Slipstream: Ebb-and-Flow Consensus on a DAG with Fast Confirmation for UTXO Transactions

TL;DR

Slipstream is a BFT protocol that uses a DAG structure to achieve fast UTXO transaction confirmation and flexible consensus ordering, supporting high Byzantine fault tolerance and quick finality.

Contribution

It introduces a novel DAG-based BFT protocol with dual ordering modes and an integrated payment system enabling rapid UTXO transaction confirmation.

Findings

Supports up to 50% Byzantine nodes in optimistic mode

Achieves fast UTXO confirmation within three rounds during synchrony

Provides a novel double-spend resolution method using DAG structure

Abstract

This paper introduces Slipstream, a Byzantine Fault Tolerance (BFT) protocol where nodes concurrently propose blocks to be added to a Directed Acyclic Graph (DAG) and aim to agree on block ordering. Slipstream offers two types of block orderings: an optimistic ordering, which is live and secure in a sleepy model under up to 50% Byzantine nodes, and a final ordering, which is a prefix of the optimistic ordering and ensures safety and liveness in an eventual lock-step synchronous model under up to 33% Byzantine nodes. Additionally, Slipstream integrates a payment system that allows for fast UTXO transaction confirmation independently of block ordering. Transactions are confirmed in three rounds during synchrony, and unconfirmed double spends are resolved in a novel way using the DAG structure.