Building on Starknet: Cairo, ZK Proofs, and the STARK Stack

Starknet is an Ethereum ZK rollup developed by StarkWare, using STARK-based validity proofs rather than the SNARK-based proofs used by zkSync or Polygon zkEVM. It uses Cairo — a custom language purpose-built for provable computation.

STARKs vs SNARKs

Both are zero-knowledge proof systems, but they differ in trust assumptions and performance. SNARKs require a trusted setup (a ceremony that generates parameters — if the ceremony is compromised, proofs can be forged). STARKs require no trusted setup — they're transparent. STARKs are also post-quantum secure. The tradeoff: STARK proofs are larger than SNARK proofs, making verification on Ethereum more expensive. But for Starknet, the proof is amortized across many transactions, making per-transaction costs competitive.

Cairo: The Language

Cairo (current version: Cairo 1.x, Rust-inspired) is a Turing-complete language designed to produce STARK-provable computation. Every Cairo program is provable — the STARK system can generate a proof that the computation was correctly executed. Cairo's type system enforces provability constraints. The language has improved dramatically from the early Cairo 0 (assembly-like) to Cairo 1 (Rust-like syntax with traits, generics, and strong types).

Starknet Contracts

Starknet contracts are Cairo programs with specific entry points (constructors, external functions, view functions). The standard library (starknet-cairo-corelib, OpenZeppelin Cairo Contracts) provides ERC-20, ERC-721, and access control implementations. Development tooling: Scarb (the Cairo package manager and build tool), Starknet Foundry (testing and deployment framework inspired by Ethereum Foundry).

Native Account Abstraction

Starknet has no native Ethereum-style EOAs. Every account on Starknet is a smart contract — account abstraction is native to the protocol, not a layer on top. All signatures are verified by the account contract itself, meaning you can implement any signature scheme (ECDSA, multisig, passkeys) without a protocol change. This is the purest implementation of account abstraction available.

The Ecosystem

DeFi: JediSwap, Ekubo (DEX with concentrated liquidity), zkLend (lending), Nostra (DeFi suite). NFTs: Aspect, Unframed. Gaming: Realms (Bibliotheca DAO). Infrastructure: Argent X (leading Starknet wallet, supports passkey-based login), Braavos (wallet with hardware signer). STRK is the native token used for gas.

Developer Experience

Cairo has a steeper learning curve than Solidity but a shallower one than Rust. The Rust-like syntax is familiar to many developers. The Starknet Book (book.starknet.io) is the canonical developer resource. Starknet Foundry provides a similar testing experience to Ethereum Foundry. The main friction: Cairo's execution model is fundamentally different from the EVM — porting EVM contracts to Cairo requires rethinking, not just translating.