ZKrollup

zkRollup is a type of Layer 2 scaling solution for blockchains, particularly Ethereum, that uses zero-knowledge proofs to validate off-chain transaction batches. In a zkRollup, user transactions are processed outside the main chain and the resulting state transition is proven correct with a cryptographic zero-knowledge proof. A rollup operator posts the proof, a new state root, and a compact set of transaction data to the Layer 1 blockchain. A specialized verifier on L1 checks the validity proof; if it verifies, the new state is accepted. To maintain data availability, the system publishes transaction data on L1 or uses data-availability schemes that keep proofs small while still enabling withdrawals.

Security and performance: Because validity proofs guarantee correctness, zkRollups inherit the security of the underlying L1. They offer high throughput and lower fees compared with on-chain execution, and finality is tied to L1 confirmation since a valid proof settles the state immediately. Challenges include the complexity and cost of generating proofs for arbitrary smart contracts and ensuring robust data availability.

Examples and ecosystem: Notable implementations include zkSync, StarkNet (STARK-based), and Polygon zkEVM, each with different prover technologies and aims for EVM compatibility. zkRollups are commonly contrasted with optimistic rollups, which rely on fraud proofs and dispute periods. In practice, they enable scalable DeFi, payments, and general smart-contract use while preserving strong base-layer security.