# LBFT: An Asynchronous Committee-Based Blockchain Storage Strategy on Zero Trust Model
###### Abstract  
The high storage costs brought by the full-replication storage strategy adopted in most existing blockchain systems have become the main bottleneck to system scalability. To address the above, we propose an asynchronous committee-based blockchain storage strategy named lightweight BFT (LBFT), which can be applied to more diverse scenarios with better system performance. It is the first blockchain storage scheme that is designed on the conception of the zero-trust model, achieving higher-level security and fending off internal, as well as external attackers. In addition, it makes the following progress on system performance on the premise of maintaining the merits of the blockchain: (1) decreases communication complexity by involving only a part of the nodes in each decoding round; (2) enhances the robustness of the scheme regardless of the time assumption of the network; (3) improves the computational efficiency in the encoding and decoding process; and (4) reduces the storage costs and improves system scalability. In addition, we implemented experiments on LBFT and two other existing blockchain-based storage strategies, and the experimental results showed that LBFT indeed has significant improvements in system performance.  
zero-trust model; blockchain; Byzantine fault tolerance; Reed-Solomon coding; asynchronous network +
Footnote †: journal: Applied  
leaving traces that might be utilized by attackers [4]. In contrast, a public blockchain is more decentralized, in which any node can join the system without authorization and has equal access to its resources. Additionally, BFT-Store employs the Threshold Signature (TS), which depends on a certain Trusted Third Party (TTP) or a center node (i.e., dealer) to deliver the keys, which is contradictory to decentralization and increases the risk of key disclosure, increasing the risk of attacks on the TTP.  
On the other hand, except for the conventional consensus phase, the additional ES encoding and decoding processes, which involve all the peers, inevitably degrade the system performance (e.g., increase the communication bits and response time) to a certain extent.  
To address above, we consider improvement from two aspects: (1) how to strengthen the decentralization of the system as much as possible; (2) how to avoid the loss of system performance caused by abandoning the full-replication strategy.  
Firstly, to enhance decentralization, we aim to design a storage strategy that is based on a higher-level security model, known as the zero-trust model. Instead of focusing on perimeter defenses in the traditional trust model, it labels all the network traffic as untrusted and requires strict verification, regardless of whether the packets are transmitted from internal or external networks. Additionally, we employ a Certificateless Aggregate Signature (CLAS) scheme, which eliminates the reliance on the TTP to generate, store, and update the keys of the nodes.  
Secondly, inspired by a committee-based protocol named SCP [5], placing the nodes in different committees and running an internal consensus protocol within each committee concurrently, we propose a feasible solution in which only a part of the nodes is involved in each decoding round for data access. To further reduce the communication and computational complexity, we partition the original blocks before encoding. To address the above, we propose an asynchronous storage strategy for the public blockchain named lightweight BFT (LBFT), which is the first blockchain storage strategy that can adapt to the zero-trust model.