CRBFT: A Byzantine Fault-Tolerant Consensus Protocol Based on Collaborative Filtering Recommendation for Blockchains

Byzantine fault tolerant (BFT) consensus protocols are becoming an appealing solution to blockchains. As most blockchain systems are deployed on Wide Area Networks (WANs), with each node acting on behalf of its entity, partially synchronous BFT protocols that rely on network synchrony to elect a single leader can be ill-suited. In contrast, asynchronous protocols have no such timing assumptions. Existing asynchronous protocols confront challenges in terms of both flexibility and performance.

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.

In response to new and innovating blockchain-based systems with Internet of Things (IoT), there is a need for consensus mechanisms that can provide high transaction throughput and security, despite varying network quality. Honeybadger was the first practical, asynchronous Byzantine Fault Tolerance (BFT) consensus protocol, achieving high scalability and robustness without making any timing assumptions regarding the network. To improve the current asynchronous consensus protocols, we designed Asynchronous Byzantine Fault Tolerance (ABFT) consensus protocol through integrating threshold Elliptic Curve Digital Signature Algorithm (ECDSA) signatures and optimization of erasure coding parameters, as well as additional implementation-level optimizations. We implement a prototype of ABFT, and evaluate its performance at scale in a global WAN network and a network affected by asymmetric network degradation. Our results show that ABFT provides considerably higher performance, significantly lower computational overhead, and greater scalability than its predecessors. ABFT can reach up to 38.700 transactions per second in throughput. Furthermore, we empirically show that ABFT is unaffected by asymmetric network degradation within the fault threshold.

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.

Blockchain is a decentralized distributed ledger database. Consensus protocol is the core protocol of blockchain to solve Byzantine agreement problem. To let all blockchain nodes reach an agreement, the most commonly used Byzantine consensus protocol are Practical Byzantine Fault Tolerance (PBFT) protocols. PBFT requires that the number of malicious nodes <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$t$</tex> is less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n/3$</tex> ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex> is the total number of nodes), while quantum ones can raise the upper bound from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n/3$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n/2$</tex> . However, there is a problem with quantum Byzantine consensus protocols, that is, the lack of malicious-degree evaluation. When the primary and reporting nodes are malicious, the number of agreements rounds and communication overhead will be significantly increased. Thus, a prevention mechanism for quantum consensus protocols is proposed in this paper, which includes two measures to prevent (or constrain) the malicious behaviors: (1) The trust-value calculation method to judge the honesty of nodes, which adjust the value according to nodes' behaviors using our trust-value evaluation formula; (2) The dual signature method to verify the legitimacy of reporting messages, which requires two nodes to agree and sign a message. The security analysis shows that our prevention mechanism can effectively prevent malicious nodes from being the primary node and substantially reduce the false messages from dishonest nodes.

The Internet of Things (IoT) implementation experience has escalated the security, privacy and scalability concerns and there is more worry that the advent and execution of quantum computers will put the classical cryptography algorithms RSA and ECC at risk. The study deals with the acute problem of providing security solutions to IoT data transmission in a post-quantum world, where lattice-based post-quantum cryptography (Kyber-512 cryptography encryption, Dilithium signatures) is combined with a streamlined blockchain system. The given system would encrypt IoT sensor data through quantum-proof algorithms and record hashbooks on the blockchain and secure data confidentiality, integrity, and authenticity. The low-latency, resource-friendly, energy-efficient verification capability of the proposed consensus protocol is optimized based on Practical Byzantine Fault Tolerance (PBFT) consensus protocol. Evaluation Experimental evidence has shown encryption accuracy of at least 99.97%, low bit error rates, and deterministic low computation time $(\mathbf{2}. \mathbf{4}-\mathbf{3}. \mathbf{9 0 ~ m s}$ encryption, 2.6-4.10 ms decryption at varying packet sizes. Blockchain throughput is set up at $230 \mathrm{Tx} / \mathrm{s}$ where the finality times are below 1.5 s at a 5 KB block size. The findings validate the possibility of scalable, quantum-resistant and tamper proof IoT communication that is essentially future-proofing against new quantum threats to critical infrastructures.

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.

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.

Byzantine Fault Tolerant (BFT) protocols serve as a fundamental yet intricate component of distributed data management systems in untrustworthy environments. BFT protocols exhibit different design principles and performance characteristics under varying workloads and fault scenarios. The proliferation of BFT protocols and their growing complexity have made it increasingly challenging to analyze the performance and possible application scenarios of each protocol. This demonstration showcases BFTGym , an interactive platform that allows audience members to (1) evaluate, compare, and gather insights into the performance of various BFT protocols under a wide range of conditions, and (2) prototype new BFT protocols rapidly.

