A Novel Quantum Byzantine Consensus Protocol Based on Malicious Node Prevention Mechanism

Blockchain has been widely used in finance, the Internet of Things (IoT), supply chains, and other scenarios as a revolutionary technology. Consensus protocol plays a vital role in blockchain, which helps all participants to maintain the storage state consistently. However, with the improvement of network environment complexity and system scale, blockchain development is limited by the performance, security, and scalability of the consensus protocol. To address this problem, this paper introduces the collaborative filtering mechanism commonly used in the recommendation system into the Practical Byzantine Fault Tolerance (PBFT) and proposes a Byzantine fault-tolerant (BFT) consensus protocol based on collaborative filtering recommendation (CRBFT). Specifically, an improved collaborative filtering recommendation method is designed to use the similarity between a node’s recommendation opinions and those of the recommender as a basis for determining whether to adopt the recommendation opinions. This can amplify the recommendation voice of good nodes, weaken the impact of cunning malicious nodes on the trust value calculation, and make the calculated results more accurate. In addition, the nodes are given voting power according to their trust value, and a weight random election algorithm is designed and implemented to reduce the risk of attack. The experimental results show that CRBFT can effectively eliminate various malicious nodes and improve the performance of blockchain systems in complex network environments, and the feasibility of CRBFT is also proven by theoretical analysis.

Associations of exposure to per- and polyfluoroalkyl substances mixture with the numbers of lymph nodes in colorectal cancer patients

A major design to improve scalability and performance of blockchain is sharding, which maintains a distributed ledger by running classical Byzantine Fault Tolerance (BFT) protocols through several relatively small committees. However, there are several drawbacks with the existing sharding protocols. First, the sharding mechanism which ensures that each committee is strongly bias-resistant either weakens the decentralization or reduces the performance of the protocol. Second, BFT protocols are either unresponsive or take quadratic communication complexities under a byzantine leader. Third, they cannot defend against transaction censorship attacks. Finally, nodes do not have enough motivation to follow the protocol and selfish nodes can obtain more rewards through collusive behaviors. A recent study proposes HotStuff – a BFT protocol that achieves linear view-change and optimistic responsiveness. In this paper, we present HotDAG, a hybrid consensus protocol based on HotStuff via sharding in the permissionless model. By employing the parallel Nakamoto consensus protocol, we present a decentralized and bias-resistant sharding mechanism. HotDAG has a linear communication complexity on transaction confirmation by introducing a scalable BFT protocol and an inter-committee consensus mechanism based on blockDAG. By achieving an unpredictable leader rotation, HotDAG prevents the censorship attacks. At the same time, HotDAG provides an incentive mechanism that is compatible with the scalable BFT protocol to encourage nodes to actively participate in the protocol. Finally, we formally prove the security and analyze the performance of HotDAG.

Cyberspace Mimic Defense (CMD) has fundamentally changed the situation of traditional network security defense through Dynamic Heterogeneous Redundancy (DHR) architecture. Presently, research on DHR architecture is based on the trustworthiness of the arbiters and schedulers. However, in practical applications, the core logic is generally deployed on a single server, which is vulnerable to single points of attack and failure, thus damaging the entire system’s security. This paper proposed a decentralized DHR architecture, which transfers the arbitration and scheduling logic to all executors. Based on the Practical Byzantine Fault Tolerance (PBFT) protocol, this paper designed the consensus protocol used in the decentralized DHR architecture to ensure the consistency of the status of each executor. Theoretical analysis and experiments show that the architecture is more secure than the traditional DHR architecture and can tolerate Byzantine faults.

Hyperledger Fabric is a widely-used permissioned blockchain platform for enterprise consortium applications. It adopts Practical Byzantine Fault Tolerance (PBFT) algorithm as the consensus protocol in its version 0.6. Faulty replicas could intentionally delay messages, be not responsive and send inconsistent messages to different replicas. Faulty clients and replicas could also launch denial-of-service attack to make resources unavailable. The malicious behavior significantly undermines the system. However, the existing performance evaluation for Fabric is accomplished in a fault-free environment without malicious behaviors. In this paper, we analyze the impact of malicious behavior, design malicious behavior patterns and test the blockchain performance on Hyperledger Fabric.

