Abstract
Liquidity fragmentation across Ethereum Layer 2 (L2) execution environments remains a primary bottleneck to achieving scalable, seamless decentralized application ecosystems. Existing cross-rollup bridging solutions rely either on slow Layer 1 (L1) canonical settlement mechanisms, which induce multi-day latency for Optimistic Rollups, or centralized off-chain liquidity providers that introduce capital inefficiency and counterparty risks. In this paper, we present CROSS-L2, a novel, verifiable state-relay protocol designed for direct, low-latency cross-rollup asset transfers and arbitrary message passing without intermediary liquidity lockups. CROSS-L2 leverages succinct recursive Zero-Knowledge SNARK (zk-SNARK) state proofs and a decentralized light-relayer network to continuously verify state root updates directly between source and target rollups. By decoupling state verification from L1 execution while maintaining L1-equivalent cryptographic security, CROSS-L2 reduces cross-rollup asset transfer settlement times from several hours or days to under 45 seconds. Empirical evaluation across testnet deployments bridging Arbitrum, Optimism, and zkSync Era demonstrates an 82% reduction in end-to-end latency and a 65% decrease in transaction gas costs compared to conventional canonical L1 relaying. Furthermore, we provide formal security proofs confirming that CROSS-L2 preserves full safety and liveness guarantees against re-organization attacks and malicious relayer collusion.
