What is formal verification of smart contracts?

Formal verification of smart contracts can prevent errors, vulnerabilities, and other adverse situations. In this process, human experts translate the logic of smart contracts into mathematical statements, then use automated tools to compare the actual logic against models of the contract’s expected behavior for model checking. Combining formal verification with manual audits allows for a comprehensive assessment of the security of smart contracts.

Introduction

Smart contracts are computer programs deployed on the blockchain that automatically execute when certain conditions are met. They can be very simple or extremely complex, holding assets worth millions or even billions of dollars.

If a smart contract code has security vulnerabilities, it could lead to devastating consequences, such as theft of all assets held. In 2021, due to a spelling error in a smart contract, the automated market maker (AMM) Uranium Finance was hacked and stolen $50 million.

Similarly, in 2021, a single coding error caused Compound Finance to mistakenly distribute $80 million in rewards. In 2022, a bug in a smart contract led to the Wormhole Bridge being hacked and stolen $320 million.

Therefore, it is crucial to get the smart contract code right from the start. Smart contracts are open-source, meaning that once deployed, the code becomes public. If hackers discover errors, they can exploit them immediately. Additionally, routine security patching over time becomes ineffective because smart contract code is usually immutable after deployment.

How does smart contract verification work?

Formal verification of smart contracts involves representing the contract’s logic and expected behavior as mathematical statements. Then, auditors use automated tools to check whether these statements are correct.

The process involves:

• Defining the contract specifications and expected properties using formal languages.
• Converting the contract code into formal representations, such as mathematical models or logic.
• Using automated theorem proving or model checking to verify the contract’s specifications and properties.
• Repeating the verification process to identify and fix any errors or deviations from expected behavior.

Why is smart contract verification important?

Using mathematical reasoning helps ensure that formally verified smart contracts are free from errors, vulnerabilities, and other adverse issues. Verification also increases trust and confidence in the contract because its properties have been rigorously tested and proven to be correct and reliable.

The following examples illustrate how smart contract verification can help prevent significant financial losses and other catastrophic outcomes.

Uniswap

Uniswap is a well-known AMM. During the development of Uniswap V1, formal verification was performed. Before release, this verification identified and fixed some rounding errors, preventing the funds of Uniswap V1 from being drained.

Balancer

Balancer V2 is also a verified AMM. Formal verification uncovered and fixed a fee calculation bug in the flash loan feature, which could have made the platform vulnerable to theft.

SafeMoon

SafeMoon V1, after deployment, was found to have an extremely minor bug through formal verification. If this bug had gone unnoticed, the contract owner could have potentially regained control of the contract after relinquishing ownership by performing certain operations.

Most manual audits of SafeMoon V1 forks missed this bug because it required analyzing specific combinations of program variable values to detect. Humans can easily overlook this issue, but machines can catch it promptly.

How formal verification and manual audits work together

Formal verification provides a systematic, automated way to check the contract’s logic and behavior against its expected properties. This makes it easier to identify and fix potential errors or vulnerabilities, especially complex or subtle issues that are difficult for manual inspection.

Manual audits involve experts reviewing the code, design, and deployment of the contract. Auditors leverage their experience and expertise to identify security risks and assess the overall security posture. They can also verify whether the formal verification process was correctly executed and check for issues that automated tools might miss.

By combining formal verification with manual audits, we can conduct a comprehensive security assessment of smart contracts. This increases the likelihood of discovering and fixing vulnerabilities. Essentially, it is a deep defense strategy that leverages the strengths of both human expertise and machine automation.

Conclusion

To ensure the security of smart contracts, it is essential to combine formal verification with manual audits, providing a thorough and comprehensive evaluation of their security posture.

While formal verification can be resource-intensive, it is a worthwhile investment for contracts with high value or high risk. After all, security is paramount, and prioritizing safety helps keep smart contracts free from errors, vulnerabilities, and unintended adverse behaviors. **$BNT **$BROCCOLI