An improved blockchain-based multi-region Federated Learning framework for crop disease diagnosis

Because of its excellent properties of fault tolerance, efficiency and availability, the practical Byzantine fault tolerance (PBFT) algorithm has become the mainstream consensus algorithm in blockchain. However, current PBFT algorithms have problems such as inadequate security of primary node selection, high communication overhead and network delay in the process of consensus. To address these problems, we design a novel efficient Byzantine fault tolerance algorithm based on credit grouping, called CG-PBFT. First, we propose a new credit evaluation model to obtain nodes’ credit values and introduce an optimized three-way quick sorting algorithm to divide nodes into the master-node group, the consensus-node group and the observation-node group, which have different privileges. The nodes in the observation-node group are restricted from participating in consensus, which reduces the communication overhead and improves consensus efficiency. Second, we propose an optimized selection method for the primary node based on a voting mechanism whereby the consensus-node group and observation-node group vote to produce the primary node, which reduces the probability of malicious nodes acting as the primary node and improves the security of primary node selection. Finally, the identity conversion mechanism between node groups is designed, and the actual behavior of nodes within different groups is given credit rewards or punishment, so as to keep an incentive for nodes to participate in appropriate system behavior and improve the working enthusiasm of nodes. The experimental simulation results show that compared with existing PBFT algorithms, the CG-PBFT algorithm improves the average throughput by 51.3% and reduces the average delay by 64.5%; it greatly improves the operating efficiency of the system and can be more suitable for application in the consortium blockchain scenarios.

As smart cities become more decentralized, the need for reliable and secure cyber-physical systems (CPS) that guarantee safe interactions and secure data storage without loss of privacy is continuously increasing. Blockchain is a rapidly emerging technology in this domain. It demonstrated effectiveness thanks to the cryptographic mechanisms it utilizes and to its immutability. Private blockchains are the most suited to applications that require privacy and confidentiality when data is very sensitive. In this case, the most commonly used consensus protocol is Practical Byzantine Fault Tolerance (PBFT). However, PBFT requires the participation of all nodes in the consensus process, which increases bandwidth consumption and consensus delay significantly. In this paper, we propose an adaptive PBFT protocol called APBFT that optimizes the number of nodes participating in the consensus based on their response time and credibility. Therefore, we reduce the amount of communication and the response delays. We maintain the asynchrony of the algorithm so that it remains resilient to DoS attacks. The simulation results show that our algorithm outperforms the original PBFT in terms of delays and message traffic.

Byzantine Fault Tolerant (BFT) protocols provide powerful guarantees in the presence of arbitrary machine failures, yet they do not scale. The process of creating new, scalable BFT protocols requires expert analysis and is often error-prone. Recent work suggests that localized, rule-driven rewrites can be mechanically applied to scale existing (non-BFT) protocols, including Paxos. We modify these rewrites--- decoupling and partitioning---so they can be safely applied to BFT protocols, and apply these rewrites to the critical path of PBFT, improving its throughput by 5×. We prove the correctness of the modified rewrites on any BFT protocol by formally modeling the arbitrary logic of a Byzantine node. We define the Borgesian simulator, a theoretical node that simulates a Byzantine node through randomness, and show that in any BFT protocol, the messages that a Borgesian simulator can generate before and after optimization is the same. Our initial results point the way towards an automatic optimizer for BFT protocols.

Routing protocols for Delay and Disruption Tolerant Networks (DTNs) are prone to suffer from malicious behavior of nodes. Particularly, in the acknowledgment counterfeiting attack, malicious nodes forge acknowledgments in order to negatively impact network performance by removing from buffer messages that were not yet delivered to the destination. This paper proposes a new buffer management mechanism as a countermeasure against the acknowledgement counterfeiting attack in DTNs. The mechanism does not immediately drop acknowledged messages but it will drop these messages first if the buffer is full. Our mechanism also does not rely in any authentication method because we do not try to identify malicious nodes. The analysis considers traces of three real networks and results show our proposal mitigates the attack because the number of malicious nodes do not reduce the delivery rate. In addition, the proposed countermeasure outperforms the main countermeasure against this kind of attack found in literature, providing higher delivery rates up to 142%.

