Lux Consensus

Quasar Family of Consensus

Quasar is the consensus engine for the Lux network. It provides unified consensus for linear chains (P-Chain, C-Chain) and DAG chains (X-Chain) with post-quantum finality via three independent cryptographic signing paths.

Sub-Protocols

Protocol	Role	Package
Photon	K-of-N committee selection via Fisher-Yates sampling with luminance-weighted reputation	protocol/photon
Wave	Per-round threshold voting with FPC (Fast Probabilistic Consensus)	protocol/wave
Focus	Confidence accumulation: beta consecutive successes = local finality	protocol/focus
Nova	Linear chain consensus mode (P-Chain, C-Chain) -- wraps Ray	protocol/nova
Nebula	DAG consensus mode (X-Chain) -- wraps Field	protocol/nebula
Prism	DAG geometry: frontiers, cuts, uniform peer sampling	protocol/prism
Horizon	DAG order-theory: reachability, LCA, transitive closure, skip lists	protocol/horizon
Flare	DAG certificate/skip detection via 2f+1 quorum	protocol/flare
Ray	Linear chain finality driver: Wave + Focus + Sink	protocol/ray
Field	DAG finality driver: Wave + safe-prefix commit	protocol/field
Quasar	BLS + Ringtail + ML-DSA threshold signing, epoch management	protocol/quasar

Signing Modes

Each cryptographic layer is independently toggleable:

Mode	Layers	Use Case
BLS-only	BLS12-381 threshold	Fastest classical consensus
BLS + ML-DSA	BLS + FIPS 204 ML-DSA-65	Dual with PQ identity proof
BLS + Ringtail	BLS + Ring-LWE 2-round threshold	Dual with PQ threshold proof
BLS + Ringtail + ML-DSA	All three in parallel	Full Quasar (triple mode)

IsTripleMode() returns true when all three paths are configured. TripleSignRound1 runs BLS + Ringtail + ML-DSA signing in parallel goroutines.

Architecture

consensus/
  protocol/
    photon/       Committee selection (Emitter + Luminance)
    wave/         Threshold voting + FPC
      fpc/        Fast Probabilistic Consensus selector
    focus/        Confidence counter (beta tracker)
    prism/        DAG cuts, frontiers, uniform sampling
    horizon/      DAG reachability, LCA, skip lists
    flare/        DAG cert/skip classification (2f+1)
    ray/          Linear chain driver (Nova uses this)
    field/        DAG finality driver (Nebula uses this)
    nova/         Linear chain consensus mode
    nebula/       DAG consensus mode
    chain/        Block interface primitives
    quasar/       BLS + Ringtail + ML-DSA threshold signing
  engine/         Consensus engine (Chain, DAG, PQ wrappers)
  core/           Core types, DAG structures
  types/          Block, Vote, Config, Bag
  config/         Parameter presets (single, local, testnet, mainnet)
  runtime/        VM wiring (chain IDs, validators, logging)
  pkg/wire/       Wire protocol credentials (ML-DSA-44/65/87 + BLS + Ed25519)
  bench/          Benchmarks
  version/        Re-exports github.com/luxfi/version

Consensus Flow

Linear Chains (Nova)

Photon (select committee) -> Wave (threshold vote) -> Focus (count beta) -> Ray (decide) -> Sink

DAG Chains (Nebula)

Photon (select committee) -> Wave (threshold vote per frontier vertex)
  -> Flare (cert/skip) -> Horizon (safe prefix) -> Field (commit ordered prefix) -> Committer

Quasar PQ Finality

After consensus decision, the Quasar signing layer produces threshold certificates:

1. BLS: single-round threshold share via crypto/threshold
2. Ringtail: 2-round Ring-LWE threshold via luxfi/ringtail/threshold
3. ML-DSA-65: single-round FIPS 204 identity signature

All three run in parallel. A block is quantum-final when all configured certificate layers are valid.

Key Hierarchy

Layer	Key Type	Purpose
Node-ID	Ed25519	P2P transport auth
Validator-BLS	BLS12-381	Classical finality votes
Validator-PQ	Ringtail (Ring-LWE)	PQ finality shares
Validator-ID	ML-DSA-65 (FIPS 204)	PQ identity attestation
Wallet (EVM)	secp256k1	User transaction signatures
Wallet (X-Chain)	secp256k1	UTXO locking

Quick Start

import "github.com/luxfi/consensus"

chain := consensus.NewChain(consensus.DefaultConfig())

ctx := context.Background()
if err := chain.Start(ctx); err != nil {
    log.Fatal(err)
}
defer chain.Stop()

block := &consensus.Block{
    ID:       consensus.NewID(),
    ParentID: consensus.GenesisID,
    Height:   1,
    Payload:  []byte("Hello, Lux!"),
}
if err := chain.Add(ctx, block); err != nil {
    log.Fatal(err)
}

Configuration

// Auto-configure based on validator count
params := consensus.GetConfig(21) // mainnet defaults

// Or use presets
consensus.SingleValidatorParams() // 1 node, dev
consensus.LocalParams()           // 5 nodes, local
consensus.TestnetParams()         // 11 nodes, testnet
consensus.MainnetParams()         // 21 nodes, production

Benchmarks

Measured on Apple M1 Max:

Component	Operation	Time/Op
Wave	Vote round	3.38 us
Photon	K-of-N selection	3.03 us
Luminance	Brightness update	72 ns

ZAP wire protocol (measured, bench/):

Configuration	Throughput
Single connection	114K TPS
20 parallel connections	376K TPS
50 conns + batch 1000	20.26M TPS

Testing

GOWORK=off go test ./...
GOWORK=off go test -bench=. ./bench/

Security Model

1. Pre-quantum: Attacker must corrupt >= 1/3 stake to fork
2. Q-day (BLS broken): Lattice certificates prevent unsafe finalization
3. Post-quantum: Security rests on Module-LWE (Ringtail) + Module-LWE/SIS (ML-DSA)

License

BSD 3-Clause. See LICENSE.