Latest Developments and Applications of Blockchain Consensus Protocols

Blockchain technology, as a decentralized distributed ledger technology, is fundamentally based on the consensus mechanism. The consensus mechanism directly affects the scalability and security of blockchain systems. This article will focus on the latest developments in the asynchronous Byzantine Fault Tolerance (BFT) consensus mechanism, especially its unique advantages in dealing with network latency and partial node failures.

Overview of Asynchronous BFT Model

In the asynchronous BFT model, the system consists of 3f+1 processes, where f processes may be maliciously compromised. Processes communicate through asynchronous channels, with message delivery delays controlled by the adversary. Each process has a public-private key pair for signing and verification, ensuring the authenticity and integrity of the messages.

Basic Requirements of Blockchain Consensus Protocol

The blockchain consensus protocol aims to achieve agreement among all honest nodes on the state of the blockchain. Its basic requirements include:

1. Activity: In infinite execution, there exists an infinitely long determined Blockchain.
2. Consistency: If there are two decided Blockchains, one must be a prefix of the other.
3. P Quality: In the decided Blockchain, the proportion of transactions input by honest nodes is at least p.

Challenges of the Current Asynchronous Consensus Protocol

The fastest asynchronous consensus protocol was once considered to be the 2-chain VABA, with an expected latency of 9.5δ. However, research has found that this protocol has multiple attack vectors that may undermine its consistency and liveness. These attacks include exploiting deficiencies in authentication checks, abusing promotion strategies, and relaxing the definition of leader authentication, among others. Despite the introduction of innovative mechanisms such as running multiple parallel instances, these issues have not been fully resolved.

New Protocol Design: 2PAC (2-Phase Asynchronous Consensus)

Based on the analysis of existing protocols, researchers proposed the 2PAC protocol, which significantly improves performance by simplifying and optimizing the Consensus process. 2PAC includes two variants:

1. 2PAClean:

   • Achieve +90% throughput and 9.5δ expected latency
   • The message complexity is O(n²)
   • Improve efficiency by eliminating unnecessary interactions and computational overhead.

2. 2PACBIG:

   • The fastest Blockchain Consensus protocol under the current message complexity O(n³).
   • The fault-free single MVBA runtime is 4δ, significantly reducing latency.

Super Fast Pipeline Block

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

Quantitative Results Analysis

Through theoretical analysis and practical testing, 2PAClean has an expected delay of 9.5δ in the worst case and 6δ in good conditions (no faults and semi-fair scheduler). In contrast, the expected delay of sMVBA is 10δ, with 6δ in good conditions. 2PAClean reduces the worst-case delay by 0.5δ while maintaining the same good condition delay. Furthermore, the throughput of 2PAClean improves by 80% to 100% compared to the chain-based sMVBA.

2PACBIG, as the O(n³) message complexity protocol, has a single MVBA runtime of 4δ, surpassing all existing protocols in speed. The ultra-fast pipelined Block design allows s2PAClean and s2PACBIG to achieve pipelined Block decision times of 4δ and 3δ respectively, further enhancing the protocol's performance.

Calculation Evaluation Results

Extensive computational evaluations show that 2PAClean and 2PACBIG exhibit excellent performance under various network conditions, especially in high-latency and high-failure-rate environments. 2PAClean achieves a good balance between message transmission delay and computational complexity, while 2PACBIG realizes lower latency through parallelization and optimization of the voting process.

Future Research Directions

1. Protocol optimization: Further simplify and optimize the protocol structure, reducing unnecessary message passing and computational overhead.
2. Security Analysis: In-depth analysis of the new protocol's security under various attack scenarios to ensure reliability in practical applications.
3. Practical Application: Apply the new protocol to actual Blockchain systems to verify its performance in a real network environment.

Conclusion

This study provides a detailed analysis of the advantages and disadvantages of current asynchronous Blockchain Consensus protocols and proposes two new protocol designs: 2PAC and ultra-fast pipelined Blocks. These new designs demonstrate significant advantages in increasing throughput and reducing latency, offering important references for the future development of Blockchain technology. Through continuous research and optimization, Blockchain technology is expected to play a more important role in the future digital economy, and the new generation of Consensus protocols will provide a solid foundation for the development of this technology.