加密,可以解决B/S架构对中心节点过于依赖等问题。     

基于条件代理重加密的区块链医疗数据共享模型

医疗数据具有较高的私密性和敏感性，然而以往的医疗数据共享过程中往往采取中心化的集中式存储，这带来了数据隐私泄露和非法篡改的风险。针对上述问题，文中将区块链和代理重加密技术结合起来，提出基于条件代理重加密的区块链医疗数据共享模型。各级医院组成联盟区块链，采用改进的实用拜占庭共识机制选取代理节点，提高了节点达成共识的效率。借助于云服务器海量的存储能力，将患者的医疗数据存储在云服务器，联盟区块链中保存条件摘要密文，数据请求者在联盟链上进行条件搜索获取患者医疗数据，同时利用代理重加密技术实现特定数据请求者和第三方用户之间的细粒度共享。实验结果证明，基于条件代理重加密的区块链医疗数据共享模型在通信和计算开销方面更具优势。     

基于超图和MuSig2聚合签名的联盟链主从多链共识机制

针对多链式区块链采用主链最终共识机制,导致主链负载大,制约从链性能等问题,论文提出一种基于超图和MuSig2聚合签名的联盟链主从多链共识机制.首先根据超图理论,构建以横贯超图为主链,子超图为从链的联盟链主从多链架构;然后借鉴分治思想,结合“背书-排序-验证”的共识方式,构建分层分类共识机制,通过分类处理交易降低主链负载压力;最后构建基于MuSig2聚合签名的联盟链多方背书签名方法,提升背书签名的验证效率.性能分析表明：基于MuSig2聚合签名的联盟链多方背书签名安全可靠,基于超图和MuSig2聚合签名的分层分类共识机制具有强一致性和线性时间复杂度.实验结果表明：基于MuSig2聚合签名的多方背书方法的总效率是椭圆曲线数字签名算法（Elliptic Curve Digital Signature Algorithm,ECDSA）的1.55倍,分层分类共识机制能够提升12.5%的共识效率.该机制具有较高性能,可满足企业多样化业务需求.     

用于图片交易的混合共识机制

随着信息技术的发展,越来越多的用户通过线上网站传输图像、浏览照片、交易版权。近年来,由于元宇宙概念逐渐引发热议,通过区块链进行的图片交易越来越多。区块链是一种分布式的数据库账本,拥有去中心化、防篡改、不依赖可信第三方等优良特性,但现有的区块链共识方案在处理图片交易时,存在奖励单一,过程复杂等不足。本文研究改进了工作量证明算法与实用拜占庭算法,并设计了基于工作积分的节点分级机制用于沟通公有链和联盟链;提出了基于双链的混合共识机制,以弥补现有共识机制在处理图片交易时节点选举随意,缺少奖惩机制的不足。实验表明,新的混合共识机制在处理图片交易时减少了通信开销,提高了交易速度。     

基于凝聚型层次聚类的PBFT优化共识机制

面对粮食联盟链网络中的大量共识节点,由于传统实用拜占庭容错(practical Byzantine fault tolerance,PBFT)共识算法效率低下,导致通信能耗过高,从而极大地增加信息泄露和数据造假的风险。针对上述难题,本文提出了一种基于凝聚型层次聚类(agglomerative hierarchical clustering,AHC)的PBFT优化共识算法。首先,利用AHC算法对所有网络共识节点进行目标划分和聚类;其次,使所有簇并行发生PBFT共识;最后,通过簇间主节点共识达成消息一致。实验结果表明,该改进算法能够有效降低能量开销,并提高共识效率和吞吐量。     

基于信誉值的实用拜占庭容错改进算法研究

共识问题是区块链中的核心问题,针对联盟链常用的实用拜占庭容错算法(PBFT)中主节点选取随意、网络通信量大、公平性较低等问题,提出一种基于信誉值的PBFT改进算法。首先改变信誉值主节点选取方式,然后优化共识流程,节点的累计信誉作为判断达成共识的条件。达成共识时没有参与共识过程的节点或恶意节点的信誉值降低,降低的信誉值均分给成功参与共识的节点。经过多次共识后,故障或恶意节点对共识的影响变小,提高了算法的公平性。     

