Consensus Layer

Arc’s consensus protocol provides deterministic finality in under one second. It is built on Malachite, a high-performance implementation of the Tendermint Byzantine Fault Tolerant (BFT) protocol, and uses a Proof-of-Authority (PoA) validator set. As a developer, you don’t interact with consensus directly, but it defines the guarantees you can rely on when building payment, trading, or settlement applications.

​

Core properties

Arc consensus is designed for institutional-grade performance and trust:

• Deterministic finality: A transaction is either unconfirmed or final. Once finalized, it cannot be reversed or reorganized.
• Low latency: Blocks finalize in less than one second under normal conditions.
• High throughput: Benchmarks show 3,000+ TPS with 20 validators and sub-second latency. Smaller validator sets can reach 10,000+ TPS.
• Validator accountability: Validators are regulated institutions with operational and compliance obligations.
• Optimistic responsiveness: The Tendermint protocol implemented by Malachite ensures block production and transaction confirmation proceeds as fast as the network permits, with no extra timeouts or artificial delays.

​

Proof-of-Authority validator set

Arc uses a permissioned Proof-of-Authority (PoA) model.

• Validators are selected, known institutions with reputations, compliance requirements, and operational guarantees (such as uptime SLAs and SOC 2 certification).
• Geographic distribution ensures resilience. Validators run across multiple global regions.
• Block production is rotated among validators to ensure fairness and liveness.

This design provides stronger assurances for regulated finance by replacing anonymous economic incentives with institutional accountability.

​

How Tendermint consensus works in Malachite

To order and finalize transactions, Arc uses the Tendermint BFT consensus protocol, implemented in the Malachite consensus layer. At a higher level, Tendermint works as follows:

1. Propose
   • One validator is chosen as proposer for a round.
   • The proposer bundles transactions into a block and broadcasts it.
2. Pre-vote
   • Validators broadcast votes indicating whether they consider the block valid.
3. Pre-commit
   • Validators broadcast a second round of votes.
   • If more than two-thirds of validators pre-commit to the same block, it is locked in.
4. Commit
   • The block is finalized and appended to the chain.
   • Transactions inside the block are now irreversible.

This two-phase voting process ensures consensus safety: two conflicting blocks cannot both be finalized. As a result, block reorganizations are impossible, and each block is finalized quickly and deterministically. The diagram below illustrates the high-level concept behind this process.

​

Deterministic finality

Unlike probabilistic models (like proof-of-work), Arc provides certainty about finality.

• Once a block is finalized, it cannot be reverted without collusion of at least two-thirds of validators.
• There is no need for developers to wait for multiple confirmations.
• Applications can release funds or complete trades immediately after confirmation.

For developers, this reduces complexity since you don’t need rollback logic, and you can provide users with instant settlement guarantees.

​

Performance characteristics

Arc is engineered for low latency and high throughput. In testnet environments, you can expect performance characteristics similar to the following:

• 3,000 TPS with 20 globally distributed validators.
• <350 ms finality under benchmark conditions.
• >10,000 TPS with reduced validator counts (for example, 4 validators).
• Future roadmap includes multi-proposer support (see below), which can increase throughput by ~10X, and consensus optimizations that can cut latency by ~30%.

These metrics make Arc suitable for high-frequency payments, trading, and settlement systems.

​

Multi-proposer

The Malachite roadmap includes a planned upgrade called multi-proposer. This feature allows multiple validators in the network to propose blocks in parallel, rather than sequentially. By enabling concurrent block proposals, multi-proposer can significantly increase network throughput and improve overall scalability.

​

Security guarantees

Arc combines protocol-level safety with institutional safeguards:

• Safety: With <1/3 faulty validators, consensus guarantees no conflicting blocks can be finalized.
• Liveness: The system continues to make progress as long as ≥2/3 of validators are online and honest.
• Accountability: Validators are regulated institutions with compliance obligations, making malicious behavior costly in the real world.
• Resilience: Geographic distribution reduces correlated downtime and attack risk.

​

Developer implications

For developers, consensus guarantees that:

• Your transactions settle instantly and irreversibly.
• You don’t need to design around chain reorganizations or probabilistic confirmations.
• Arc can handle institutional workloads with high TPS and low latency.
• Validator accountability ensures the network remains secure and compliant, even at scale.

​

Roadmap

Malachite continues to evolve:

• Multi-proposer support: Multiple proposers per height increase overall throughput.
• Latency optimizations: New protocol variant reduces consensus rounds from three to two.
• Permissioned Proof-of-Stake transition: Over time, Arc may evolve from PoA to a permissioned PoS model, allowing broader validator participation while maintaining compliance.

These upgrades will further strengthen Arc as infrastructure for global financial applications.