MPC

Threshold signing engine -- CGGMP21 (ECDSA), FROST (EdDSA/Schnorr), BLS, SR25519, and post-quantum lattice signatures (Pulsar M-LWE, Corona R-LWE, and double-lattice composition) via the embedded thresholdd dispatcher. No full private key reconstruction, ever.

go get github.com/luxfi/mpc

Architecture

luxfi/mpc is a production MPC node (mpcd) that performs distributed key generation and threshold signing across a cluster. Each node holds a key share; t of n nodes must cooperate to produce a signature. The full private key never exists on any single machine, in memory or on disk.

Protocols

Protocol	Curve / Lattice	Key Type	Use
CGGMP21	secp256k1	secp256k1	Bitcoin, Ethereum, Lux C-Chain, all EVM L2s, XRPL
FROST	Ed25519	ed25519	Solana, TON, Polkadot, Cardano, Substrate chains
BLS	BLS12-381	bls	Lux consensus, beacon chain, aggregated signatures
SR25519	Ristretto255	sr25519	Substrate/Polkadot native
Pulsar	M-LWE (FIPS 204 / ML-DSA-65 threshold)	pulsar	Post-quantum threshold signing — bridge anchors, strict-PQ profile
Corona	R-LWE (Corona)	corona	Post-quantum threshold signing — orthogonal lattice family to Pulsar
Double-lattice	Pulsar ⊕ Corona	double-lattice	Composed u32_be(len) ‖ pulsar_sig ‖ corona_sig — both must verify

Pulsar, Corona, and double-lattice are exposed via the embedded threshold dispatcher (--threshold-listen, default 127.0.0.1:7300), which is luxfi/threshold/pkg/thresholdd. The dispatcher is a JSON-RPC 2.0 surface shared with cggmp21 / frost / bls — one wire, six schemes — and is consumed by the teleport bus (~/work/lux/teleport/mpc/src/signers/). The wire format is documented in ~/work/lux/threshold/CLAUDE.md under "thresholdd — unified JSON-RPC daemon".

Validator key slots vs. engine protocols (truthful naming). The KMS validator-key API (pkg/api/handlers_kms.go; hanzo KMS) provisions two slots per validator whose NAMES do not describe their cryptography: the "bls" slot is secp256k1 signed via CGGMP21 threshold ECDSA — NOT bls12-381 aggregation — and the "corona" slot is ed25519 signed via FROST — NOT the Corona R-LWE lattice protocol and NOT post-quantum. The bls12-381, Pulsar/Corona lattice, and double-lattice schemes in the table above are thresholdd engine capabilities, not the validator-custody path. Lux consensus BLS is a native per-validator bls12-381 key (PoP + aggregation), never threshold-custodied by this service.

Threshold Model

t >= floor(n/2) + 1

A 2-of-3 cluster tolerates 1 compromised or offline node. A 3-of-5 cluster tolerates 2. The threshold is configurable at key generation time.

Transport Modes

Consensus (default): Peer-to-peer ZAP protocol with built-in PoA consensus. No external dependencies. Nodes discover each other via --peer flags. This is the production path.

Legacy: NATS pub/sub + Consul service discovery. Deprecated but still supported via --mode=legacy.