一种基于ε-greedy的领导选举方法

随着区块链的广泛部署,无人协同等延迟敏感型的应用对区块链系统的低时延需求日益提高。在协同场景下,区块链节点通常跨地域部署,节点异构性较强。在基于领导节点的拜占庭容错(Byzantine Foult Tolerant, BFT)共识协议中,不稳定的或能力较差的领导节点将导致不必要的高延迟,并降低区块链的可用性,特别是在资源有限的移动或传感器网络下。针对上述问题,提出了ε-LE,一种带有网络感知的领导选举方法,基于节点到领导节点的通信延迟测量结果,采用ε-greedy策略对领导节点进行选择,使得当前性能较优或网络中关键位置的节点具有更高概率成为领导节点,从而优化共识延迟。相较于AWARE等方法,ε-LE实现O(N)的通信复杂度,更加适用于具备线性通信复杂度的共识协议。实验结果表明,ε-LE能够选择可优化集群共识延迟的节点作为领导节点,在线性拓扑网络中实现了约21%的吞吐量提升。     

异步区块链支持的安全频谱共享

针对目前频谱稀缺的困境,一个经济有效的解决方案是将未充分利用的授权频谱以机会的方式分配给未授权用户。然而,实现大规模频谱共享面临激励缺失、隐私泄露、安全威胁和时延过大等挑战。利用区块联盟链技术的安全机制,设计了由频谱接入层、区块链网络层、区块链共识层构成的区块链动态频谱接入系统。该系统采用异步实时拜占庭容错(Practical Byzantine Fault Tolerance,PBFT)改善共识延时,设计基于最优匹配算法的匹配方案,提高频谱复用率。经仿真验证,该方案频谱复用率提升近6%。相比于实时拜占庭机制,所提方案减少了系统延时,提升吞吐量近129%。     

Research on sybil attack in defense blockchain based on improved PBFT algorithm

Aiming at the problem that sybil attack has great harm to block chain technology,a method to improve the PBFT algorithm in the alliance chain to defend against sybil attacks was proposed.Firstly,using the idea of consensus algorithm based on proof of rights and interests,a reputation model was established,the reputation value of each node accorded to the behavior of each node in the consensus process was calculated,and different discourse rights accorded to the size of the reputation value was given.Then pre-commit phase was added to the PBFT algorithm to reduce the number of communication between nodes.The solution through formal analysis and reasoning and security testing shows that the improved PBFT algorithm can not only effectively defend against sybil attacks in the blockchain,but also make the performance of the blockchain system in terms of TPS and block generation delay.     

Extensive game analysis and improvement strategy of DPOS consensus mechanism

Delegated proof-of-stake ( DPOS) consensus mechanism is widely adopted in blockchain platforms, but problems exist in its current applications. In order to explore the security risks in the voting attack of the DPOS consensus mechanism, an extensive game model between nodes was constructed, and it was concluded that the DPOS consensus mechanism relies too much on tokens, and the possibility of node attacks is very high. In order to solve the problems of frequent changes of DPOS consensus mechanism nodes, inactive node voting, excessive reliance on tokens, and malicious nodes, a dynamic, credible, and attack-evading DPOS consensus mechanism was proposed. In addition, the Python simulation results show that the improved Bayesian voting algorithm is effective in calculating node scores.     

Imp Raft: a consensus algorithm based on Raft and storage compression consensus for IoT scenario

In order to meet various challenges in the Internet of things (IoT), such as identity authentication, privacy preservation of distributed data and network security, the integration of blockchain and IoT became a new trend in recent years. As the key supporting technology of blockchain, the consensus algorithm is a hotspot of distributed system research. At present, the research direction of the consensus algorithm is mainly focused on improving throughput and reducing delay. However, when blockchain is applied to IoT scenario, the storage capacity of lightweight IoT devices is limited, and the normal operations of blockchain system cannot be guaranteed. To solve this problem, an improved version of Raft (Imp Raft) based on Raft and the storage compression consensus (SCC) algorithm is proposed, where initialization process and compression process are added into the flow of Raft. Moreover, the data validation process aims to ensure that blockchain data cannot be tampered with. It is obtained from experiments and analysis that the new proposed algorithm can effectively reduce the size of the blockchain and the storage burden of lightweight IoT devices.     

