The next 700 BFT protocols

Abstract

Modern Byzantine fault-tolerant state machine replication (BFT) protocols involve about 20,000 lines of challenging C++ code encompassing synchronization, networking and cryptography. They are notoriously difficult to develop, test and prove. We present a new abstraction to simplify these tasks. We treat a BFT protocol as a composition of instances of our abstraction. Each instance is developed and analyzed independently.To illustrate our approach, we first show how our abstraction can be used to obtain the benefits of a state-ofthe-art BFT protocol with much less pain. Namely, we develop AZyzzyva, a new protocol that mimics the behavior of Zyzzyva in best-case situations (for which Zyzzyva was optimized) using less than 24% of the actual code of Zyzzyva. To cover worst-case situations, our abstraction enables to use in AZyzzyva any existing BFT protocol, typically, a classical one like PBFT which has been tested and proved correct.We then present Aliph, a new BFT protocol that outperforms previous BFT protocols both in terms of latency (by up to 30%) and throughput (by up to 360%). The development of Aliph required two new instances of our abstraction. Each instance contains less than 25% of the code needed to develop state-of-the-art BFT protocols.

RBFT: Redundant Byzantine Fault Tolerance

“…Previous works (e.g., Zyzzyva [14] or PBFT [5]) have shown that the bottleneck in BFT protocols is actually cryptography, not network usage. Interestingly, the BFT protocol that currently provides the highest throughput uses TCP [11]. This protocol, called Chain, implies the smallest number of cryptographic operations at the bottleneck replicas, hence its very good performance.…”

“…An alternative could be to change the master instance to the instance which provides the highest throughput. This would require a mechanism to synchronize the state of the different instances when switching, similar to the switching mechanism of Abstract [11]. We will explore this design in our future work.…”

“…The wide range of research carried out in the field of BFT in the last decade primarily focused on building fast BFT protocols, i.e., protocols that are designed to provide the best possible performance in the common case (i.e. in the absence of faults) [5], [11], [13], [14]. More recently, interest has been given to robustness, i.e., building BFT protocols that achieve good performance when faults occur.…”

ByzID: Byzantine Fault Tolerance from Intrusion Detection

“…PERFORMANCE EVALUATION In this section we evaluate the performance of ByzID by comparing it with three well-known BFT protocols-PBFT [6], Zyzzyva [27], Aliph [21], and an implementation of the crash fault tolerant protocol-Paxos [29]. All of the protocol implementations are based on Castro et al's implementation of PBFT.…”

“…Such RSMs are referred to as Byzantine faulttolerant (BFT). Despite significant progress in making BFT practical [6,21], it has not been widely adopted, mainly because of the complexity of the techniques involved and high overheads. In addition, BFT is not a panacea, since there are a variety of attacks, such as various performance attacks that BFT does not handle well [2,9].…”