Proof of Work vs Ethereum vs BFT: HotStuff, Tendermint, Narwhal+Tusk, and Solana
This post compares Proof of Work (PoW) and Ethereum’s Proof of Stake (PoS) against modern BFT systems: HotStuff, Tendermint, Narwhal + Tusk, and Solana. The goal is to make the tradeoffs clear: finality, data availability, ordering, execution model, and performance.
Quick mental models
- PoW (Bitcoin‑style): probabilistic finality, open participation, longest‑chain rule.
- Ethereum PoS (Gasper): fork choice (LMD‑GHOST) + finality (Casper FFG) with epochs.
- HotStuff: BFT finality via quorum certificates (QCs), leader‑based.
- Tendermint: round‑based prevote/precommit with deterministic finality per height.
- Narwhal + Tusk: decouple data availability (Narwhal DAG) from ordering (Tusk BFT).
- Solana: high‑throughput PoS with Tower BFT and a time source (PoH).
- Cardano: PoS with Ouroboros, probabilistic settlement and epoch‑based leadership.
Comparison table
| System | Data availability | Ordering | Finality | Execution |
|---|---|---|---|---|
| PoW | Implicit via propagation | Longest chain | Probabilistic | After blocks, reorgs possible |
| Ethereum PoS | Implicit + gossip | LMD‑GHOST | Finality via FFG | After slots, finality at epochs |
| HotStuff | Explicit via QC chain | Leader proposals | Deterministic | After commit |
| Tendermint | Explicit via proposal + gossip | Per round | Deterministic | After commit |
| Narwhal + Tusk | Explicit via Narwhal DAG | Tusk orders references | Deterministic | After ordering by reference |
| Solana | Implicit + turbine | PoH + Tower BFT | Probabilistic (fast confirmations) | Parallel runtime |
| Cardano | Implicit + gossip | Ouroboros chain selection | Probabilistic (settlement by depth) | After blocks |
What “data availability” means here
- PoW / Ethereum / Solana: availability relies on propagation and gossip. If the block spreads, it is assumed available.
- HotStuff / Tendermint: availability is tied to votes and the ability to verify the proposal.
- Narwhal + Tusk: availability is explicit and separate from ordering; consensus never orders missing data.
Where Ethereum differs from PoW
Ethereum’s PoS stack has two layers:
- Fork choice (LMD‑GHOST): decides the head of the chain.
- Finality (Casper FFG): finalizes checkpoints every epoch when enough stake votes.
That means Ethereum has probabilistic head selection but deterministic checkpoint finality, unlike PoW which is probabilistic at every depth.
How BFT systems differ from PoW/PoS
- BFT finality: HotStuff, Tendermint, and Tusk provide deterministic finality once a quorum is reached.
- Membership: BFT protocols assume a known validator set (or a committee per epoch).
- Performance: BFT systems often achieve higher throughput and lower latency than PoW.
Solana’s approach
Solana combines a time source (Proof of History) with Tower BFT to reduce voting overhead and push throughput. It achieves fast confirmations but still relies on probabilistic finality under the hood.
Summary
- PoW: simple and open, but probabilistic finality and slower throughput.
- Ethereum PoS: hybrid of probabilistic fork choice with deterministic checkpoint finality.
- HotStuff/Tendermint: BFT consensus with deterministic finality and strong safety.
- Narwhal + Tusk: separates data availability from ordering, improving performance.
- Solana: high throughput with PoH + Tower BFT, fast confirmations.
- Cardano: PoS with Ouroboros and probabilistic settlement via chain depth.
Each design reflects a different set of tradeoffs between openness, finality, throughput, and network assumptions.