Latest Developments and Applications of Blockchain Consensus Protocol

Blockchain technology, as a representative of decentralized distributed ledger technology, is fundamentally based on consensus mechanisms. The performance of consensus mechanisms directly affects the scalability and security of blockchain systems. This report focuses on the latest developments of Asynchronous Byzantine Fault Tolerant State Machine Replication (BFT SMR) protocols, delving into the current fastest asynchronous protocols and their existing issues, while proposing two innovative protocol designs.

Overview of Asynchronous BFT Model

In the asynchronous BFT model, the system consists of 3f + 1 processes, of which f may be maliciously compromised. The processes communicate via asynchronous channels, and message transmission delays are unpredictable. Each process has a public-private key pair to ensure the authenticity and integrity of the messages.

Core Requirements of Blockchain Consensus Protocol

1. Liveness: Ensure that there exists an infinitely long finalized Blockchain in infinite execution.
2. Consistency: Among any two determined Blockchain, one must be a prefix of the other.
3. Quality: It has been decided that the proportion of transactions input by honest nodes in the Blockchain reaches the preset threshold.

Current Challenges of Asynchronous Consensus Protocols

Currently, the sMVBA protocol has become the fastest asynchronous MVBA protocol with an expected delay of 10δ. The previously considered fastest 2-chain VABA protocol (expected delay of 9.5δ) has been found to have multiple security vulnerabilities, including a lack of authentication checks, the use of promotion strategies that hinder liveness, and consistency issues resulting from the relaxation of leader authentication definitions.

Innovative Protocol Design

1. 2PAC (2-Phase Asynchronous Consensus)

The 2PAC protocol significantly improves performance by simplifying and optimizing the consensus process. It includes two variants:

• 2PAClean: Achieved over 90% throughput improvement, expected latency is 9.5δ, message complexity is O(n²).
• 2PACBIG: The current message complexity is O(n³) for the fastest Blockchain consensus protocol, with a single MVBA run time of only 4δ under fault-free conditions.

2. Super Fast Pipeline Block

This new design significantly reduces the latency of pipeline Blocks. By introducing a fast path mechanism, under a fair scheduler, the decision time for pipeline Blocks may even be less than that of non-pipeline Blocks. This mechanism guarantees fast path latency in all executions, unaffected by faulty processes.

Performance Evaluation

Theoretical analysis and practical testing show that:

• 2PAClean is expected to have a worst-case delay of 9.5δ and a best-case delay of 6δ.
• The throughput of 2PAClean is improved by 80%-100% compared to the chain-based sMVBA.
• The single MVBA runtime of 2PACBIG is 4δ, outperforming all existing protocols.
• The ultra-fast pipeline design allows s2PAClean and s2PACBIG to achieve pipeline block decision times of 4δ and 3δ, respectively.

Future Research Directions

1. Further simplify and optimize the protocol structure, reducing unnecessary messaging and computational overhead.
2. In-depth analysis of the security of the new protocol under various attack scenarios.
3. Apply the new protocol to actual 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 points the way for the future development of Blockchain Consensus protocols, which is to achieve higher throughput and lower latency by simplifying protocol structures and optimizing the Consensus process. These innovations not only theoretically prove their superiority but also demonstrate excellent performance in practical tests, providing new ideas for achieving efficient and secure Blockchain Consensus protocols.