# Challenges of PBFT-Inspired Consensus for Blockchain and Enhancements over Neo dBFT
## 6 Conclusions and Future Works  
In this paper, we explore variants of PBFT-inspired consensus for blockchain, focusing on the dBFT consensus of the Neo Blockchain and raising theoretical background for the underlying peer-to-peer network and for blockchains. We analyze the first and second generations of dBFT consensus (dBFT 1.0 and 2.0), which have been running on Neo's Mainnet. Inspired by the common challenge faced by consensus of guaranteeing one block finality (without issues related to chain forks or sporks), this paper explores possible Byzantine attacks and frequent natural network failures. Based on a deep understanding and generalization of the PBFT principles extended to 1 BF on blockchain, we introduce improvements for the second generation of dBFT 2.0 (namely dBFT 2.0+). It involves the use of proofs during change views, which can help the system to avoid isolated committed nodes in normal operations (without intentional Byzantine agents), reinforcing that committing locally implies in committing globally. This study also presents directions for a third generation with multiple block proposals, namely dBFT 3.0, by adding an additional consensus negotiation phase (being composed of four phase: PrepareRequest, PrepareResponse, Pre-Commit and Commit). We analyze the impacts on consensusiveness considering a double speakers proposal, which is experimentally validated, estimating that network instability issues could be faced on 12% of cases (requiring change views). A speed-up mechanism is also verified, indicating that only three of the four consensus phases would be typically used on practice (the additional Pre-Commit phase could be skipped). In addition, blacklisting techniques that could restrain Byzantine attackers are highlighted, which would keep a track of the \"consensus message trails\". For the future, we intend to expand the analysis of the \(f+1\) replicated speakers proposal for a greater number of nodes, then, verifying the impact of the proposed strategy when \(f+1\) nodes propose blocks simultaneously. We also plan to compare with pure asynchronous consensus \begin{table}
\begin{tabular}{l l l l l} \hline \hline  & & \multicolumn{3}{c}{**dBFT Proposals**} \\ \hline
**Name** & **Phases** & **Issues Faced** & **Worst Case** & **Detailed Explanation** \\ \hline \multirow{4}{*}{dBFT 2.0+} & \multirow{4}{*}{3 phases} & \multirow{4}{*}{Challenges with persistent faulty nodes (one block-time is lost during every round).} & \multirow{4}{*}{0 sporks} & Message proofs during change view resolve the synchronous condition from dBFT 2.0, & \\  & & & &  for extreme scenarios where nodes are constantly failing, and delays are isolating committed nodes. \\ \hline \multirow{4}{*}{dBFT 3.0-WS2 (or dBFT 3.0)} & \multirow{4}{*}{3–4 phases} & Multiple proposals & \multirow{4}{*}{0 sporks} & \multirow{4}{*}{0 sporks} \\  & & in the first view may impair liveness. & & & \\  & & Impossible conflicts may require a new consensus after change view, & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ \hline \multirow{4}{*}{dBFT 3.0-WS2+ (or dBFT 3.0+)} & \multirow{4}{*}{3–4 phases} & \multirow{4}{*}{0 sporks} & Change views will occur if there are two persistent faulty priority and backup primaries. There are still undecided situations in which change views consistently keep decisions reached in previous (similarly as in dBFT 2.0+). \\  & & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison for the dBFT variants proposed in this studyimplementations and validate them using network message delivery assumptions by performing real-scenario network simulations. The group of authors contain researchers with a variety of backgrounds, from applied Computers Scientists to specialists in Optimization, Cryptography and Game Theory. The team has been formed throughout the open-source project Neo, which connected these members into different events that they participated together in the USA, China and Brazil.