Packages

cmd/mpcd/            Daemon binary (CLI, API server, node lifecycle)
pkg/mpc/             Core MPC node -- session management, key generation, signing
  keygen_session.go    CGGMP21 distributed key generation
  signing_session.go   CGGMP21 threshold signing (secp256k1)
  signing_session_frost.go  FROST threshold signing (Ed25519)
  bls_keygen_session.go     BLS key generation
  bls_signing_session.go    BLS threshold signing
  sr25519_keygen_session.go SR25519 key generation
  sr25519_signing_session.go SR25519 threshold signing
  reshare_session.go   Key resharing (rotate shares without changing public key)
  recovery.go          Key share recovery
  tfhe_session.go      FHE threshold decryption sessions
pkg/api/             HTTP API (key generation, signing, key info, health)
pkg/transport/       P2P transport (consensus mode ZAP, legacy NATS)
pkg/messaging/       PubSub abstraction over transport layer
pkg/db/              Key share storage (SQLite default, PostgreSQL optional)
pkg/kvstore/         Encrypted key-value store (AES-256, age encryption)
pkg/keyinfo/         Key metadata management
pkg/identity/        Node identity (Ed25519 keypair, mutual authentication)
pkg/backup/          Encrypted periodic backups
pkg/encryption/      AES-256-GCM encryption for key material at rest
pkg/kms/             KMS integration for secret management
pkg/hsm/             HSM provider abstraction (env, AWS, GCP)
pkg/client/          Go client library for MPC API
pkg/event/           Event types (keygen, sign, reshare)
pkg/eventconsumer/   Event processing pipeline
pkg/protocol/        Wire protocol messages
pkg/settlement/      Trade settlement signing
pkg/smart/           Smart contract transaction construction
pkg/custody/         Custody policy engine
pkg/integrity/       Key share integrity verification
pkg/txtracker/       Transaction lifecycle tracking

Security Properties

• Key shares encrypted at rest with AES-256-GCM (key from HSM/KMS)
• Inter-node messages authenticated with Ed25519 signatures
• No key share leaves the node unencrypted
• Resharing rotates shares without changing the public key or requiring all nodes
• Backup files encrypted with age (modern, audited encryption)
• Secret key bytes zeroed from memory after use (pkg/mpc/secret.go)

Quick Start

Consensus Mode (recommended)

# Node 0
mpcd start --node-id node0 --listen :9999 --api :9800 \
  --threshold 2 --peer node1:9999 --peer node2:9999

# Node 1
mpcd start --node-id node1 --listen :9999 --api :9801 \
  --threshold 2 --peer node0:9999 --peer node2:9999

# Node 2
mpcd start --node-id node2 --listen :9999 --api :9802 \
  --threshold 2 --peer node0:9999 --peer node1:9999

Generate a Wallet

curl -X POST http://localhost:9800/v1/keygen \
  -H "Content-Type: application/json" \
  -d '{"wallet_id": "w-001", "key_type": "secp256k1"}'

Sign a Transaction

curl -X POST http://localhost:9800/v1/sign \
  -H "Content-Type: application/json" \
  -d '{"wallet_id": "w-001", "message": "0xdeadbeef...", "key_type": "secp256k1"}'

Go Client

import "github.com/luxfi/mpc/pkg/client"

c := client.New("http://localhost:9800")
result, err := c.CreateWallet("w-001", "secp256k1")
sig, err := c.Sign("w-001", txHash, "secp256k1")

Configuration

config.yaml or environment variables (config keys uppercased — Viper AutomaticEnv):

mode: consensus
environment: local          # mainnet | testnet | local
mpc_threshold: 2
max_concurrent_keygen: 2
db_path: "."                # SQLite (default), or postgres:// URL
backup_enabled: true
backup_period_seconds: 300
backup_dir: backups

All secrets are sourced from KMS via --hsm-provider=env|aws|gcp. No plaintext secrets in config.

Deployment

Docker Compose

docker compose up

Kubernetes

cd k8s && kubectl kustomize . | kubectl apply -f -

K8s manifests are in k8s/ with Kustomize overlays. Production deployment uses cloudbuild.yaml for CI/CD to GHCR.

Testing

go test ./...       # 331 test functions

# End-to-end (3-node cluster)
cd e2e && make test

Papers

• Lux Threshold MPC -- protocol specification, security proofs
• Lux LSS MPC -- linear secret sharing in MPC
• Lux Validator MPC -- MPC integration with validator nodes
• Lux HSM Boundary -- HSM trust boundary analysis
• Lux FHE MPC Hybrid -- FHE threshold decryption via MPC
• Lux M-Chain MPC -- MPC chain architecture

Dependencies

• luxfi/threshold -- CGGMP21 and FROST protocol implementations
• luxfi/fhe -- FHE threshold decryption sessions
• luxfi/hsm -- HSM abstraction layer
• hanzoai/base -- Application framework

License

Lux Ecosystem License v1.2. See LICENSE.