Introduction to Formal Verification of Smart Contracts
Formal verification converts a smart contract’s expected behavior and code logic into mathematical expressions, then uses automated tools to check whether they are consistent. It is effective at identifying complex and subtle issues, but cannot completely replace expert audits; combining the two provides a more comprehensive security assessment.
Why Formal Verification Is Necessary
Smart contracts are deployed on blockchains, where they can execute automatically under predefined conditions and manage assets. Because their code is usually public and often difficult to modify after deployment, any error can be exploited quickly. Therefore, high-value or high-risk contracts require particularly rigorous pre-launch checks to ensure that the code behaves as expected.
How the Verification Process Works
Experts first use a formal language to describe the contract’s specifications and required properties, then convert the actual code into a mathematical model or logical statement. Automated theorem-proving or model-checking tools subsequently check whether the code satisfies the specifications. When discrepancies are found, developers fix the issues and repeat the verification until the results meet the requirements.
What Issues Can It Identify
Formal verification systematically analyzes different combinations of states and variables, making it suitable for finding subtle defects such as rounding errors, incorrect fee calculations, and abnormal permission states. The cases in the evidence show that some issues are difficult to identify through manual line-by-line inspection but may be detected through automated analysis, thereby reducing the risk of serious losses.
Why Manual Audits Are Still Necessary
Mathematical verification depends on the specifications being written correctly and cannot cover all risks at the design, deployment, and business levels. Manual audits can draw on experience to examine code architecture, security assumptions, and issues overlooked by tools, while also confirming that the verification process is reasonable. Combining the two leverages the systematic nature of machines and the judgment of experts to create defense in depth.
Original Tutorial
https://www.binance.com/zh-CN/academy/articles/what-is-formal-verification-of-smart-contracts