In today’s world, there is a significant advancement in the development of blockchain-based technologies and data replication systems. These areas heavily rely on the communication between user groups, making consensus a crucial aspect for their proper functioning. While most consensus protocols are leader-based, this approach may not always be suitable. In the case of blockchain projects, relying on a single leader to process all transactions can become a bottleneck for scalability and opens up the possibility of censorship. This paper aims to highlight the advantages and fundamental principles of fault-tolerant leaderless consensus algorithms. It also presents the implementation of a blockchain simulator featuring the renowned Democratic Byzantine Fault Tolerant (DBFT) consensus algorithm. The simulator is subjected to various attacks in order to test its operational effectiveness. By design, the DBFT algorithm ensures resistance against censorship, although it does come at the expense of increased communication complexity and challenges in block composition.

Byzantine Fault Tolerance (BFT) protocols can be divided into synchronous BFT protocols, partially synchronous BFT protocols, and asynchronous BFT protocols according to communication delay. Asynchronous BFT protocols are widely used because they can tolerate uncertain communication delays in the real world. However, asynchronous BFT protocols need to perform many rounds of broadcasts to reach agreement on a transaction subset, which consumes a lot of communication, computing, and storage resources. In this paper, we present Volia, an asynchronous BFT protocol which resolves above problem.We design new broadcast protocol to reduce the number of broadcast rounds needed for agreement. It reduces the communication overhead. Voting broadcast is used to maintain the order of transaction subsets rather than threshold signature to reduce computation cost. Above mechanisms speeds up the agreement phase, reduces the accumulated transaction subsets waiting for agreement and thus saves storage resources. We conduct experiment on Volia and the results show that Volia exhibits about 2~65× throughput, 2~25% latency, and 30% storage cost compared to other asynchronous BFT protocols.

Blockchain-based solutions for Internet of Things (IoT) networks constitutes a current trend in cybersecurity and brings significant benefits into current centralized IoT-based health monitoring systems by addressing security challenges. Complex and power intense blockchain solutions do not perform satisfactory in the resource-constrained IoT, and especially Internet of Medical Things (IoMT), devices of these systems due to the latter's limited processing power, storage capacity, and battery life. Therefore, in this paper, we propose a scalable Practical Byzantine Fault Tolerance (PBFT) consensus algorithm for IoMT blockchains to: i) enhance scalability in IoMT blockchains, ii) reduce communication overhead, iii) enhance security while reducing the computational cost for suitability to the resource constraint nature of IoMT devices, iv) facilitate decentralized accountability, and v) eliminate single point of failure.

It is critical to achieve the following objectives in partially synchronous Byzantine Fault Tolerance (BFT) protocols: (1) two-phase commit regime, (2) standard optimistic responsiveness, and (3) linear communication complexity. These three properties significantly affect the efficiency of BFT protocols. A number of attempts, such as HotStuff and Tendermint, have been made to solve this problem, but they typically manage to achieve only a subset of these properties. In this work, we propose a two-phase BFT protocol called TockCuckoo that fully achieves the aforementioned three properties. A primary challenge in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">two-phase</i> BFT protocols is HiddenLock: when a leader lacks visibility into the latest locked block states of honest replicas, it cannot safely proceed, potentially stalling the protocol. To address this issue, we introduce the proactive voting paradigm, which explicitly distinguishes between rejection and non-receipt states. After global stable time, an honest leader can always collect sufficient votes through proactive voting, enabling quick responses. TockCuckoo operates in continuous rounds of proactive voting, ensuring responsiveness. The proactive voting process requires only linear communication overhead, which directly results in TockCuckoo achieving linear communication complexity overall. Furthermore, we introduce TockCuckoo+, an extension of TockCuckoo. By introducing a cross-pipelined design, TockCuckoo+ enables more frequent block proposals without sacrificing the key characteristics of TockCuckoo, leading to improved throughput. Our experiments in wide-area networks demonstrate that, TockCuckoo reduces commit latency by 20% to 40% compared to HotStuff across different network sizes, and TockCuckoo+ achieves a throughput increase of 1.1× to 1.5× over HotStuff.

Many state-machine Byzantine Fault Tolerant (BFT) protocols have been introduced so far. Each protocol addressed a different subset of conditions and use-cases. However, if the underlying conditions of a service span different subsets, choosing a single protocol will likely not be a best fit. This yields robustness and performance issues which may be even worse in services that exhibit fluctuating conditions and workloads. In this paper, we reconcile existing state-machine BFT protocols in a single adaptive BFT system, called ADAPT, aiming at covering a larger set of conditions and use-cases, probably the union of individual subsets of these protocols. At anytime, a launched protocol in ADAPT can be aborted and replaced by another protocol according to a potential change (an event) in the underlying system conditions. The launched protocol is chosen according to an 'evaluation process' that takes into consideration both: protocol characteristics and its performance. This is achieved by applying some mathematical formulas that match the profiles of protocols to given user (e.g., service owner) preferences. ADAPT can assess the profiles of protocols (e.g., throughput) at run-time using Machine Learning prediction mechanisms to get accurate evaluations. We compare ADAPT with well known BFT protocols showing that it outperforms others as system conditions change and under dynamic workloads. © 2015 IEEE.

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.