Formal verification of smart contracts from the perspective of concurrency

Abstract

Blockchain is an emerging technology with broad applications. As an important application of the blockchain, smart contracts can formulate trading rules to manage thousands of virtual currencies. Nowadays, the IoT (Internet of Things) combined with blockchain has become a new trend and smart contract can implement different transaction demands for IoT-blockchain systems. Once there exits vulnerability in the smart contract program, the security of the virtual currency will not be guaranteed. However, ensuring the security of smart contracts is never an easy task. On the one hand, existing smart contracts cannot identify fake users or malicious programs, which is difficult to be regulated at present; on the other hand, smart contracts involving in multiple trading users are very similar to shared-memory concurrent programs. To deal with these problems, this study uses formal verification methods, adopting the Communicating Sequence Processes (CSP) theory to formally model concurrent programs. Then the FDR (Failure Divergence Refinement), a refinement checker or model checker for CSP, is utilized to successfully detect the vulnerability regarding concurrency in one smart contract public in Ethereum. The results show the potential advantage of using CSP and FDR tool to check the vulnerability in smart contracts especially from the perspective of concurrency.