Understanding Code Reuse in Smart Contracts

Smart contracts are programs that automatically execute on the blockchain system such as Ethereum. Everybody can write and deploy smart contracts on Ethereum, which causes a large collection of similar contracts via code reuse. In practice, code reuse in smart contract may amplify severe threats like security attacks, resource waste, etc. In this paper, we conduct an empirical study of code reuse in smart contracts for understanding the code reuse practice in the smart contract ecosystem. We first collect 146,452 open-source smart contract projects from Ethereum and then perform a detailed analysis. We first study how often the smart contract projects reuse and then we identify the top reused smart contracts and analyze how the developers revise smart contracts during reuse. Our research suggests that the code reuse in smart contract is quite frequent because about 26% contract code blocks are reused and the average time of reuse is 14.6. And the top reused contracts are almost all related to ERC20 token, which reveals that the current smart contract ecosystem is relatively homogenous. At last, we summarize 7 common types of code revision in smart contracts.