Switchboard On-chain programs can’t access off-chain data directly. They rely on oracles to bring in information such as asset prices, event outcomes, or API responses. Without these oracles,...

Formally Verifying Nonces.Sol in OpenZeppelin Nonces, which stands for "number used once" are used in digital signature schemes to prevent replay attacks. For the purposes of this article, we assume...

Introduction to Formal Verification Formal verification is the process of mathematically proving a program adheres to a specification. This article introduces conceptually how formal verification...

FFT Friendly Finite Fields In order to carry out the FFT algorithm in a finite field (the Number Theoretic Transform), there needs to be $k$-th roots of unity such that $k$ is a power of 2. Ideally,...

ERC-20 Token on Starknet ERC-20 tokens on Starknet work the same way as on Ethereum. In fact, STRK (Starknet's fee token) is itself an ERC-20 token; there's no special "native" token at the protocol...

Constructors in Cairo A constructor is a one-time-call function executed during contract deployment to initialize state variables, perform contract setup tasks, make cross-contract interactions and...

Cairo Components Part 1 Components in Cairo behave like abstract contracts in Solidity. They can define and work with storage, events, and functions, but they can’t be deployed on their own. The...

Components Part 2: OpenZeppelin ERC-20 Tutorial In Component Part 1, we learned how to create and use a component within a single file. We built a from scratch and integrated its storage, events, and...

Events in Starknet Events emit data from contract execution into the transaction receipt. The receipt holds metadata about what happened during the execution, which can be queried or indexed by...

Cheatcodes in Starknet Foundry A "cheatcode" in Foundry is a mechanism that allows contract tests to control environment variables such as caller address, the current timestamp, and so on. In this...

Function Visibility in Cairo Cairo does not have "internal" and "pure" modifiers (or any other modifiers for that matter) like Solidity does. Recall that marking an block with tells Cairo to include...

Access Control in Cairo Access control defines who can call specific functions or modify contract behavior. This article explains how Cairo implements access control using the macro. A Review of...