关键词: 智能合约, 多访问控制, 重入攻击, 形式化验证, 银行存取款

Abstract: In order to solve the problem of reentry attacks caused by the vulnerability of smart contracts in handling external contract calls, a smart contract reentry attack defense method based on Multiple Access Controls (MAC) is proposed. By using MAC, only the contract owner is allowed to make calls and prevent functions from repeatedly entering the same transaction during execution; at the same time, the state variable is modified to store the secure contract address and update the contract state. Finally, formal verification is used to run the defended smart contract. In this paper, we verifies the method with a bank deposit and withdrawal transaction model. The experimental results show that the smart contract using this defense method can effectively solve the problem of reentry attacks when external contracts are invoked. Compared with other mainstream defense methods, it has higher feasibility, effectiveness, logical correctness and comprehensibility; compared with the undefended contract, the defended smart contract reduces the equivalent memory usage by 64.51%, and the running time is also shortened.

Key words: smart contract, multiple access controls, reentry attacks, formal authentication, bank access