Protocol Berg v2: Nikita Polianskii - Starfish: push based dissemination can be efficient

Thu, Oct 2, 2025, 12:00 AM

Current DAG-based BFT protocols face a critical trade-off: certified DAGs provide strong security guarantees but require additional rounds of communication to progress the DAG construction, while uncertified DAGs achieve lower latency at the cost of either reduced resistance to adversarial behaviour or higher communication costs. We present Starfish, a partially synchronous DAG-based BFT protocol that achieves the security properties of certified DAGs, the efficiency of uncertified approaches and linear amortized communication complexity. The key innovation is Encoded Cordial Dissemination, a push-based dissemination strategy that combines Reed-Solomon erasure coding with Data Availability Certificates (DACs). Each of the $n=3f+1$ validators disseminates complete transaction data for its own blocks while distributing encoded shards for others' blocks, enabling efficient data reconstruction with just $f+1$ shards. Building on the previous uncertified DAG BFT commit rule, Starfish extends it to efficiently verify data availability through committed leader blocks serving as DACs. For large enough transaction data, this design allows Starfish to achieve $O(n)$ amortized communication complexity per committed transaction byte. Experimental evaluation against state-of-the-art DAG BFT protocols demonstrates Starfish's robust performance under steady-state and Byzantine scenarios. Our results show that strong Byzantine fault tolerance, high performance, and low communication complexity can coexist in DAG BFT protocols, making Starfish particularly suitable for large-scale distributed ledger deployments. Protocol Berg v2 12-13 June 2025 Berlin https://v2.protocol.berlin