Flow: Separating Consensus and Compute -- Execution Verification

TL;DR

This paper presents an improved blockchain architecture that separates consensus from computation, distributing verification across multiple nodes to significantly enhance throughput while maintaining security.

Contribution

It introduces a distributed verification process that parallelizes result checking, refining previous designs to increase scalability and efficiency.

Findings

Throughput is significantly increased compared to traditional architectures.

Verification is distributed and parallelized across multiple nodes.

The system maintains safety and liveness guarantees.

Abstract

Throughput limitations of existing blockchain architectures are well documented and are one of the most significant hurdles for their wide-spread adoption. In our previous proof-of-concept work, we have shown that separating computation from consensus can provide a significant throughput increase without compromising security. In our architecture, Consensus Nodes only define the transaction order but do not execute transactions. Instead, computing the block result is delegated to compute-optimized Execution Nodes, and dedicated Verification Nodes check the computation result. During normal operation, Consensus Nodes do not inspect the computation but oversee that participating nodes execute their tasks with due diligence and adjudicate potential result challenges. While the architecture can significantly increase throughput, Verification Nodes still have to duplicate the computation fully. In this paper, we refine the architecture such that result verification is distributed and parallelized across many Verification Nodes. The full architecture significantly increases throughput and delegates the computation work to the specialized Execution Nodes and the onus of checking it to a variety of less powerful Verification Nodes. We provide a full protocol specification of the verification process, including challenges to faulty computation results and the resulting adjudication process. Furthermore, we formally prove liveness and safety of the system.