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Documentation Index

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Arc’s consensus layer is built on Malachite, a high-performance, open-source implementation of the Tendermint Byzantine Fault Tolerant (BFT) protocol. BFT consensus ensures the network reaches agreement on a single history of transactions even if some validators behave maliciously or go offline. Arc uses a Proof-of-Authority (PoA) validator set to order transactions, produce blocks, and deliver deterministic finality — the guarantee that committed blocks are permanent and can never be reversed or reorganized — in under one second.

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How Malachite consensus works

For how this fits into the broader architecture, see the system overview. Each block passes through a four-step pipeline. A rotating proposer assembles transactions, and all validators participate in two rounds of voting before the block is committed.
  1. Propose — A validator selected as proposer for the current round bundles pending transactions into a block and broadcasts it.
  2. Pre-vote — Every validator evaluates the proposed block and broadcasts a vote on its validity.
  3. Pre-commit — Validators broadcast a second vote. If more than two-thirds of validators pre-commit to the same block, it proceeds to commit.
  4. Commit — The block is finalized and appended to the chain. Every transaction in the block is irreversible.
This two-phase voting process (pre-vote + pre-commit) guarantees that two conflicting blocks can never both be finalized, making reorganizations impossible.

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Proof-of-Authority validator set

Arc uses a permissioned Proof-of-Authority (PoA) model instead of anonymous economic staking. Validators are selected, known institutions with compliance obligations and operational guarantees. For details on operating a validator node, see running a node.
  • SOC 2 certified — Validators meet audited security and availability standards.
  • Geographic distribution — Nodes run across multiple global regions to reduce correlated downtime.
  • Rotating proposer — Block production rotates among validators to ensure fairness and liveness.
  • Uptime SLAs — Each validator commits to operational availability requirements.
This design replaces anonymous economic incentives with institutional accountability, providing stronger assurances for regulated finance.

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Performance characteristics

Performance also depends on the execution layer, which processes transactions within each block. Malachite delivers optimistic responsiveness: blocks are produced as fast as the network permits, with no artificial delays or extra timeouts.
MetricValueConditions
Throughput3,000+ TPS20 globally distributed validators
Finality<350 msBenchmark conditions
Peak throughput10,000+ TPS4 validators

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Security guarantees

Arc combines protocol-level safety with institutional safeguards:
GuaranteeDescription
SafetyWith fewer than one-third faulty validators, consensus guarantees that no conflicting blocks are finalized.
LivenessThe network continues to produce blocks as long as two-thirds or more of validators are online and honest.
AccountabilityValidators are regulated institutions, making malicious behavior costly beyond protocol penalties.
ResilienceGeographic distribution reduces the risk of correlated outages or targeted attacks.
The deployment model provides additional detail on how validators are geographically distributed.

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Roadmap

The Malachite roadmap includes multi-proposer support (multiple validators propose blocks in parallel for higher throughput), a protocol optimization that reduces consensus from three rounds to two for lower latency, and a potential transition from Proof-of-Authority to permissioned Proof-of-Stake to broaden validator participation while maintaining compliance requirements.