Latest Progress Research Report on Blockchain Consensus Protocol

This report delves into the current state of the development of Blockchain Consensus protocols, with a focus on analyzing the latest advancements in Asynchronous Byzantine Fault Tolerant State Machine Replication (BFT SMR) protocols. Currently, sMVBA is considered the fastest Asynchronous MVBA protocol, with an expected latency of 10δ. The report also introduces two new protocol designs, namely 2PAC (2-Phase Asynchronous Consensus) and Ultra-Fast Pipelined Block, showcasing significant improvements in throughput and latency.

Blockchain technology, as a decentralized distributed ledger technology, ensures the integrity and consistency of data through consensus mechanisms. The consensus mechanism is the core of the blockchain system, and its performance directly affects the scalability and security of the blockchain. Asynchronous Byzantine Fault Tolerance (BFT) consensus mechanisms have unique advantages in dealing with network delays and partial node failures, making them a focus of research.

Model and Definition

In the asynchronous BFT model, the system consists of n = 3f + 1 processes, where f processes may be maliciously compromised by adversaries. These processes communicate with each other through asynchronous channels, and the message delivery delay is controlled by the adversaries. Each process has a pair of public and private keys for signing and verification, ensuring the authenticity and integrity of the messages.

Blockchain Consensus

The blockchain consensus protocol aims to enable all honest nodes to reach an agreement on the state of the blockchain. Specifically, each node continuously receives new transactions and packages them into blocks, ensuring that these blocks are agreed upon by all honest nodes through the consensus protocol. The blockchain consensus protocol needs to meet the following basic requirements:

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

Challenges of the Current Asynchronous Consensus Protocol

Current asynchronous consensus protocols face challenges from various attack vectors that could undermine the protocol's consistency and liveness. For example, attacks resulting from a lack of verification and authentication, attacks that hinder liveness by exploiting elevation strategies, and consistency attacks arising from relaxed definitions of leader authentication. Although some protocols have introduced new mechanisms, such as running multiple parallel instances concurrently, these issues have not yet been fully resolved.

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

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

1. 2PAClean:

   • Achieved +90% throughput and an expected delay of 9.5δ, with a message complexity of O(n²).
   • The efficiency of the protocol has been improved by eliminating unnecessary interactions and computational overhead.

2. 2PACBIG:

   • It is currently the fastest Blockchain consensus protocol with a message complexity of O(n³).
   • The faultless single MVBA runtime is 4δ, which greatly reduces latency.

Super Fast Pipeline Block

Researchers proposed a new pipelined Block design that significantly reduces the latency of pipelined Blocks. By introducing a fast path mechanism, under a fair scheduler, the decision time of pipelined Blocks is even smaller than that of non-pipelined Blocks. This mechanism ensures low latency for the fast path across all executions and is not affected by the behavior of faulty processes.

Quantitative Results

Through theoretical analysis and practical testing, 2PAClean has an expected delay of 9.5δ in the worst case, while in the good case (no faults and semi-fair scheduler) it is 6δ. In comparison, the expected delay of sMVBA is 10δ, with a good case of 6δ. Therefore, 2PAClean reduces the worst-case delay by 0.5δ while maintaining the same good-case delay. Additionally, the throughput of 2PAClean improves by 80% to 100% compared to the chain-based sMVBA, mainly due to the new design that avoids unnecessary Block drops and computational overhead.

2PACBIG, as a protocol with message complexity O(n³), has a single MVBA runtime of 4δ, which is faster than all existing protocols. Additionally, the ultra-fast pipelined block design allows s2PAClean and s2PACBIG to achieve pipelined block decision times of 4δ and 3δ, respectively, further enhancing the performance of the protocol.

Calculation Evaluation

To verify the performance of the new protocol, researchers conducted extensive computational evaluations. The results showed that 2PAClean and 2PACBIG exhibited excellent performance under various network conditions, especially in environments with high latency and high failure rates. Specifically, 2PAClean achieved a good balance between message transmission latency and computational complexity, while 2PACBIG realized lower latency through parallelization and optimization of the voting process.

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 protocol structures and optimizing the consensus process.

Future Research Directions

1. Protocol optimization: Further simplify and optimize the protocol structure, reducing unnecessary message passing and computational overhead.
2. Security Analysis: Conduct an in-depth analysis of the new protocol's security in 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.

This report provides a detailed analysis of the advantages and disadvantages of current asynchronous Blockchain Consensus protocols and proposes two new protocol designs, namely 2PAC and ultra-fast pipeline blocks. The new designs show significant advantages in increasing throughput and reducing latency, providing important references for the future development of Blockchain technology. These new protocols have not only demonstrated their superiority theoretically but also showcased outstanding performance in practical tests, offering new ideas for achieving efficient and secure Blockchain Consensus protocols.

Through continuous research and optimization, Blockchain technology will 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.