基于节点动静态指标的电网节点重要度的评估研究

随着智能电网技术的不断发展,对高可靠性的智能电网的精确评估提出了更高的要求。智能电网中重要节点的故障将会导致大规模停电,因此对智能电网中重要节点的评估是评估智能电网可靠性程度的重要体现。文中针对节点所处的局部环境、全局属性、网络拓扑结构以及节点所承载负荷等级等多个不同的动静态综合指标进行研究,以这些综合指标模型来评估节点在智能电网中的重要度,最后使用TOPSIS方法将动静态指标糅合,共同对智能电网节点重要度进行评估,并对IEEE-30节点进行了仿真验证。结果显示节点6的重要度较高,应对其重点保护。     

基于区块链的频谱设备网络中防御拜占庭攻击的分布式共识机制

针对大规模、超密集部署移动互联网和物联网引发的精确频谱共享需求,基于区块链技术提出联网海量个人无线设备构成频谱设备网络:频谱管理服务器、移动基站、个人无线设备形成云计算与边缘计算相结合的频谱设备网络架构,以频谱数据获取、频谱区块添加、频谱数据传输、频谱数据采集的激励构成了基于区块链的频谱设备网络的基本运行机制,通过感知节点共识融合、验证节点共识验证、簇头节点共识确认,在一定置信度下的假设检验判断是否有恶意感知节点发动伪造频谱数据的拜占庭攻击。仿真结果表明分布式共识机制在防御恶意感知节点伪造频谱数据的拜占庭攻击上的有效性和可靠性。     

Distributed cooperative spectrum sensing based on reinforcement learning in cognitive radio networks

Spectrum sensing is an initial task for the successful operation of cognitive radio networks (CRN). During cooperative spectrum sensing, malicious secondary user (SU) may report false sensing data which would degrade the final aggregated sensing outcome. In this paper, we propose a distributed cooperative spectrum sensing (CSS) method based on reinforcement learning (RL) to remove data fusion between users with different reputations in CRN. This method regards each SU as an agent, which is selected from the adjacent nodes of CRN participating in CSS. The reputation value is used as reward to ensure that the agent tends to merge with high reputation nodes. The conformance fusion is adopted to promote consensus of the whole network, while it’s also compared with the decision threshold to complete CSS. Simulation results show that the proposed method can identify malicious users effectively. As a result, the whole CRN based on RL is more intelligent and stable.     

Performance analysis and comparison of PoW,PoS and DAG based blockchains

In the blockchain, the consensus mechanism plays a key role in maintaining the security and legitimation of contents recorded in the blocks. Various blockchain consensus mechanisms have been proposed. However, there is no technical analysis and comparison as a guideline to determine which type of consensus mechanism should be adopted in a specific scenario/application. To this end, this work investigates three mainstream consensus mechanisms in the blockchain, namely, Proof of Work (PoW), Proof of Stake (PoS), and Direct Acyclic Graph (DAG), and identifies their performances in terms of the average time to generate a new block, the confirmation delay, the Transaction Per Second (TPS) and the confirmation failure probability. The results show that the consensus process is affected by both network resource (computation power/coin age, buffer size) and network load conditions. In addition, it shows that PoW and PoS are more sensitive to the change of network resource while DAG is more sensitive to network load conditions.     

多域协同的TDD大规模组网方法研究

如何在有着大量、广域、时变协同需求的海量节点间和多维资源约束下实现网络服务能力最大化是时分双工（time-division duplex,TDD）移动通信大规模组网面临的核心问题。从架构角度进行研究,创新性地提出适用于TDD大规模组网的全局协同优化架构,分为无线连接层、信号处理层和服务控制层,通过层间全局协同优化和层内资源域高效转化实现多维资源成本与网络服务能力的最优化。基于该架构,聚焦无线连接层的空口资源,对多资源域协同转化的无线组网方法进行深入研究,明确了时域、频域、空域、码域等多资源域协同转化机理,并设计了相应的无线组网机制。4G/5G现网实践验证结果表明,所提TDD大规模无线组网架构和方法可在有效控制干扰的同时高效利用各域资源,实现网络服务能力最大化。