Lux Consensus

Lux runs Quasar, a leaderless DAG-native consensus engine with hybrid classical + post-quantum finality. Each round produces a QuasarCert that combines BLS12-381 aggregate signatures with two independent post-quantum proof paths (Pulsar threshold + ML-DSA identity), so a break of any single cryptographic primitive does not break finality.

Quasar Sub-Protocols

Each component owns one concern. They compose into two engine modes (linear chains and DAG chains).

Round flow

Linear (Nova): Photon → Wave → Focus → Ray → Sink

DAG (Nebula): Photon → Wave (per frontier vertex) → Flare → Horizon (safe prefix) → Field → Committer

QuasarCert: Hybrid Finality

Each finalized round emits a QuasarCert:

type QuasarCert struct {
    BLS        []byte    // BLS12-381 aggregate (~48 B classical fast path)
    Pulsar   []byte    // Pulsar/Ring-LWE 2-round threshold proof (~33 KB PQ)
    MLDSAProof []byte    // Z-Chain Groth16 rollup of N × ML-DSA identity sigs (~192 B)
    Epoch      uint64
    Finality   time.Time
    Validators int
}

A QuasarCert verifies if and only if the configured layers all verify. Each layer is independently toggleable:

Selectable at runtime via the CONSENSUS_PQ_MODE env var or config.PQMode field.

Pulsar (Threshold Layer)

The Pulsar layer is implemented by Pulsar (github.com/luxfi/pulsar/threshold) — Lux's variant with DKG2 and the Pulsar-SHA3 hash suite (KMAC over cSHAKE256, NIST SP 800-185).

Measured performance (Apple M1 Max, single round)

ZAP wire protocol (zero-copy, replaces JSON-RPC for inter-node messages): single-conn 114K TPS, 50 conns + batch 1000 = 20.26M TPS.

Properties

Liveness. Round driver makes progress whenever a 2f+1 fraction of the network is reachable. No single leader.

Safety. Holds whenever fewer than f Byzantine validators participate (committee size 3f+1). The classical layer (BLS) and post-quantum layers (Pulsar / ML-DSA) sign the same payload, so an adversary that breaks one primitive still has to defeat the other layers.

PQ safety. Even an attacker with full quantum capability cannot forge a triple-mode cert without breaking both Ring-LWE (Pulsar) and ML-DSA simultaneously — see LP-105 §7 and ~/work/lux/proofs/quasar-cert-soundness.tex App. E for the parameter-tightness argument.

Scalability. Per-node communication is O(k) per round (committee size, not validator-set size). Quasar scales to thousands of validators without degrading finality.

Chain assignments

Further reading

• LP-110 Quasar Consensus
• LP-113 Wave Voting
• LP-115 Horizon Finality
• github.com/luxfi/consensus — the implementation
• Run a validator