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Quasar Full Protocol Example

Complete demonstration of the Lux Quasar consensus protocol showing all components working together to achieve sub-second quantum-resistant finality.

What is Quasar?

Quasar is Lux's unified consensus protocol that combines multiple cutting-edge consensus techniques:

Fast Probabilistic Consensus (FPC) - Prevents stuck states with dynamic thresholds
Wave Protocol - Metastable convergence through repeated sampling
Horizon/Flare - DAG-based finality detection
Post-Quantum Signatures - Pulsar lattice + BLS fusion

Together, these achieve 2-round quantum finality in <1 second.

Running the Example

cd examples/quasar_full
go run main.go

Running the Tests

# From consensus root
cd ../..
go test ./examples/quasar_full/... -v

# With coverage
go test ./protocol/wave/fpc/... -v -cover
go test ./protocol/flare/... -v -cover
go test ./protocol/horizon/... -v -cover

What The Example Demonstrates

Part 1: FPC Dynamic Thresholds

Shows how FPC uses a PRF (SHA-256) to select different thresholds each round:

Prevents consensus from getting stuck
Maintains Byzantine fault tolerance
Deterministic but varied selection

Example output:

Round  0: α=13/20 (θ=0.650) [█████████████░░░░░░░]
Round  1: α=11/20 (θ=0.550) [███████████░░░░░░░░░]
Round  2: α=15/20 (θ=0.750) [███████████████░░░░░]

Part 2: Wave Consensus & Block Finalization

Demonstrates REAL block finalization:

Block creation and addition to chain
Validator vote collection
Confidence building through repeated sampling
Final consensus decision

Shows actual timing: typically <100μs for block processing.

Tests all 7 critical Horizon algorithms:

IsReachable - DAG connectivity analysis
LCA - Lowest Common Ancestor for parallel blocks
ComputeSafePrefix - Find finalized vertices
ChooseFrontier - Byzantine-tolerant parent selection
Antichain - Identify concurrent vertices
Horizon - Advance event horizon boundary
BeyondHorizon - Check if vertex is immutably finalized

Part 4: Complete Quasar Flow

Visualizes the complete 2-round protocol:

Round 1 (~500ms): Classical BFT

FPC threshold selection
Wave repeated sampling
BLS signature aggregation

Round 2 (~300ms): Quantum Finality

Horizon finality detection
Flare certificate verification
Pulsar post-quantum signatures
Event horizon advancement

Total: <1 second with quantum resistance

Test Coverage

The test suite includes:

✅ FPC threshold selection (determinism + variety)
✅ Block finalization (single to multi-validator)
✅ Horizon reachability (forward + backward)
✅ LCA computation
✅ Safe prefix detection
✅ Frontier selection with BFT
✅ Event horizon advancement
✅ Certificate threshold validation
✅ Full protocol integration
✅ Performance benchmarks

Run go test -v -cover for detailed coverage report.

Key Concepts

Byzantine Fault Tolerance

Quasar ensures safety with f < n/3 Byzantine faults:

n=20 validators tolerates f=6 faults
Certificate needs ≥2f+1 = 13 validators
Safety: Can't have both cert and skip (mutual exclusion)

Metastable Consensus

Wave protocol achieves convergence through:

Random sampling of k validators
Check if ≥α prefer this block
Repeat until β consecutive successes
FPC varies α to prevent stuck states

DAG Finality

Horizon/Flare detect finality in parallel DAG:

Certificate: ≥2f+1 validators support vertex
Skip: ≥2f+1 validators don't support vertex
Safe Prefix: Vertices that are ancestors of all frontier
Event Horizon: Immutability boundary (cannot be reverted)

Quantum Resistance

Pulsar provides post-quantum security:

Lattice-based cryptography (NTRU/ML-KEM family)
Fused with BLS for 2-round finality
Resistant to Shor's algorithm (quantum attacks)

Architecture

Quasar Protocol
    │
    ├── Round 1: Classical BFT
    │   ├── FPC (threshold selection)
    │   ├── Wave (metastable convergence)
    │   └── BLS (signature aggregation)
    │
    └── Round 2: Quantum Finality
        ├── Horizon (reachability analysis)
        ├── Flare (certificate verification)
        └── Pulsar (PQ signatures)

Performance

From benchmarks in this example:

FPC threshold selection: ~100ns per round
Block finalization: ~30μs
Horizon algorithms: ~1μs per operation
Full protocol: <1 second total

Safety Guarantees

✓ Safety: No two conflicting blocks can both finalize
✓ Liveness: Finality in <1s (non-adversarial)
✓ Byzantine Tolerance: Works with f < n/3 faults
✓ Quantum Resistance: Secure against quantum computers

Learn More

Simple Consensus - Basic chain consensus
01-Simple Bridge - Cross-chain integration
02-AI Payment - AI-powered consensus

Lux Consensus v1.22.0 - Quantum-resistant finality in <1 second

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