Reducing Latency of DAG-based Consensus in the Asynchronous Setting via the UTXO Model

DAG-based consensus has attracted significant interest due to its high throughput in asynchronous network settings. However, existing protocols such as DAG-rider (Keidar et al., PODC 2021) and “Narwhal and Tusk” (Danezis et al., Eurosys 2022) face two undesired practical issues: (1) high transaction latency and (2) high cost to verify transaction outcomes. To address (1), this work introduces a novel commit rule based on the Unspent Transaction Output (UTXO) Data Model, which allows a node to predict the transaction results before triggering the commitment. We propose a new consensus algorithm named “Board and Clerk”, which reduces the transaction latency by half for roughly 50% of transactions according to our experiments. As the tolerance for faults escalates, more transactions can partake in this latency reduction. In addition, we also propose the HyperBlock Model with two flexible proposing strategies to tackle (2): blocking and non-blocking. Using our proposed strategies, each node first predicts the transaction results if its proposal is committed and packs this result as a commitment in its proposal. The hyper-block packs the proposal’s signature, and the consensus layer outputs to prove the transaction results.