The constant growing on the number of vehicles is increasing the complexity of traffic in urban and highway environments. It is paramount to improve traffic management to guarantee better road usage and people’s safety. Through efficient communications, Vehicular Ad hoc Networks (VANETs) can provide enough information for traffic safety initiatives, daily traffic data processing, and entertainment information. However, VANETs are vulnerable to malicious nodes applying different types of net-work attacks, where an attacker can, for instance, forge its position to receive the data packet and drop the message. This can lead vehicles and authorities to make incorrect assumptions and decisions, which can result in dangerous situations. Therefore, any data dissemination protocol designed for VANET should consider security issues when selecting the next-hop forwarding node. In this paper, we propose a security scheme designed for position-based routing algorithms, which analyzes nodes position, transmission range, and hello packet interval. The scheme deals with malicious nodes performing network attacks, faking their positions forcing packets to be dropped. We used the Simulation of Urban MObility (SUMO) and Network Simulator-version 3 (NS-3) to compare our proposed scheme integrated with two well-known position-based algorithms. The results were collected in an urban Manhattan grid environment varying the number of nodes, the number of malicious nodes, as well as the number of source-destination pairs. The results show that the proposed security scheme can successfully improve the packet delivery ratio while maintaining low average end-to-end delay of the algorithms.

Many recent research works have proposed distributed ledger technology (DLT) that employs Byzantine fault-tolerant (BFT) consensus protocols as the underlying core primitive to create a total order among all transactions. Compared to many Proof-of-Work (PoW) blockchains, this design typically benefits from increased performance, energy efficiency and proven liveness and safety characteristics. While BFT protocols have the potential to create highly resilient infrastructures, some questions yet remain to be answered. This paper sketches our current and future research on how DLTs can benefit from making the underlying BFT protocol adaptive towards the system's environment (e.g., geographic decentralization or system scale) and resilient against attacks of malicious replicas that are targeted at degrading the overall system performance.

An improved practical Byzantine fault tolerance (Practical Byzantine Fault Tolerant consensus algorithm based on reputation, RPBFT) algorithm based on grouping and reputation value voting is proposed for the problems of high communication complexity, poor scalability, and random selection of master nodes of the practical Byzantine fault tolerance (PBFT) consensus algorithm of the consortium chain. First, the consistency process is optimized to take the response speed of nodes to each group leader as the basis of grouping, and the intragroup consensus is performed. The group leader then takes the result of intragroup consensus and participates in extra-group consensus to reduce the frequency and time of internode communication. Second, the reputation model and voting mechanism are proposed, and the group leader is generated by node reputation value voting, which enhances the initiative and reliability of trusted nodes and reduces the abnormal nodes as group leader. Finally, a simulation and performance testing system based on this improved scheme is built to prove the effectiveness as well as the usability of the scheme through simulation experiments. The experimental results show that when the number of network nodes is 36, the throughput of the RPBFT algorithm is six times that of PBFT. Therefore, the consensus delay is reduced by 91.7%, and the communication overhead is reduced by 37.8%.

Focused on the problem of master node selection and communication overhead in the Practical Byzantine Fault Tolerance (PBFT) consensus algorithm which applied to the consortium blockchain, this paper proposes an Egalitarian Practical Byzantine Fault Tolerance (ePBFT) consensus algorithm based on the PBFT algorithm. First, the concept of the primary node is diluted, so that each node in the chain is equal and efficient. Secondly, the consensus process is optimized to improve the efficiency of the consensus, the communication overhead is reduced to half of the PBFT in the case of less view changes. The experimental results show that the ePBFT algorithm and the PBFT algorithm are compared in the same environment, and the throughput is improved when the communication overhead and delay are reduced.

ABSTRACTQuality of service (QoS) provisioning in mobile ad hoc networks (MANETs) is one of the fundamental concerns in this area. Autonomous mobility of nodes is one of the main factors affecting the network QoS. A lack of fixed infrastructure and central control on the nodes complicate guaranteeing the QoS in MANETs. Security is a major factor affecting the QoS in such networks. This paper proposes a new routing method based on trust among the nodes and applies a clustering approach to MANETs. This routing scheme can calculate the trustworthiness of the route and the shortest routes to the destination by avoiding identified malicious nodes. The effects of node mobility and number of malicious nodes on routing performances are investigated in the reported research. Simulation is used to show the effectiveness of the proposed approach in comparison with a categorized trust method, Ad hoc On‐demand Distance Vector, trust vector‐based Ad hoc On‐demand Distance Vector, and trust vector‐based dynamic source routing in terms of end‐to‐end delay, network throughput, and packet delivery ratio at the expense of a moderate increase in the routing overhead. The proposed trust‐based routing method finds the trustworthy route by applying end‐to‐end trust calculation and finds the optimal route by performing clustering scheme from the source node to the destination node. In the extended proposed routing method, adding a nonce‐based encryption scheme results in improved packet delivery ratio, network throughput, and malicious node detection rate. Copyright © 2013 John Wiley & Sons, Ltd.