Crystality: A Programming Model for Smart Contracts on Parallel EVMs

Abstract

Scaling blockchain performance through parallel smart contract execution has gained significant attention, as traditional methods remain constrained by the performance of a single virtual machine (VM), even in multi-chain or Layer-2 systems. Parallel VMs offer a compelling solution by enabling concurrent transaction execution within a single smart contract, using multiple CPU cores. However, Ethereum's sequential, shared-everything model limits the efficiency of existing parallel mechanisms, resulting in frequent rollbacks with optimistic methods and high overhead with pessimistic methods due to state dependency analysis and locking.

This paper introduces Crystality, a programming model for smart contracts on parallel Ethereum Virtual Machines (EVMs) that enables developers to express and leverage the parallelism inherent in smart contracts. Crystality introduces Programmable Contract Scopes to partition contract states into non-overlapping, parallelizable segments and decompose a smart contract function into finer-grained components. Crystality also features Asynchronous Functional Relay to manage execution flow across EVMs. These features simplify parallelism expression and enable asynchronous execution for commutative contract operations.

Crystality extends Solidity with directives, transpiling Crystality code into standard Solidity code for EVM compatibility. The system supports two execution modes: an asynchronous mode for transactions involving commutative operations and an optimistic-based fallback to ensure block-defined transaction order. Our experiments demonstrated Crystality's superior performance compared to Ethereum, Aptos, and Sui on a 64-core machine.