What is ZK Rollup (aggregation)?

ZK Rollup with aggregation refers to the zero-knowledge proof-based Layer 2 scaling approach used by zkLink, which aggregates transactions and liquidity across multiple Layer 1 and Layer 2 networks. Unlike standard ZK Rollups that settle on a single L1, zkLink's aggregation model collects transactions from multiple chains, batches them together, and generates zero-knowledge proofs that verify the correctness of cross-chain state transitions. The system uses a network of sequencers that collect transactions from connected chains, execute them off-chain, and produce validity proofs that are then verified on each respective chain. This enables unified liquidity and atomic cross-chain operations without relying on traditional bridge mechanisms.

The aggregation approach provides the security benefits of zero-knowledge proofs — mathematical guarantees of computation correctness — while extending them across multiple blockchain ecosystems. Users can interact with assets and applications on different chains through a single interface, with the ZK proofs ensuring that cross-chain state transitions are valid. The main challenge is the computational overhead of generating proofs that cover cross-chain operations, which is more complex than single-chain ZK Rollup proofs. The system inherits security from each connected chain's L1, as the validity proofs must be verified by on-chain contracts on each respective network. This differs from bridge-based approaches where security depends on the bridge operators.

zkLink launched its mainnet in early 2024 as a multi-chain ZK Rollup infrastructure. The project connects multiple Layer 1 and Layer 2 networks, enabling applications to access liquidity across chains. zkLink Nova, built on this infrastructure, operates as a Layer 3 aggregated rollup that settles on multiple L2s simultaneously. The project represents an evolution of the ZK Rollup concept from single-chain scaling to cross-chain aggregation, addressing the liquidity fragmentation problem that arises from the proliferation of separate blockchain networks. The team has built on the broader ZK proof ecosystem, leveraging advances in proof systems and recursive composition to make cross-chain aggregated proofs practical.