Latest Developments and Future Prospects of Blockchain Consensus Protocols

Blockchain technology, as a decentralized distributed ledger technology, is fundamentally based on the consensus mechanism. The performance of the consensus mechanism directly affects the scalability and security of the blockchain. Recently, the Asynchronous Byzantine Fault Tolerance (BFT) consensus mechanism has become a research hotspot due to its advantages in dealing with network latency and partial node failures.

Overview of Current Asynchronous Consensus Protocol

Currently, there have been significant breakthroughs in the field of Asynchronous BFT State Machine Replication (SMR) protocols. Although the 2-chain VABA protocol was once regarded as the fastest asynchronous protocol, claiming an expected delay of 9.5δ, research has revealed multiple security vulnerabilities that affect its consistency and liveness. Therefore, the sMVBA protocol is now considered the fastest asynchronous MVBA protocol, with an expected delay of 10δ.

New Protocol Design: 2PAC

To address the issues with the existing protocol, researchers proposed the 2PAC (2-Phase Asynchronous Consensus) protocol. This protocol significantly improves performance by simplifying and optimizing the consensus process. 2PAC has two main variants:

1. 2PAClean:

   • Achieved +90% throughput and 9.5δ expected latency
   • The complexity of the message is O(n²)
   • Improved protocol efficiency by eliminating unnecessary interactions and computing overhead.

2. 2PACBIG:

   • The current message complexity is O(n³) for the fastest Blockchain Consensus protocol.
   • Under faultless conditions, the single MVBA runtime is only 4δ.

Ultra-fast Pipeline Block

Researchers have also proposed a new pipelined Block design that significantly reduces the latency of pipelined Blocks. This design introduces a fast path mechanism, under a fair scheduler, the decision time for pipelined Blocks may even be less than that of non-pipelined Blocks. This mechanism ensures fast path latency in all executions and is unaffected by the behavior of faulty processes.

Performance Evaluation

Theoretical analysis and practical testing indicate that the expected delay of 2PAClean in the worst case is 9.5δ, and in the good case (no failures and semi-fair scheduler) is 6δ. In contrast, the expected delay of sMVBA is 10δ, with a good case of 6δ. 2PAClean reduces the worst-case delay by 0.5δ while maintaining the same good-case delay. Additionally, the throughput of 2PAClean is improved by 80% to 100% compared to the chain-based sMVBA.

2PACBIG, as a protocol with message complexity O(n³), has a single MVBA execution time of 4δ, faster than all existing protocols. The ultra-fast pipelined Block design enables s2PAClean and s2PACBIG to achieve pipelined Block decision times of 4δ and 3δ respectively, further enhancing the performance of the protocol.

Future Research Directions

1. Protocol optimization: Further simplify and optimize the protocol structure, reducing unnecessary messaging and computational overhead.

2. Security Analysis: In-depth analysis of the new protocol's security under various attack scenarios to ensure its reliability in practical applications.

3. Practical Application: Apply the new protocol to real blockchain systems to verify its performance in real network environments.

With the continuous development of Blockchain technology, the asynchronous BFT Consensus protocol will play an increasingly important role in ensuring security and improving performance. The design of 2PAC and ultra-fast pipelined Blocks demonstrates the future direction of Blockchain Consensus protocols, which is to achieve higher throughput and lower latency by simplifying the protocol structure and optimizing the Consensus process. These new protocols not only prove their superiority in theory but also demonstrate excellent performance in practical testing, providing new ideas for achieving efficient and secure Blockchain Consensus protocols.

With the deepening of research and continuous optimization of technology, Blockchain technology is expected to play a more important role in the future digital economy, and the new generation of Consensus protocol will provide a solid foundation for the development of this technology.