What is a ZK rollup?
A ZK rollup (Zero-Knowledge rollup) is a Layer 2 scaling solution that batches Ethereum transactions and submits a cryptographic proof (validity proof) to L1 demonstrating the resulting state is correct. Unlike optimistic rollups, ZK rollups don’t rely on challenge windows: finality is achieved immediately once the proof is verified. Major ZK rollups: zkSync Era, StarkNet, Polygon zkEVM, Linea, Scroll.
How ZK rollups work
Four-step lifecycle. (1) Off-chain execution: sequencer executes transactions and computes resulting state. (2) Proof generation: prover generates a cryptographic proof (typically PLONK or STARK variants) that the state transition is correct. (3) L1 verification: Ethereum verifies the proof using a verifier smart contract. (4) Immediate finality: state is finalised once L1 verification passes.
ZK rollup advantages
Three structural benefits. (1) Fast withdrawals: no 7-day challenge window, withdrawals can complete in minutes-to-hours. (2) Stronger security: mathematical proofs rather than economic assumptions. (3) Privacy potential: ZK proofs can hide transaction details while proving validity. The tradeoff: higher computational complexity and currently limited EVM compatibility for some implementations.
Proof system variants
Two dominant proof systems. (1) SNARKs (Groth16, PLONK): smaller proof sizes but require trusted setup. (2) STARKs: larger proofs but no trusted setup needed, quantum-resistant. zkSync uses PLONK; StarkNet uses STARKs; Polygon zkEVM uses PLONK-based system.
EVM compatibility spectrum
Four levels of zkEVM compatibility (Vitalik Buterin’s classification). (1) Type 1: fully Ethereum-equivalent. (2) Type 2: EVM-equivalent. (3) Type 3: almost EVM-equivalent. (4) Type 4: high-level language equivalent. Lower types provide better compatibility; higher types provide better performance.
Türkiye context
For Türk DeFi developers and traders, ZK rollups offer faster withdrawal experience compared to optimistic rollups: material for trading workflows requiring rapid L1 access. The mathematical security model also provides stronger guarantees for high-value applications. Türk regulated entities may favour ZK rollups for the mathematical (vs. economic) security model.
Related: Optimistic Rollup, Validity Proof, Sequencer, PLONK.
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