ZK Rollups: Validity Proofs & Prover Networks

What you'll learn

• The Validity-Proof Bet
• zkSync Era and the ZK Stack
• StarkNet: STARKs and Cairo
• The zkEVM Lineup: Polygon, Linea, Scroll, Taiko
• Prover Networks and Hardware Reality

Key terms

ZK rollup (validity rollup)

A rollup that submits a zero-knowledge proof with every batch, allowing the L1 contract to verify state correctness in a single transaction rather than waiting for a fraud-proof window.

SNARK

Succinct Non-interactive ARgument of Knowledge. A small (~200-500 byte) cryptographic proof of computation correctness, often based on elliptic-curve pairings. Requires a trusted setup ceremony.

STARK

Scalable Transparent ARgument of Knowledge. A hash-based proof system with no trusted setup, post-quantum security, but larger proofs (~100-200 KB). Used by StarkNet and StarkEx.

zkEVM

A ZK proof system that supports the full Ethereum Virtual Machine bytecode. Vitalik's taxonomy: Type 1 (fully Ethereum-equivalent), Type 2 (bytecode-equivalent), Type 3 (mostly equivalent), Type 4 (high-level language equivalent).

Cairo

StarkNet's native language. Rust-flavored, designed for STARK proving efficiency. Enables optimizations impossible in EVM bytecode but creates a barrier for Solidity developers.

Based rollup

A rollup where transaction sequencing is performed by L1 Ethereum validators rather than a separate L2 sequencer. Taiko is the leading example.

Boojum

zkSync Era's current proving system. SNARK-based, PLONK-style arithmetization, designed for incremental aggregation and acceptable proof times.

AggLayer

Polygon's cross-chain settlement layer that aggregates state proofs from multiple Polygon CDK chains. Part of the strategic pivot away from monolithic Polygon zkEVM (sunsetting July 1, 2026).

Prover network

Decentralized infrastructure (Risc Zero Boundless, Aligned Layer, Succinct, =nil; Foundation) for submitting and verifying ZK proofs. Aims to decentralize the prover bottleneck in production ZK rollups.