Mint and Burn Rules for ERC-721 Introduction ERC-721 is the Ethereum standard for non-fungible tokens, widely used to represent digital property. Like any form of property, it revolves around supply...

Using “requireInvariant" in Rules and Invariants Up until now, we’ve either written a rule to verify specific behaviors or an invariant to verify properties that must always hold true throughout the...

Formally Verify an ERC-20 Token Introduction In this chapter, we formally verify Solmate’s ERC-20 implementation, which includes the following: Standard state-changing functions: , , Standard view...

Introduction to Invariants in Certora Up until now, we’ve focused on verifying the behavior of individual methods or sequences of methods — ensuring that a specific function call or set of calls,...

Partially Parametric Rules for ERC-721 Introduction This chapter is the final part (5/5) of the code walkthrough of OpenZeppelin’s ERC-721 CVL specification which formally verifies the following...

Preserved Block and Its Role in Invariant Verification An invariant is a property that must always hold true after a smart contract is deployed and throughout its execution. At first glance,...

Constraining the Ghost Values in Rules In the previous chapter, we learned how ghost variables allow information to flow from hooks into rules. We also learned that: At the start of the verification...

Constraining Ghosts in Invariants In the previous chapter, we saw how unconstrained ghost variables can lead to false positives. We also learned how a statement can be used to effectively constrain...

Formally Verify Solady WETH Introduction ETH, widely used in DeFi for swaps, liquidity provision, staking, and collateral, needs an ERC-20-compatible version so protocols can interact with it through...

Invariants for ERC-721 Introduction In previous chapters, we explored how CVL invariants work: properties that must hold throughout all contract execution. Invariants can function as preconditions in...

Loops in CVL: Path Explosion and Loop Unrolling Loops are one of the most common programming constructs, but they remain challenging to reason about in formal verification. While a loop in Solidity...

SafeMint and SafeTransfer Rules in ERC-721 Introduction This chapter is the fourth part (4/5) of our code walkthrough of OpenZeppelin’s ERC-721 CVL specification and focuses on formally verifying...