# Albatross: An optimistic consensus algorithm

## TL;DR

Albatross is a novel Proof-of-Stake consensus algorithm that combines speculative BFT with periodic finality guarantees, achieving high performance and strong probabilistic finality in blockchain networks.

## Contribution

It introduces a new PoS consensus protocol that merges speculative BFT with periodic finality, supported by formal security proofs and practical implementation.

## Key findings

- Achieves near-theoretical maximum performance for PoS consensus
- Provides strong probabilistic finality with periodic Tendermint finality
- Secure under standard BFT assumptions

## Abstract

The consensus protocol is a critical component of distributed ledgers and blockchains. Achieving consensus over a decentralized network poses challenges to transaction finality and performance. Currently, the highest-performing consensus algorithms are speculative BFT algorithms, which, however, compromise on the transaction finality guarantees offered by their non-speculative counterparts. In this paper, we introduce Albatross, a Proof-of-Stake (PoS) blockchain consensus algorithm that aims to combine the best of both worlds. At its heart, Albatross is a high-performing, speculative BFT algorithm that offers strong probabilistic finality. We complement this by periodically guaranteeing finality through the Tendermint protocol. We prove our protocol to be secure under standard BFT assumptions and analyze its performance both on a theoretical and practical level. For that, we provide an open-source Rust implementation of Albatross. Our real-world measurements support that our protocol has a performance close to the theoretical maximum for single-chain Proof-of-Stake consensus algorithms.