# LBFT: An Asynchronous Committee-Based Blockchain Storage Strategy on Zero Trust Model
### Related Work
The Practical Byzantine Fault Tolerance (PBFT) protocol only requires that the messages will be delivered within \(\Delta\) after a global stabilization time (GST) and tolerates up to \(\lfloor\frac{n}{3}\rfloor\) (where \(n\) is the number of nodes) Byzantine faults [23]. In addition, the classic protocol HotStuff is also a notable example of a partially synchronous protocol [24]. Aardvark shifts the focus from improving peak throughput to maintaining acceptable and predictable protocols even when Byzantine faults occur. Due to the successful application of blockchain technology, BFT protocols have been applied in a wider area, and their design goal shifts to further relax the time assumption. The network connection may be unreliable, and the delay may be time-varying [1]. Various works construct asynchronous BFT protocols that can make progress even if the time assumption does not hold. The notable HoneyBadger-BFT and Dumbo can achieve consensus in an asynchronous network but suffer from a relatively high communication complexity [25; 26]. In addition to robustness, asynchronous protocols always have a higher efficiency compared with synchronous protocols. Generally, synchronous BFT protocols are parameterized by an assumed network latency, which is much larger than the actual one, and obviously the efficiency of these protocols depends on the pre-set latency [26]. On the contrary, asynchronous protocols are more efficient because they make progress as soon as the messages are delivered, without relying on any time bound. **Whole-network or committee-based BFT protocols. ** The majority of existing BFT protocols require the whole system to broadcast and verify the inputs so that the system can eventually achieve consensus on the output. As a consequence, these protocols always suffer from high communication complexity. The first practical asynchronous BFT protocol, HoneyBadger-BFT, has \(n^{2}\) or even \(n^{3}\) terms in communicated bits [25]. Another notable protocol, multi-valued validated Byzantine agreement (MVBA), also achieves \(O(Ln^{2}+\lambda n^{2}+n^{3})\) (where \(L\) is the input length, and \(\lambda\) is the security parameter) in [27] in communication complexity. To reduce communication, several improved protocols are constructed, but they do not radically overturn the whole network involved in consensus and just mildly reduce the number of communicated bits [27; 28]. On the other hand, whole-network participation also results in a low efficiency for two reasons: (1) some of the broadcast protocol instances may terminate very slowly due to the unstable network, so the subsequent operations will be delayed; (2) the large scale concurrent execution will sharply degrade efficiency [29]. To address the above, many committee-based schemes have been proposed. [PERSON] et al. design several committee-based frameworks and algorithms for energy trading systems by combining a hierarchical-optimization scheme with blockchain technology, to replace the traditional coordination center with a delegation consisting of several chosen participants [30; 31; 32]. In addition, the previous works [10; 33] propose an improved delegated Proof-of-Stake (DPoS) scheme and related election mechanism, in which only a part of nodes can be the candidates of the delegation responsible for generating and verifying blocks, thus achieving higher effectiveness and security than PoW and PoS mechanisms. In contrast to the execution of \(n\) ABA instances in HoneyBadger-BFT, Dumbo-1 selects \(K\) out of \(n\) parties (where \(K\) is a security parameter independent of \(n\)) and lets them execute the ABA protocol to decrease the running time from \(O(\log n)\) to \(O(\log K)\)[25; 26; 34]. In another committee-based BFT protocol, SCP [5], the parties are randomly divided into different committees and each committee runs an internal consensus protocol in parallel, to reach higher efficiency.